If Fossils Could Talk - Final!!

This topic submitted by Adriann, Scot, Jen N. and Brian ( stuckeae@muohio.edu ) on 12/13/99 .

There may be some funny spacing in this because of graphics that are included in our paper! Enjoy!

If Fossils Could Talk
GLG 205
Dr. Hays Cummins
14 Dec 99

Scot Chappel
Brian Meeker
Jennifer Nolen
Adriann Stuckey

Introduction
In the Miami Valley area the Ordovician time period is very well exposed. At some specific sites, such as Hwy 1 near Brookville, Indiana, many successive layers of Ordovician bedrock filled with fossils are out in the open. At these sites comparisons between the layers and among the samples from one layer are interesting to examine. This research project looked solely at brachiopod species, because of their relative ease in identifying, and compared three different layers to determine if the environment of deposition was similar or not. It also examines the similarities and differences in the individual samples within each layer to look at the patchiness and determine the horizontal variations in species at one preserved moment in time. We expect that there will be some similarity within the layers and less similarity between the layers.
Ordovician
History:
Approximately 510 million years ago the North American plate was located near the equator, placing Ohio and Indiana in the Southern Hemisphere. Tropical to subtropical seas dominated the landscape, covering the majority of Ohio and Indiana throughout the Ordovician, Silurian, and most of the Devonian periods (Caster, p.16). Due to the enormous amounts of tectonic activity throughout the Paleozoic, (i.e. opening and closing of the Atlantic Ocean) warm shallow seas continually transgressed and regressed across the North American plate.
The Paleozoic began as the Iapetus Ocean, or proto-Atlantic, began widening throughout the Cambrian period. Soon into the Ordovician period, the continental plates binding the Iapetus Ocean changed directions and started to close. As continental collision initiated between North America and Europe, small island arcs and a massive mountain system formed to the east of Indiana. The Taconic Orogeny was located near the site of the modern day Appalachian Mountains, and persisted throughout the Late Ordovician. Ohio and Indiana were located on the passive margin of this compressive episode, therefore not directly involved with the uplift. Although soon after the Taconic Orogeny began, the Queenston Delta carried vast amounts of eroded sediments westward into the shallow epicontinental seas of Ohio and Indiana (Hansen, p.2). These sediments, consisting mostly of mud, were deposited throughout the waters of the states, forming the Late Ordovician shale recorded in the strata that we see today. A small section of the Ordovician period is visible from the surface in southwestern Ohio and southeastern Indiana, although only exposing the youngest of the Ordovician strata (see Appendix A). The Cincinnati Arch (or anticlinal structure/dome) formed when crustal material began bulging upward after sediment deposition. Since then this structure has been under intensive erosional processes, consequently exposing the younger Ordovician strata at the surface (Caster, p. 15).
The Brookville Roadcut:
As mentioned above, the Upper Ordovician strata is exposed at the surface throughout southeastern Indiana. The Brookville roadcut (highway 1) consists of four formations that comprise the upper half of the Cincinnatian Series, the very youngest of all Ordovician rocks. This series is noted for 200 meters of interbedded blue-gray shales and gray fossiliferous limestone (Pope, i1).
The Ordovician is known as a period in time when warm shallow waters dominated the lands. Much of what the tropics look like today, with their coral reefs and marine organisms (i.e. gastropods, bivalves, brachiopods and bryoza), are what Indiana and Ohio looked like throughout the Paleozoic. The marine organisms, dominated by bryoza and brachiopods, precipitated the mineral aragonite (later forming calcite), which is a carbonate substance. As benthic communities developed and died, their calcareous skeletons coated the ocean floor forming the limestone rocks of today. On the other hand, as silt and clay from the near-by Taconic Mountains washed into the seas of Indiana, it covered the skeletal fragments of organisms and formed the blue-gray shale layers (Caster, p.15). The clay, silt, and skeletal fragments mentioned above settled to the bottom, and became lithified from the overlying weight of material, into the four formations exposed at the Brookville road cut.
The 4 Formations:
The Arnheim formation is the oldest of the four, and constitutes the very bottom of the road cut. Caster states, "the thickening and thinning of the Arnheim, its rubbly nature, and the abraded condition of the fossils, seem to indicate shoaling of the sea." This layer consists primarily of shale with minor amounts of limestone, indicating a deeper depositional environment.
The Waynesville formation is also primarily shale, yet contains increased amounts of even-bedded limestone layers within. Many collectors prefer this formation due to the abundance of trilobites and well-preserved fossils, this layer is also rich in Flexicalymene (lowest member) and Resserella meeki (middle member) (Caster, p.18-19).
The Liberty formation is very similar to the Waynesville formation lithologically, except it contains slightly more layers of thin-bedded limestone. As we progressively move up in the strata, the percentage of limestone slowly increases due to a shallow marine environment of deposition (Hansen, p.6).
The Whitewater formation is the youngest of the four, and contains the highest abundance of limestone layers, therefore indicating a shallow, high-energy environment. The massive limestone layers contain many large cephalopods, and new species of bryoza (Caster, p.19).
Geologists consider the Ordovician Period the most famous of Ohio and Indiana's Paleozoic rock systems. The unbelievable abundance and diversity of well-preserved fossils, and the alternating layers of limestone and shale far surpass any other system. The tropical waters of Indiana not only dominated the state, but most of the North American plate during this period.
Brachiopods
Brachiopods are sessile (non-mobile) benthonic (bottom living) shelf dwellers, dominating the littoral environment (beach conditions) to bathyl depths (200-400m) (Jones, p.17). They have persisted from the Cambrian period to now recent times, yet flourished in the warm Paleozoic seas.
Shell Morphology:
Brachiopods have a calcareous or phosphatic external shell consisting of two valves (shells) of different sizes, the pedicle and brachial (Articulate, Col.1). The valves share a plane of symmetry which bisects the valves perpendicular to the hingeline and passes through the two beaks.

