investigating poorly known historic context: dating ... minnesotas prehistory pri fre s… · were...

INVESTIGATING POORLY KNOWN HISTORIC CONTEXT: DATING MINNESOTA’S PREHISTORY

By

Linda Scott Cummings

With assistance fromR. A. Varney,Peter Kováčik,

andCaitlin A. Clark

PaleoResearch Institute, Inc.Golden, Colorado

PaleoResearch Institute Technical Report 2015-030

Prepared for

The Oversight Board of the Statewide Survey of Historical and Archaeological Sites and the

Minnesota Historical SocietySt. Paul, Minnesota

April 2017

TABLE OF CONTENTS

INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Charred Botanic Remains and Charcoal Identification . . . . . . . . . . . . . . . . . . . . . . . . . . 1AMS Radiocarbon Dating - Charcoal and Botanic Remains . . . . . . . . . . . . . . . . . . . . . 2AMS Radiocarbon Bone Collagen Extraction and Dating . . . . . . . . . . . . . . . . . . . . . . . . 3AMS Radiocarbon Charred Bone Dating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Ceramic Residue for AMS Radiocarbon Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Task 1: Summarize What is Currently Known About Absolute Dating in Minnesota . . . 6Task 2: Evaluate the Reliability of Existing Dates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Brainerd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Task 3: Submit Suitable Materials from Existing Archaeological Collections to Suitable Laboratories for Dating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9LaMoille (12WN1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Dating Reference Fish and Wild Rice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Recommendations for Future Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18TABLE 1

PROVENIENCE DATA FOR SAMPLES FROM VARIOUS SITES IN MINNESOTA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

TABLE 2 MACROFLORAL REMAINS FROM VARIOUS SITES IN MINNESOTA . . . . . 27

TABLE 3INDEX OF MACROFLORAL REMAINS RECOVERED FROM VARIOUSSITES IN MINNESOTA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

TABLE 4RADIOCARBON RESULTS FOR SAMPLES FROM VARIOUS SITES INMINNESOTA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

TABLE 5RADIOCARBON AND OSL RESULTS FOR BRAINERD WARE SAMPLES FROM VARIOUS SITES IN MINNESOTA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54FIGURE 1. ALL AMS RADIOCARBON SAMPLES PLOTTED OVER

GROUNDWATER PROVINCES, MINNESOTA, USA. . . . . . . . . . . . . . . . . . . . 55FIGURE 2. PLOT OF ALL DATES ON CHARRED FOOD CRUST IN

MN DATABASE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56FIGURE 3. MULTIPLOT OF DATES FROM BRAINERD CULTURE SITES

GROUPED BY MATERIAL CLASS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57FIGURE 4. MULTIPLOT OF DATES FROM BRAINERD CULTURE SITES

GROUPED BY SITE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

i

FIGURE 5. ALL CHARRED AND UNCHARRED BONE AMS RADIOCARBONSAMPLES, MINNESOTA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

FIGURE 6. SKETCH OF ROOT MASSES AND ABOVE-GROUND VEGETATIONFOR TYPICAL PRAIRIE PLANTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

APPENDICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61APPENDIX A. ALL AMS RADIOCARBON RESULTS FROM ARCHAEOLOGICAL

SITES, MINNESOTA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62APPENDIX B. CALIBRATIONS OF NEW AMS RADIOCARBON DATES RUN BY

PALEORESEARCH INSTITUTE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63APPENDIX C. MULTIPLOTS OF EXISTING AMS RADIOCARBON RESULTS,

MINNESOTA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64APPENDIX D. GIS MAPPED AMS RADIOCARBON RESULTS, MONTANA. . . . . . . 65APPENDIX E. SUMMARY OF WORK DONE PRESENTED AT THE COUNCIL

FOR MINNESOTA ARCHAEOLOGY CONFERENCE, HELD INST. PAUL, FEBRUARY, 2017. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

REFERENCES CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

ii

INTRODUCTION

Minnesota’s radiocarbon dataset accumulated between 1959 and 2015 includes datesobtained using appropriate and available state-of-the-art techniques. Five major objectiveswere identified for the Dating Minnesota’s Prehistory Project. These objectives are identified asfollows:

1) Summarize what is currently known about absolute dating in Minnesota.2) Evaluate the reliability of existing dates.3) Submit suitable materials from existing archaeological collections to suitablelaboratories for dating.4) Update and refine the existing absolute dating database.5) Write an analytical report that summarizes the results of the project and providesdirections for future research in archaeological absolute dating in Minnesota.

METHODS

A variety of methods were used by different labs over the years that radiocarbon dateswere processed for sites in Minnesota. The methods reviewed here are applicable only tochemical pre-treatment performed at PaleoResearch Institute in Golden, Colorado. Thesemethods are presented with the intent to educate concerning state-of-the art chemical pre-treatment during the twenty-first century.

Charred Botanic Remains and Charcoal Identification

Charred botanic remains were examined under a binocular stereo microscope at amagnification of 10x, with some identifications requiring magnifications of up to 70x. Theremains were recorded as charred and/or uncharred, whole and/or fragments. Macrofloralremains were identified using manuals (Martin and Barkley 1961; Musil 1963; Schopmeyer1974) and by comparison with modern and archaeological references.

Charcoal fragments were broken to expose fresh cross, radial, and tangential sections,then examined under a binocular microscope at a magnification of 70x and under a NikonOptiphot 66 microscope at magnifications of 320–800x. The weights of each charcoal typewere recorded.

Charcoal was identified using manuals (Carlquist 2001; Hoadley 1990; Martin andBarkley 1961; Musil 1963; Schopmeyer 1974; Schweingruber et al. 2011, 2013) and bycomparison with modern and archaeological references. Clean laboratory conditions were usedduring identification to avoid contamination of charcoal and botanic remains to be submitted forradiocarbon dating. All instruments were washed between samples, and the sample wasprotected from contact with modern charcoal.

Samples from archaeological sites commonly contain both charred and uncharredremains. Many ethnobotanists argue that unless there is a specific reason to believe otherwise,only charred remains are considered prehistoric (Minnis 1981:147). Minnis (1981:147) states

1

that it is "improbable that many prehistoric seeds survive uncharred through commonarchaeological time spans." Few seeds survive longer than a century, and most survive for amuch shorter period of time (Harrington 1972; Justice and Bass 1978; Quick 1961). It ispresumed that once seeds have died, decomposing organisms work to decay the seeds. However, sites with unusual levels of preservation, such as caves, waterlogged areas, and veryarid areas can contain uncharred prehistoric remains. Interpretation of uncharred remains aspart of the prehistoric record relies on these unusual conditions for preservation.

AMS Radiocarbon Dating - Charcoal and Botanic Remains

Charred botanic and charcoal samples submitted for radiocarbon dating were identifiedand weighed prior to selecting subsamples for pre-treatment. Identification allows assignmentof average lifespan to botanic items dated, which is relevant when evaluating accuracy ofradiocarbon dates. Dates on charcoal from trees that live for several to many centuries can(and often do) predate the activity being dated by a few to several centuries. Twigs usuallyrepresent ten or fewer years of growth, so approach the level of accuracy typical of annuals. Dating the outer rings of a tree just under the bark also results in an accurate date, reflecting thelast few years of life of the tree.

The remainder of each subsample that proceeds to pre-treatment, if any, is curatedpermanently at PaleoResearch Institute. Selected subsamples are vacuum freeze-dried,freezing out all moisture at -107 EC and < 10 millitorr. Then samples are treated with cold pH 2hydrochloric acid (HCl), followed by cold 6N HCl. Samples then are heated to approximately110 EC while in 6N HCl. This step is repeated until the supernatant is clear. This step removesiron compounds and calcium carbonates that hamper humate compound removal, so it is vital,particularly in iron-rich areas, that it is repeated until the supernatant is clear. Next, the samplesare subjected to 0.05-5% potassium hydroxide (KOH) to remove humates using both coldsolutions and solutions that are heated. Once again, the samples are rinsed to neutral and re-acidified with pH 2 HCl between each KOH step. This step is repeated until the supernatant isclear, signaling removal of all humates, then the samples are rinsed to neutral. After humateremoval, samples are made slightly acidic with pH2 HCl. Thoroughly charred charcoal samplesthen are subjected to a concentrated, hot nitric acid bath, which removes all modern and recentorganics. This treatment is used only on well charred materials, as unburned, partially burned,or vitrified samples do not withstand nitric acid treatment. Previous testing has shown that nitricacid oxidizes vitrified material, which has a shiny, glassy appearance, so vitrified charcoal alsois not treated with nitric acid. This treatment is not used on unburned or partially burnedsamples because it oxidizes unburned material. Each sample is freeze-dried, then combined ina quartz tube with a specific ratio of cupric oxide (CuO) and elemental silver (Ag) in quantitiesbased on the mass of carbon in the sample. The tubes are hydrogen flame-sealed undervacuum.

Standards and laboratory background wood samples are treated to the same acid andbase processing as wood and charcoal samples of unknown age, with the exception that theyare not subjected to the concentrated, hot nitric acid bath because it oxidizes unburnedmaterial. A radiocarbon “dead” EUA wood blank from Alaska that is more than 70,000 years oldor a wood blank from the Gray Fossil site in Washington County, Tennessee, dated to theHemphillian stage of the late Miocene, 4.5-7 MYA (currently beyond the detection capabilities ofAMS) are used to calibrate the laboratory correction factor. In addition, standards of known

2

age, such as Two Creeks wood, dated to 11,800 RCYBP, and TIRI Sample “B” (Belfast Pine),with a consensus age of 4503 ± 6 RCYBP (Gulliksen and Scott 1995), the Third InternationalRadiocarbon Inter-comparison (TIRI) Sample “G” (Fugla Ness Pine) with a consensus age of39,784 ± 620, TIRI Sample “L” with a consensus age of 12,788 ± 30, TIRI Sample “B” (BelfastPine) with a consensus age of 4503 ± 6, and TIRI Sample “J” (Bulston Crannog wood) with aconsensus age of 1605 ± 8 (Gulliksen and Scott 1995), the Fifth International RadiocarbonInter-comparison (VIRI) Sample “F” with a consensus age of 2513 RCYBP, VIRI Sample “H”with a consensus age of 9528 RCYBP and others from the Third International RadiocarbonInter-comparison (TIRI) or Fifth International Radiocarbon Inter-comparison (VIRI) are used tohelp establish the laboratory correction factor. After the requisite pre-treatment, a quantitysimilar to submitted samples of each wood standard are sealed in quartz tubes. Once all thewood standards, blanks, and submitted samples of unknown age are prepared and sealed intheir individual quartz tubes, they are combusted at 820 EC, soaked for an extended period oftime at that temperature, and allowed to cool slowly, enabling the chemical reaction that extractscarbon dioxide (CO2) gas.

Following this last step, all samples of unknown age, the wood standards, and thelaboratory backgrounds are sent to The Center for Applied Isotope Studies in Athens (CAIS),Georgia, where the CO2 gas is processed into graphite. The graphitized samples are placed inthe target and run through the accelerator, generating numbers that are subsequently convertedinto radiocarbon dates. Data presented in the discussion section are displayed as conventionalradiocarbon ages and calibrated ages using IntCal13 curves on OxCal version 4.2.4 (BronkRamsey and Lee 2013; Bronk Ramsey 2009; Reimer et al. 2013). This probability-basedmethod for determining conventional ages provides a calibrated date reflecting the probability ofits occurrence within a given distribution (signaled by the amplitude [height] of the curve). Thismethod is different from the intercept-based method of individual point estimates that providesno information concerning probabilities. As a result, the probability-based method offers morestability to the calibrated values than those derived from intercept-based methods, which aresubject to adjustments in the calibration curve (Telford et al. 2004).

AMS Radiocarbon Bone Collagen Extraction and Dating

Organic compounds comprise about 30% of bone. Of this fraction, 90–95% is collagen,a fibrous protein that provides bone with strength and flexibility. Uncharred bones submitted forradiocarbon dating are evaluated for possible collagen recovery. They are evaluated for color(light to dark tan) and post depositional modifications including staining, root etching, rodentgnawing, weathering, cracking, flaking, and sediment/caliche coating. A small quantity of boneis selected from each sample for decalcification, and the surface is cleaned by rinsing withreverse osmosis deionized (RODI) water, sonicating in RODI water, scraping the surface with anew razor blade, or a combination of the two processes. Then the bone samples aredecalcified under refrigeration using cold, dilute, distilled hydrochloric acid (HCl), allowing thecollagen to remain. Collagen samples are rinsed with RODI water many times to removeincidentally produced mineral salts. Many labs stop at the end of this step when preparing bonefor dating; however, we find that additional processing with dilute potassium hydroxide (KOH) isrequired to remove depositional and taphonomic contaminants. Therefore, dilute KOH is addedto each bone sample, which is allowed to sit for 24 hours to remove humates, after which thecollagen is rinsed to neutral with RODI water, freeze-dried, and gelatinized using 0.06 M pH2HCl at 90EC, putting the collagen into solution. Typically, collagen samples vary in color

3

between very light yellow and yellow to brown, which indicates the presence of fulvic acidcontaminants that can be removed with XAD resin. Approximately 200 µL of XAD-4 resin isadded to the 0.06 M pH2 HCl solution of each sample to trap the fulvic acid contaminants duringcollagen gelatinization. Then, residual particulate contamination and XAD resin (containingadsorbed fulvic acid) are syringe-filtered from the collagen gel solution using a new 0.45-µmfilter. Typically, the purified collagen solutions range in color from clear to extremely light yellowafter XAD and filtration and are lyophilized using a vacuum system, freezing out all moisture at -107EC at <10 millitorr. Finally, the samples are combined with cupric oxide (CuO) and ultra-pure elemental silver (Ag), in quantities appropriate for the sample sizes, in quartz tubes andthen flame-sealed under vacuum.

