Ordovician Life in Ohio - Research Paper Example

Ordovician Life in Ohio One of the most notable elements in the state of Ohio are sea life fossils that existed during the Ordovician period. As is well recognized during this geologic period the Ohio was at the bottom of the ocean and its present day geological elements represent fossilized remains of this seafloor period. Today the most visible remains of this period are in the rocks and geological formations that protrude into the Ohio atmosphere. Once such example of this is the Cincinnati Arch or Platform, a geological element that formed in the Ordovician period. In addition to these elements, there exists tremendous sea life that has surfaced in fossil form throughout Ohio. This essay functions to consider the Ordovician sea life in the state of Ohio. In developing this examination it presents a brief investigation into the geological and general scientific elements related to the Ordovician period, and then investigates the sea life that existed during this time. Ordovician Background The Ordovician period is a categorical definition of a period in geologic history. It roughly covers the time between 488 and 443 million years ago and falls within the Paleozoic Era. The period itself was named after a Celtic tribe of the Ordovices and gained its definition in the 19th century. The period itself is recognized as starting during the Cambrian-Ordovician extinction events. In total the period lasted for approximately 44.6 million years and concluded with the onset of the Ordovician-Silurian extinction event, which distinguishes nearly 60% of marine genera (Moore, Teichert 1978). These dates and distinguishing elements represent slight estimations, as they shift occasionally with the discovery of new radiometric patterns; the exact time period differs as sources disagree over various data elements. Within the Ordovician period there are a great many subdivisions, as distinguished by the years in which they occurred. One of the primary concerns of this era is in relation to paleogeography. Paleogeography indicates that during this period sea levels were generally high (Moore and Teichert 1978). Indeed, it’s been noted that the Ordovician period witnessed the As one later considers the Ordovician period in terms of the state of Ohio they will recognize that sea level and continent positioning was drastically different. During this period the southern area continents were part of one whole referred to as Gondwana. In addition to Gondwana there was also the continent of Baltica and Siberia, both which are now parts of present-day northern Europe, but at the time separate entities. In terms of the state of Ohio, the North American content was linked and referred to as Laurentia. There was tremendous geological change during this period, with underwater volcanoes emerging that would go on to form the Appalachian mountain range. Ordovician Life Abundant life emerged during the Cambrian period, and this life carried over to the proceeding Ordovician period. This life evolved and divided into new species many of which existed throughout what would later become the Ohio region. While fossilized sea life has been discovered throughout Ohio, perhaps the most prominent discoveries have come in the southwestern region of the state. It has even jokingly been noted that if one were to remove all of the Ordovician rocks from the Cincinnati area, then the state would once again fall below sea level. While there are a variety of sea life fossils that have been discovered in Ohio, scientists have identified a number as the most prominent. One of the most prominent such sea life fossils in Ohio are bryozoans. It’s been indicated that these animals, “lived in branching, treelike colonies or flattened, encrusting masses on shells of other invertebrates. In some areas bryozoans litter the outcrop. Brachiopods are no less spectacularly abundant than bryozoans and are a favorite of the beginning collector. They range in size from tiny species to the walnut-sized Platystrophia ponderosa“ (Hansen, pg. 5). The bryozoan itself still exists in the modern world. These animals feed through filters and implement a retractable lophophore collection of tentacles. As is expected these animals existed and continue to exist at trench levels. Colonies of these animals are referred to as zooids. In many of the Ohio fossil discoveries there are groups of zooids discovered, which is characteristic of bryozoan fossils in the Ohio region. Trilobites Another major sea life fossil creature discovered in Ohio are trilobites. Trilobites are notable as they have been recognized as the official state fossil. It’s been noted that the “remains of these arthropods are found in considerable abundance in some beds. The most common Cincinnatian trilobite, Flexicalymene , is best known from the Corryville Member of the Grant Lake Formation and from the middle part of the Waynesville Formation. Much less common are well-preserved specimens of Isotelus , Ohio's official State Fossil. This trilobite may have reached lengths of nearly 2 feet” (Hansen, pg. 5). Notably different than bryozoans, the trilobites are an extinct species. They emerged well before the Ordovician period, evolving into existence in the Early Cambrian period and continuing well into the Ordovician era where they flourished, before ultimately going extinct during the Devonian period. Still, they are recognized as one of the most successful of all early sea animals, having existed for approximately two-hundred and seventy million years. While trilobite refers to one specific categorical