The Pennsylvania State University

The Graduate School

College of Earth and Mineral Sciences

STRATIGRAPHY AND PALEOENVIRONMENTS OF THE RED

HILL SITE NEAR HYNER, PENNSYLVANIA

A Thesis in

Geoscience

by

Daniel Adam Peterson

© 2010 Daniel Adam Peterson

Submitted in Partial Fulfillment of the Requirements

for the Degree of

Master of Science

May 2010

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The thesis of Daniel Adam Peterson was reviewed and approved* by the following: Mark E. Patzkowsky Associate Professor of Geosciences Thesis Advisor Rudy L. Slingerland Professor of Geology Russell W. Graham Associate Professor of Geosciences Earth and Mineral Sciences Museum Director Katherine H. Freeman Professor of Geosciences Associate Department Head of Graduate Programs

*Signatures are on file in the Graduate School

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ABSTRACT

The Red Hill outcrop on Route 120 near Hyner, Pennsylvania, consists of repeating cycles of

mostly fining-upward facies ranging from siltstones and lower fine massive sandstones at the base

of the cycles to mudstones near the top of each cycle. In the readily accessible portions of the

outcrop, a wide variety of vertebrate and plant material can be found. Vertebrates recognized from

Red Hill include various fishes (placoderms, chondrychthyans, acanthodians, actinopterygians, and

sarcopterygians) as well as two early tetrapods first identified at this site (Hynerpeton bassetti and

Designathus rowei). Strata at Red Hill appear cyclical and are interpreted to represent two stages of

fluvial deposition. Stage I avulsive deposits include crevasse-splay sandstone bodies and sandy

siltstone channel fills, overlain by the fossiliferous siltstones and interbedded erosional-based

sandstones. These beds are overlain by simple paleosol packages that indicate Stage II avulsive

deposition. High sedimentation rates on the Catskill Delta combined with regularly avulsing fluvial

systems likely led not only to an excellent taphonomic setting for preserving early tetrapods, large

freshwater fish, and a variety of other fossil material, but also created a highly dynamic

environment in which these organisms were interacting and evolving.

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TABLE OF CONTENTS

List of Figures...................................................................................................................................... v

List of Tables….................................................................................................................................. vi

Acknowledgements………………………………………………………………………..………. vii

Introduction……………………………………………………………………………………...….. 1

Geologic Setting…………………………………………………………………………………….. 2 Appalachian Basin and Acadian Orogeny…………………………………..…………..….....… 2 Catskill Delta……………………………………………………………………………………. 4 Red Hill…………………………………………………………………………………………. 4

Methods……………………………………………………………………………………...……... 6

Data………………………….…………………………………………………..………...…....…... 9 Lithologic descriptions…..…………..…….………………………………………..………....... 9 Facies proportions…………………………………………………………………....………... 12 Sand body geometry……..…………………………………………………………….……..... 12 Results of fossil material survey……..………………………………………………………... 16

Discussion…………………………………………………………….………………………...…. 16 Evidence for avulsive processes…………………...……………………………...……….…... 16 Further avulsion studies…………………………………………………………...…….……... 22 Circumstantial evidence supporting an avulsion model…………………………….……...….. 23 Significance for alluvial packages in the geologic record, early tetrapod evolution, and fossil prospecting…………………………………………………………………………………….. 24 Possible limitations of the Red Hill and further work………………………..…………..……. 29

Conclusion…………………………………………………………….…………………………… 30

Works Cited……………………………………………………….……………………....…….…. 32

Appendix A – Fossil sampling location data……………….………….………….………...……... 36

Appendix B – Individual fossil data………………….………………….………………….….….. 37

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LIST OF FIGURES

Figure 1. Late Devonian (363 Mya). After Clack, 2002…...……………………………………… 3

Figure 2. Block diagram showing Acadian Mountains, Catskill Delta and Appalachian Basin….... 5

Figure 3. Pennsylvania map showing Red Hill outcrop………………………………………..…... 6

Figure 4. Photomosaic of outcrop with seven measured sections………...….………..………….. 13

Figure 5. Flat-based sandstone (facies F)…………………………………….……………....…… 15

Figure 6. Schematic model of Saskatchewan avulsion belt……………………………………..... 19

Figure 7. Cross section of avulsive sediments…………………………………………….……..... 19

Figure 8. Aerial photo of a trunk channel and crevasse splay in Saskatchewan………..………… 21

Figure 9. Aerial photo of Saskatchewan floodplain during avulsion……………………………... 22

Figure 10. Correlated sections showing lithofacies and avulsive interpretation ………………..... 26

Figure 11. Photomosaic and drawing of Stage I and Stage II at Red Hill………………………… 27

Figure 12. Schematic model of Stage I and Stage II deposits…………………………………….. 28

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LIST OF TABLES

Table 1. Facies of lower portion of Red Hill outcrop……………………………………………... 14

Descriptions of color, texture, geometry, internal structure, contacts, and fossil material found in

the accessible lower portion of the Red Hill outcrop

Table 2. Interpretation of paleoenvironments………………………………………………….…. 25

Descriptions of facies placed in interpretive paleoenvironmental context

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ACKNOWLEDGMENTS

I would like to thank Mark Patzkowsky for helping me through the rough periods and guiding me

toward completion. I would like to thank my other committee members, Rudy Slingerland and

Russell Graham for their continued support and advice throughout the data-gathering and writing

process. I am extremely appreciative for the help of Doug Rowe, the Red Hill site curator, who was

on site nearly every day that I was, and who was an invaluable source of information on fossil

locations and identifications at the outcrop. I would like to thank Ted Daeschler and Walt Cressler

for talking over their thoughts on the site and my research with me. Thanks also to everyone at

Penn State who helped with my learning process including, but certainly not limited to, Doug

Edmonds, Zachary Krug, Jocelyn Sessa, James Bonelli, Matthew O’Donnell, Ellen Currano, Peter

Flemings, and Peter Wilf. I would like to thank Ray Rogers, my advisor and friend at Macalester

College who often had a useful bit of advice to help get me through. And most of all, I would like

to thank my parents Mark and Julie Peterson and my sister Leah Peterson for loving, supporting and

advising me through all my trials and endeavors.

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Introduction

The nature of the Late Devonian world into which the earliest tetrapods crawled is of great interest

in evolutionary studies. Even so, there is still no consensus as to the environments in which

tetrapods first evolved or the evolutionary impetus for leaving their aquatic habitats and venturing

onto land. In the early part of last century, Alfred Romer hypothesized that the basins of the Old

Red Sandstone continent were characterized by regularly occurring semi-arid seasons that

pressured the first tetrapods to migrate from drying pools to wetter, more permanent ones (1933).

The theory was widely accepted and was consistent with the general idea that redbeds are a strong

indictaor of dry spells that would account for such behavior. Inger (1957) cited several studies

showing that contemporary red soil beds form almost exclusively in warm, humid, rainforest-like

conditions, often lacking any dry season or semi-arid conditions. He suggested that terrestrial

conditions in the Late Devonian were likely far more hospitable to aquatic animals than Romer had

envisioned. Orton (1954) suggested that tetrapod limbs were not, at least initially, adapted as a

means of locomotion on land at all. Rather, these robust limbs were used to dig into the mud to

stay cool and moist during estivation. However, certain living lungfishes (close relatives of the

early tetrapods) commonly burrow into the mud with limbs distinctly dissimilar to those of early

tetrapods (Clack 2002). Moreover, this leaves unanswered the question of why early tetrapods

eventually became terrestrial, and what those paleoenvironments looked like.