Standards, blanks, and laboratory background samples are treated in the same manneras bone samples of unknown age submitted for radiocarbon dating. Bone standards includesamples of known age, such as the Fifth International Radiocarbon Inter-comparison (VIRI)Sample “F” with a consensus age of 2513 RCYBP, and a modern “Levish” bison bone with aconsensus age of 180 RCYBP. Radiocarbon blanks, such as the Beaufort whale bone sampledating to over 70,000 radiocarbon years and Oxalic Acid I (OXI), made from modern Frenchsugar beets, are prepared to establish laboratory backgrounds. After the requisite pre-treatment, a quantity of each bone standard similar to that of the unknown-age sample is sealedin a quartz tube. OXI requires no pretreatment beyond vacuum drying. All samples arecombined with quantities of cupric oxide and elemental silver appropriate for the sample size ina quartz tube. Once all bone standards, blanks, laboratory backgrounds and the unknown-agesample are prepared and sealed in their individual quartz tubes, they are combusted at 820 EC,soaked for an extended period of time at that temperature, and slowly allowed to cool, enablingthe chemical reaction that extracts carbon dioxide (CO2) gas.

As stated above, for the charcoal samples, the quartz tubes containing CO2 gas from allsamples of unknown age, standards, and laboratory backgrounds are sent to the Center forApplied Isotope Studies (CAIS) at the University of Georgia in Athens, Georgia, where the CO2

gas was processed into graphite, then analyzed using an accelerator mass spectrometer(AMS), subjecting the samples to an ion beam.

Reference modern fish bones were cut from the flesh of fresh fish, then the bones wereboiled in RODI to remove the flesh. Dried bones from 1939 were boiled in RODI water. Next,the bones, whether modern or collected in 1939, were dried, then submerged in a mixture ofchloroform and methanol to remove fats/lipids. Next, the bones were placed in the glass bowl ofa soxhlet extractor. This apparatus cycles a chloroform and methanol mixture through thecontainer with the bones. After the chemicals fill the chamber containing the bone the volumeof liquid drains into the lower bowl of the soxhlet extractor where it is heated and distilled. Theresulting chloroform/methanol steam travels upward through a glass tube surrounded by coldwater, condensing, then dropping into the container with the bone, filling it to maximum capacityprior to draining into the base of the extractor to be heated again. The bones were treatedthrough many cycles of liquid exchange in the soxhlet extractor to remove fats/lipids and washthe bones free of any remaining residue. It is this step of flushing away the fats/lipidsassociated with the bones that distinguishes the soxhlet treatment from soaking the bones inthe same chemical mixture, then pouring the liquid off the bones. The soaking method neverquite removes all of the fats/lipids. After the extraction is complete the bones are removed fromthe soxhlet extractor and vacuum dried.

4

AMS Radiocarbon Charred Bone Dating

Burned bone can occur in various forms (partially burned, charred, and calcined), eachof which possesses varying characteristics that affect the method of processing prior toradiocarbon dating. Partially burned bone must be divided prior to processing, as portions intransition between burning stages tend to require different processing techniques. Charredbone, black all the way through so it resembles charcoal, has been exposed to heat thatthroughly dehydrates the collagen. Calcined bone is chalky white or bluish white, and reflectscomplete combustion of organic elements in the bone, including the collagen (Whyte 2001:438),transforming it to a structural carbonate. Therefore, burned bones are treated using thestandard charcoal treatment protocol, described above, while calcined bone is rejected. Charred bone samples selected for radiocarbon dating are weighed prior to removingsubsamples of appropriate size for pre-treatment. Any remaining sample is either returned orcurated at PaleoResearch.

Ceramic Residue for AMS Radiocarbon Analysis

First, a portion of the charred food crust was removed from the interior of each sherd. These samples are placed in a glass 15-ml vial with a mixture of chloroform and methanol(CHM) to remove lipids and other organic substances that are part of the food residue. Thefood crust and CHM solvent are allowed to sit, covered, for 48 hours. Following this, the solventis pipetted off and new CHM is poured into the container, then vacuum freeze-dried, freezingout all moisture at -107 EC and < 10 millitorr, then weighed. The samples are treated with coldpH 2 hydrochloric acid (HCl), followed by cold 6N HCl. Subsequently, the samples aresubjected to hot (at least 110 EC) 6N HCl treatments until the supernatant is clear. This stepremoves iron compounds and calcium carbonates that hamper removal of humate. Next, thesamples are subjected to 2.5% potassium hydroxide (KOH) to remove humates. Once again,the samples are rinsed to neutral and re-acidified with pH 2 HCl between each KOH step. Thisstep is repeated until the supernatant is clear, signaling removal of all humates. Finally, thesamples are rinsed to neutral, then made slightly acidic with pH 2 HCl. The samples are freeze-dried, then combined in a quartz tube with a specific ratio of cupric oxide (CuO) and elementalsilver (Ag) in quantities based on the mass of carbon in the sample. The tubes are hydrogenflame-sealed under vacuum.

The remainder of the process, involving standards and laboratory background samplesand calibration is identical to the process described above for wood charcoal and botanicremains.

DISCUSSION

Specific tasks were identified for the Dating Minnesota’s Prehistory Project that are addressed in the text below.

5

Task 1: Summarize What is Currently Known About Absolute Dating in Minnesota

Radiocarbon dates from archaeological sites in Minnesota spans the Holocene(Appendix A). Plotting all of the archaeological sites on GIS maps with a groundwaterbackground facilitated visualizing the existing radiocarbon record (Figure 1).

Taken as a whole, this examination of data suggests long occupations for culturalperiods or site occupations that otherwise appeared to reflect relatively short intervals. Dateson bones from some areas appear to reflect ancient occupations, whereas dates on charcoalsuggested more recent occupations. Disconnect between dates on a regional scale has madewriting regional syntheses difficult, if not impossible. Individual sites appear to have beenoccupied for many thousands of years due to the span of dates represented. A recentpublication about Brainerd ware (Hohman-Caine and Syms 2012) suggests not all dates onceramic residues or charred food crusts from Brainerd sites are accurate. These authors noteda correlation between the oldest dates and unusually depressed 13C/12C isotope ratios, manyof which were lower than -30. A plot of ceramic food crust radiocarbon dates against 13C/12Cisotope ratios (Figure 2) does not yield a consistent correlation suggesting older dates correlatewith depressed 13C/12C ratios. However, all dates older than 2000 BP, except one that has areported 13C/12C ratio, yielded 13C/12C isotope ratios more depleted than -23.10.

Thus far, it is not possible to demonstrate a positive correlation between 13C/12C ratioand ancient dates. It is not yet possible to examine the possibility that depleted 13C/12C ratioscan be used as predictors of radiocarbon age offsets because an insufficient quantity of charredfood crust dates have been repeated using the CHM technology. In addition, the CHMtechnology cannot be applied to animal bones, as ancient carbon has been integrated into theirentire system, meaning that all parts of animals with carbon depletion will date “too old”.

Therefore, a thorough review of the entire state radiocarbon database was undertaken toprovide a framework for evaluating radiocarbon dates. This study seeks to provide guidelinesfor more fully understanding the existing Minnesota state radiocarbon database, as well asproviding additional radiocarbon dates on materials from sites identified by the Minnesota StateHistorical Society (Tables 1, 2, 3, and 4 and Appendix B).

Task 2: Evaluate the Reliability of Existing Dates

This task included creating multiplots of all existing dates in the database (Appendix C). Multiplots were organized in temporal order at each site, and by material and temporal order forBrainerd sites. Specific issues noted during this analysis are addressed in this section.

Brainerd

Located in Crow Wing county to the west-southwest of Duluth, north of St. Cloud, andwest-northwest of Minneapolis, the Brainerd site has yielded radiocarbon dates that spanapproximately 7000 years. The age of Brainerd ceramics is an important concern in Minnesotaarchaeology and embodies samples from three major classes of material: charcoal, bone, andcharred food crust (residue). Therefore, it is used as an appropriate proxy within the state todiscuss issues that affect radiocarbon dating throughout the state. The problem of dating

6

Brainerd ceramics has been under consideration for some time, and was the subject of aspecific study supported by the Minnesota Arts and Cultural Heritage Fund several years ago(Hohman-Caine and Syms 2012), but yet the age of Brainerd ceramics remains unresolved.This document presents several analyses of the dates obtained by Hohman-Caine and Symsand provides insights into ways in which ambiguous results have come about. Additionally, wewere asked to give some attention to the accuracy of residue for dating as part of this study,and analysis of the Brainerd data speaks to that.

Hohman-Caine and Syms obtained 40 new AMS age determinations from Brainerdcontext: 10 on bone, 14 on charcoal, and 16 on residue scraped from pottery sherds. In sodoing, they made the assumption that all samples were drawn from Brainerd components andare associated with the occupation being dated. There is no reason to question the validity ofthis assumption. It is, therefore, valid to expect to be able to use these dates collectively tocalibrate all dates and infer from the results an age and interval of time for this ceramic tradition.The series of dates should indicate a reasonably constrained interval, and one which is crediblerelative to the timing of early ceramics in the broader area of the Great Lakes/Midcontinent. Thisinvokes a second assumption, viz., that all dates are accurate, which is to say that the reportedages reflect the true age of the target event, which in this case is the age of the componentdated (Dean 1978).

This second assumption takes its warrant from fundamentals of radiocarbon datingpractice. The ages that are most likely to be accurate are those on annual or short-lived organicremains. Ceramic residue is one of those materials that has received recent attention. Itcomprises food cooked in vessels. and that food can be expected to be contemporaneous withthe occupation. Bone also is considered a short-lived material. In principle, therefore, eachmaterial should produce accurate dates; in practice, however, each of these materials hasproved problematic. Bone has a fairly long history of development of techniques for yieldingages that can be shown to be accurate when compared with an independent measure of age(Taylor and Bar-Yosef 2014:75-82). More recently techniques, such as use of XAD resin(Stafford Jr. et al. 1988; Waters and Stafford 2007), have provided consistent and accurateages. Residue has been shown in a number of instances, including several not far fromMinnesota in North America (Ahler et al. 2007; Roper 2013), to yield ages that are offset (in thedirection of being too old) by amounts varying from essentially negligible, to several hundredyears. A freshwater reservoir effect (FRE) is often cited as the likely problem, and we agree thatit likely is or can be a factor. In addition, we suspect that old carbon may have been taken intothe residue from other sources. Taylor and Bar-Yosef’s (2014:62) characterization of eachresidue sample as a “unique geochemical entity” seems to perfectly capture the situation.Several avenues of work are being pursued in both Europe and North America that addressmeasures to counteract this to obtain dates on residue that are congruent with age assays onother materials of known accuracy, such as corn or seeds, neither of which have known issueswith accuracy, as long as the measured ages are corrected for fractionation.

Charcoal, long the standard material used for dating, is the one of the three basicmaterials used for estimating the age of Brainerd pottery for which the assumption of accuracyis, a priori, least likely to be warranted. This is because charcoal is susceptible to the old woodproblem, i.e., the age offset, or inbuilt age, that results from the progressive radiocarbon deathof inner tree rings before (sometimes well before) the tree as an organism dies. Unless the outerrings of a tree are dated, the received age, while an accurate age of the sample, referred to asthe dated event (Dean 1978), will not be accurate for the target event. Even then, one cannot

7

be totally confident that the wood is contemporaneous with the occupation, since housingtimbers can be reused, or wood that was dead and down for an unknown amount of time beforeuse may be represented. Further, conifers live longer than deciduous trees and may havegreater age-offsets, depending, of course, on from where in a log the particular sample derived(a factor usually unknown).

Given all this, therefore, we might, in principle, expect the bone and residue dates for theBrainerd pottery to be congruent with one another and accurate for the target event, althoughwe also should be prepared for this to not be so for a variety of reasons such as contaminationor incomplete laboratory pre-treatment of the sample. Further, research suggests morecomplex reasons that bone and residue dates are not congruent. These include ingestion ofancient carbon, perhaps DIC, from water and/or feeding on plants that grew in water containingDIC. We expect the charcoal dates to be somewhat, and variably, age-offset relative to theshort-lived materials.

These expectations are evaluated using several analyses available in the Oxcal program(Bronk Ramsey 2009). All analyses used the current version of Oxcal, version 4.2.4 andIntCal13 (Reimer, et al. 2013).

A basic, and very telling, first analysis is simply to sort samples by material, calibrate theages, and portray them on a multiplot. Figure 3 presents this analysis and clearly shows thatthe expectations are not met and that the three sets of dates are not congruent with oneanother. Instead, they form three populations of dates. All are age-offset. Bones date areerratically distributed over a totally unrealistic interval of nearly seven thousand radiocarbonyears. Dates on charred food crust are far less erratic, but still span an unrealistically longinterval of around three thousand radiocarbon years, with many of them dating to years BC.Remarkably, and with one wildly erratic exception, the charcoal dates are overall the youngestof the dates, in spite of a priori expectations that they should be the oldest.

A second portrayal of the dates also is effective. Figure 4 shows the same datesarranged by site. Since there are varying numbers of each material within any given site, and itis not always the case that all three materials are represented, letters (b, c, or r) are affixed tothe sample number to indicate material. Within each site, the bone (b), charcoal ©, and charredfood crust ® dates are shown in that order. Two sites stand out as particularly clear examplesof the difficulties reflected in Figure 4. Site 21CA67 has multiple dates on each of bone,charcoal, and charred food crust. While each material appears somewhat concordant within itsmaterial class, it is clear that the three materials each portray the age differently. The results for21CW247 are even more dramatic. Here, both the bone and charcoal dates are highly erraticand dissimilar from one another, while the better-behaved charred food crust dates are stillrather spread out over around 1500 radiocarbon years.

Hohman-Caine and Syms (2012) also report OSL dates for Brainerd ware recoveredfrom four counties (Table 5). These dates constrain manufacture and use of this style of potteryto between 2730 and 1150 years BP, a span of nearly 1600 years. Direct comparison of OSLand radiocarbon dates on bone and charred food crust (Table 5) suggests considerablevariability in the bone and charred food crust records.

Certainly, it is possible that any particular age obtained on any of the materials isaccurate. The spread of ages in all classes of materials, however, and particularly the lack of

8

ability to compare any of these with short-lived materials that have a substantial chance of beingaccurate, make it impossible to know which, if any, are accurate. Therefore, it is not possible togive any age determination credibility, and all must be considered potentially suspect.

Association of charcoal dates with ceramics (net-impressed, horiz-corded) suggeststhese ceramics have been defined by dates on either charred food crust or burned bones thatdate “too old” relative to dates on charcoal from the same contexts. I recommend that dates onmaize, nutshell, and charcoal be accepted as the most reliable. When other dates differ fromthe range established by dates on these items, those older dates should be examined for thepossibility that they were obtained on either aquatic plants such as wild rice or animals that livein or consume other animals or plants from aquatic environments. Testing recent bones ofanimals presumed to have primarily a land-based diet is required to more fully understandradiocarbon dates on land mammals living in Minnesota.