The pedicle (or ventral) valve tends to be larger, contains the more prominent beak, and holds the attached pedicle muscle. In some cases this pedicle muscle acts as a stalk, which anchors the organism to the substrate. The brachial (or dorsal) valve is smaller in size, and contains the attached lophophore. This lophophore is a spiral or folded organ used for generating feeding currents and trapping food particles, and thus brachiopods are filter feeder (Jones, p.17-18).

The valves are generally hinged together at the posterior end by two teeth in the pedicle valve that fit in two sockets in the brachial valve. The valves are held together by contracting and relaxing their muscles. Many brachiopods contain visual scars on the inside of their valves, due to the once attached muscles.
Inarticulate vs. Articulate:
There are two very important classes of brachiopods, the inarticulate and articulate. Many believe the inarticulate were the precursors of the articulate because they appear in the fossil record prior to the articulated. Regardless, the articulated class is much more important due to their abundance. Inarticulate brachiopods have unhinged valves, lack teeth and sockets, and have a calcium phosphate-chitin shell. While the articulated brachiopods have hinged valves, bear well-defined teeth and sockets and a calcium carbonate shell (Articulate).
Method
The road cut near Brookville, Indiana on Highway 1 has tiers that follow the plane of the layers. To determine which tiers to sample from we used a random number table. We sampled from three tiers, one near the bottom, one closer to the middle and another not quite all the way to the top. Once on the tier to be sampled, we had Scot walk the length of it and count how many steps he took. We then used the random number table to select four spots on the wall. Each one of us went to a spot and collected a sample of about 30 cm2 no matter how many pieces it required. We climbed up above the broken piles of shale at the bottom of the wall and tried to break rocks out of the layers to be sure that the samples we were collecting actually belonged to that specific layer. Unfortunately, that was not always possible and we had to use pieces that seemed to fit in nearby. We repeated the same process on each of the three tiers and labeled which layer the rocks came from.
We then cleaned the rocks and carefully examined them to determine the number of whole individuals of each species that were on the top surface of the rock (see Appendix B for raw numbers). We used a ruler to approximate the surface area that we examined to determine if we had the same amount of material from each stratum. We also noted every other unique characteristic of the rocks, such as composition (shale or limestone), amount of broken shells and other prominent species besides brachiopods that may provide more information about the similarities or differences between the layers and samples (see Appendix C).
Results
We evaluated our data based on species and genus. We used two basic tests, the Index of Similarity and Species Richness. According to the Index of Similarity, Strata 1 was not at all similar to either of the other two strata, but Strata 2 and 3 had an index of .5714. Very few of the individual samples were similar to any of the other samples from their strata and none of the samples from the third strata were similar to each other (see Appendix D). Based on genus, there was much more similarity. All three of the strata had a similarity index of at least .2 with each other. There were still very few samples that were similar to other samples in their strata and no samples similar to each other in Strata 3 (see Appendix D).
According to Species Richness indicators, Strata 2 was the most rich with a value of 1.97.
The other two strata were both above .7. Of the 19 total samples that we have, only 7 have more than one species and three of the samples had no whole species visible on the top surface.
Each stratum had its own unique set of species. Strata 1 only had 5 different species, strata 2 had 9 different species and strata 3 also had 5 different species. In each stratum the distribution of the species was also different as seen in the pie graphs in Appendix E.