The oldest tetrapods currently known are Obruchevichthys and Elginerpeton from the Frasnian of

Latvia and Russia (Ahlberg 1995). Both were described over a century ago, but have only recently

been classified as tetrapods (Ahlberg 1995). There is still some debate as to whether

Obruchevichthys falls within or just outside of the tetrapod clade (Ahlberg 1995; Clack 2002).

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These earliest tetrapods are followed in the Famennian by Acanthostega, Ichthyostega, Designathus

and Hynerpeton, the last of which was discovered at the Red Hill locality near Hyner, PA (Clack

2002.) More recently, Tiktaalik, a transitional organism between the Sarcopterygians (lobe-finned

fish) and tetrapods, was described in meandering stream facies from the early and middle Frasnian

of Ellesmere Island, Nunavut, Canada (Daeschler et al. 2006).

Initial paleoenvironmental descriptions of Red Hill were made as vertebrate material was being

discovered. These interpretations combined the general overview of the environments present on

the Late Devonian Catskill Delta with specific observations of the fossil-bearing beds (e.g.

Daeschler, et al. 1994; Woodrow, et al. 1995; Daeschler 2000a, b). The prevailing interpretation of

paleoenvironments at Red Hill describes the lateral migration of a large broad river channel with

seasonal drying of the proximal floodplain (Woodrow et al. 1995). This interpretation of Red Hill

supports the general notion that early tetrapod environments were seasonally dry in this and other

previously described locations, but does not necessarily support the evolutionary model set forth by

Romer. This paper aims to examine in greater detail the sedimentary beds that contain fossils of

Hynerpeton and Designathus roweii as well as a host of lungfishes, sharks, plants and charcoal, and

to provide a model for the depositional environments typical of the Hyner Late Devonian tetrapod

fossil bed.

Geologic Setting

Appalachian Basin and Acadian Orogeny

The Old Red Sandstone continent, given its name for the abundance of red-colored sediments

deposited there, was fully assembled by the end of the Devonian and consisted of Baltica,

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Figure 1 – Paleogeography during the Late Devonian (363 Mya). After Clack, 2002.

Armorica, and Laurentia (Woodrow 1985). Just prior to the onset of the Acadian orogeny, the

Appalachian basin was an underfilled foreland basin that had been subsiding since the Late

Precambrian (Faill 1985). The Catskill Sea filled the basin and was separated from the world ocean

by the Appalachian peninsula to the south and east. It joined the world ocean to the southwest and

west, though it is likely that interaction was limited by an archipelago (Woodrow 1985). The

northward extent of the Catskill Sea is inferred based on the occurrence of evaporites in what is

now Hudson Bay, suggesting a saline bay at least this far north (Woodrow 1985). During the Early

and Middle Devonian, the Appalachian basin experienced very little subsidence. As this Acadian

orogenic event proceeded, the foreland basin underwent rapid subsidence, most significantly in the

eastern portion in what is now Pennsylvania and New York (Faill 1997b). Specifically, estimates

indicate that the subsidence rate at the Hyner locality in Clinton County, Pennsylvania increased

from 5-10m/MY during the Early Devonian, to 25-50m/MY during the Middle Devonian, up to

150-175m/MY during the Late Devonian (Faill 1985).

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Catskill Delta

The term “Catskill Delta” is generally used to describe the terrigenous sediments deposited in the

rapidly subsiding Appalachian Basin during the Middle and Late Devonian, though it is apparent

that not just one, but numerous river systems fed the basin with sediments from the South and East

during this time (Sevon 1985; Faill 1987b). The Catskill Formation has been interpreted to

comprise facies ranging from immature braided stream depositional systems in the east (Sevon

1985) to turbidite deposits in the west (Lundegard, et al. 1985). Non-marine fluvial facies of New

York and Pennsylvania, relevant to the present study, comprise grey channel sand bodies and grey

to red siltstone and mudstone packages with thin (meter-scale or thinner) sandstone strata (Bridge

2000). Rivers on the lower (northwestern) portion Catskill Delta nearer to the inland sea were

sinuous and migrated laterally across alluvial plains (Gordon and Bridge 1987). Levees (and

possibly proximal floodplains) hosted Archaeopteris forests, while lycopsids populated wetland

and lakeshore sediments (Cressler 1999). Figure 2 depicts the paleogeography of the Catskill Delta

of Pennsylvania in the Late Devonian.

Red Hill

The Red Hill outcrop in Clinton County, near Hyner, Pennsylvania on Route 120 (see Figure 3 for

map), is of special interest within the Catskill Delta. The outcrop consists of a roadcut

approximately 1km long and contains very fine grey and reddish brown sandstone bodies

surrounded by red, green and brown siltstones and mudstones. The discoveries of some of the

earliest known amphibians in North America as well as a variety of fish and plant fossils have made

the Red Hill outcrop an important study area.

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Figure 2 – Block diagram showing Acadian Mountains, Catskill Delta, and Appalachian Basin of the present-day mid-Atlantic

region of North America. (After Slingerland et al. 1989)

The rocks here belong to the uppermost member of the Catskill Formation, the Duncannon Member

(Woodrow, et al. 1995). Based on a palynological study of the outcrop, the rocks at Red Hill occur

in the upper Fa2c part of the Upper Famennian stage of the upper Devonian (Traverse 2003). In

one previous published analysis of the site, four lithofacies were described and briefly interpreted:

red hackly-weathering mudstone, red pedogenic-mudstone, greenish-gray mudstone and very fine

grained sandstone, and flat-laminated gray sandstone (Woodrow, et al. 1995). The descriptions of

these facies are elaborated upon in the present study.

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Figure 3 – Pennsylvania map showing location of Red Hill outcrop near Hyner along PA Route 120. Eastern end of site is located at

a lat.-long. of 41 20’11.81”N and 77 39'29.45"W. Numbers indicate Interstate 80, US Route 220, and PA Routes 120 and 144.

Methods

Prior to examining the Red Hill outcrop in detail and measuring section, photographs were taken of

the entire length of the outcrop with the eventual goal of stitching together a panorama view of Red

Hill. This panorama could then be used to follow individual beds and contacts from one end to the

other and to show large scale geometries of the outcrop as a whole.

Starting at the eastern end of the outcrop, a digital photograph was taken of the base – the

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accessible portion -- of the outcrop. Moving west after each photograph, an adjacent photograph

was taken, with approximately one third of the frame overlapping with the previous frame. This

yielded overlapping photos showing the entire fossil-bearing zone.

The photos were processed using Adobe Photoshop in order to stitch them together in a reasonably

accurate way. Each photo required adjustment due to perspective before two adjacent photos could

be stitched together. Because of the photographer’s perspective at ground level, parallel vertical

lines converged towards the top of each photo, making it necessary to stretch the upper portion of

each photo in order to eliminate overlapping errors. The photos could then be stitched together

with reasonable accuracy by lining up easily recognizable features in the overlapping portions. The

final product consisted of several long scrolls containing a panoramic view of the outcrop. The

results of this process can be seen in Figures 4, 5, and 10.

The photomosaic aided in performing more detailed analyses of the outcrop, including measuring

section and locating important sand bodies, channel fills, and previous fossil quarries. Measured

sections were chosen to overlap with units previously described by Woodrow, et al. (1995), include

the well-known fossil localities, and to depict the key lithologic features and changes that

characterize the fossiliferous portions of the outcrop. Sections were measured at a centimeter scale

using a Jacob staff and Brunton compass. Contacts between facies were marked on the

photomosaic and typical samples from each facies were collected for further analysis in the lab.