Discussing the Minnesota database by material dates appears to be more informativethan reviewing individual dates from sites, as the same comments are likely for all or mostmaterials of a given group (bones, charcoal, charred nutshell and seed). Dates on shells areexpected to have similar offsets to dates on bottom dwelling fish.

Task 3: Submit Suitable Materials from Existing Archaeological Collections to Suitable Laboratories for Dating

This task was undertaken largely by personnel at the Minnesota Historical Society tosatisfy internal priorities. Doctors Linda Scott Cummings and Donna C. Roper traveled to theMinnesota Historical Society offices in May 2015 to participate in new sample selection. Samples were collected from multiple sites including LaMoille, which had not been radiocarbondated previously (Table 1).

LaMoille (12WN1)

No radiocarbon dates have been run prior to this project for LaMoille. The site exhibitsWoodland ceramics, including Brainerd ware. Samples submitted for AMS radiocarbon analysisfrom LaMoille include burned bone, unburned bone, and a single charred walnut shell fragment. In addition, four fish bones, recovered from fish caught in 1939, were analyzed to provideinformation concerning the possibility that dissolved inorganic carbon (DIC), which contributesold carbon in water systems, affected dates on plants and/or animals that lived within thataquatic system.

Portions of all eight of the charred or burned bones were processed normally, involvingacid-base-acid chemical pre-treatment. Charred or burned bones are chemically pre-treated inthe same manner as charcoal. The bone fragments fell apart during the initial acid (HCl)treatment. After discussion, we proceeded with a dilute base (potassium hydroxide – KOH)treatment. Unfortunately, all eight of the samples dissolved in this treatment. Enough of eachcharred bone was retained to attempt chemical pre-treatment a second time. Again,hydrochloric acid processing was completed, with measurable, but not complete, damage to thecharred bone fragments. The base treatment, using KOH, was not attempted due to the factthat the bones were lost previously. Burned or charred bones were assessed both by

9

archaeologists and personnel at PaleoResearch Institute and deemed to be burned. Althoughour first assessment of the burned bone was that it was at least partially charred or burned, itsbehavior in acid suggests that it was either merely discolored or so lightly charred that the bonewas not stabilized. Burned bone is chemically pre-treated in the same manner as charcoalbecause charred bone is stabilized in a manner similar to wood charcoal. Due to the fact thatcollagen is burned in place, it is available for dating as part of the charred matrix. It cannot beisolated in the same manner that collagen is isolated from uncharred bone. Disaggregation ofthe apparently burned bone in acid, followed by dissolution in base, is a strong indication thatthe bone was not burned or was very lightly burned. Therefore, the darkening of the bone wasa chemical, rather than a heat, process.

Dates returned for charred bones from LaMoille ranged from 6869 ± 22 RCYBP (Level1), which calibrates to 5770–5720 BC to 4160 ± 22 RCYBP (Level 11), which calibrates to2880–2680 BC (Table 4 and Appendix B). Uncharred bone was processed to remove collagen,which proceeded through the gel stage, then received XAD treatment to remove absorbedhumic compounds and fulvic acid. After XAD treatment the bone collagen gel was clear ratherthan brown, indicating removal of these compounds. These dates ranged from 7387 ± 28RCYBP (Level 2), calibrating to 6380–6210 BC, to 4558 ± 25 RCYBP, calibrating to 3370–3130BC, on uncharred bone gel treated with XAD, providing a similar spread to dates obtained oncharred bone, with both groups of bones exhibiting ancient dates for LaMoille. A single walnut(Juglans) shell fragment, recovered from Level 10 and representing the only charred botanicremain available from this site, yielded a radiocarbon age of 2532 ± 23 RCYBP, which calibratesto 800–590 BC. This charred short-lived botanic is 2100 radiocarbon years more recent thanthe date on a charred mammal long bone fragment recovered from the same level (10),suggesting an offset of approximately 2100 radiocarbon years for the bones, although it wouldbe dangerous to apply this offset regularly to all bones from this site (or any other) in an attemptto more fully understand the local chronology. The deviation of dates on burned and unburnedbone from the charred nutshell suggests that any offset for these bone dates is the result of dietof the animals rather than post depositional contamination. Interestingly, dates on large- andmedium-size animal bones are as ancient as the date on duck bone, suggesting their diets alsointroduced ancient carbon into their systems.

The discrepancy between dates on charred (6869–4160 RCYBP) and uncharred bone(7387–4558 RCYBP) at LaMoille is negligible. Dates on mammal bones and duck bones weresimilar rather than being discrepant. Because ducks derive much of their diet from aquaticplants they were expected to date older than land mammals, but this was not the case. Incontrast, the discrepancy between dates on bone and the date on charred nutshell is large(2100 radiocarbon years for the single bone and charred nutshell recovered from Level 10,suggesting a systemic issue dating bones. Return of very similar radiocarbon ages for charredand uncharred bones, the latter treated with XAD, points to diet of the animals, rather than post-depositional contamination, as the most likely source of ancient carbon that produces very olddates from bones.

Dates on bone from LaMoille fit the pattern observed for bone dates in general fromMinnesota – they are the oldest dates for each site or cultural complex. The trend holds true forbird bones (grouse, large bird, and duck) and unidentified mammal bones. This suggests inputfrom DIC into the diets of animals. Mapping bone dates on a state map (Figure 5 and Appendix D) shows distribution of the oldest bones primarily at sites along the Minnesota River,along the Red River of the North (and on land just east of the river) as it flows along the

10

northwestern border of Minnesota, and a few in the western portion of the south-centralgroundwater province. Isolated locations of older bone dates also are observed in a few placesalong the upper portion of the Mississippi River prior to its confluence with the Minnesota River,then along the Mississippi River in the southeast portion of the state. At present all bone datesfrom Minnesota should be considered to be older than corresponding botanic remains, with thepossible exception of dates on wild rice, which are discussed later.

LaMoille thick pottery, described from an almost complete vessel recovered in Levels 10,11, and 12, may be more accurately dated by its association with the charred walnut nutshellfrom Level 10 than through association with dated bones. This provides a tentative date forLaMoille thick pottery of 2352 ± 23 RCYBP, calibrating to 800–590 BC.

Dating Reference Fish and Wild Rice

Radiocarbon dating reference specimens of fish, caught in 1939 and 2015, and wild rice,harvested in 2015, has clarified several issues concerning radiocarbon dating charred foodresidues. The most important points for dating charred food crust from ceramics includeobservations that some or many dates obtained on charred food crust that has been scrapedfrom ceramics is “too old” relative to the anticipated context. Inconsistency in the amount ofoffset has made determining an appropriate correction factor impossible.

Experimental chemical pretreatment (using non-polar solvents) of charred food residuesthat have been removed from ceramics has produced both age-appropriate dates and datesthat remain “too old” for their contexts. Examination of radiocarbon dates on charred foodcrusts from ceramics from sites in Minnesota and dates on charred food crust removed fromceramics from sites outside Minnesota has produced a cadre of dates, some of which may becompared directly with dates on annuals from the same context. To better understand dates oncharred food crust it is important to date likely components of food, preferably specimens thatwere collected prior to the atomic era, although more recent specimens also provide valuableinformation.

Very recent re-dating of four samples of curated charred food crust (PRI 2334, 2335,2336, and 2435) (Table 4 and Appendix B) included the chloroform/methanol chemical pre-treatment, because those samples were processed and radiocarbon dated in 2011 byPaleoResearch Institute prior to our knowledge that dates on charred food crust might bediscrepant. Two of the four dates returned were basically identical to the original dates (1128 ±16 and 1138 ± 22 BP, 1754 ± 16 and 1755 ± 22 BP), indicating that removal of fats/lipids withchloroform/methanol was not required for that charred food crust. Sample PRI-5654 yielded aslightly older date (1843 ± 22 BP compared to the original 1658 ± 22 BP). The fourth date (PRI-5653), was more recent by approximately 150 years (3121 ± 23 BP compared to the originaldate of 3270 ± 30 BP), although it still appears to contain ancient carbon. All three of thesedates have been entered into the Minnesota State Radiocarbon Database (Appendix A) withtheir new radiocarbon identification numbers.

The most important factor yet identified that influences radiocarbon dates of charredfood residues appears to be dissolved inorganic carbon (DIC) within the carbon reservoir inwhich fish and other aquatic organisms live. At the onset of this study current experimentalresearch by Scott Cummings and published research by others (Philippsen 2015) points

11

primarily into aquatic animals and animals that consume a diet of aquatic organisms as the mostlikely contributors of ancient carbon to our food supply. Examples of experimental work includePhilippsen (2015) and others who have dated fish caught in the North Sea and moose, who eataquatic plants. The age offset reported for moose was approximately 800 radiocarbon years.

Recent research by Santos and Reyerson examining carbon occluded in phytoliths ofgrasses illuminates the ability of grasses to pull dissolved inorganic carbon up through theirroots, depositing it within silica phytoliths distributed throughout the plants (Alexandre et al.2016; Reyerson et al. 2016 10478; Santos et al. 2016). Research into plant growth conditionsand their affect on carbon sequestered in phytoliths shows that organic matter taken up by plantroots (from soil organic matter) is deposited in plant cells (Gallagher et al. 2015), providing oneexplanation for a route of intake of ancient carbon. The focus of this work has been to identifythe most likely contamination for carbon occluded within phytoliths, as phytoliths have provedproblematic for radiocarbon dating. These experimental works dating phytoliths from modernplants under different growing conditions also indicate that ancient carbon is present in otherplant cells, not only cells that accumulate silica and produce phytoliths. Data are presented inthe online supplement of Reyerson (2016).

The current work funded by the state of Minnesota included radiocarbon dating fishcaught in 1939 and additional fish caught in 2015, as well as wild rice harvested in 2015. Because fish and wild rice caught and harvested from the same lake or water system have notyet been dated as matched pairs, this is recommended for the future. A pattern is emergingfrom the few dates available on these reference fish from Minnesota. The two apparentcontrolling factors include geographic distribution of the water systems on the landscape andtrophic level of the fish dated. Dates returned from historic or modern reference samplesdisplay differences for the glaciated and non-glaciated parts of the state. Dates fromsoutheastern Minnesota tend to have a greater offset than do dates from northeasternMinnesota. Volcanic rocks are interspersed with layers of shale in the northeastern portion ofthe state. The Rove Formation of sedimentary rocks is noted in the northeastern portion ofCook County, extending into Ontario. Glaciers eroded the shales, leaving behind the moreresistant volcanic deposits. When the Laurentide Ice Sheet melted and retreated glacial lakesformed. Glacial Lake Duluth formed at the southwestern margin of the Superior lobe, occupyinga larger area than present-day Lake Superior. Glacial Lake Duluth drained through the St. Croix River Valley into the Mississippi River. The outlets along the Kettle and Nemadji Rivers inMinnesota likely exhibit similar geological formations and are expected to yield similarradiocarbon offsets. The Bois Brule River in Wisconsin also should fall within the parameters ofthe Kettle and Nemadjii Rivers for radiocarbon offsets. Glacial Lake Agassiz in northwesternMinnesota occupied the present Red River Valley of Minnesota and neighboring North Dakota. The lake formed when glaciers to the north blocked that drainage route, creating a proglaciallake south of the ice. Water from this lake overflowed the continental divide at Browns Valley,Minnesota, draining through the Traverse Gap into the present Minnesota River Valley. Eventually the continental divide at Browns Valley formed the headwaters for the north-flowingRed River of the North, which forms the border between Minnesota and North Dakota. Thesoutheast-flowing Minnesota River, a tributary of the Mississippi River, originates on the otherside of this divide, draining a watershed of nearly 17,000 square miles. The Lake Agassizlakebed comprised lake muds and silts, leaving an extremely fertile landscape behind as itdrained. The lakebed likely received massive quantities of ancient carbon that was part of theglacier including, but not limited to, algae, animal feces and animal carcasses deposited on thesurface of the glacier. This water system is expected to have a distinct radiocarbon offset. No

12

bedrock erosion or kettle lake formation is evident in this area. Recent reference samples fromanimals and aquatic plants from each of these geological areas of the state should be AMSradiocarbon analyzed to establish patterns of offset for these geologically distinct areas.

Although examining the individual radiocarbon ages and their calibrated ranges appearsto be the most obvious means for comparison, I have elected to include fraction Modern (orpercent Modern) carbon values for each of these reference dates to make comparison betweenthe fish caught in 1939 and those caught in 2015 more straight forward. When examining dateson the fish caught in 1939, it is very important to compare trophic level of the four fish examined. The bottom feeders yielded the oldest dates, while fish who fed on other fish and also flies,larvae, and “air breathers” dated less old, suggesting their diets were a mixture of organismscontaining ancient DIC and organisms expected to contain only or primarily atmospheric carbon. Carp, an introduced bottom feeder in the Mississippi River, yielded the greatest offset ofapproximately 1223 years, followed by catfish, sturgeon, and walleye, the latter of which yieldedthe most recent offset of approximately 300 years (Table 4).

Fish caught in 2015 continued this trend. Most interesting is the fact that two of the wildrice samples harvested in 2015 yielded offsets similar to those obtained on fish from similarportions of Minnesota. This fact highlights the importance of dating both aquatic plants growingin river and lake systems and fish caught from those same systems – then comparing the resultin dates. This exercise is expected to reveal patterns that reflect the geological history of thestate of Minnesota. Dissolved inorganic carbon is anticipated to be more abundant in aquaticsystems in areas where the underlying geology contains soluble bedrock. Conversely, glaciatedportions of the state appear to have offsets of far less magnitude. A future study that examinesmultiple lakes and rivers of each aquatic system in the state has the potential to generate a mapof the state with observed offset values. What is unknown at this point in the research iswhether individual aquatic systems exhibit change in quantities of dissolved inorganic carbon(DIC) along their length. Changes are anticipated to reflect the underlying geology for eachaquatic system. Currently offsets are noted to be greatest in the southeast part of the state,suggesting that offsets will not remain stable within any aquatic system that transects multiplegeological units.

