Introduction: Every aspect of our surroundings, everything we witnessed at the two sites that we visited and everything geologically related can be tied together with a few simple concepts. A central component of those simple concepts is known as the Wilson Cycle. The Wilson Cycle has a massive impact on not only the two sites that we visited, but literally everywhere around the world. By understanding the principles of the Wilson Cycle, we are able to unearth details about a location such as what geologic era it belongs to, what type of plate boundary it is, as well as what type of tectonic activity that was required to allow it to form. In essence, everything relates back to the Wilson Cycle, as evidenced in the following pages.
Geologic Background:
PALEOZOIC:
The Paleozoic era was is the earliest of the three geologic eras and spans from about 542 to 251 million years ago. Numerous events that significantly impacted the overall structure of the earth took place during this time period. The Paleozoic Era is divided into six different subcategories which include: the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. Early in the Paleozoic the continents were far apart but moving tectonic plates caused continents to move together into one large continent called Pangaea. Some of the significant geologic events that occurred during the Paleozoic era includes the evolution of a large number of animals, some of which are distant ancestors to modern organisms, between 530 and 520 million years ago. Also during this time period, there was an introduction to animals without backbones (invertebrates). Organisms such as corals, brachiopods, mollusks, and arthropods populated the early and middle parts of the Paleozoic era. A massive extinction event known as “The Great Dying” marked the end of the Paleozoic era. During this mass extinction, as many as 96 percent of species in the oceans became extinct; however, these species did not disappear all at once. It took nearly 9 million years for the mass extinction to wipe out all the species.
MESOZOIC:
The Mesozoic era is a geologic era which took place from 251 to 5 million years ago. It is often referred to as the age of reptiles due to the dominance that that species had during this time period. One of the most prominent reptiles during the Mesozoic era was the dinosaur. Some dinosaurs were herbivores, or plant-eaters, which meant that they preyed on the flesh of other organisms. In addition to dinosaurs, other organisms also played a role during the time of the Mesozoic era. One example would include birds. Birds became prominent during the late Mesozoic and evolved from a small group of carnivorous dinosaurs. Also, to a lesser extent, mammals evolved during this time period; however, mammals were relatively small, compromised of very few species, and were often preyed on by dinosaurs. The end of the Mesozoic was marked by the K-T extinction event. This is the extinction that killed the dinosaurs as well as countless other species. The species that survived this extinction later went on to be abundant afterwards. The likely causes of the extinction event include a large asteroid impact, erupting volcanoes, and climate change. There is evidence that all three of these happened.
Observations:
OLD MILL PARK The first location we visited was called Old Mill Park and was located 38 degrees 19 min 11.6 sec N and 77 degrees 28 min 34.6 sec W with an elevation anywhere between 7-20 feet. The park was rich in geologic features, some which included a wide variety of rocks and minerals. Among these well sorted varieties were the likes of Mica, Quartz, Feldspar, Muscovite, Pyroxene, and Hornblende. Upon observation, we found that despite the wide range of minerals present, the outcrop lacked the presence of Calcite. We discovered this by dropping acid on the rocks and seeing if the was a fizzy reaction. There was not, thus indicating the absence of Calcite. Something else that caught our attention at the outcrop was the crystalline textures of the rocks (See figure 2a). By looking at the crystalline structures as well as the foliations in the rock, we were able to determine that the rocks found at the park were of the metamorphic variety. Some of the rocks we found were Gneiss as well as some Schist (See figure 2b).
ALUM SPRINGS PARK
The second location we visited was also a park, known as Alum Springs Park. It was located 38 degrees 17 min 17.8 sec N and 77 degrees 29 min 0.9 sec W with an elevation ranging from 80-100 feet. Almost immediately upon arriving at the outcrop, we were able to point out the obvious sedimentary features present (See figure 2c). For example, there were sandy grains found in between the rocks and the particles were well sorted and rounded. Just like at the previous location, we found a wide variety of rocks and minerals present. Some of them included quartz, feldspar, some coal and various sedimentary rocks including arkosic conglomerate. At this particular location, we took our observations a bit further and through the use of some tools, we found out the strike as well as the dip of the outcrop. The strike was calculated at 325 degrees N and the dip at 80 degrees E. One of the prominent features of the outcrop was the abundant vascular trees (See figure 2d) that were found there. In addition to the live trees surrounding the area, there were also fossils of them found within the rocks.
Interpretations:
OLD MILL PARK: The observations we made in our field notes were key in helping us determine the geologic history of the outcrops we visited. For example, in Old Mill Park, we identified two different types of rocks, which included Gneiss and Schist. Using the knowledge we acquired throughout the course, such as how metamorphic rocks come to be, as well as the observations we made in the outcrop (foliations, etc.), we can conclude that these rocks were formed under immense heat and pressure. By determining this, we also learn that the rocks most likely formed on the lithosphere when the Appalachians Mountains were first beginning to take shape. Additionally, through our observations, we found out how old the rocks were as well as what geologic era they were a part of. By examining criteria such as elevation level, mineral composition, and longitude and latitude we were able to determine that the rocks were approximately 300-400 million years old and were from the Devonian Period.

ALUM SPRING PARK: Alum Springs Park proved to have a much different geologic history than that of Old Mill Park, despite the two places sharing some of the same characteristics. This is why applying prior knowledge in addition to our observations was important in investigating the outcrop further. One difference between the two parks was the change in rock type that was associated with Alum Springs as opposed to Old Mill. Sedimentary rocks were the more dominant rocks found at Old Mill. Embedded within those rocks we found multiple traces of fossils of vascular trees. This is important because it allows us to narrow down the geologic age of the outcrop. Since there are fossils of vascular trees, we can conclude that rocks aren’t any older then the era in which the trees formed.
SYNTHESIS:
By pulling all of our observations and interpretations together, from both locations, it is quite easy to notice the obvious implications of their relationship to the Wilson Cycle. For example, the metamorphic rocks found at Old Mill Park gives us insight as to what happened, geologically speaking, in the past. As we know, metamorphic rocks can only form under immense heat and pressure deep in the Earth’s crust. By simply identifying this fact we are able to determine that Old Mill Park was either a declining ocean basin or there was no ocean basin at all. Also through the application of Wilsonian principles in combination with the observations made at Old Mill, we can take an educated guess and assume, given the evidence, that there was an “earlier” Atlantic.
Similarly, Alum Springs can also be broken down and evaluated more thoroughly by relating it to Wilsonian tectonics. Earlier, in our observations we noted that the geologic nature of Alum Springs was a Sedimentary one. We noted the strike and the dip of the location while also pointing out important features such as the abundant vascular trees as well as the fossils found. All of those features are accounted for under the Wilson Cycle. By examining these features we were able to determine that Alum Springs formed in the upper crust of the earth. The sedimentary rocks point of the obvious deposition of sandy grains which we found to have occurred in the late Cretaceous period. As we also noted in our observations, the rocks found in Alum Springs were not deformed. This means that Alum Springs was not a collisional setting, therefore indicating that the Atlantic was opening up (new ocean basin). This very concept is embedded within the Wilson Cycle and is known as the Juvenile stage. Overall, the message of this report is clear. The Cycle and Wilsonian tectonics apply to everything geologically related. Both play a major role in helping us understand the world and its components. As we found during our observations, understanding the Cycle is the prerequisite to conducting geological research.