For each facies, the following data were collected when possible: grain-size, sorting, shape and

roundness, color, reaction to hydrochloric acid, sedimentary structures, geometry of beds and units,

nature of the contacts between beds and units, as well as any fossil material that was present. In

cases where a hand lens was insufficient to determine certain characteristics, samples were

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examined in the lab under a binocular microscope.

Seven detailed sections were measured, drawn, and correlated with the photomosaic. Figure 4

shows where each section is located in the outcrop. Locations for sections were chosen based on

the safety and accessibility of the outcrop in various places. The Red Hill outcrop consists of

alternating ledges, slopes, and cliff faces that hinder an investigator’s ability to reach portions more

than about 8-10 meters above the base. An attempt was made to reach the upper portions using a

safety rope and climbing equipment, but this method was deemed unfeasible for covering the span

of the outcrop. Thus, sections are limited to the lower (known fossil-bearing) portions of the

outcrop. Beds and units between the measured sections were interpolated in Figure 10. Vertical

measures were taken in numerous additional locations. This facilitated more accurate placement of

non-tabular sand bodies between measured sections.

Fossil distributions in the fossiliferous horizons were determined by fossil counts using a square

wooden frame measuring 0.5 m by 0.5m divided with string into four quadrants labeled A, B, C

and D respectively, moving clockwise from top left to bottom left. Choosing random locations to

sample in an outcrop with limited accessibility proved to be a challenge. Counts were made at each

of the measured sections, with further counts being made between sections. Each location is

approximately 15 m apart, though this varies based on accessibility. At each location, the frame

was placed at two vertical locations within the fossil-bearing zone, one approximately 1 m above

the base and the other 0.5 m below the upper contact with the paleosol. Each location was plotted

on the cross-section diagram and was described based on its vertical location in the outcrop. The

strike of the outcrop was taken at each location in order to determine any patterns of directional

bias on the outcropping of fossils. When possible, a count was made from one location in the

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overlying paleosol. Each count consisted of a tally and description of all fossils measuring more

than 2 mm in any dimension. Dip angle, dip direction, and trend were also recorded for these

fossils, when applicable. Description of each fossil includes the dimensions of the portion visible

in the outcrop, the nature of the fossil material, when possible, as well as the orientation within the

bed and the nature and its relationship to other fossils within that bed (i.e. ‘concentration of bone

fragments within a cut-and-fill feature 20 cm deep and 1 m wide.’) An approximate count was then

taken of all fragments that were smaller than 2 mm in all dimensions. Photos were taken of each

location, and were often taken of individual quadrants as well as individual fossil deposits and

fossils.

Data

Lithologic Descriptions

In the lower, fossiliferous portion of the outcrop, centimeter-scale changes in lithology were

grouped into lithologic facies comprising decimeter- and meter-scale packages, some of which

appear to repeat themselves in the less accessible portions of the outcrop just above. Refer to

Figure 4 for section-specific descriptions

Facies A: Facies A consists of brownish red silty very fine sandstone. It exhibits moderate

bioturbation, which obscures most bedding. The thickness of the facies varies across the eastern

portion of the outcrop at its base. Geometry of the facies is difficult to determine, since its base is

generally below ground level and the entire facies dives below ground level to the west. Facies A

is a cliff-former. At the base of sections 2, 5, 6, and 7, it grades upwards into a red shale (facies B).

In sections 4, 5, 6, and 7, beds of Facies A are overlain by a sharper contact with a red, bioturbated

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clay layer (facies C).

Facies B: Facies B consists of lens-shaped packages of red silty clay shale that interfinger with,

and pinch out into facies A. It is a slope-former and is often difficult to observe because it is

typically covered with colluvium and vegetation. Facies B has a gradational lower contact with the

coarser-grained beds of facies A and is overlain by sharp contacts with facies A above. It also seen

overlying facies H in sections 2-7.

Facies C: Facies C consists of red, silty clay and exhibits some mottling and green sandstone

stringers. It appears to be bioturbated and has none of the shaly parting of facies B. It pinches out

to the west, but it is difficult to follow eastward due to colluvium and vegetation cover. It appears

to be similar to facies H, though slickensides are not easily recognizable in facies C. This may also

be due to the covered state of the beds. Facies C grades upwards into red clay shale (facies D).

Facies D: Facies D consists of red and light green clay shale. It is tabular, eventually pinching out

to the east and west. Approximately the top 30 cm of facies D is light green in color. This facies

contains some plant material and charcoal from early wildfires (Cressler 1999; 2001). In section 6,

facies D grades upwards into green siltstone (facies E). In sections 4 and 5 it is overlain by a sharp

contact with a grey sandstone body (facies F).

Facies E: Facies E consists of light to dark green flat-laminated siltstone with some very fine sand.

The siltstone interfingers with beds of sandstone. It contains abundant plant material and charcoal.

It is also the facies in which Hynerpeton was first discovered (refer to Figure 10). Facies E is

measured in sections 3 and 6 and is overlain by a gradational contact with a brownish red

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fossiliferous siltstone (facies G).

Facies F: Facies F consists of resistant cliff-forming beds of very fine sandstone that can be

followed varying distances before thinning and pinching out at their margins. Planar cross-bedding

is often visible on fresh surfaces. It is mostly planar in form, with several striking exceptions,

ranging in thickness from less than 10cm to about 150cm. In the lowest layer of facies F seen at

Red Hill (sections 5 and 7), there is a noticeable portion of positive relief. In the next layer of

facies F (near section 1), the basal contact exhibits a significant cut-and-fill feature extending down

into facies I below – the largest of its kind seen at the outcrop. Facies F does not appear to be

present in again until very near the top of the outcrop. When present, facies F is overlain by a sharp

contact with facies G. In places, it also appears laterally to and interfingers with facies G.

Facies G: This facies comprises the major fossil-bearing zone of the Red Hill outcrop. It consists

of siltstones with cyclical, thin very fine sandstone beds often forming cut-and-fill features.

Bedding is visible throughout at thicknesses of between two and five centimeters, with planar

cross-bedding apparent in a few locations. Bedding is occasionally disturbed by root traces and

small burrows (~2cm in diameter). Much of the Red Hill fossil material is found in lag deposits

along bedding as well as in small pockets within finer-grained material in facies G.

Facies H: Facies H consists of red, hackly weathered, massive mudstones with slickenside

surfaces forming slopes at several levels in the outcrop. It is measured in all seven sections and

occurs twice in section 1. Identification of similar slope-forming layers in inaccessible portions of

the outcrop is quite easy. Verification of lithology, however, is made difficult by the debris and

vegetation cover of these beds. In the lower portions of the outcrop, these layers consist mostly of

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clay-sized particles with a small amount of silt. Very fine sandstone stringers are often present

within muddy portions of facies H. Caliche nodules about one centimeter in diameter are visible

throughout the facies. Root traces are common in facies H and appear as tapered vertical forms,

often made up of reduced light green silts against the red oxidized sediments. The top of this

facies may exhibit some shaly bedding. The upper contact is slightly undulating and is generally

overlain be facies B.

Facies proportions

Facies G makes up the largest portion of the measured sections, composing approximately one third

of each section. Facies H is the second most abundant facies, composing around 15-20% of each

section. Facies B composes 5-10% of each section, with better representation in sections 5 and 7.

Facies A, C, E, and F are not found in every section and each represent about 5-10% of the sections

in which they are found.

Sand Body Geometry

The geometries of sand bodies in the Red Hill outcrop are of particular interest in interpreting the

nature of the depositional environments. The sandstone beds in the eastern portion of the outcrop

are composed of facies F. The flat base of the lowest bed of facies F (Figure 4: sections 5 and 7),

when traced across the outcrop, coincides with the base of the vertebrate fossil-bearing zone

defined by Woodrow, et al. (1995). These beds are pictured in Figure 5.

