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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
ii
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
iii
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.
iv
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
v
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
vi
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
vii
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.
1
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).
2
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,
3
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).
4
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.
5
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.
6
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
7
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
8
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
9
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
10
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
11
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
12
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
13
Figure 4 – Photomosaic of outcrop with seven sections (1-7) in their horizontal locations below. Each section’s base is
approximately at road level.
14
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
16
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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35
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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