Mammoth Remains Study in the Upper Missouri BasinAndy Baldus, Bob Russman, Ross Thornock

GEOS 330: Quaternary Geochronology, Spring 2011

Discussion and Introduction

•The isotope cycle of 14C is displayed in Figure 1(1).• Atmospheric concentration of 14C is considered constant and in equilibrium with live organisms•The (14C) isotopes decay rate per min per gram (dpm/g) is measured for the potential of the sample 14C to decay to 14N

•Standard method - count of beta particle dispersal •AMS (accelerated mass spectrometer) determines remaining mass•Analyzes the decayed organic assemblages of dead organisms

•Asymptotic relationship of decay rate versus the half-life time•Calculates in “years before present” (yr. BP – before 1950)•The standard time formula in Data section•After 1950 - Nuclear testing abnormally increased 14C production

•Calib602 program •Translates yr. BP to calibrated (or calendar – cal. yr. BP) years • Translates data using proxy master chronology.

References1 G. Rapp and C.L. Hill, Geoarchaeology: The Earth-Science Approach to

Archaeological Interpretation, Second Edition (2006), Yale University Press.2 Christopher L. Hill, Stratigraphic and geochronologic contexts of mammoth

(Mammuthus) and other Pleistocene fauna, Upper Missouri Basin (northern Great Plains and Rocky Mountains), U.S.A., Quaternary International 142–143 (2006) 87–106

 3 A. J. Stuart, P. A. Kosintsev, T. F. G. Higham & A. M. Lister, Pleistocene to Holocene extinction dynamics in giant deer and woolly mammoth, Nature | Vol 431 | 7 October 2004, pp. 684-689

 4 Caitlin E. Bucka, Edouard Bard, A calendar chronology for Pleistocene mammoth and horse extinction in North America based on Bayesian radiocarbon calibration, Quaternary Science Reviews 26 (2007) 2031–2035

 5 Michael Hofreiter, Adrian Lister, Mammoths, Current Biology Vol 16 No 10,R347-8 6 James Steele, Gustavo Politis, AMS 14C dating of early human occupation of

southern South America, Journal of Archaeological Science 36 (2009), 419–429. 7 Greenland ice-core stations: Camp Century, Dye-3, GRIP, GISP2, Renland and

NorthGRIP. J. Quaternry Science 16, pp. 299–307 (2001).

Conclusions

CalculationsCalculations:• Time = (0.8033 x (ln(Observed 14C value)/(Initial 14C)))-[yrm-1950])

• Initial 14C = initial atmospheric 14C activity = 13.56 dpm/g• Yrm = the year the data was observed and measured

• Half-life = 5568 year – half-life equals the time needed for half of the sample mass of isotopic 14C to decay.

Using 14C dating, this study analyzes Mammoth remains in the Upper Missouri Basin from sites in Montana and Wyoming. The data was culled from a paper by Christopher L. Hill(2), a professor at Boise State University. These prehistoric elephants (woolly Mammoths) were present in North America via migration across the land bridge(5). Their eventual extinction has been suggested by a number of sources as a result of their inability (possibly thru non-adaptability) to survive the warming interglacial periods, their loss of habitat, and their predation by humans (3)(4)

(5). Using 14C and other dating techniques, the Clovis culture presence in North America has been dated as early as 13,000 cal. Yr. BP(6)(4). Complimenting this data is a chart of the extinction and time line for mammoths in Europe and Siberia including the last mammoths on Wrangel Island, northeastern Siberia, about 4000 cal. yr. BP (fig. 2)(5). Figure 3 displays the AMS dating of the samples in cal. yr. BP displayed with a 2σ (2 sigma = 95% possibility of being in this range) value. Figure 4 shows the Greenland Core chronology with 18O values. The less negative the value indicates higher temperature (interglacial period)(1) (7).  

Figure 3. AMS 14C dates for Mammoth samples calibrated using Calib602 to 2-sigma (Leters/number coresponds to location/sample#. Ex: A1=Anzick site, sample 1)

Figure 4. Greenland Ice Core Data - 28K cal. yr. BP. 18O isotope(7). Higher del 18O correspond to interglacial periods and lower correspond to glacial periods.

Fig 1. 14C cycle of generation and decay(1) Fig 2. Extinction graph mammoths in Europe & Russia(5)

Radiocarbon (14C) Dating Process

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Results

Site results:Though the Natural trap cave samples do fit the mammoth habitation time period exhibited by the other sites they have very loose time constraints. Thus they are useful for indicating Mammoth presence but maybe not much else.

Time Gap?:Excluding samples N1-N5, we see a lack of data from ~15K to ~22K yrs BP. However, this doesn’t really correlate to a warm period which begs the question: Why aren’t they there? It could be that the Natural cave site data is more accurate than it appears. It could also be that this area experienced a warming trend not seen in Greenland. Or, there could simply be undiscovered mammoth remains in the area just begging to fill in the time gap. The truth is unapparent at this time to us.

Mammoth habitation period coincides with glacial periods:Mammoths were present during cooler glacial periods as suggested by the ice core data(fig.4) and the span of calibrated ages: ~25K to ~11K cal. yr. BP. Non-adaptability to the warming trend may have led to extinction of mammoths as well(3)(4)(5).

Mammoth disappearance is coincident with earliest Clovis dates: The disappearance of mammoths in this area coincides and slightly

overlaps the earliest recorded Clovis dates. The of Clovis culture may have added to the decline of the Mammoth in this area(3)(4)(5). .

Mammoth results1. Mammoth dates range from ~25K to ~11K cal. Yr. BP (Calib602 data)2. Clovis dates begin at 13,000 cal. yr. BP(6)(4)

3. Bolling Warming trend at ~14,000(4)and later one after Younger Dryas glacial period at ~11,000 cal. yr. BP (fig.4)

Site results1. For multiple samples sites, sites share tight time spans (2000 yr spans,

error included) except the Natural trap cave site (13 Kyr)(fig.5)2. Samples group around 13,000 and 23,000 cal. yr. BP(excluding Natural

trap cave samples) (Calib602 data)

Site Natural Trap Cave Deer Creek Mammoth Blacktail Cave Anzick

time span (yrs) 12845 1487 1576 2029

Fig 5. Age range of samples from sites with multiple samples (first letter of site name corresponds to sample name)