At the easternmost end of the exposure, the basal sand body comprises the lower two meters of the

fossil-bearing zone. Here, a thin layer of siltstone separates two beds of sandstone. Decimeter-

scale planar cross-bedding is visible in a few locations. The body is wedge-shaped, thinning

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Figure 4 – Photomosaic of outcrop with seven sections (1-7) in their horizontal locations below. Each section’s base is

approximately at road level.

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Facies Color, etc Texture Form / Geometry Sedimentary Structures Contacts Fossils

A

Brownish red

V.f.l sand to silt

Wedge or planar; thickness varies across lowest portion of outcrop; cliff-former

Moderately bioturbated, minimal visible bedding

Grades into shale in places; sharper contact with bioturbated clay in others

None visible

B

Red Silty clay Lens; thins until disappearing in facies A

Shaly Gradational lower contacts, sharper upper contacts

None visible

C

Red Silty clay Wedge or lens; pinches out to west, geometry unclear to east

Mottled; very bioturbated, not shaly; green stringers of v.f.l. sand to silt (coloration may to be secondary)

Gradual upper contact None visible

D

Red; light green

Clay Lens; thins in both directions

Shaly; ~3dm at top is light green (likely secondary)

Overlain by gray sandstone with sharp contact in places; elsewhere grades into green siltstone

Some plant material, charcoal

E

Light to dark green with some dark red

Silt with some v.f.l-v.f.u sand

Lens; varies locally in thickness from 35cm at max thinning until absent in both directions

Alternates between bioturbated siltstone and v.f.l.-v.f.u. sandstone

Lower contact marked by sharp increase in grain size; overlain by brownish red fossiliferous siltstone

Abundant plant material and charcoal

F

Grey V.f.l. sandstone

Wedge; thins until dis-appearing at various locations; locally also outcrops as a large lens as well as a ~1m- thick positive-relief structure

Cross-bedding visible in a few places; possibly obscured by weathering and water-staining on some surfaces

Sharp lower and upper contacts

None visible

G

Brownish red

Silt, some v.f.l. sand

Planar and tabular, thickness does not vary greatly over visible extent of facies

Bedding at 2-5cm scale marked by 2-10mm coarse green vfl sand at base, overlain by silty, less weathered beds, overlain by finer-grained, more weathered beds; many shallow cut-and-fills carved into underlying beds; planar X-bedding visible in some beds; occasional burrows ~2cm in diam.

Sharp lower contact with Facies F; fairly sharp upper contact with 8-10 cm of transitional shaly siltstone in places

Small bone beds and individual deposits yield nearly all animal material found at the site including scales, spines, plates, bone, teeth, as well as apparent lungfish burrows (Rowe 2006) and some root traces

H

Dark red Mudstone with some silt

Hackly weathering distorts any bedding; several intervals of light green vfl sandstone; large slickenside surfaces; cm-scale caliche nodules; shaly parting in upper 8cm

Sharp, undulating upper contact

None visible

Table 1 – Descriptions of facies of fossil-bearing zone

15

gradually to the west until it is completely absent from the section for about 86 meters. At that

location on the same horizon, a flat-based convex-up sand body becomes traceable when its

thickness is about 5cm. This body thickens steadily to a maximum of about 100cm before thinning

again farther to the west. This portion of the sandy body stretches about 16m from east to west,

with the middle 5m containing the thickest portion. Once it pinches out to the west, it is not seen

again before the horizon dives below road level.

Above these sand bodies lies a fining-upward sequence of sediments, which is in turn overlain by a

second localized sand body approximately 80m farther west. This body appears as an obvious cut-

and fill feature – one of many in this sediment package, but by far the largest. Measuring

approximately 30m across and 1.5-2m deep, it is quite visible up close and from a distance. This

feature appears to have carved down through facies B. Figure 6 displays the overall context of sand

bodies and cut-and-fill features.

Figure 5 – Flat-based sandstone (facies F) at eastern end of Red Hill outcrop

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Results of Fossil Material Survey

Approximately 750 fossils and fossil fragments were counted from 34 locations throughout the

study area, covering facies G, H, and I. Refer to Appendix A for fossil sampling locations and total

fossil counts at each location. Detailed observations were made on 87 fossils with at least one

visible dimension exceeding 2 mm. Refer to Appendix B for data on individual fossils. A survey

of the fossil material found within the major known fossil-bearing zone revealed several large-scale

patterns and some finer-scale observations. Most obviously, all animal fossil material observed in

the survey was found in the lower portions of facies G. Fossil material was observed and tallied in

9 out of 17 sample sites from facies G, with fossil counts ranging from 1 to approximately 400. It

should be noted that although fossils were occasionally observed outside of sampling areas in the

upper portion of facies G, none fell within the random sampling grids. In contrast to facies G, none

of the 12 sample sites from facies H yielded any fossil material. Likewise four samples taken from

the overlying facies I (distal splay) and one sample from the upper portion of an overlying bed of

facies H yielded no fossil material. Constraints on accessibility to upper portions of the outcrop

prevented further investigation into these beds, though these general patterns appeared to hold true

at least throughout the lowest five to seven meters of the outcrop.

Discussion

Evidence for Avulsive Processes

The patterns of deposition in the fossiliferous zone of Red Hill are consistent with well known

modern avulsion sites such as the Cumberland Marshes in Saskatchewan, Canada (Smith, et al.

1989). Crevasse splays in the Saskatchewan breakout area (Figure 6) have caused most of the

regional aggradation that has occurred since the initial levee breach in 1873 (Smith, et al. 1989).

17

Avulsions can be described in terms of two stages. Stage I begins when flow is diverted from the

trunk channel. Depositional packages that form within the avulsion belt during Stage I include

progradational crevasse-splay sands, crevasse-splay complex silts, interchannel wetland silts and

muds, abandoned channel fills, and channel sands from the constant carving of new minor channels

into the other deposits mentioned. Stage I ends and Stage II begins when flow diverts back into the

previous trunk channel, or when a new channel begins to handle the entirety of flow. Depositional

packages that form within the avulsion belt during Stage II resemble typical floodplain deposits of

slowly accumulating clays and possibly organics. Stage II deposition also includes the main

channel sands. Several recent studies conclude that an avulsive system cycles through these two

systems with a typical period on the order of 1000 years (Smith et al. 1989; Slingerland and Smith

2004).

Stage I deposits consist of sediments deposited by expanding flows and typically exhibit

depositional basal contacts with the existing substrate below. Wide and shallow channels are often

incised into the splay deposits. Regular reworking of sediment, increased channelization, and

coalescing of Stage I splays are common features during this portion of an avulsion. These

sedimentary packages accumulate at relatively high rates. At the Red Hill locality, Facies D, E, F,

and G are interpreted as Stage I deposits. Stage II deposits consist of overbank floodplain

deposition occurring during periods of normal flooding which does not involve diverting the flow

of the trunk channel. At the Red Hill locality, paleosols and a few shales (Facies A, B, C, and H)

are interpreted as Stage II deposits. (Table 2 gives descriptions and interpretations of each facies.)