delineation, within this category there are a great variety of exoskeletons. For these reasons, the fossilized remains of these creatures discovered in the Ohio region varies along a great spectrum. Still, there are a number of elements that have been noted to be characteristic of these sea creatures. Generally, when fossilized remains of these creatures are discovered the exoskeleton is the only element that remains; however it’s been noted that in specific Cincinnati regions a collection of soft body parts have been discovered in addition to exoskeleton elements (‘Ohio Trilobites’). Trilobites have been discovered within both shale beds and limestone in the region; it’s been noted that the shale beds have produced the most fossilized discoveries. Within trilobites in the Ohio region, there are a number of prevalent fossils discovered. While over twenty types of trilobite fossils have been discovered, the major trilobites from the Ordovician period in the region are Flexicalymene, Isotelus, Cryptolithus, and Cesaurus. The Flexicalymene are recognized as the most prominent of the Ordovician trilobites discovered in the Ohio region. Within this fossil, there are three main species that have been discovered: meeki, retrorsa, and granulosa. Generally the size of these fossils is two inches long, which fossilized discoveries generally being of enrolled specimens. The next most prominent trilobite fossil discovered in the Ohio region is the Isotelus (‘Ohio Trilobites’). Like most Ordovician fossils, these fossils are in large part discovered embedded in rocks in the Cincinnati area. These fossils are more rare however, and are in large part discovered fragmented, with complete segments being a rare discovery. In large part scientists must collate enrolled specimens after that have been drawn out of a shale bed. Still, to find the most non-mutated segments it’s necessary to collect them from fresh and unweathered shale beds. For these reasons, fully in-tact specimens rarely exist, as the shale rock that would otherwise preserve these fossilized remains is prone to deterioration, carrying with it the broken down fossilized remains. More common areas of finding preserved specimens are in shale holdings, as these rock beds are not as prone to deterioration. As a result, it’s necessary to consider the important elements these rocks hold in the preservation of trilobite fossilized remains. In these regards, the most prominent rocks that contain fossils are maximus, brachycphalus, and gigas, with brachycephalus being the most prominent container of Isotelus fossils. Another notable aspect of Isotelus fossils are that they are recognized as the largest of the trilobites, with some discovered fossils being as large as foot and a half long. The final of the prominent Trilobite fossils discovered in the Ohio region are Cryptolithus tesselatus. These fossils are also referred to as the ‘lace collar’ because they contain a notable frizziled collar around the fringe of their cephalon. These fossils are recognized as being the most rare of the discovered fossils in the Ohio region, perhaps because they also represent the oldest of the fossils in the region. These fossils are not a particularly large specimen as they generally measure around two inches. Crinoids and Blastoids Other prominent Ordovician fossils discovered in the Ohio region are crinoids and blastoids. While these fossils have been discovered throughout the state, one of the most prominent areas they have been identified are in the Falls of Ohio. These fossils are broadly categorized in the phylum Echinodermata. This phylum contains a broad variety of fossilized remains and sea life specimens. For instance, commonly recognized Echinodermata fossils include starfish, sand dollars, and sea urchins. These fossils are similar to bryzoans as they both remain existent in the contemporary world; however, they are generally contained at around 300 meters or greater depth (Springer 1921). If there is a unifying feature of these fossils it is that they represent the spiny skinned specimens. These specimens also demonstrate a pentameral symmetry, indicating their body is organized in multiples of five. These fossils relation to the Ohio region carries a number of notable elements. One of the prominent characteristics of these fossils is their oftentimes being mistaken for planets. For instance, discoveries of these in the Cincinnati region were initially believed to be plants, as they illustrated a long, stem-like structure and it was only later that they were discovered to be crinoids. Crinoids are recognized as having a water vascular system that distributes oxygen through their tissues. In essence, these fossilized creatures once implemented seawater as their blood. Unique from other Ordovician fossils discovered in the Ohio region, these fossils did not have the ability to move. It’s perhaps for these reasons that many of the fossils have been preserved; for example, when a storm or rock sledge came through this sea life did not enjoy the luxury of moving, so they would be buried by the downfall and fossilized for future generations. Crinoid and blastoid fossils discovered in the Ohio region share a number of common elements, which is the primary reason behind their being classified together. The reasons they are classified as separate entities is perhaps most prominently linked to differing exoskeletons, known as the calice and thecae (Springer 1921). In terms of discovering crinoids and blastoids in Ohio the crinoid calice and the blastoid thecae are very rare to find. Indeed, the Ohio Falls region as