SUMMARY AND CONCLUSIONS

Sources of carbon in the state of Minnesota represent unique challenges for interpretingthe radiocarbon record. Factors that introduce carbon into the system include, of course,carbon dioxide from the atmosphere – the obvious carbon source upon which radiocarbondating is predicated. Other sources of carbon include dissolved inorganic carbon, which hasbeen discussed in the literature for decades and is being identified as the most likely contributorto food crust and animal bone radiocarbon dates that are “too ancient” in northern Europe. Another potential source is organic carbon derived from animal feces deposited on the glaciersas they accumulated and bacteria and other microscopic organisms living within the glaciers. When glaciers melted organic carbon was released onto the landscape and made its way intoriver systems and lakes. From recent research published by Santos and Reyerson we knowthat grasses take up carbon through their roots. That carbon appears to be distributedthroughout the plant, not sequestered preferentially inside phytoliths.

13

Applying the principles already studied and acknowledging that the archaeologicalrecord from the Holocene and the charred food crust record includes plants that grew in aquaticsettings and fish that lived in rivers and lakes, it is now obvious that better understanding thearchaeological chronology for the state of Minnesota, which in anchored by radiocarbon dates,requires considerable further study of reference materials. When the plants were harvested andthe fish caught, cooking these foods introduced a mixed bag of carbon into residues that built upon ceramic vessels and into the bodies of humans and animals that consumed that food. Whatis less well understood is any potential affect of mixed ancient and age appropriate carbon thatcontributed to the diet of land animals. Results of radiocarbon dating four fish caught in 1939from the Mississippi River in the vicinity of the LaMoille site suggest that trophic level of the fish,reflecting dietary input, controlled the amount of radiocarbon offset, which is expected to vary bydrainage system or watershed and underlying geology.

A review of the Minnesota state radiocarbon record yields patterns worthy of note. Inparticular, dates on Brainerd ware ceramics date older than anticipated for a ceramic complex. In the 1980s Stan Ahler recognized that dates on charred food crusts often were too old andprovided unreliable chronological information for the northern Plains. Therefore, herecommended that charred residue obtained from ceramics not be dated. Dates on mammalbones from Minnesota also provide a too-ancient chronology. Often comparison with dates onshort-lived terrestrial plant remains is impossible, as they are not present in the archaeologicalrecord. Charcoal appears to provide the most accurate chronology for Minnesota. Rather thanaccept dates on food crust as “dangerous” PaleoResearch Institute has endeavored to create achemical protocol that removes ancient carbons included in fats/lipids that remain mobile incharred food crust. Initial testing of this chemical protocol on charred food crust has yieldedgenerally good results, indicating that this method, employing a mixture of chloroform andmethanol, can be used in the laboratory to obtain age appropriate dates in many or most cases.

Radiocarbon dates on animal bones in Minnesota are often the oldest obtained forindividual sites, cultural complexes, or within geographic areas. At present, the reason for thisdiscrepancy has not been researched and remains unexplained. We recommend not datingadditional archaeological bone until original radiocarbon research can be conducted on recentspecimens to verify that land animals, as well as fish and ducks (and other birds living on thewater or harvesting prey from the water) yield discrepant dates.

Thus far, dating modern and historic reference fish and modern reference wild riceprovides insights concerning the presence of ancient carbon, hence the diversion into thequestion of the origin of carbon contained in the plants and animals comprising food whenevaluating Charred food crust dates. The most ancient dates on modern and historic referencefish were obtained on four fish from the Mississippi river caught in 1939 near the LaMoille site. Dates obtained on these four fish do not overlap, but span an interval of approximately 900years (from approximately 1223 ± 24 To 307 ± 23 RCYBP). Obviously the carp, catfish,sturgeon, and walleye, which were caught live, were not hundreds of years old. Yet, theirradiocarbon dates span 1223 to 307 BP. Clearly, these fish ingested ancient carbon, probablydissolved inorganic carbon (DIC). Trophic level is implicated in the wide spread in the daterange.

Exploratory use of an additional chemical pre-treatment protocol in the laboratory prior toradiocarbon dating charred food residue has met with considerable success. Adding a mixtureof polar and non-polar solvents to the existing acid-base-acid protocol removes fats/lipids

14

thought to contain more ancient carbon introduced when cooking fish or other animals. Theobjective was to reduce the material being dated to only or primarily the carbohydrateconstituent.

Pyrolysis, which does not rely on reactions with oxygen, water, or other chemicals, is theprocess of forming a golden-brown (or darker) crust in carbohydrates or protein. Pyrolysis ofcarbohydrates begins at temperatures above 100°C (212°F), proceeding in proteins at highertemperatures. Fats/lipids rarely burn, but do volatize, giving off smoke at substantially highertemperatures. Therefore, the portion of food cooked in a vessel that rises to the neck or rim ofthe vessel and is above the level of the water is the most likely to char. Observing cookingpasta, we determined that carbohydrate-rich debris also is expected on the outside of the rimand neck of vessels, whereas soot from fires is expected on the lower portion of the outside ofthe vessel. This observation guides our sampling protocol.

The Maillard reaction, between amino acids and reducing sugars, is responsible for thedistinctive flavor of browned foods. Seared red meat, pan-fried foods, cookies, biscuits andbread all obtain their characteristic flavor from the Maillard reaction. This non-enzymaticbrowning typically proceeds rapidly between 140 and 165°C (280 to 330 °F). Carmelization andpyrolysis become more pronounced at higher temperatures (Chichester 1986; Maillard 1912). Relatively low temperatures could easily char starch and other carbohydrates, which have atendency to rise to the top of the water column when boiled. The neck and rim of ceramicvessels obviously attain sufficient heat to char carbohydrates, as charred food residue isobserved in this portion of vessels. In areas where maize is known to have been used,phytoliths from maize cobs/cupules have been recovered in charred food residue recoveredfrom the rim of ceramic vessels. A visual summary accompanies this report in Appendix E,which contains the PowerPoint presentation from the Council for Minnesota ArchaeologyConference, held in St. Paul during February 2017.

Recommendations for Future Study

While this current research has pointed to problem areas for radiocarbon dating aquaticmaterials (fish and wild rice), it has barely scratched the surface by examining relatively fewreference samples. In addition, radiocarbon dates on animal bones, whether charred oruncharred, provide the most ancient portions of the state chronology. Application of XADtechnology as part of the chemical pre-treatment protocol for uncharred bones removed post-depositional contamination, but did not yield a date concordant with a charred annual botanic inthe single level where both were dated from the LaMoille site. Dates on bone from that siteprovided a chronology that appeared to be internally consistent, but likely too ancient by a fewthousand years. That estimate is based on the discrepancy between the dated mammal boneand walnut nutshell fragment from Level 10, which were 2100 radiocarbon years apart.

Therefore, a research project is recommended to address dating animal bones of knownage, likely from curated collections that have not been treated with preservatives. In addition,some freshly caught specimens should be included in the research, as fraction Modern valuesmay be compared with those from the curated specimens to observe degree of discrepancy withthe date of harvest. Animals should be obtained from each of the identified watersheds for thestate to examine variations in the degree of offsets for each area. Radiocarbon datingreference fish should continue and be expanded to include fish of various trophic levels from

15

each of the major watersheds of the state. In addition, aquatic plants known to be part of thenative diet should be paired with fish samples to assess the offset for various plants obtainedfrom the same water systems.

An exhaustive study of dating carbon occluded inside grass phytoliths indicates grassestake up ancient carbon from the sediments in which they grow. Dating four modern (reference)wild rice seeds (caryopses) in this project produced results consistent with that concept. Whenmapped on the landscape, these seeds dated older than their harvest year (2015) by amountsvery similar to reference fish bones dated from similar portions of the state.

Obtaining dates that are “too old” on plant seeds necessitates expanding the study ofMinnesota dates. One possibility that has not yet been articulated, and thus not explored, is thepossibility that a relationship exists between the ratio of plant tissues growing submerged(whether in water or simply in the ground) to plant tissues that photosynthesize atmosphereabove ground and the amount of radiocarbon offset (or lack thereof). This concept is importantin areas with DIC and irrelevant in other areas. This ratio should be predictive for the amount ofDIC capable of entering the plant system and, thus, altering the determined radiocarbon age. Figure 6 depicts typical root masses and above-ground vegetation for typical prairie plants. Themodel that has driven radiocarbon dating assumes all carbon taken up by plants is obtained asCO2 from the atmosphere, while water necessary for growth is obtained from the ground. Theproducts of photosynthesis are sugar (C6H12O6) and oxygen (O2). However, when ancientcarbon is taken up from the water system, it arrives in usable form for the plants. The plantuses all carbon that enters its system, rather than discriminating between carbon sources. Therefore, comparison of the ratio of roots, leaves, and/or stems that constitute a plant’sunderground structures with leaves and/or stems that constitute the same plant’s atmosphericstructures allows creation of a ratio of expected contribution from dissolved inorganic carbon(DIC), when it is present, and atmospheric carbon. If this assumption, derived from recentresearch into carbon uptake by grasses during studies focused on dating carbon sequestered inphytoliths, is correct, dating wood charcoal should, in most cases, provide relatively accuratedates, as the ratio of leaves to roots highly favors carbon uptake from the atmosphere. Werecommend dating reference and/or modern twigs from shrubs (e.g. Salix (willow), Alnus (alder),Betula (birch) and others) growing in wetlands from all watersheds in the state to test thishypothesis because these shrubs are the most likely to have leaf to root ratios allowingsignificant uptake of ancient carbon that could influence the radiocarbon date. Dates on theseplants should be compared to dates on trees with large leaf to root ratios that have very littlepotential to be affected by uptake of ancient carbon. Therefore, twigs and/or outer rings ofmodern trees should be dated to facilitate this comparison.

Radiocarbon dating plants growing in or near aquatic systems and evaluating the plantsfor their ratio of roots to above-ground photosynthesizing structures is expected to yieldvaluable data. Pursuit of this research topic should include obtaining sediments from wetlandsand lakes throughout Minnesota, then processing those sediments to keep soil organic matter(SOM), then radiocarbon date that SOM. This might require some separation of components ofthe SOM and dating these components separately.

When selecting bones from reference fish, ducks, moose, deer, elk, badgers, muskrats,and other animals for radiocarbon dating from each watershed it is important to pair collection ofplants from that watershed with the bones, as much as possible. The next important milestoneto understand radiocarbon dating within the Minnesota archaeological record must focus on

16

radiocarbon dating curated and modern reference specimens and basal organic matter toidentify contribution of ancient carbon to all components of the ecosystem that are part of theexisting Minnesota radiocarbon database.

17

TABLES

18

TABLE 1PROVENIENCE DATA FOR SAMPLES FROM VARIOUS SITES IN MINNESOTA

PRI No.(AMS)

Access.No.

Feat.No. Level Box Item Analysis

Cambria (21BE2):

4784 601-128A Zea mays kernels ABAN AMS 14C Date

4785 601-128B Zea mays kernels ABA AMS 14C Date

4883 601-127 127 Sec. 4bottom

387 Charcoal MacrofloralAMS 14C Date

Mtn. Lake site (21CO1):

4988 A75:6:32,92, etc.

Fox Lake (maybe transitional),Charred food crust

AMS 14C DateFTIR

Poole site (21FA72):

4759 1986.64.28.70ZM

1563AY

Zea mays kernel AMS 14C Date

4760 1986.64.28.70PH

1563AY

Phaseolus seed AMS 14C Date

Pederson site (21LN2):

4989 A74:5:1045 Charred food crust AMS 14C DateFTIR

5040 Humate AMS 14C Date







19

TABLE 1 (Continued)

PRI No.(AMS)

Access.No.




Wilford (21ML12):

4879 763-10-11 10 1256 Charcoal MacrofloralAMS 14C Date

4843 780-11-29 11 1159 Elk scapula fragment,longitudinal cracking, flakingalong edges, light root etching,black spots on surface may becharcoal or sediment staining,with roots present in cancellousbone.

AMS 14C Date

4889 763-30-5 30 pit 1307 Charcoal MacrofloralAMS 14C Date

4814 F43ZM 43 BaileyBox

Corn (Zea mays), charred AMS 14C Date

4815 F43JN 43 BaileyBox

Nutshell AMS 14C Date

4844 736-56-9 56 932 Bison calcaneus (left),longitudinal cracking, surfaceflaking, mild sediment staining,and some rodent gnawing.

AMS 14C Date

4894 763-56 56 1011 Charcoal MacrofloralAMS 14C Date

4816 F56 56 BaileyBox

Wild rice (Zizania) seeds AMS 14C Date

4817 F65JN 65 BaileyBox

Nutshell AMS 14C Date

4818 F65ZZ 65 BaileyBox


4761 F82 82 Wild rice (Zizania) seeds AMS 14C Date

4819 F91 91 BaileyBox


4886 F112 112 1302 Charcoal MacrofloralAMS 14C Date

20

TABLE 1 (Continued)

PRI No.(AMS)

Access.No.


4881 780-112-3 112 1231 Charcoal MacrofloralAMS 14C Date


4995 780.123.42 933 Onamia shoulder, Charred foodcrust

AMS 14C DateFTIR

4996 790.122.1 933 Sandy Lake Rim, Charred foodcrust

AMS 14C DateFTIR


4888 F132 132 932 Charcoal from post mold MacrofloralAMS 14C Date





4890 F238 238 2.3 1165 Charcoal MacrofloralAMS 14C Date

4845 794-238-6A

238 1241 Five bone fragments including 3partially calcined medium/largemammal long bone fragments, 1fully calcined medium/largemammal bone, and 1 charredmedium mammal bone (selectedfor dating).

AMS 14C Date

4997 794-248-1 248 48 Kathio Rim sherd, Charred foodcrust

MacrofloralAMS 14C DateFTIR



4821 F316ZZ 316 BaileyBox


21

TABLE 1 (Continued)

PRI No.(AMS)

Access.No.


4820 F316AM 316 BaileyBox

Chenopodium seeds/Amaranthaceae perisperm

AMS 14C Date


Ft. Ridgely (21NL8):

4846 126-3 1289 Bison scapula (from hoe), limitedsurface root etching.