Figure 6 depicts a crevasse splay complex prograding downstream before eventually being

abandoned. Figure 7 depicts a cross-section of the avulsion belt. The avulsive cycle and its

18

associated sediments consist of everything above the existing floodplain surface (the black bed at

the base of the section) up through the next floodplain surface that forms after the channel is

stabilized. Avulsion sediments are dominated by fine-grained material – silts, clays, shales -- with

flat-based, laterally restricted sandstone bodies as well as cut-and-fill sandstone features that scour

out existing beds located proximal to the node of avulsion and at points of high energy flow in the

avulsion belt. This model closely matches beds observed at Red Hill. Near the base of the

correlated section in Figure 10, there is a series of fine-grained silt and clay beds capped by a

paleosol. This bed is interpreted as an ancient floodplain surface. This surface is overlain by shale

in the western portion. This shale is interpreted as a shallow floodplain lake, ponded against a

previous levee or other topographic high. An aerial view of the Cumberland Marshes shows this to

be a common occurrence. Figure 8 shows how such lakes form as flow is redirected from a trunk

channel through a crevasse splay, out onto the floodplain. The shales that correspond to this mode

of deposition at Red Hill are Facies D, and they contain abundant plant material and charcoal,

likely originating on nearby floodplain levees. Facies D is laterally restricted and is not seen farther

west.

As the initial crevasse splay progrades out onto the floodplain and down-slope, beds of sandy

siltstone and sandstone are deposited. The flat-based, positive-relief sand body (Facies F) in the

middle of the correlated section (Figure 10) is interpreted as a crevasse-splay bar deposit. To both

the east and west of this feature are scoured channels in-filled with light to dark green sandy

siltstone (Facies E). These beds contain abundant plant and material as well as the main articulated

vertebrate fossils. At the eastern end of the outcrop, there is a flat-based sandstone wedge that

pinches out to the west (see Figure 5 for photo). All of these coarse-grained beds occur in

approximately the same horizon. Surrounding them are shaly flood basin deposits (Facies D) and

19

silty, reworked, highly fossiliferous beds (Facies G) containing thin sandstone stringers and

abundant cut-and-fill features. This set of facies looks remarkably similar to the cross-section of

the Cumberland Marsh (Figure 7). Above this package, a paleosol (Facies H) has formed. This is

interpreted as a period during which the avulsion belt has been abandoned and flow has been

Figure 6 – Schematic model of Saskatchewan avulsion belt. (I) shows an avulsive complex prograding downstream during Stage I

of an avulsion. (II) shows the avulsion belt during Stage II, after a new trunk channel has stabilized (After Smith et al.1989).

Figure 7 – Cross-section of avulsive cycle sediments after a new trunk channel has formed. Points X and Y refer to Figure 6 (Smith

1989).

20

consolidated in one new channel. The top of this paleosol marks the top of the first major avulsive

cycle seen at Red Hill. In Figure 10, this package is marked by two bold lines running through the

correlated section. A similar avulsive cycle is seen in Figure 7. Above this package, another shale

(Facies I) is overlain by another flat-based and cut-and-filled sandstone (Facies F). This appears to

be the beginning of another avulsive cycle, though only the westernmost section could be measured

through its entire thickness.

It appears that these avulsive cycles are repeated two more times immediately above the two

measured cycles, but reaching this portion of the outcrop is too dangerous without safety

equipment, and was not measured for this study. Figure 11 depicts interpreted Stage I and Stage II

deposits up through the outcrop. (Figure 11 is similar to a schematic model presented by

Slingerland and Smith (2004) and depicted in Figure 12.) Facies are inferred at these heights based

on apparent grain size and resistance to weathering. If they are indeed avulsive cycles, it appears

they are progressively thinner up section, suggesting Red Hill is farther from the node of avulsion

during each successive cycle. This can be seen in Figure 11, along with the major features of the

lowermost cycles. There is one wedge-shaped cliff-forming sand body visible from road-level near

the top of the outcrop, as well as a large multi-storeyed channel body that forms a cliff tens of

meters thick in the far western portion of the outcrop. This trunk channel may be the result of one

the avulsive cycles, though further investigation would be necessary to make such a claim. Upper

portions of the outcrop cannot be accessed without special equipment. It is possible to access these

areas using climbing equipment and safety rope harnessed to trees at the apex of the hill, but this

method inhibits lateral movement along the outcrop. However, with sufficient time and

21

Figure 8 – Aerial photo of Saskatchewan breakout area. A breached levee has allowed the crevasse channel to partially divert flow from the trunk channel to the surrounding floodplain. In this case, a lake has ponded against a pre-existing levee (Slingerland and Smith 2004).

assistance, it may be feasible to continue this study on the upper portions of Red Hill.

Simple paleosol packages may be a recognizable trait of avulsive deposits in alluvial deposits.

These packages consist of slightly pedogenically modified fine-grained sediments and essentially

unmodified ribbon and sheet sandstone bodies with some cut-and-fill features (Kraus 1996). The

mudrocks generally show some evidence of slight pedogenesis including occasional mottling, often

associated with root traces, and slickensides typical of the shrinking and swelling of fine-grained

sediments exposed to a seasonal wet-dry climate. Individual horizons are rarely identifiable,

indicating that soil formation was impeded by high rates of sedimentation (Kraus 1996). Pedogenic

slickensides are easily recognizable in the simple paleosols of the Red Hill outcrop. They are

visible as smooth, slightly curved surfaces in the clay layers and, and they form many of the angled

ledges seen throughout the outcrop.

22

Figure 9 – Aerial photo of Saskatchewan breakout area. The floodplain eventually becomes tiled with ponds and island bordered by stream levees (Slingerland and Smith 2004). .

It is also possible to deduce where on the floodplain various packages of mudrocks were found

based on variations in matrix and mottling colors. These variations are typical of modern alluvial

soils, and they indicate different degrees of saturation, and thus different topographic settings and

distances from trunk channels (Kraus 1996). Further work on the site could attempt to parse out the

floodplain using these pedogenic phenomena. This could be of some use if it offered an

approximate location for the trunk channel during each avulsion cycle.

Further avulsion studies

There has been much work done on sites of river avulsions in the Holocene, including the

Cumberland Marshes in Saskatchewan, Canada (Smith, et al. 1989; Smith and Perez-Arlucea 1994;

23

Perez-Arlucea and Smith 1999; Morozova and Smith 2003; Slingerland and Smith 2004), the

Rhine-Meuse Delta in the Netherlands (Stouthamer 2001; Makaske and Berendsen 2007), the

Mississippi in the central United States (Aslan et al. 2005), and others. Observations made in these

and similar studies have proven invaluable in parsing ancient floodplain sediments now believed to

have been deposited during ancient avulsive events, including sites in Pakistan (Willis and

Behrensmeyer 1994; Bridge, et al. 2000), Wyoming (Kraus and Aslan 1993; Kraus and Bown

1993; Davies-Vollum and Wing 1998), Spain (Mohrig, et al. 2000), and elsewhere.

Circumstantial evidence supporting an avulsion model

There are numerous lines of circumstantial evidence supporting an avulsion model for the

sedimentary deposits at the base of Red Hill, from the continental and regional framework to

specific features seen in the outcrop itself. First, the paleogeographic and tectonic context provides

abundant circumstantial evidence, with initial conditions conducive to repeated avulsive events on

the alluvial plain. With the subsidence of the Appalachian foreland basin and large volumes of

available source sediment being created by the Acadian orogeny to the southeast, a meandering

channel delivering sediment to the alluvial plain was likely to become perched above the

surrounding topography rather quickly. While it is possible to instigate an avulsive cycle without

creating a substantial gradient advantage (Aslan and Autin 2005), floodplain aggradation is a

primary factor in bringing about the necessary conditions (Slingerland and Smith 2004). At a

certain threshold of slope differential between the existing channel and the drop down to the

alluvial plain, a breached channel will nearly always lead to an avulsive system. Studies of modern

rivers bear this out, showing that river channels are rarely superelevated to the point where the river

bed reaches the average elevation of the floodplain (Mohrig, et al. 2000). On the Catskill delta in

the Late Devonian, with subsidence rates estimated at 150-175m/MY (Faill 1985) and an abundant

24

sediment source in the uplifting Acadian mountains, channels likely reached this superelevation

threshold with regularity. This would suggest that river avulsions were likely a common

occurrence, delivering large volumes of sediment to the floodplain.

