You can get a Word copy of this exercise to print out and take on your trip here.
Introduction, Visit the Falls of the Ohio web site before continuing. Note that access to the park is free, but the Interpretive Center has a $4 admission for adults (a buck for kids under 13). There is a $2 parking fee if you do not visit the Interpretive Center. You do not have to visit the interpretive center to complete this exercise. You should also visit the Fossils of Kentucky web site. Also read the Courier Journal press release for tips to get the most out of your trip. If you're interested in a hike or canoe trip, check out this web page.
Fossils are the remains or traces of an organism from prehistoric times (older than 4000 BC). Most organisms do not fossilize and those that do are usually destroyed by geological processes or they never surface for examination. Fossils are usually formed when an organism is covered by sediments that then harden into sandstone, slate, mudstone or flint. Organisms also fossilize when they are buried in volcanic ash or entombed in tar or tree sap. Some of the most common fossils are either mold or petrifaction fossils. A mold fossil forms when the material surrounding the organism hardens followed by removal of the organic matter. This leaves behind an impression (or mold) of the organism. Petrifaction fossils are formed through two main processes: permineralization and replacement. Permineralized fossils are created when ground water percolates through the remains of the organism and leaves behind minerals in the cellular spaces. Petrified wood is an example of a permineralized fossil. Replacement fossils are formed when ground water first dissolves out the tissue and then leaves minerals in their place. Both types of petrifaction fossils are generally composed of either SiO2 or CaCO3.
The fossils exposed at the Falls are from the Devonian Period and were deposited between 395 and 345 million years ago. During that time the Kentucky-Indiana area was beneath a warm tropical ocean. We were located about 20 degrees South of the Equator. Movements of the earth's crust have since brought us to our present location. Visit the Paleomap Project to see how the earth has changed over the last 1100 million years. You can also see an animation here:
Figure 1. A trilobite.To learn more about
trilobites, go
here and
here
The Devonian seas were characterized by numerous creatures, including fish, trilobites, crinoids, brachiopods, various mollusks, and abundant coral species. Unfortunately, few fish remains have been preserved at the Falls site and it is unlikely that you’ll find any fossil evidence of these creatures. Although trilobites (Figure 1) can be found at the park, they are far and few between at our sites, so don't be disappointed if you don't see any (there are two at site B).
Figure 2. Study sites at the Falls of the
Ohio. NOTE: The A site no longer exists because of construction at the
park.
The area you will be studying is shown in figure 2. Make sure to run though the figures at the web site first since they have considerably more detail than shown in this figure. This location is directly below the interpretive center. If you park in the main lot (behind the interpretive center), Steps will lead you to the area near the upper right of figure 2. This picture was taken from the steps that lead to the back entrance of the interpretive center. Because of the way fossils and sediments are deposited, the higher ground represents more recent deposits so, as you move from sites A through E, the fossils you are observing were deposited earlier in the earth’s history. NOTE: The A site no longer exists because of construction at the park.
Figure 3. A highway road cut showing
layered deposits
The various layers deposited at the bottom of the sea are best seen at a highway road cut (Figure 3). In the figure, the light-colored sediments at the base of the cut were formed as mud, dead organisms, and muck collected at the bottom of the sea. As time passed, more silt (this time darker) settled over the previous sea floor and buried them. Over time, the sediments hardened and fossilized to form the structures shown in figure 3. Since the only way sedimentary rock formations can be produced is through the process described above, it is clear that the top layers are the youngest of the deposits.
Figure 4. Fossilized animal remains at the
Falls of the Ohio More on brachiopods is
here.
Site A in figure 2 is our highest altitude location, and therefore represents the most recent of the fossils you’ll be exploring is the Paraspirifer acuminatus zone (named after the most prominent animal), laid down approximately 345 million years ago. In these sediments you’ll find brachiopods, cup corals and paraspirifers (creatures similar to clams; Figure 4).
Figure 5. A comparision of bryozoans (A)
with coraline algae (B). See a living bryozoan
here.
You’re also likely to find bryozoans if you look carefully (Figure 5a). Don’t confuse the bryozoans with coraline algae (actually a plant; Figure 5b). Note the segmented structure of the coraline algae at about 7:00 in the figure. Such structures are missing in the bryozoan fossils.
Figure 6. Fossilized crinoid remains. More
on crinoids is
here.
Further back in time at site B you’ll find many of the same creatures found above, as well as the fossilized remains of crinoids (Figure 6). Crinoids are relatives of star fish that possess a stem-like stalk to which flower-like whorl of tentacles is attached (Figure 6a). You will not find fossil specimens of this quality at the falls, but you will see numerous fossils representing the remains of their stems (Figure 6b).
Figure 7. The cave zone (Site C).
Site C is located on the river side of the park, down from site B. This cliff area (Figure 7) shows the layering described for the a road cut (Figure 3).