AMS 14C Date

4998 126.5 1289 Charred food crust AMS 14C DateFTIR

Winter site (21PN17):

4847 713-8 2 4 885 Seven fragments of extremelyweathered or calcined mammalbone from the 1971 excavation,lower levels

AMS 14C DateFailed

4896 713-91 15 Float sample, 4 jars MacrofloralAMS 14C Date

4762 634.118 1329 Charred log, exterior AMS 14C Date

Schilling site (21WA1):

4999 2167-171(166.12,166.13)

Charred food crust AMS 14C DateFTIR

LaMoille (21WN1):

4848 21617 1206 Carp cranial bone reference AMS 14C Date

4849 21616 1206 Catfish mandible (right)reference

AMS 14C Date

4850 216-18 1206 Sturgeon cranial bone reference AMS 14C Date

4851 216-19 1206 Walleye pike opercle (left)reference

AMS 14C Date

4842 21612 12 1206 Medium/large mammal longbone shaft fragment; burned(dark tan, black, blue); with heatflaking, chipping, and cracking.

AMS 14C Date

22

TABLE 1 (Continued)

PRI No.(AMS)

Access.No.


4841 216-11 11 1206 Two medium/large mammal longbone shaft fragments, partiallyburned (darkened, charred, andcalcined), the larger fragmentwas selected for processing anddisplayed limited longitudinalcracking with a caliche film onthe cortical surface.

AMS 14C Date

4840 216-10C 10 1206 Two mammal long bone shaftfragments, the blackened smallmammal tibia shaft fragmentwas selected for processing anddisplayed limited root etching,and slight surface cracking withflaking.

AMS 14C Date

4763 216-10 10 1206 Walnut shell fragment AMS 14C Date

4863 216-9 9 1206 Darkened large mammal longbone fragment.

AMS 14C Date

4862 216-8 8 1206 Darkened large mammal ribfragment.

AMS 14C DateFailed

4861 216-7 7 1206 Large mammal long bonefragment, possible tool, red color(possibly pigment) on interiorsurface, slight root etching andscratches on exterior surface,partially charred (charred portionselected for dating).

AMS 14C Date

4860 216-6 6 1206 Three uncharred bird bonesincluding two coracoids (rightand left), possibly grouse, andthe proximal humerus (right) of alarge bird with root etching onsurface (selected for dating).

AMS 14C Date

4839 PRI-106 6 641 Medium/large mammal vertebrafragment, uncharred.

AMS 14C Date

4859 PRI-105 5 1206 Large bird long bone (possiblefemur), uncharred with rodentgnawing, mild surfaceweathering, and slight pressurecracking.

AMS 14C Date

23

TABLE 1 (Continued)

PRI No.(AMS)

Access.No.


4857 PRI-104U 4 1206 Medium/large mammal bone,uncharred, slight weathering,and surface erosion.

AMS 14C Date

4858 PRI-104C Charred proximal end of a birdtibiotarsus (left).

AMS 14C Date

4855 216-3 3 1206 Anatidae (duck family) proximalhumerus (right), uncharred withslight rodent gnawing on shaft.

AMS 14C Date

4856 PRI-103 3 641 Three medium/large mammalbone fragments including apartially burned possiblevertebra fragment, a calcinedpossible long bone fragment,and a partially burned long boneshaft fragment (charred endselected for dating).

AMS 14C Date

4854 PRI-102 2 641 Medium mammal long bonefragment from artifact.

AMS 14C Date

4852 PRI-101U 1 1206 Two uncharred bone fragments,including a medium/largemammal rib blade fragment withsurface weathering and slightsediment staining (selected fordating).

AMS 14C Date

4853 PRI-101C 1 Three bone fragments includingtwo partially burnedmedium/large mammal longbone shaft fragments, and acharred small animal long boneshaft fragment (selected fordating).

AMS 14C Date

Rynearson (21FA97):

4882 1986-65-3 lowerpit

1562AY

Charcoal MacrofloralAMS 14C Date

Great Oasis (21MU2):

4864 240-159 159 1271 Bison scapula (from sickle),wear and weathering along thespine.

AMS 14C Date

24

TABLE 1 (Continued)

PRI No.(AMS)

Access.No.


4865 TU 1-11 B 15–18in.

Large mammal, possibly bison, possible vertebral fragment,some dark sediment staining,uncharred.

AMS 14C Date

4866 TU 1-17 C 15–19in.

Large mammal, possibly bison,long bone shaft fragment,uncharred with rodent gnawing.

AMS 14C Date

4867 TU 1-50 16–17in.

Large mammal, possibly bison,mandible fragment, uncharred.

AMS 14C Date

Reprocessed Charred Food Crust:

23345652

GGFE-01 Charred food crust from interiorof ceramicsherds

AMS 14C Date

23355623

GGLAC-2 Charred food crust from interiorof ceramicsherds

AMS 14C Date

23365654

GGFL-4 Charred food crust from interiorof ceramicsherds

AMS 14C Date

24355655

MIACCC-1 Charred food crust from St.Croix potrim sherd; expected age ofaround1200 - 1500 BP

AMS 14C Date

Reference Samples:

5324 WR FoxCreek

Wild rice (Zizania), unnamedpond on Fox Creek

AMS 14C Date

5481 Charred wild rice (Zizania),unnamed pond on Fox Creek

AMS 14C Date

5325 WR RiceRiver

Wild rice (Zizania), Rice Riverflowage south of Bigfork

AMS 14C Date

5482 Charred wild rice (Zizania), RiceRiver flowage south of Bigfork

AMS 14C Date

5326 WR IslandRiver

Wild rice (Zizania), Island River,Lake County

AMS 14C Date

5483 Charred wild rice (Zizania),Island River, Lake County

AMS 14C Date

25

TABLE 1 (Continued)

PRI No.(AMS)

Access.No.


5111 DNR 1DOW:09016700

Channel catfish vertebra, LakeFond

AMS 14C Date

5112 DNR 2DOW:38000400

White sucker vertebra, LakeCoffee

AMS 14C Date

5113 DNR 3DOW:16080500

White sucker vertebra, LakeElbow

AMS 14C Date

5114 DNR 11DOW:16080500

Northern pike vertebra, LakeElbow

AMS 14C Date

5115 DNR 4DOW:21012300

Northern pike Vertebra, Lake Ida AMS 14C Date

5116 DNR 5DOW:38000400

Northern pike vertebra, LakeCook

AMS 14C Date

5117 DNR 7DOW:18040300

Northern pike vertebra, LowerCullen Lake

AMS 14C Date

5118 DNR 8DOW:15001600

Northern pike vertebra, LakeItasca

AMS 14C Date

5119 DNR 9DOW:33004000

Northern pike vertebra, LakeAnn

AMS 14C Date

5120 DNR 10DOW:33004000

White sucker vertebra, Lake Ann AMS 14C Date

26

TABLE 2 MACROFLORAL REMAINS FROM VARIOUS SITES IN MINNESOTA

Sample Charred Uncharred Weights/

No. Identification Part W F W F Comments

Cambria (21BE2):

601-127 Sample Weight 1.199 g

CHARCOAL/WOOD:

Ulmus rubra** Charcoal 1 1.1993 g


FLORAL REMAINS:

Zea mays** Kernel 3 8 0.6537 g

Poole site (21FA72):

1986.64.28.70 Sample Weight 1.226 g

21FA72 FLORAL REMAINS:

Box: 1563AY Monocot Stem 3 0.0135 g

Phaseolus** Seed 1 0.0267 g

Zea mays Cupule 5 12 0.0873 g

Zea mays** Kernel 1 60 0.5855 g

Vitrified tissue 4 0.0955 g

NON-FLORAL REMAINS:

Rock X Few

Wilford (21ML12):

763-10-11 Sample Weight 1.231 g

Feature 10 CHARCOAL/WOOD:

Box: 1256 Ulmus thomasii** Charcoal 1 1.2314 g



Pit Pinus strobus Charcoal 1 0.2123 g

Box: 1307 Quercus - Erythrobalanusgroup**

Charcoal 1 0.2399 g

F43ZM Sample Weight 0.040 g

Feature 43 FLORAL REMAINS:

Bailey Box Zea mays** Cupule 2 0.0396 g

F43JN Sample Weight 0.111 g


Bailey Box Juglans cinerea** Nutshell 2 0.1111 g

27

TABLE 2 (Continued)





Box: 1011 Betula** Charcoal 1 0.2466 g

Pinus strobus Charcoal 1 0.2512 g

F56 Sample Weight 0.080 g


Bailey Box Zizania** Caryopsis 5 4 0.0799 g

F65JN Sample Weight 1.140 g


Bailey Box Juglans cinerea** Nutshell 25 0.8063 g

F65ZZ Sample Weight 0.1648 g



CHARCOAL/WOOD:

Salicaceae twig Charcoal 1 0.0095 g

Unidentified hardwood twig Charcoal 2 0.0263 g



Zizania** Caryopsis 2 53 0.1861 g



Box: 1231 Quercus root Root 1 ic 0.7402 g






Box: 1302 Picea** Charcoal 1 0.5641 g



Box: 1231 Root - vitrified Root 1 0.0798 g

CHARCOAL/WOOD:

Conifer Charcoal 2 0.0219 g

Pinus strobus** Charcoal 3 0.2191 g

28

TABLE 2 (Continued)





Box: 1302 Periderm (Bark) 3 0.0515 g

Vitrified tissue 1 0.0317 g

CHARCOAL/WOOD:

Total charcoal > 2 mm 0.1276 g

Acer - soft maple group** Charcoal 3 0.0321 g


Quercus - vitrified Charcoal 3 0.0622 g

Ulmaceae - vitrified Charcoal 1 0.0167 g



Box: 932 Celtis** Charcoal 1 ic 6.4150 g



Box: 1304 Pinus strobus** Charcoal 1 0.6039 g



Box: 1313 Root - vitrified Root 1 1.3677 g



Box: 1302 Pinus strobus** Charcoal 2 0.4781 g

Unidentified hardwood - root Root 1 0.0652 g



Box: 1302 Pinus strobus - vitrified** Charcoal 1 0.2575 g



Box: 1313 Pinus** Bark scale 12 0.2991 g



Level 2.3 Pinus strobus Charcoal 1 0.1792 g

Box: 1165 Quercus - Erythrobalanusgroup**

Charcoal 1 0.3722 g

29

TABLE 2 (Continued)





Box: 426 Picea** Charcoal 10 0.2546 g



Box: 1165 Picea Charcoal 1 0.1017 g

Quercus - Erythrobalanusgroup**

Charcoal 2 0.6688 g

F316ZZ Sample Weight 0.268 g



Unidentified A Seed 1 0.0009 g

F316CH Sample Weight 0.012 g


Bailey Box Amaranthaceae** Perisperm 35 10 0.0091 g

Chenopodium Seed 1 16 0.0030 g



Box: 1165 Larix Charcoal 1 0.0204 g


Populus** Charcoal 2 0.1203 g

Unidentified hardwood Charcoal 1 ic 0.0126 g

Unidentified hardwood - twig Charcoal 2 ic 0.0218 g




Rubus** Seed 3 1 0.0029 g

Periderm (bark) 5 0.0628 g

Roots X Numerous

Rootlets X Numerous

Sclerotia X X Numerous

30

TABLE 2 (Continued)



713-91 CHARCOAL/WOOD:

Feature 15 Total charcoal > 2 mm 34.1417 g

(Continued) Pinus strobus Charcoal 24 6.9335 g

Pinus strobus Charcoal 4 ic 0.0572 g

Pinus strobus - vitrified Charcoal 10 1.6848 g

Pinus strobus twig Charcoal 1 0.2069 g

Pinus strobus cf. Root 1 0.6834 g

NON-FLORAL REMAINS:

Insect Chitin X Few

Rodent fecal pellets X X Moderate

634.118 Sample Weight 19.695 g

Box: 1329 CHARCOAL/WOOD:

Pinus strobus** Charcoal 1 0.0454 g

LaMoille (21WN1):


Level 10 FLORAL REMAINS:

Box: 1206 Juglans cinerea** Nutshell 1 0.5928 g

Rynearson (21FA97):


Lower pit FLORAL REMAINS:

Box: 1562AY Zea mays** Kernel 3 0.0715 g

CHARCOAL/WOOD:

Fraxinus Charcoal 9 0.4923 g

Ulmaceae Charcoal 1 0.0272 g

NON-FLORAL REMAINS:

Rock 1

W = WholeF = FragmentX = Presence noted in sampleg = gramsmm = millimetersic = incompletely charred**= Submitted for AMS 14C Dating

31

TABLE 3INDEX OF MACROFLORAL REMAINS RECOVERED FROM VARIOUS SITES IN MINNESOTA

Scientific Name Common Name

FLORAL REMAINS:

Amaranthaceae Includes Goosefoot and Amaranth families

Chenopodium Goosefoot, Pigweed

Juglans cinerea Butternut

Monocot A member of the Monocotyledonae class ofAngiosperms, which include grasses, sedges, lilies,and palms

Periderm Technical term for bark; Consists of the cork(phellum) produced by the cork cambium, as well asany epidermis, cortex, and primary or secondaryphloem exterior to the cork cambium

Pinus Pine

Rubus Raspberry, Blackberry, etc.

Vitrified tissue Charred material with a shiny, glassy appearance

Sclerotia Resting structures of mycorrhizae fungi

CULTIGENS:

Phaseolus Common bean, Navy bean, Field bean, Kidney bean,Pinto bean, Black bean, Tepary bean, Lima bean,Scarlet runner bean, etc

Zea mays Maize, Corn

Zizania Wild rice

CHARCOAL/WOOD:

Acer - Soft maple group Soft maple group - Rays are 1-5 seriate

Betula Birch

Celtis Hackberry

Conifer Cone-bearing, gymnospermous trees and shrubs,mostly evergreens, including the pine, spruce, fir,juniper, cedar, yew, hemlock, redwood, and cypress

Larix Larch

Picea Spruce

Pinus Pine

Pinus strobus Eastern white pine

Fraxinus Ash

32

TABLE 3 (Continued)

Scientific Name Common Name

CHARCOAL/WOOD (Continued):

Quercus Oak

Quercus - Erythrobalanus group Red oak group - Species in the red oak group exhibitopen earlywood vessels and thick-walled, roundlatewood vessels

Salicaceae Willow family

Populus Aspen, Cottonwood

Ulmaceae Elm family

Celtis Hackberry

Ulmus rubra Slippery elm

Ulmus thomasii Rock elm

Unidentified hardwood Wood from a broad-leaved flowering tree or shrub

NON-FLORAL REMAINS:

Chitin A natural polymer found in insect and crustaceanexoskeleton

33

TABLE 4RADIOCARBON RESULTS FOR SAMPLES FROM VARIOUS SITES IN MINNESOTA

PRI AMS No.& Sample No.