Significance for alluvial packages in the geologic record, early tetrapod evolution, and fossil

prospecting

To expand our understanding of the paleoenvironments and paleoecology of early tetrapods, it is

helpful to be able to predict what types of large-scale depositional packages are most likely to yield

significant fossil material. By identifying instances of channel avulsion, and thus instances of rapid

deposition in fluvial environments, we can refine our methods of prospecting for fossil deposits.

An avulsive model of deposition holds special significance when applied to paleoenvironments that

hosted some of the earliest known tetrapods. Regardless of the impetus for the evolutionary

development of robust forelimbs in tetrapods and some ancestral lobe-finned fish, it is rather easy

to place such developments in the context of rapidly evolving channels and ephemeral ponds and

wetlands that may have been rather commonplace on the Catskill Delta during the Late Devonian.

Figures 8 and 9 provide some insight into the type of landscapes that may have hosted the earliest

terrestrial vertebrates.

As for the prospecting of future tetrapod sites, it is useful to realize that such an environment also

lends itself to bursts of extremely high sedimentation rates and rapid burial of organic material.

More specifically, a cursory survey of fossil material at the Red Hill locality reveals a strong

preservation bias. All fossil material that was found occurs in Stage I deposits, especially in the

lower portions of these deposits (Facies D and E and the lower ~1.5m of Facies F.)

25

Interpretation of Paleoenvironments

Facies

Label

Description Interpretation

A Brownish red bioturbated sandy siltstone Proximal well-drained floodplain – sediments deposited on

or near alluvial ridge

B Lenses of red silty clay shale In-filled abandoned channels and depressions on floodplain

C Red bioturbated silty clay with mottling and

green sandstone stringers

Floodplain paleosol – sediments deposited farther from

alluvial ridge; experienced seasonal saturation, causing

mottling and reduction of iron in sediments; sand deposited

during occasional overbank sheetflow events

D Red and light green clay shale containing

plant material and charcoal

Poorly drained distal floodplain (pond, wetland) –

sediments deposited in standing water or high water-table

environment; reduction of minerals and preservation of

carbon material

E Light to dark green siltstone and very fine

sandstone containing plant material and

charcoal

Swampy wetlands on proximal floodplain – coarser-grained

sediments deposited in standing water; reduction of

minerals and preservation of carbon material

F Hard grey very fine lower sandstone Proximal crevasse splay and channel bar– formed in

avulsion belt proximal to nodes of avulsion (levee breaches)

G Moderate to hard, dark red mudstone with

some silt; bedding visible on a 2-5cm scale;

burrows ~2cm in diameter

Several beds of fossil pavement; 2-5cm

thick; well-indurated; light green coloration

common; fragments range 1-5mm with very

few up to 60mm; larger fragments are

approx. planar and lie flat; smaller

fragments are often vertical or at an angle

Stage I Avulsion: Proximal crevasse splay complex –

formed in avulsion belt and consisting of a range of grain

sizes delivered by small channels that continuously

reworked sediment in the crevasse splay

H Soft dark red mudstone with some silt;

hackly weathering distorts bedding;

interbeds of light green, very fine sandstone;

large slickenside surfaces; upper 8cm show

shaly parting; slope-former; sharp, slightly

undulating upper contact

Stage II Avulsion: Paleosol – formed on floodplain during

long periods of relatively low sedimentation while channel

belt was spatially confined

Table 2 – Interpretation of paleoenvironments

26

Figure 10 – Seven correlated sections showing lithofacies as well as avulsion interpretation.

27

Figure 11 – Photomosaic of eastern portion of Red Hill outcrop and drawing of Stage I and Stage II avulsion deposits.

28

Figure 12 – Schematic model of Stage I and Stage II avulsion deposits. This model is applied to Red Hill in Figure 11 (Slingerland and Smith 2004).

There are two main taphofacies interpreted in Facies G: 1) Basal lags; and, 2) Defecation deposits

(Graham 2009, pers. comm..). Both types of deposits consist of small broken pieces of bone, teeth,

scales, plates. Basal lag deposits are found in small cut-and-fill features within the siltstones of

Facies G, and are typically associated with localized sandstone beds. This material has likely been

transported and thus is time-averaged and has poor ecological fidelity. Defecation deposits, on the

other hand, may represent broken remains of a single individual or a few individuals that lived very

near to the site of burial. Further work on these taphofacies may reveal new information on the

ecology of the vertebrates at the Red Hill locality.

In addition, the outcrop exhibits channel –margin and standing water taphofacies. The tetrapod

Hynerpeton was found in a channel-margin setting (Facies E between sections 2 and 3), while

abundant plant material and occasional arthropods and rhizodontids have been found in standing

water deposits (Facies D and E) (Daeschler and Shubin 1994; Rowe 2006, pers. comm..).

29

Possible limitations of the Red Hill and further work

Stouthamer (2001) indicated in a description of Holocene avulsions in the Netherlands that it was

impossible to conclude that an avulsive event was associated with a particular crevasse-splay

complex based only on a two-dimensional outcrop. For the purposes of this project, however,

merely recognizing a crevasse-splay complex is enough to conclude a mode of deposition that

differs significantly from repeated and gradually accumulating overbank deposits. Whether a trunk

channel permanently altered its course or ultimately returned to its original channel is not overly

relevant to determining a deposition model. This contention by Stouthamer is partly a question of

the precise definition of the term “avulsion.” As Slingerland and Smith (2004) noted, the term

“avulsion” has primarily been used to describe a total diversion of a parent, or trunk, channel into a

new channel on a floodplain. They suggest, however, that the term is also appropriate in describing

short-term and partial flow-switching (Slingerland and Smith 2004). In this sense, an avulsive

event has occurred when flow from a trunk channel has been permanently or temporarily diverted

out of the channel and onto the adjacent floodplain. Any crevasse-splay involving a significant

redirection of flow for some period of time, then, can be considered an avulsive event, even in the

absence of direct evidence of a parent channel or a new channel.

It would be possible to strengthen understanding of depositional process and paleoenvironments at

Red Hill in a few ways. Kraus and Gwinn (1997) use geochemical analysis to contrast soil profiles

from similar paleosols in the Willwood Formation of Bighorn Basin in Wyoming at different

phases of development in order to gauge the depositional environment of each. This would allow a

finer parsing of the fining-upward cycles that appear to dominate the lower portion of the outcrop

and give a sense of deposition rate and relative position on the floodplain of each cycle on the

floodplain. Perhaps more valuable would be a broader study of the Duncannon Member of the

30

Catskill Delta around Central Pennsylvania. Sites suitable to such expansion of the study area are

currently limited in number and scope. But with new construction and maintenance on current road

cuts, it may become possible to place the alluvial packages at Red Hill in a broader basinal context

by determining how they extend away from the study area. A better three-dimensional view of the

packages could also illuminate the source of these sediments and give a sense of overall flow

directions of the minor channels evidenced by the small cut-and-fill features ubiquitous in the Stage

I avulsion sediments. With a clearer picture of the flow depth and superelevation of the channels

delivering sediment to the Red Hill site, the initial conditions would become clearer. This would

provide a more complete picture of the typical cycle of channel aggradation followed by levee

breach and crevasse-splay deposition.