Discussion
Examining the geologic record for information from the past is not an easy task. We ran into many stumbling blocks right from the start when we were attempting to collect our samples. There was no real way to be sure that we were collecting samples from that specific tier without breaking rocks out of the wall, which was not always possible. We tried our hardest to find pieces that were already in the process of eroding out of the wall so that we could be sure they were deposited in that specific site, but that lessened our level of random sampling. That could also have caused biases in the samples that we collected. Perhaps some species lived only in the more disturbed areas that would have been preserved as shale making it more susceptible to erosion. Those species would be represented in a higher percentage than the species that live in low energy environments that tend to produce more limestone.
To attempt to correct this problem in the future, we could bring hammers to break large rocks out of the wall in the hopes of being more accurate. We could also simply collect more samples. As it was we examined about 2000cm2 in each stratum. Perhaps a greater sampling area would help correct for any sampling biases that do occur.
It is not that surprising that in spite of the difficulty sampling and examining the data that we came up with many zeros indicating no similarity. Perhaps different statistical tests could have provided more data to interpret. The Ordovician time period lasted for millions of years and the likelihood that two preserved niches are alike is fairly rare. This is especially true when the conditions of the Ordovician in the Miami Valley are considered. The Ordovician was dominated by shallow seas in this area. Shallow depositional environments are notorious for variety and irregularity. Over time the shoreline was retreating and so the environment in the same area separated by a million years could be vastly different.
This high level of variability in depositional environment is most definitely the cause of the patchiness and differences between samples that are from the same layer. Small changes like current and size of sediment being deposited greatly change the dynamics of the environment and presumably the species that would choose to live there.
We did not believe that the samples would be exactly alike, but we thought there would be more similarity than there turned out to be. The differences make more sense when you look at them with the conditions of the Ordovician time period in mind. An inch or two of Ordovician rock can include shallow and deep-water environments. Both of which are drastically different. We also thought that the differences between the layers would be more apparent, and that we would be able to determine which layer (Arnheim, Waynesville, Liberty or Whitewater) our samples represented. Unfortunately, we would need to be experts to determine which layer our samples come from.
In future research it would be interesting to see if the other phyla also fluctuate as much as the brachiopods do. If all of the phyla fluctuate it would lend more credibility to the belief that the changes in environment caused the differences in the diversity of the species.

Bibliography
Articulate Brachiopods of the Richmond Group: non-technical aid in identifying Richmond group brachiopods to genus. The Karl Limper Geology Museum. April, 1997.
Caster, K. E., Dalve, E.A., & Pope, J. K. Elementary Guide to the Fossils and Strata of the Ordovician in the Vicinity of Cincinnati, Ohio. The Cincinnati Museum of Natural History, 1955.
Davis, R. A. Cincinnati Fossils: An Elementary Guide to the Ordovician Rocks and Fossils of the Cincinnati, Ohio, Region. Cincinnati Museum of Natural History, 1981.
Gray, H. H. Lithostratigraphy of the Maquoketa Group (Ordovician) in Indiana. Bloomington, Indiana: The State of Indiana, 1972.
Hansen, Michael. The Geology of Ohio-The Ordovician. Ohio Geology. Columbus, Ohio: Fall 1997.
Jones, B.G., J.W. Pemberton, and A.J. Wright. "Sedimentology and Palaeontology". Geos102, Spring
Session. University of Wollongong. Australia, Fall 1998.
MacDaniel, R. P. Upper Ordovician Sedimentary and Benthic Community Patterns of the Cincinnati Arch Area. Chicago, Illinois: University of Chicago Department of Duplication, 1976.
Meeker, Brian. On site Photographer. October 3, 1999.
Pope, J. K. & Martin, W. D. Miami University Geology Field Trip Guide to Localities on Indiana Route 101 between Brookville and Liberty. Miami University, 1998.