SampleIdentification

AMS 14CDate*

1-sigma CalibratedDate (68.2%)


δ13C(o/oo)

Cambria (21BE2):

PRI-4784601-128A

Zea mayskernel, charred(ABAN)

812 ± 23RCYBP

740–690CAL yr. BP

770–680CAL yr. BP

-6.66

AD 1210–1260 AD 1180–1270

PRI-4785601-128B

Zea mayskernel, charred(ABA)

863 ± 23RCYBP

790–740CAL yr. BP

900–860;830–810;800–700CAL yr. BP

-13.53

AD 1160–1210 AD 1050–1090AD 1120–1140AD 1150–1250

PRI-4883601-127

Ulmus rubra,charcoal

927 ± 23RCYBP

910–790 CAL yr. BP

920–790 CAL yr. BP

-24.6

AD 1040–1160 AD 1030–1160

Mtn. Lake site (21CO1):

PRI-4988A75:6:32, 9, 2

Charred foodcrust

2205 ± 27RCYBP

2310–2290;2280–2230;2210–2140 CAL yr. BP

2320–2140 CAL yr. BP

-21.0

360–340 BC; 330–280 BC;260–200 BC

370–190 BC

Poole (21FA72):

PRI-47591986.64.28.70

Zea mayskernel, charred

668 ± 22RCYBP

670–650;590–560CAL yr. BP

680–630;600–560CAL yr. BP

-9.03

AD 1280–1300AD 1360–1390

AD 1270–1320AD 1350–1390

PRI-47601986.64.28.70

Phaseolusseed, charred

640 ± 22RCYBP

660–640;590–560CAL yr. BP

670–620;610–550CAL yr. BP

-26.8

AD 1290–1310AD 1360–1390

AD 1280–1330AD 1340–1400

34

TABLE 4 (Continued)



AMS 14CDate*



δ13C(o/oo)

Pederson site (21LN2):

PRI-4989A74:5:1045

Charred foodcrust

1906 ± 23RCYBP

1880–1820 CAL yr. BP

1930–1810CAL yr. BP

-20.53

AD 70–130 AD 20–140

PRI-5040A74:5:1045

Humate 1762 ± 24RCYBP

1710–1690;1680–1620 CAL yr. BP

1740–1570 CAL yr. BP

-19.36

AD 240–260;AD 270–330

AD 210–380

PRI-4990A74:5:221

Charred foodcrust

1926 ± 26RCYBP

1900–1820 CAL yr. BP

1930–1820 CAL yr. BP

-22.5

AD 50–130 AD 20–130

PRI-5041A74:5:221


1700–1610 CAL yr. BP

1720–1560 CAL yr. BP

-20.00

AD 250–340 AD 230–390

PRI-4991A73:7:1177

Charred foodcrust

1736 ± 23RCYBP

1700–1610 CAL yr. BP

1710–1560 CAL yr. BP

-24.85

AD 250–340 AD 240–390

PRI-4992A74:5:1205

Charred foodcrust

1989 ± 25RCYBP

1990–1980;1970–1890 CAL yr. BP

2000–1880 CAL yr. BP

-22.74

40–30 BC; 20 BC–AD 60

50 BC–AD 70

PRI-4993A73:7:654

Charred foodcrust

2265 ± 36RCYBP

2350–2300;2240–2180 CAL yr. BP

2350–2290;2270–2150 CAL yr. BP

-23.88

400–350 BC;290–230 BC

410–340 BC;320–200 BC

PRI-5044A73:7:654


1970–1890 CAL yr. BP

2000–1870 CAL yr. BP

-24.17

20 BC–AD 60 50 BC–AD 80

35

TABLE 4 (Continued)



AMS 14CDate*



δ13C(o/oo)

PRI-4994A74:5:177

Charred foodcrust

1654 ± 24RCYBP

1600–1580;1570–1530 CAL yr. BP

1620–1520;1460–1440CAL yr. BP

-25.76

AD 350–370; AD 380–420

AD 330–430; AD 490–510

PRI-5045A74:5:177


1520–1450;1430–1370 CAL yr. BP

1530–1340 CAL yr. BP

-25.65

AD 430–500;AD 520–580

AD 420–610

Wilford (21ML12):

PRI-4879763-10-11

Ulmus thomasiicharcoal

375 ± 22RCYBP

500–430; 350–330 CAL yr. BP

510–420; 380–320 CAL yr. BP

-23.6

AD 1450–1520;AD 1600–1620

AD 1440–1530;AD 1570–1630

PRI-4843780-11-29

Bone collagen,elk scapula

445 ± 25RCYBP

520–490 CAL yr. BP

530–470CAL yr. BP

-21.1

AD 1430–1460 AD 1420–1480

PRI-4889763-30-5

Quercus-Erythrobalanusgroup charcoal

1627± 22RCYBP

1560–1520;1460–1440 CAL yr. BP

1600–1580;1570–1410 CAL yr. BP

-25.3

AD 390–430;AD 490–510

AD 350–370;AD 380–540

PRI-4814F43

Zea mayscupule, charred

380 ± 14RCYBP

500–460;350–340CAL yr. BP

510–430;350–330CAL yr. BP

-10.6

AD 1450–1490AD 1600–1610

AD 1440–1520AD 1600–1620

PRI-4815F43

Juglans cinereanutshell,charred

404 ± 15RCYBP

510–480CAL yr. BP

510–460;350–340CAL yr. BP

-26.8

AD 1440–1470 AD 1440–1490AD 1600–1610

36

TABLE 4 (Continued)



AMS 14CDate*



δ13C(o/oo)

PRI-4844736-56-9

Bone collagen,bison calcaneus

379 ± 22RCYBP

500–450; 350–330 CAL yr. BP

510–420; 380–320 CAL yr. BP

-21.2

AD 1450–1500;AD 1600–1620

AD 1440–1530;AD 1570–1630

PRI-4894763-56

Betula charcoal 334 ± 22RCYBP

460–420; 400–310 CAL yr. BP

470–310 CAL yr. BP

-26.1

AD 1490–1530;AD 1550–1640

AD 1480–1640

PRI-4816F56

Zizaniacaryopsis,charred

404 ± 15RCYBP

510–480CAL yr. BP

510–460;350–340CAL yr. BP

-24.8

AD 1440–1470 AD 1440–1490AD 1600–1610

PRI-4817F65


372 ± 14RCYBP

490–450; 350–330CAL yr. BP

500–430;360–330 CAL yr. BP

-26.6

AD 1460–1500AD 1600–1620

AD 1450–1520AD 1590–1620

PRI-4818F65


631 ± 15RCYBP

660–630;600–560CAL yr. BP

660–620;610–550CAL yr. BP

-25.8

AD 1290–1320AD 1350–1390

AD 1290–1330AD 1340–1400

PRI-4761F82


388 ± 22RCYBP

510–460;350–340CAL yr. BP

510–420;360–330CAL yr. BP

-26.06

AD 1440–1490AD 1600–1610

AD 1440–1530AD 1590–1620

PRI-4819F91


435 ± 15RCYBP

510–490 CAL yr. BP

520–480 CAL yr. BP

-27.0

AD 1440–1460 AD 1430–1470

37

TABLE 4 (Continued)



AMS 14CDate*



δ13C(o/oo)

PRI-4886F112

Picea charcoal 324 ± 21RCYBP

440–350;340–310CAL yr. BP

470–300CAL yr. BP

-25.2

AD 1510–1600;AD 1610–1640

AD 1480–1650

PRI-4881780-112-3

Pinus strobuscharcoal

473 ± 21RCYBP

530–500CAL yr. BP

540–500CAL yr. BP

-25.0

AD 1420–1450 AD 1410–1450

PRI-4887F116

Acer, soft maplegroup charcoal

312 ± 21RCYBP

430–360; 330–300 CAL yr. BP

460–300 CAL yr. BP

-25.8

AD 1520–1590;AD 1620–1650

AD 1490–1650

PRI-4995780.123.42

Charred foodcrust

1686 ± 23RCYBP

1610–1550 CAL yr. BP

1700–1670;1630–1530 CAL yr. BP

-26.33

AD 340–400 AD 250–280; AD 320–420

PRI-4996790.122.1

Charred foodcrust

610 ± 23RCYBP

650–620; 610–580; 570–550CAL yr. BP

660–540CAL yr. BP

-28.77

AD 1300–1330;AD 1340–1370; AD 1380–1400

AD 1290–1410

PRI-5046790.122.1


500-420; 380–320 CAL yr. BP

510–310 CAL yr. BP

-26.97

AD 1450–1530;AD 1570–1630

AD 1440–1640

PRI-4888F132

Celtis charcoal,incompletelycharred

216 ± 21RCYBP

300–280; 170–150; 10–0 CAL yr. BP

310–270; 190–140; 20–... CAL yr. BP

-25.0

AD 1650–1670;AD 1780–1800;AD 1940–1950

AD 1640–1680;AD 1760–1810;AD 1930–...

38

TABLE 4 (Continued)



AMS 14CDate*



δ13C(o/oo)

PRI-4895F143


668 ± 21RCYBP

670–650; 590–560 CAL yr. BP

680–630; 600–560 CAL yr. BP

-26.0

AD 1280–1300;AD 1360–1390

AD 1270–1320;AD 1350–1390

PRI-4884F166


449 ± 21RCYBP

520–500 CAL yr. BP

530–480 CAL yr. BP

-24.8

AD 1430–1450 AD 1420–1470

PRI-4885F170

Pinus strobuscharcoal,vitrified

555 ± 21RCYBP

630–600; 560–530 CAL yr. BP

640–590; 570-520 CAL yr. BP

-26.5

AD 1320–1350; AD 1390–1420

AD 1310–1360;AD 1380–1430

PRI-4880F209

Pinus barkscale, charred

323 ± 21RCYBP

440–350; 340–310 CAL yr. BP

470–300 CAL yr. BP

-25.7

AD 1510–1600;AD 1610–1640

AD 1480–1650

PRI-4890F238


281 ± 21RCYBP

430–390;320–290CAL yr. BP

430–350;330–280CAL yr. BP

-27.3

AD 1520–1560;AD 1630–1660

AD 1520–1600;AD 1620–1670

PRI-4845794-238-6A

Bone, charredmammal

350 ± 22RCYBP

470–420; 380–320 CAL yr. BP

490–420; 410–310 CAL yr. BP

-22.4

AD 1480–1530; AD 1570–1630

AD 1460–1530; AD 1540–1640

PRI-4997794-248-1

Charred foodcrust

1482 ± 23RCYBP

1390–1340 CAL yr. BP

1410–1310 CAL yr. BP

-25.78

AD 560–610 AD 540–640

PRI-4893F260

Picea charcoal 322 ± 21RCYBP

440–350; 340–310 CAL yr. BP

460–300 CAL yr. BP

-24.9

AD 1510–1600;AD 1610–1640

AD 1490-1650

39

TABLE 4 (Continued)



AMS 14CDate*



δ13C(o/oo)

PRI-4892F277


316 ± 21RCYBP

430–360; 330–310 CAL yr. BP

460–300CAL yr. BP

-26.1

AD 1520–1590;AD 1620–1640

AD 1490–1650

PRI-4821F316


421 ± 15RCYBP

510–490 CAL yr. BP

520–470 CAL yr. BP

-25.6

AD 1440–1460 AD 1430–1480

PRI-4820F136

Amaranthaceaeperisperm,charred

399 ± 14RCYBP

510–470 CAL yr. BP

510–460; 350–340 CAL yr. BP

-28.1

AD 1440–1480 AD 1440–1490AD 1600–1610

PRI-4891F340

Populuscharcoal

348 ± 21RCYBP

470–420; 380–320 CAL yr. BP

490–420; 410–310 CAL yr. BP

-26.2

AD 1480–1530;AD 1570–1630

AD 1460–1530;AD 1540–1640

Ft. Ridgely (21NL8):

PRI-4846126-3

Bone collagen,bison scapula

685 ± 44RCYBP

680–640; 590–560 CAL yr. BP

700–620; 610–550 CAL yr. BP

-14.0

AD 1270–1310;AD 1360–1390

AD 1250–1330;AD 1340–1400

PRI-4998126.5

Charred foodcrust

611 ± 23RCYBP

650–620; 610–580; 570–550 CAL yr. BP

660–540 CAL yr. BP

-22.76

AD 1300–1330;AD 1340–1370;AD 1380–1400

AD 1290–1410

40

TABLE 4 (Continued)



AMS 14CDate*



δ13C(o/oo)


PRI-4896713-91

Rubus seed,charred

125 ± 22RCYBP

270–210; 150–130; 120–60; 40–20 CAL yr. BP

280–180; 150–10 CAL yr. BP

-29.0

AD 1680–1740;AD 1800–1820;AD 1830–1890;AD 1910–1930

AD 1670–1770;AD 1800–1940

PRI-4762634.118


182 ± 21RCYBP

290–260;220–140;20 cal BP–...CAL yr. BP

290–260;220–140;30 cal BP–...CAL yr. BP

-24.64

AD 1660–1690AD 1730–1810AD 1930–...

AD 1660–1690AD 1730–1810 AD 1920–...