Conclusion

The Red Hill site has proven to be an extremely valuable source of Late Devonian vertebrate fossil

material and has provided us with numerous insights into early lineages of tetrapods and their

ancestors, the lobe-finned fish. By parsing out the facies in which this material is most often found,

we can produce an even more detailed picture of where these lineages evolved and why they are so

well preserved at this site. The fossil-bearing zone, made up of facies D, E, F, and G (as well as the

non-fossiliferous facies H), is interpreted as a Stage I avulsion package. Facies D is a shale that

formed in a laterally-restricted pond on the ancient floodplain as flow was diverted from the parent

channel. Facies E and F were deposited as the crevasse splay prograded onto the floodplain.

Facies G formed as small shallow channels migrated across the avulsion belt, reworking the

sediments until most of the diverted flow stabilized in a new channel or channels and a paleosol

developed, capping the package. The avulsive model of deposition presented here is supported by

31

the stratigraphy and sedimentology of the site as well as by fossil occurrence data, and it appears to

be the most appropriate model to describe the paleoenvironments found at the Red Hill outcrop.

In future studies of similar sedimentary packages, the avulsive model may be able to provide

researchers with clues as to likely facies in which to begin searching for tetrapod material as well as

associated fossil material. This could certainly be of use on the Catskill Delta, where one would

expect to find similar events of avulsion and rapid deposition along the numerous channel systems

that carried sediment out of the newly formed Acadian Mountains into the Appalachian Basin. But

it may also prove applicable to sites as yet unassociated with avulsive deposition or early tetrapod

environments.

32

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34

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35

Woodrow, D. L., Ed. (1985). The Catskill Delta. Boulder, Colorado, The Geological Society

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deposition sites of the Devonian Catskill and the Old Red Facies." GSA Bulletin 84: 3051-3064.

36

Appendix A – Fossil sampling location data

Appr

ox. h

oriz.

po

s. (m

)

Facie

s

Top/

Bott

om

Out

crop

Str

ike

(deg

E o

f N)

Foss

ils (#

) >1m

m

Foss

ils (#

) >2m

m

Foss

ils (~

tota

l #)

Phot

os (#

)

Date

25 B Top 105 0 0 0 2 11/26/200829 H Bottom 120 0 0 0 1 11/26/200831 G Bottom 105 21 16 170 7 11/26/200833 G Bottom 76 4 2 9 7 11/26/200838 G Bottom 120 0 0 0 5 11/26/200840 G Top 125 0 0 0 6 11/26/200858 G Bottom 125 14 2 60 6 11/26/200861 G Top 140 0 0 0 1 11/26/200861 G Bottom 140 0 0 0 1 11/26/200883 G Top 136 0 0 0 3 12/8/200886 G Bottom 210 0 0 0 5 12/8/200888 G Bottom 109 4 4 4 5 12/8/2008

100 G Bottom 135 0 0 0 1 12/8/2008100 G Top 117 0 0 0 1 12/8/2008102 G Bottom 178 0 0 0 1 12/8/2008117 G Bottom 107 38 26 400 10 12/8/2008117 G Top 108 0 0 0 1 12/8/2008132 G Bottom 104 0 0 0 1 12/8/2008138 G Bottom 141 0 0 0 1 12/8/2008144 G Bottom 125 0 0 0 5 12/8/2008144 G Top 129 0 0 0 5 12/8/2008157 G Bottom 104 1 1 1 1 12/14/2008157 G Top 115 0 0 0 4 12/14/2008157 G Top 135 0 0 0 1 12/14/2008171 G Bottom 96 11 11 50 7 12/14/2008171 G Top 100 0 0 0 1 12/14/2008173 G Bottom 128 11 11 60 6 12/14/2008173 G Top 132 0 0 0 4 12/14/2008173 G Top 124 0 0 0 5 12/14/2008186 G Bottom 102 1 1 8 1 12/14/2008186 G Top 110 0 0 0 1 12/14/2008204 G Bottom 120 0 0 0 1 12/14/2008204 G Top 128 0 0 0 1 12/14/2008223 G Top 130 0 0 0 5 12/14/2008

37

Appendix B – Individual fossil data Fo

ssil

ID#

Loca

tion

(I-

#)

App

rox.

hor

iz. (

m)

Faci

es

Upp

er /

Low

er

Out

crop

Str

ike

(deg

E

of N

)

Qua

dran

t

Foss

il Ty

pe

(cm

) V

is. L

engt

h

(cm

) V

is. W

idth

(cm

^2)

X-se

ctio

n ar

ea

~Dip

dir

(de

g E

of N

)

Dip

(de

g)

Tren

d (d

eg E

of

N)

Not

es

1 16 31 G Lower 79 A Scale 1 0.1 0.1 215 45 -C-F 20cm deep, ~2m wide; red hackly s i l ts tone

2 16 31 G Lower 79 A Scale 1 0.1 0.1 75 75 - "3 16 31 G Lower 79 A Scale 0.5 0.1 0.05 - 0 - "4 16 31 G Lower 79 A Scale 0.5 0.1 0.05 112 45 - "5 16 31 G Lower 79 B Spine 1 0.5 0.5 - 0 94 "6 16 31 G Lower 79 B Bone 3 1.5 4.5 - 0 159 "7 16 31 G Lower 79 B Scale 1 0.2 0.2 135 20 - "8 16 31 G Lower 79 B Scale 1 0.2 0.2 - 0 - "9 16 31 G Lower 79 B Scale 0.8 0.2 0.16 195 15 - "

10 16 31 G Lower 79 B Scale 0.8 0.1 0.08 - 0 - "11 16 31 G Lower 79 B Scale 0.5 0.1 0.05 - 0 - "12 16 31 G Lower 79 B Frag? 0.3 0.1 0.03 - 0 - "13 16 31 G Lower 79 B Frag? 0.3 0.1 0.03 - 0 - "14 16 31 G Lower 79 B Frag? 0.2 0.2 0.04 - 0 - "15 16 31 G Lower 79 B Frag? 0.2 0.1 0.02 - 0 - "16 16 31 G Lower 79 C Frag? 0.2 0.1 0.02 - 0 - Not in C-F; fa i rly mass ive s i l ts tone

17 17 33 G Lower 50 A Plate 2 0.5 1 - 0 -Continuous bed w/ scattered foss i l s ; hackly red s i l ts tone

18 17 33 G Lower 50 A Plate 1 1 1 - 0 - "19 17 33 G Lower 50 B Bone? 2 2 4 - 0 29 "

20 17 33 G Lower 50 C Spine 1.5 0.5 0.75 - 0 49Across severa l thin beds ; mass ive red s i l ts tone

21 17 33 G Lower 50 D Plate 1 0.5 0.5 - 0 - "22 17 33 G Lower 50 D Plate 0.5 0.5 0.25 - 0 - "23 17 33 G Lower 50 D Plate 0.5 0.5 0.25 - 0 - "