Figure 8. The Brevispirifer gregarius Zone
Site C also will include brachiopods, cup corals and paraspirifers (creatures similar to clams; Figure 8).
Figure 9. Branching coral
This area is the best for viewing a darkly-colored 6-inch thick layer known as the Brevispirifer gregarius Zone (Figure 8). This zone has numerous brachiopods, cup corals, and paraspirifers. Below this layer we have the cave zone. This is the first place where you can find an unusual coral-like organism known as stromotoporoids as well as many branching corals (Figure 9).
Figure 10. Stromotoporids in the coral zone (Site D)
Below the cave zone and flowing to the river we have the coral zone (Site D; figure 2). Along with the numerous corals, you’ll also find stromotoporoids (Figure 10). Stromatoporoids are thought to be either a specialized coral or perhaps a sponge. I think they look like algal mats. You’ll find lots of them near the banks of the river. Site E (Figure 2) is also considered to be in the coral zone, but you’ll find different species mixtures and abundance at that site.The other figures in the above pane show other fossils you're likely to see.
Figure 11. Barnacles and crinoids More on barnacles is
here.
Sites D and E will also show a variety of Barnacles and crinoids. Figure 11 shows some of the forms commonly found at these sites.
As you can see, the corals dominate this community. Read more about coral reef communities here (Be sure to check out the Patch Reef and Bank Reef communities too)
Figure 12. Branching Coral.
Methods. Remember to bring a water bottle (for you and to pour on fossils to bring out structural details. A magnifying glass would be a good idea too! For the analyses you will be doing it is not important that you correctly identify the species. If, for example, you classify all the barnacles as "other coral", that will not affect your results. You just need to be consistant. For each of the sites at the Falls of the Ohio, identify a 5 square meter area that appears representative of the site. For the cave zone (Site C), make sure the 5 square meter area is horizontal and includes the Brevispirifer gregarius zone (Figure 8). Count the number of fossils of each type and enter on a tally sheet (a data sheet in Excel format can be printed out here). When presented with a jumble of broken fossils, each piece should be counted as an individual except when their orientation makes it clear that the fragments belong to the same individual (Figs 9,12). Additional examples of fossils you are likely to encounter can be found HERE.
You also need to visit two road cuts to compare to the Falls data (careful!). Whenever you are working with a cliff surface it is better to have a narrow study area (say half a meter high and 10 meters long) to insure that the fossils are taken from the same time period (in reality, a half meter section would cover millions of years). Depending on the area you choose for site A, you may have to do a cliff sample. Instead of road cuts you could also study a stream bed with exposed rocks (or any rock out-cropping). Just make sure you don't use a site where the rocks have been placed there (like the fossils around the Louisville Zoo Entrance since there's no way to be sure that they are from the same time period. However, the large rocks on the lawn to to the right of the visitor's center (as you face the river) appear to be from the same time period. Instead of a road cut you could also explore other sites at the falls (even across the river). The main point in choosing two other sites is to make sure they are removed from the main study site.
Analysis and Report. Enter your data (counts of species vs. site) into an Excel spreadsheet (Information on using Excel can be found here). Plot the number of each species vs. habitats (a 3-d plot would be nice here- species, location, count). Next, perform the species diversity calculations (button below) for each of the sites and the total across all sites for the falls and for your two road cuts. Plot the diversity indices vs. habitat. Next, get the total number for each species across all habitats. Sort the species by size and pay attention to the top 10 species only. Open the Similarity program (button below; You can look at the tutorial for this program here). Your 10 top species are the 10 variables requested by the program. Enter "10" in the box at the top and hit the ENTER key. Then enter the 10 sorted species, starting with the most abundant and working down to the least abundant. Next, enter the number of sites (7). Now enter the site names. When finished, press the ENTER VALUES button. You will then be asked to enter the counts for your data. Pay attention to the combination since you must input the proper value. When you are finished with the entries press the RUN ANALYSIS button and a dendogram will be displayed.
Questions
- For the Falls of the Ohio, have the species assemblages changed over time? Which species dominate each of the time periods represented by the different sites?
- Does species diversity change with time at the Falls? If so, what do you think might explain these changes?
- From your readings on the behavior and ecology of the corals and other species, what can you tell me about the anchient oceans inhabited by the species at different times at the Falls (temperature, salinity, depth, etc.).
- What organisms are "missing" from the fossil beds? Why do you think they're not represented?
- Compare the species assemblages and diversity found at your two sites with that of the Falls. Of what use might it be to examine the total diversity at the Falls?
- From the similarity analysis, which of the sites at the Falls are most alike. Which speiceis are most important in describing these similarities (not necessarily all of the top ten)?
- Does the similarity analysis provide clues to the age of your road cuts? Explain. How about the diversity analysis?
- How might diversity be related to stability of an ecosystem?