Schilling site (21WA1):

PRI-49992167-171(166.12,166.13)

Charred foodcrust

2500 ± 25RCYBP

2720–2690;2640–2610;2600–2500CAL yr. BP

2730–2480 CAL yr. BP

-24.77

770–740 BC;690–660 BC;650–550 BC

780–540 BC

LaMoille (21WN1):

PRI-484821617

Bone collagen,carp cranial

746 ± 23RCYBP

690–660 CAL yr. BP

730–660 CAL yr. BP

-25.3

AD 1260–1290 AD 1220–1290

PRI-484921616

Bone collagen,catfish mandible

1223 ± 24RCYBP

1230–1210;1190–1170;1160–1080 CAL yr. BP

1260–1200;1190–1060 CAL yr. BP

-24.5

AD 720–740; AD 760–780; AD 790–870

AD 690–750; AD 760–890

41

TABLE 4 (Continued)



AMS 14CDate*



δ13C(o/oo)

PRI-4850216-18

Bone collagen,sturgeon cranial

945 ± 23RCYBP

930–900; 870–800 CAL yr. BP

930–790 CAL yr. BP

-24.0

AD 1020–1050; AD 1080–1150

AD 1020–1160

PRI-4851216-19

Bone collagen,walleye pikeopercle

307 ± 23RCYBP

430–360; 330–300 CAL yr. BP

460–300 CAL yr. BP

-16.6

AD 1520–1590; AD 1620–1650

AD 1490–1650

PRI-4842216-12

Bone, charredmedium/largemammal longbone fragment

5025 ± 62RCYBP

5890–5800;5770–5660 CAL yr. BP

5910–5640;5630–5620 CAL yr. BP

-24.0

3950–3850 BC;3820–3710 BC

3970–3690;3680–3670 BC

PRI-4841216-11

Bone, charredmedium/largemammal longbone fragment

4160 ± 22RCYBP

4830–4790; 4770-4690;4680–4620 CAL yr. BP

4830–4780;4770–4610;4600–4580 CAL yr. BP

-23.3

2880–2850 BC;2820–2740 BC;2730–2680 BC

2880–2830 BC;2820–2660 BC;2650–2640 BC

PRI-4840216-10C

Bone, charredsmall mammaltibia shaftfragment

4634 ± 22RCYBP

5450–5400;5330–5310CAL yr. BP

5460–5370;5330–5300CAL yr. BP

-24.6

3500–3460 BC;3380–3360 BC

3510–3420 BC;3390–3350 BC

PRI-4763216-10


2532 ± 23RCYBP

2740–2700;2640–2610;2590–2540CAL yr. BP

2750–2690;2640–2610;2600–2490CAL yr. BP

-25.22

800–750 BC690–660 BC640–590 BC

800–740 BC690–660 BC650–550 BC

42

TABLE 4 (Continued)



AMS 14CDate*



δ13C(o/oo)

PRI-4863216-9

Bone, darkenedlarge mammallong bonefragment

4750 ± 25RCYBP

5590-5510;5490–5470 CAL yr. BP

5590–5490;5380–5330 CAL yr. BP

-23.7

3640–3560 BC;3540–3520 BC

3640–3510 BC;3430–3380 BC

PRI-4861216-7

Bone, charredlarge mammallong bonefragment

4545 ± 24RCYBP

5310–5280;5170–5130;5110–5070 CAL yr. BP

5320–5260;5250–5210;5190–5050 CAL yr. BP

-22.4

3370–3330 BC;3220–3180 BC;3160–3120 BC

3370–3310 BC;3300–3260 BC;3240–3100 BC

PRI-4860216-6

Bone collagen,large birdhumerus

4558 ± 25RCYBP

5320–5280;5160–5140;5110–5080 CAL yr. BP

5320–5260;5230–5210;5190–5060 CAL yr. BP

-21.3

3370–3330 BC;3220–3190 BC;3160–3130 BC

3380–3310 BC;3280–3260 BC;3240–3110 BC

PRI-4839PRI-106

Bone collagen,medium/largemammalvertebra

4384 ± 28RCYBP

4980–4870 CAL yr. BP

5040–4860 CAL yr. BP

-22.3

3030–2920 BC 3090–2910 BC

PRI-4859PRI-105

Bone collagen,large bird longbone fragment

4473 ± 25RCYBP

5280–5160;5130–5100;5070–5040 CAL yr. BP

5290–5030;5010–4970 CAL yr. BP

-18.1

3330–3210 BC;3180–3160 BC;3120–3090 BC

3340–3150 BC;3140–3080 BC;3070–3020 BC

PRI-4857PRI-104U

Bone collagen,medium/largemammal

6802 ± 31RCYBP

7670–7610 CAL yr. BP

7690–7590 CAL yr. BP

-24.3

5720–5660 BC 5740–5640 BC

PRI-4858PRI-104C

Bone, charredbird tibiotarsus

5895 ± 24RCYBP

6740–6670 CAL yr. BP

6780–6660 CAL yr.BP

-19.2

4790–4720 BC 4830–4710 BC

43

TABLE 4 (Continued)



AMS 14CDate*



δ13C(o/oo)

PRI-4855216-3

Bone collagen,Anatidaehumerus

4572 ± 25RCYBP

5320–5280;5160–5140;5100–5090 CAL yr. BP

5450–5410;5330–5270;5170–5120;5110–5070 CAL yr. BP

-21.8

3370–3330 BC;3210–3190 BC;3150–3140 BC

3500–3460 BC;3380–3320 BC;3220–3170 BC;3160–3120 BC

PRI-4856PRI-103

Bone, charredportion ofmedium/largemammal longbone fragment

5876 ± 24RCYBP

6730–6660 CAL yr. BP

6750–6640 CAL yr. BP

-23.4

4780–4720 BC 4800–4690 BC

PRI-4854PRI102

Bone collagen,mediummammal longbone fragment

7387 ± 28RCYBP

8300–8260;8220–8170 CAL yr. BP

8320–8160 CAL yr. BP

-21.8

6350–6310 BC;6270–6220 BC

6380–6210 BC

PRI-4852PRI-101U

Bone collagen,medium/largemammal ribblade

5902 ± 27RCYBP

6750–6670 CAL yr. BP

6790–6660 CAL yr. BP

-22.2

4800–4720 BC 4840–4710 BC

PRI-4853PRI-101C

Bone, charredsmall animallong bonefragment

6869 ± 23RCYBP

7720–7660 CAL yr. BP

7790–7650 CAL yr. BP

-21.6

5770–5720 BC 5840–5700 BC

Rynearson (21FA97):

PRI-48821986-65-3

Zea mayskernel, charred

623 ± 21RCYBP

660-630; 600-580; 570-550 CAL yr. BP

660-550 CAL yr. BP

-8.5

AD 1290–1320; AD 1350–1370; AD 1380–1400

AD 1290–1400

44

TABLE 4 (Continued)



AMS 14CDate*



δ13C(o/oo)

Great Oasis (21MU2):

PRI-4864240-159

Bone collagen,bison scapula

968 ± 23RCYBP

930–900; 860–830; 810–800 CAL yr. BP

940–890; 880–790 CAL yr. BP

-14.1

AD 1020–1050; AD 1090–1120; AD 1140–1150

AD 1010–1060; AD 1070–1160

PRI-4865TU 1-11

Bone collagen,large mammalpossiblevertebra

1313 ± 24RCYBP

1290–1250;1210–1180 CAL yr. BP

1300–1230;1210–1180 CAL yr. BP

-15.2

AD 660–700; AD 740–770

AD 650–720; AD 740–770

PRI-4866TU 1-17

Bone collagen,large mammallong bonefragment

988 ± 25RCYBP

940–900; 860–830; 810–800 CAL yr. BP

960–890; 870–790 CAL yr. BP

-17.8

AD 1010–1050; AD 1090–1120; AD 1140–1150

AD 990–1060; AD 1080–1160

PRI-4867TU 1-50

Bone collagen,large mammalmandiblefragment

942 ± 23RCYBP

920–900; 870–790 CAL yr. BP

930–790 CAL yr. BP

-17.8

AD 1030–1050;AD 1080–1160

AD 1020–1160

Reprocessed Charred Food Crust:

PRI-2334GGFE-01

Charred foodcrust

1754 ± 16RCYBP

1710–1690;1680–1620CAL yr. BP

1720–1610CAL yr. BP

-26.0

AD 240–260;AD 270–330

AD 230–340

PRI-5652GGFE-01

1755 ± 22RCYBP

1710–1620CAL yr. BP

1730–1600CAL yr. BP

-25.4

AD 240–330 AD 220–350

45

TABLE 4 (Continued)



AMS 14CDate*



δ13C(o/oo)

PRI-2335GGLAC-2

Charred foodcrust

3270 ± 30RCYBP

3560–3530;3510–3450CAL yr. BP

3580–3440;3430–3400CAL yr. BP

-28.7

1610–1580 BC;1570–1500 BC

1630–1490 BC;1480–1460 BC

PRI-5653GGLAC-2

3121 ± 23RCYBP

3380–3340;3290–3270CAL yr. BP

3400–3320;3310–3250CAL yr. BP

-35.4

1430–1390 BC;1340–1320 BC

1450–1370 BC;1360–1300 BC

PRI-2336GGFL-4

Charred foodcrust

1658 ± 22RCYBP

1600–1580;1570–1530CAL yr. BP

1620–1520CAL yr. BP

-25.9

AD 350–370;AD 380–420

AD 330–430

PRI-5654GGFL-4

1843 ± 22RCYBP

1820–1730CAL yr. BP

1860–1850;1830–1710CAL yr. BP

-23.9

AD 130–220 AD 90–100;AD 120–240

PRI-2435MIACCC-1

Charred foodcrust

1128 ± 16 1060–1040;1030–980CAL yr. BP

1070–970CAL yr. BP

-26.4

AD 890–910;AD 920–970

AD 880–980

PRI-5655MIACCC-1

1138 ± 22RCYBP

1070–980CAL yr. BP

1180–1160;1150–1100;1090–960CAL yr. BP

-27.3

AD 880–970 AD 770–790;AD 800–850;AD 860–990

Reference Samples:

PRI-5324WR Fox Creek

Zizaniacaryopsis,uncharred

1.0244 ±0.0029 fM

Sep 1955–Jul 1956 May 1955–Oct 1956 -27.2

46

TABLE 4 (Continued)



AMS 14CDate*



δ13C(o/oo)

PRI-5481WR Fox Creek


1.0189 ±0.0028 fM

May 1955–Mar 1956 Apr 1955–Sep 1957 -26.9

PRI-5325WR Rice River


1.0259 ±0.0029 fM

Sep 1955–Jul 1956 May 1955–Nov 1956 -27.3

PRI-5482WR Rice River


1.0179 ±0.0028 fM

May 1955–Mar 1956 Mar 1955–Aug 1956 -28.0

PRI-5326WR Island

River


1.0505 ±0.0030 fM

Nov 2007–Jun 2008Nov 2008–Jul 2009

Jul 1956–Apr 1956Mar 2006–Apr 2006Jan 2007–Jun 2007Sep 2007–Jul 2009

-26.6

PRI-5483WR Island

River


1.0506 ±0.0029 fM

Nov 2007–Jun 2008Nov 2008–Jul 2009

Jul 1956–Apr 1957Apr 2006Feb 2007–Jun 2007

-26.5

PRI-5111DNR 1

Bone collagen,channel catfishvertebra

1.03245 ±0.00289 fM

Dec 1955–Oct 1956 Jul 1955–Apr 1957 -24.4

PRI-5112DNR 2

Bone collagen,white suckervertebra

1.07813 ±0.00305 fM

Apr 2001Feb 2002–Feb 2004Aug 2004

Nov 1956–May 1957Feb 2001–Jun 2001Nov 2001–Jan 2005

-28.3

PRI-5113DNR 3


1.04979 ±0.00300 fM

Dec 2007–Jun 2008Dec 2008–Jul 2009

Jul 1956–Apr 1957Mar 2007–Jun 2007Nov 2007–Jul 2009

-26.7

PRI-5114DNR 11

Bone collagen,northern pikevertebra

1.05008 ±0.00296 fM

Dec 2007–Jun 2008Nov 2008–Jul 2009

Jul 1956–Apr 1957Apr 2006Jan 2007–Jun 2007Oct 2007–Jul 2009

-24.5

PRI-5115DNR 4


1.0141 ±0.00287 fM

Mar 1955–Jan 1956 Feb 1955–Aug 1956 -18.0

PRI-5116DNR 5


1.07249 ±0.00300 fM

Jan 2003–Feb 2005Sep 2005

Oct 1956–May 1957Feb 2002–Jun 2002Sep 2002–Nov 2006

-27.2

PRI-5117DNR 7


786 ± 23RCYBP

730–680 CAL yr. BP

740–670 CAL yr. BP

-25.3

AD 1220–1270 AD 1210–1280

47

TABLE 4 (Continued)



AMS 14CDate*



δ13C(o/oo)

PRI-5118DNR 8


761 ± 23RCYBP

700–670 CAL yr. BP

730–670 CAL yr. BP

-25.9

AD 1250–1280 AD 1220–1280

PRI-5119DNR 9


1.01842 ±0.00293 fM

May 1955–Mar 1956 Mar 1955–Sep 1956 -26.0

PRI-5120DNR 10


1.02499 ±0.00289 fM

Sep 1955–Jul 1956 May 1955–Nov 1956 -28.6

* Reported in radiocarbon years at 1 standard deviation measurement precision (68.2%), corrected for δ13C.

fM = fraction Modern. Recent dates (falling within the time after atomic testing began) arereported as fraction Modern because calibrations can only be done using fraction Modernfor this time period. Years BP are calculated as prior to 1950, not today’s date.