24 30 58 G Lower 99 A Plate 2 0.1 0.2 - 0 - No C-F; ~4cm thick mass ize s i l ts tone bed25 30 58 G Lower 99 A Plate 1 0.1 0.1 - 0 - "26 30 58 G Lower 99 A Frag? 0.3 0.1 0.03 - 0 - "27 30 58 G Lower 99 A Frag? 0.2 0.2 0.04 - 0 - "28 30 58 G Lower 99 A Frag? 0.2 0.2 0.04 - 0 - "29 30 58 G Lower 99 A Frag? 0.2 0.1 0.02 - 0 - "30 30 58 G Lower 99 B Scale 2 0.1 0.2 235 60 - "31 30 58 G Lower 99 B Scale 1 0.1 0.1 - 0 - "32 30 58 G Lower 99 B Frag? 0.2 0.2 0.04 - 0 - "33 30 58 G Lower 99 B Frag? 0.2 0.2 0.04 - 0 - "34 30 58 G Lower 99 B Frag? 0.2 0.1 0.02 - 0 - "35 30 58 G Lower 99 B Frag? 0.2 0.1 0.02 - 0 - "36 30 58 G Lower 99 C Frag? 0.3 0.1 0.03 - 0 - Hackly red s i l ts tone lens37 30 58 G Lower 99 C Frag? 0.2 0.1 0.02 - 0 - "38 46 88 G Lower 83 A Frag? 0.5 0.5 0.25 - 0 -39 46 88 G Lower 83 A Frag? 0.2 0.1 0.02 - 0 -

40 46 88 G Lower 83 D Bone? 4 1 4 - 0 -Single bedding surface; red mass ive s i l ts tone

41 46 88 G Lower 83 D Tooth 0.7 0.1 0.07 - 0 72 "

38

Appendix B (con’t) -- Individual fossil data Fo

ssil

ID#

Loca

tion

(I-

#)

App

rox.

hor

iz. (

m)

Faci

es

Upp

er /

Low

er

Out

crop

Str

ike

(deg

E o

f N

)

Qua

dran

t

Foss

il Ty

pe

Vis

ible

Len

gth

(cm

)

Vis

ible

Wid

th (

cm)

X-se

ctio

n ar

ea (

cm^2

)

~Dip

dir

(de

g E

of N

)

Dip

(de

g)

Tren

d (d

eg E

of

N)

Not

es

42 61 117 G Lower 81 A Plate 3.5 0.2 0.7 - 0 -One continuous bed; s i l t to vfl sand; very foss i l i ferous

43 61 117 G Lower 81 A Plate 0.6 0.1 0.06 95 60 - "44 61 117 G Lower 81 A Frag? 0.2 0.1 0.02 - 0 - "

45 61 117 G Lower 81 B Plate 3 0.2 0.6 - 0 -Single bedding surface; red mass ive s i l ts tone

46 61 117 G Lower 81 B Plate 1.6 0.2 0.32 - 0 - "

47 61 117 G Lower 81 B Frag? 0.4 0.1 0.04 - 0 -Smal l fragments in three beds ; red mass ive s i l t to vfl sand

48 61 117 G Lower 81 B Frag? 0.2 0.1 0.02 - 0 - "49 61 117 G Lower 81 B Frag? 0.2 0.1 0.02 - 0 - "

50 61 117 G Lower 81 C Scale 0.7 0.1 0.07 - 0 -Minor foss i l bed above major one; mass ive red s i l ts tone; ~.75m long

51 61 117 G Lower 81 C Plate 0.5 0.3 0.15 - 0 - "

52 61 117 G Lower 81 C Scale 0.8 0.1 0.08 - 0 -

Major (high-concentration) lag depos i t; mass ive s i l t to vfl sand; ~200 foss i l s in sample area; ~1.5m long

53 61 117 G Lower 81 C Scale 0.4 0.1 0.04 - 0 - "54 61 117 G Lower 81 C Scale 0.6 0.1 0.06 - 0 - "55 61 117 G Lower 81 C Scale 0.7 0.1 0.07 - 0 - "56 61 117 G Lower 81 C Scale 0.5 0.5 0.25 - 0 - "

57 61 117 G Lower 81 D Scale 0.4 0.1 0.04 - 0 -Minor foss i l bed above major one; mass ive red s i l ts tone; ~.75m long

58 61 117 G Lower 81 D Frag? 0.3 0.1 0.03 - 0 - "59 61 117 G Lower 81 D Frag? 0.3 0.3 0.09 - 0 - "

60 61 117 G Lower 81 D Plate 0.8 0.5 0.4 184 10 - "

61 61 117 G Lower 81 D Scale 0.8 0.1 0.08 - 0 -

Major (high-concentration) lag depos i t; mass ive s i l t to vfl sand; ~200 foss i l s in sample area; ~1.5m long

62 61 117 G Lower 81 D Plate 0.5 0.3 0.15 - 0 - "63 61 117 G Lower 81 D Frag? 0.2 0.2 0.04 - 0 - "64 61 117 G Lower 81 D Frag? 0.2 0.1 0.02 - 0 - "65 61 117 G Lower 81 D Frag? 0.2 0.1 0.02 - 0 - "

66 82 157 G Lower 78 A Scale 4 0.1 0.4 - 0 - Foss i l -poor zone; red hackly s i l ts tone

67 89 171 G Lower 70 A Scale 0.35 0.1 0.035 274 10 -

Four l ightly concentrated layers within ~10cm vert.; hackly red s i l ts tone

68 89 171 G Lower 70 A Frag? 0.3 0.1 0.03 - 0 - "

69 89 171 G Lower 70 A Scale 1 0.1 0.1 - 0 - "70 89 171 G Lower 70 A Plate 2.5 0.3 0.75 - 0 - "71 89 171 G Lower 70 B Plate 1 0.3 0.3 - 0 - "

39

Appendix B (con’t) -- Individual fossil data Fo

ssil

ID#

Loca

tion

(I-

#)

App

rox.

hor

iz. (

m)

Faci

es

Upp

er /

Low

er

Out

crop

Str

ike

(deg

E

of N

)

Qua

dran

t

Foss

il Ty

pe

(cm

) V

is. L

engt

h

(cm

) V

is. W

idth

(cm

^2)

X-se

ctio

n ar

ea

~Dip

dir

(de

g E

of N

)

Dip

(de

g)

Tren

d (d

eg E

of

N)

Not

es

72 89 171 G Lower 70 B Scale 0.6 0.1 0.06 108 10 - "73 89 171 G Lower 70 B Scale 1.5 0.1 0.15 - 0 - "74 89 171 G Lower 70 B Plate 2.5 0.4 1 104 20 - "75 89 171 G Lower 70 B Plate 1 0.3 0.3 114 20 - "76 89 171 G Lower 70 B Bone? 2 0.4 0.8 - 0 - "77 89 171 G Lower 70 B Plate 2.8 0.2 0.56 - 0 - "

78 90 173 G Lower 102 A Scale 4 0.1 0.4 116 15 -Lightly concentrated bed 20cm thick; thinly bedded (1-2mm) s i l ts tone

79 90 173 G Lower 102 A Scale 3 0.1 0.3 110 15 - "80 90 173 G Lower 102 A Frag? 0.4 0.2 0.08 - 0 - "81 90 173 G Lower 102 A Plate 1 0.3 0.3 - 0 - "82 90 173 G Lower 102 A Scale 0.5 0.1 0.05 - 0 - "83 90 173 G Lower 102 A Scale 0.4 0.1 0.04 - 0 - "84 90 173 G Lower 102 A Scale 1 0.2 0.2 4 10 - "85 90 173 G Lower 102 B Scale 1 0.1 0.1 - 0 - "86 90 173 G Lower 102 B Scale 1.5 0.1 0.15 - 0 - "87 90 173 G Lower 102 B Frag? 0.4 0.1 0.04 - 0 - "88 90 173 G Lower 102 B Scale 0.8 0.1 0.08 - 0 - "

89 97 186 G Lower 76 A Frag? 0.4 0.2 0.08 - 0 -~10 foss i l s in 2cm-thick laminated bedset; s i l ty sha le