few as a dozen such fossilized discoveries have been made by the staff over the years. Perhaps one of the primary reasons for this rarity has been indicated to be that, “muscles and ligaments holding the plates of a crinoid calyx together would rot soon after the animal’s death. Unless it was buried within a month, the calyx would disintegrate. The theca of the blastoid would usually be pulverized in strong ocean currents” (Goldstein, Web). It is for these reasons that crinoid and blastoid fossils are highly prized for collectors. Nautiluses Another highly prevalent fossil discovered in Ohio during the Ordovician period is the Nautiluses. These are marine creatures of the cephalopod family. In the contemporary world only a few of these species still, as they have long-gone extinct since the time they swam freely over the Ohio region during the Ordovician period. These sea creatures were characterized by involute or evolute shells that are, “generally smooth, with compressed or depressed whorl sections, straight to sinuous sutures, and a tubular, generally central siphuncle” (Kimmell, pg. 12). The nautilus is a part of the cephalopod categorization, but the fossils discovered most clearly in Ohio are of the nautilus variety. Within the nautilus discovered in the Ohio region, there are a number of further elements that are notable. These fossils are distinguished by a number of structural elements. These sea creatures had prominent head and tentacles. Differing themselves from other cephalopods, the nautilus has a great many tentacles. One of the prominently discovered fossilized elements is the objects shell. This is also a distinguishing element of the nautilus as the sea creature is capable of completely retreating into their shell. Climatic Events and Ohio’s Natural Resources There are a number of climatic events of the period that effect Ohio’s natural resources in the contemporary world. During the Ordovician period the proto-Atlantic Ocean began to close. This would ultimately result in a collision between Europe and the continent of North America during the middle of this period. This event would ultimately be referred to as the Taconic Orogeny (Boardman, Cheetham and Rowell 1987). While this event is not noted as directly affecting Ohio’s natural resources, climatic events surrounding this occurrence are recognized as having a significant geological impact. In these regards, the Knox unconformity where the land surface bulged upwards, constitutes a significant event during the Ordovician as it created erosion that would later form a complex delta system and create large beds of shale. During these island arc collisions volcanoes emerged that would deposit large beds of volcanic ash in the region. These ash features would later be altered to a clay known as bentonite, which is now found throughout Ohio (Greene 1904). A prominent geographic feature that was formed during this period was the Cincinnati Arch. While it’s not entirely known how this arch was formed, it’s understood to have occurred during the late Ordovician period, and have been perhaps a consequence of the Taconic Orogeny. In addition to these climatic events and natural creations, a great amount of limestone creation was developed during this period. These limestone resources were developed in large part through continental shifts and other deposits that occurred throughout the Ordovician period. These elements would later go on to develop significant limestone elements throughout the North American continent, specifically the Ohio region. Conclusion In conclusion, it’s clear that the Ordovician period has played a considerable role in the fossil record of Ohio. This essay has considered the various geological and scientific elements related to the broader contextual concerns of the period. The essay has also considered prominent sea life that existed during the period and was later found fossilized in the Ohio region. In these regards, the most prominent fossils identified most prominent in the region include bryozoans, trilobites, crinoids and blastoids, and nautiluses. While these are the most prominent sea life creatures from the Ordovician period found in the Ohio region, they by no means represent a comprehensive account of the fossilized life forms, as this would take an exhaustive scholastic effort. Finally, various climatic events of the period are considered, as well as the development of natural resources that occurred as a result of events of the Ordovician period. References Boardman, R.S., Cheetham A.H. and Rowell, A.J., (1987), ‘Fossil Invertebrates’, Blackwell Scientific Publications, 713 p. ‘Ohio Trilobites’ Geo Facts No. 5. Ohio Department of Natural Resources http://www.dnr.state.oh.us/Portals/10/pdf/GeoFacts/geof05.pdf Goldstein, Alan. ‘Crinoids and Blastoids’. Falls of the Ohio. http://www.fallsoftheohio.org/DevonianCrinoids-Blastoids.html Greene, G. K., (1904), Contributions to Paleontology, Ewing & Zeller, New Albany. Hansen, Michael. (1999) Geology of Ohio -- The Ordovician. Ohio Geology. http://jrscience.wcp.muohio.edu/downloads/Ordoviciangeology.pdf Kümmel,B. (1964). Nautiloidae-Nautilida, in the Treatise on Physiology, Geological Society of America and Univ of Kansas Press, Teichert and Moore eds. Moore, R.C. and Teichert, C., (1978), Treatise on Invertebrate Paleontology, Part T, Echinodermata. ‘Ohio Trilobites’ Geo Facts No. 5. Ohio Department of Natural Resources http://www.dnr.state.oh.us/Portals/10/pdf/GeoFacts/geof05.pdf Springer, Frank, (1921). The Fossil Crinoid Genus Dolatocrinus and its Allies, U.S. National Museum Bulletin 115. Read More