48

TABLE 5RADIOCARBON AND OSL RESULTS FOR BRAINERD WARE SAMPLES

FROM VARIOUS SITES IN MINNESOTA

Lab No. Date BP Material Component Comments

Buffalo Terrace (21BK099):

OSL-Illinois

1525 ± 290 OSL sherd Elk Lake Complex One sherd

PRI-2333 1630 ± 30 Food crust split

Beta187667

1730 ± 40 Food crust split

Beta296079

5540 ± 40 Burned bone Same feature as sherd

Pamida (21BL31):

Beta298250

2610 ± 30 Horizontally-corded vessels

Unusually low 13C/12Cratios (-29.2 – 32.0),suggesting they are tooold, 15N/14N +10.6 to +12.7 suggest fish

Beta298249

2670 ± 30

Beta298248

2300 ± 30 Net-impressedvessels

Beta298247

2580 ± 30

Midway (21BL37):

Beta108831

2160 ± 50 Site close to 21BL31,13C/12C -29.1

Beta148858

2030 ± 40 Net-impressedsherd

Mikinako Sag (21BL71):

Beta 84758 260 ± 60 Charcoal Middle Prehistoric(Brainerd)

Possibly assoc w/feature,date not consideredaccurate

Beta 84759 1320 ± 50 Charcoal Not associated w/feature, not consideredgood context, rejected

49

TABLE 5 (Continued)


Kitchie Bay (21BL273):

2480 ± 90 Charcoal Elk Lake complex Dated terminus of openwater period, presentlycedar swamp

Shingobee Island (21CA28):

Beta116989

4090 ± 40 Charcoal Feature level containsBrainerd ceramics

Beta116989

Beta 4400 ± 40 Charcoal

Beta297530

4070 ± 40 Burned bone Associated w/ net-impressed ceramics infeature

Beta297531

4590 ± 40 Burned bone

Rocky Point (21CA67):

Beta296097

1730 ± 30 Burned food crust Woodland, multi-component

Net-impressed, 13C -24.2 or 23.1, 15N +13.3or 14.0, possibly maplesyrup, elongated hearth,similar to ethnogsugaring

Beta296096

1740 ± 40 Burned food crust

OSL 1710 ± 130 Sherd

Beta296098

1420 ± 30 Burned food crust Late MiddleWoodland

Horizontal cwo-stampedvessel

Beta 29610 2670 ± 30 Burned bone

Beta298251


Beta296099

630 ± 30 Charcoal

Beta296100

890 ± 30 Charcoal

50

TABLE 5 (Continued)


Maxson (21CA109):

Beta296093

790 ± 30 Charcoal Elk Lake complex FCR feature containingrim and body sherds,horiz-corded vessel, p. 48, diag crisscrossedcord impressions,undefined vesselaffiliation

Beta296094

840 ± 30 Charcoal

Beta296095

1420 ± 30 Charcoal FCR + ceramic conc,net-impressed

Roosevelt Narrows (21CA184):

Beta 75658 2610 ± 60 Burned food crust Elk Lake complex,Late Archaic &Woodland

Net-impressed, 5separate vessels?, low13C -31.7 for these 2vessels

Beta 75659 2850 ± 60 Burned food crust

Beta 76658 2710 ± 60 Burned food crust 13C -24.6



Felknor (21CA188):

Beta 92827 1870 ± 40 Burned food crust Woodland Net-impressed, split

PRI-2334 1754 ± 16 Burned food crust

Kelnhoffer (21CA226):

OSL 2350 ± 190 Elk Lake complex Horiz-corded vessel

Cass Lake 1 (21CA352):

Beta 84684 2550 ± 60 Burned food crust Horiz-corded vessel, 13C -28.6 or -33.1

Beta 84685 2600 ± 60 Burned food crust

Thunder Lake West (21CA738):

Beta296103

2180 ± 40 Burned food crust Woodland 13C -21.8, 15N +6.4

Beta296104

410 ± 30 Charcoal, sameshovel test

“Obviously bad sample”

Beta298252


51

TABLE 5 (Continued)


Beta298253

1870 ± 40 Charcoal

OSL 1810 ± 200 Sherd Partially restoredhoriz/corded

Moxness Beach (21CA737):

Beta296078

1140 ± 30 Charcoal Horiz/corded sherdsassoc w/charcoal,comment: “too recent”

50 Lakes Bluff (21CW235):

Beta144014

2580 ± 40 Burned food crust Elk Lake complex Horiz/corded in housefeature, 13C -27.0, low

OSL 2730 ± 200

Levesque (21CW247):

Beta163611

2120 ± 40 Burned food crust Multi-componentHolocene

Net-impressed, featurecontained burned boneand charcoal.

Beta187668

2240 ± 40 Burned food crust

OSL 1940 ± 680 Net-impressed

Beta296084

1850 ± 40 Burned food crust Horiz-corded

Beta296092

2400 ± 30 Bone, burned Assoc w/ B. 296084

Beta296088

110 ± 30 Charcoal Historic Ojibwe, assoc w/B. 296084

PRI-2436 2648 ± 29 Burned food crust Net-impressed.

Beta296085

1510 ± 30 Charcoal Level contained MiddleWoodland smooth-surface sherds, “toorecent”Beta

2960861470 ± 30 Charcoal

Beta296087

260 ± 40 Butternut shell Mid-level stratum,Elk Lake complexceramics

13C -26.2, 15N +1.4,calibrates to Psinomanior Ojibwe occupation

Beta296089

5360 ± 40 Charcoal, workedwooden shaft

Elk Lake complex,lower level,Archaic

52

TABLE 5 (Continued)


Beta296090

4570 ± 40 Unburned largeherbivore longbone, bonecollagen

Archaic 13C -19.6, 15N +3.9,likely elk

Beta296091

110 ± 30 Bear paw bones,burned

Same feature as elkbone

Beta297529

6050 ± 40 Bison petrouspyramid (inner earbone), bonecollagen

Early Archaic 13C -12.1, C4 grass diet,mid-Holocene, alsosuggests wetland diet,could be age offset

OSL 1150 ± 160 Late MiddleWoodland

Smooth-surface, samelevels as Brainerd

Lake Carlos Beach (21DL02):

Beta104090

1880 ± 50 Burned food crust Parallel-grooved vessel

Beta104091

1980 ± 50 Burned food crust Horiz-corded vessel, 13C-24.8 (suggests noproblem)

21HB26:

Beta 76190 2280 ± 60 Burned food crust Horiz-corded vessel, 13C-27, might indicateslightly too old

21IC12:

1890 Burned food crust Brainerd-style

21MH05:

Beta 70373 2455 ± 50 Burned food crust Net-impressed

21ML02:

Beta280545

1860 ± 40 Burned food crust Net-impressed, 13C -25.9 suggests noproblem

53

FIGURES

54

FIGURE 1. ALL AMS RADIOCARBON SAMPLES PLOTTED OVER GROUNDWATER PROVINCES, MINNESOTA, USA.

55

FIGURE 2. PLOT OF ALL DATES ON CHARRED FOOD CRUST IN MN DATABASE.

Some dates do not have 13C/12C ratios. This plot examines the correlation between oldest charred foodcrust dates and unusually depressed 13C/12C isotope ratios (Hohman-Caine and Syms 2012). For dateswith reported 13C/12C ratios, all dates older than 2000 BP, except one, yielded 13C/12C isotope ratios moredepleted than -23.10, but the reverse it not true.

56

FIGURE 3. MULTIPLOT OF DATES FROM BRAINERD CULTURE SITES GROUPED BY MATERIALCLASS.

57

FIGURE 4. MULTIPLOT OF DATES FROM BRAINERD CULTURE SITES GROUPED BY SITE.

58

FIGURE 5. ALL CHARRED AND UNCHARRED BONE AMS RADIOCARBON SAMPLES,MINNESOTA.

59

FIGURE 6. SKETCH OF ROOT MASSES AND ABOVE-GROUND VEGETATION FOR TYPICAL PRAIRIE PLANTS (Natura N.D.).

60

APPENDICES

61

APPENDIX A. ALL AMS RADIOCARBON RESULTS FROM ARCHAEOLOGICAL SITES,MINNESOTA. (MICROSOFT ACCESS DOCUMENT).

62

APPENDIX B. CALIBRATIONS OF NEW AMS RADIOCARBON DATES RUN BY PALEORESEARCHINSTITUTE. (PDF DOCUMENT).

63

APPENDIX C. MULTIPLOTS OF EXISTING AMS RADIOCARBON RESULTS, MINNESOTA. (PDFDOCUMENT).

64

APPENDIX D. GIS MAPPED AMS RADIOCARBON RESULTS, MONTANA. (PDF DOCUMENT).

65

APPENDIX E. SUMMARY OF WORK DONE PRESENTED AT THE COUNCIL FOR MINNESOTAARCHAEOLOGY CONFERENCE, HELD IN ST. PAUL, FEBRUARY, 2017. (POWERPOINTDOCUMENT). “Minnesota – Land of 10,000 Lakes: Understanding Radiocarbon Dating against theBackdrop of Landscape and Glacial History”.

66

REFERENCES CITED

Ahler, Stanley A., Craig M. Johnson, Hebert Haas, and Georges Bonani2007 Radiocarbon Dating Results. In A Chronology of Middle Missouri Plains VillageSites, pp. 53-89. Smithsonian Contributions to Anthropology. vol. 47. SmithsonianInstitution Scholarly Press, Washington, D.C.

Alexandre, Anne, Jermone Balesdent, Patrick Cazevielle, Claire Chevassus-Rosset, PatrickSignoret, Jean-Charles Mazur, Araks Hartutuyunyan, Emmanuel Doelsch, Isabelle Basile-Doelsch, Helene Miche, and Guaciara M. Santos

2016 Direct Uptake of Organically Derived Carbon by Grass Roots and Allocation inLeaves and Phytoliths. Biogeosciences 13:1693-1703.

Bronk Ramsey, C., and S. Lee2013 Recent and Planned Developments of the Program OxCal. Radiocarbon 55(2-3):720-730.

Bronk Ramsey, Christopher2009 Bayesian Analysis of Radiocarbon Dates. Radiocarbon 51(1):337-360.

Carlquist, Sherwin2001 Comparative Wood Anatomy: Systematic, Ecological, and Evolutionary Aspectsof Dicotyledon Wood. 2nd ed. Springer Series in Wood Science. Springer, Berlin.

Chichester, C. O. (editor)1986 Advances in Food Research. 30. Academic Press, Boston.

Dean, Jeffrey S.1978 Independent Dating in Archaeological Analysis. In Advances in ArchaeologicalMethod and Theory, edited by Michael B. Schiffer, pp. 223-255. vol. 1. Academic Press,New York.

Gallagher, K. L., A. Alfonso-Garcia, J. Sanchez, E. O. Potma, and G. M. Santos2015 Plant Growth Conditions Alter Phytolith Carbon, Plant Physiol. Frontiers in PlantScience 6:753. doi: 10.3389/fpls.2015.00753.

Gulliksen, S., and E. M. Scott1995 Report of the TIRI Workshop. The 15th International Radiocarbon Conference.Radiocarbon 37(2):820-821.

Harrington, H. D.1972 Western Edible Wild Plants. The University of New Mexico Press, Albuquerque.

Hoadley, Bruce1990 Identifying Wood: Accurate Results with Simple Tools. The Taunton Press, Inc.,Newtown.

Hohman-Caine, Christine A., and E. Leigh Syms2012 The Age of Brainard Ceramics. Copies available from Soils Consulting.

67

Justice, Oren L., and Louis N. Bass1978 Principles and Practices of Seed Storage. Agriculture Handbook No. 219 506.United States Department of Agriculture, Agricultural Marketing Service, Washington,D.C.

Maillard, L. C.1912 Formation of Melanoidins in a Methodical Way. Compt. Rend. 154:66.

Martin, Alexander C., and William D. Barkley1961 Seed Identification Manual. University of California, Berkeley.

Minnis, Paul E.1981 Seeds in Archaeological Sites: Sources and Some Interpretive Problems.American Antiquity 46(1):143-152.

Musil, Albina F.1963 Identification of Crop and Weed Seeds. Agricultural Handbook no. 219. U.S.Department of Agriculture, Washington, D.C.

Natura, HeidiN.D. Root Systems of Prairie Plants. Conservation Research Institute.

Philippsen, Bente2015 Like a Fish Out of Water: Is Alces alces a Semi-Aquatic Animal? Paperpresented in the Socio-Environmental Dynamics Over the Last 12,000 YearsConference, March 24-27, 2015, Kiel University, Kiel, Germany.

Quick, Clarence R.1961 How Long Can a Seed Remain Alive? In Seeds, the Yearbook of Agriculture,edited by A. Stefferud, pp. 94-99. United States Department of Agriculture, Washington,D.C.

Reimer, P. J., E. Bard, A. Bayliss, J. W. Beck, P. G. Blackwell, C. B. Ramsey, C. E. Buck, H.Cheng, R. L. Edwards, M. Friedrich, P. M. Grootes, T. P. Guilderson, H. Haflidason, I. Hajdas,C. Hatte, T. J. Heaton, D. L. Hoffmann, A. G. Hogg, K. A. Hughen, K. F. Kaiser, B. Kromer, S.W. Manning, M. Niu, R. W. Reimer, D. A. Richards, E. M. Scott, J. R. Southon, R. A. Staff, C. S.M. Turney, and J. Van Der Plicht

2013 InterCal 13 and Marine 13 Radiocarbon Age Calibration Curves 0-50,000 YearsCal BP. Radiocarbon 55(4):1869-1887.

Reyerson, Paul E., Anne Alexandre, Araks Harutyunyan, Remi Corbineau, Hector A. MartinezDe La Torre, Franz Badeck, Luigi Cattivelli, and Guaciara M. Santos

2016 Unambiguous Evidence of Old Soil Carbon in Grass Biosilica Particles.Biogeosciences 13:1269-1286.

Roper, Donna C.2013 Evaluating the Reliability of AMS Dates on Food Residue on Pottery from theLate Prehistoric Central Plans of North America. Radiocarbon 55(1):151-162.

68

Santos, Guaciara M., Anne Alexandre, and Christine Prior2016 From Radiocarbon Analysis to Interpretation: A Comment on "PhytolithRadiocarbon Dating in Archaeological and Paleoecological Research: A Case Study ofPhytoliths from Modern Neotropical Plants and a Review of the Previous DatingEvidence", Journal of Archaeological Science (2015) doi: 10.1016/j.jas.2015.06.002.” byDolores R. Piperno. Journal of Archaeological Science 71:51-58.

Schopmeyer, C. S.1974 Seeds of Woody Plants in the United States. Agricultural Handbook No. 450.United States Department of Agriculture, Washington, D.C.

Schweingruber, Fritz Hans, Annett Borner, and Ernst-Detlef Schulze2011 Atlas of Stem Anatomy in Herbs, Shrubs and Trees Vol I. Springer-Verlag, BerlinHeidelberg.

2013 Atlas of Stem Anatomy in Herbs, Shrubs and Trees Vol. II. Springer-Verlag,Berlin Heidelberg.

Stafford Jr., Thomas W., Klaus Brendel, and Raymond C. Duhamel1988 Radiocarbon, 13C and 15N Analysis of Fossil Bone: Removal of Humates withXAD-2 Resin. Geochimica et Cosmochimica Acta 52(9):2257-2267.

Taylor, R. E., and Ofer Bar-Yosef (editors)2014 Radiocarbon Dating: An Archaeological Perspective. 2nd ed. Left Coast Press,Inc., Walnut Creek.

Telford, Richard J., E. Heegaard, and H. J. B. Birks2004 The Intercept is a Poor Estimate of a Calibrated Radiocarbon Age. The Holocene14(2):296-298.

Waters, Michael R., and Thomas W. Stafford, Jr.2007 Redefining the Age of Clovis: Implications for the Peopling of the Americas.Science 315:1122-1126.

Whyte, Thomas R.2001 Distinguishing Remains of Human Cremations from Burned Animal Bones.Journal of Field Archaeology 28(3/4):437-448.

69

investigating poorly known historic context: dating ... minnesotas prehistory pri fre s… · were...

Documents