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Paleozoic Era in the geology of Indiana Essay

Paleozoic Era means “time of ancient life”. It is estimated to have occurred somewhere around 544 and 245 million years ago. During this time period, the Paleozoic era, there was a great increase in variety and development of life. Animal fauna were abundant during the Paleozoic era. It is a time when different types and forms of plants and animals flourished and became diverse and plentiful. Many with hard shells and exoskeletons appeared. As a result more organisms formed into fossils which left trail of history behind for scientists to study.

This era is very important in that is entails an explosion of animal growth in which nearly all living animals appeared and then at the end of the Paleozoic era, during the Permian sub era, suddenly a mass extinction wiped out nearly 90% of all living matter. Much research continues into the reasons why these two extreme situations occurred. (Palmer and Geismann Nov 2002) Subdivisions of the Paleozoic era are; in order of time period most recent to oldest, Permian is also referred to as the age of dinosaurs and Pangea.

Pangea was the name when the earth was considered a supercontinent. The majority of the plates had massed together and had just one ocean. The land was relatively dry and had few glaciers. Next came the sub-era, Carboniferous Pennsylvanian (high carboniferous) and Mississippian (lower carboniferous) depicted mostly by the large coal deposits in the area of modern day Pennsylvania with many coal swamps which then spread towards the Mississippi river and became more limestone.

The stratigraphy (the study of strata or layers) of the two areas is quite different as a result. This area today called Indiana is in the upper Mississippi River valley. It was mostly made up of Limestone and since sea covered much of the continent at this time, there was a large marine population. Many remnants left over were lime marked by green algae and calcium carbonate which has been eroded and formed by waves and sea water. Then came the Devonian sub era, in which small plants began to appear in the beginning and by the end large trees emerged.

Also, tetra pods (considered the first vertebrates to exist on earth) or vertebrates began to inhabit the land. Arthropods (an invertebrate having an exoskeleton, segmented body and jointed appendages), insects and arachnids (eight legged and jointed invertebrate animals in the subphylum Chelicerata) also came about during the Devonian time period. Echinoderms (creature with a limited nervous system) and a wide variety of fish also became plentiful. The Silurian era was marked by great changes in the physical makeup of the earth.

The basic climates over the earth stabilized and glaciers and their formations melted and the seas levels rose. As a result, the fish population grew by leaps and bounds. Corals reefs developed and marine life continued to thrive. Freshwater varieties and fish with jaws occurred for the first time. The Ordovician sub era was a period during the Paleozoic era when much of the northern hemisphere as mostly underwater and a large land mass was in the south called Gondwana. The land was moist and had migrated close to the South Pole.

It is known for its marine invertebrates and limited plants on land. Glaciers ultimately formed and much of the land froze and formed glaciers. This ended with mass extinction of 60% of marine life. The Cambrian era was considered the explosion where a grand diversity of life on earth boomed all of a sudden. Various types of rock were formed during the Paleozoic era. The earth was six large land masses at this time. Modern day continents were relocated and divided later on. Therefore different rocks and formations existed.

Limestone and coal are two examples of rock formed during the Paleozoic era. Sedimentary and Cambrian rock and fossils dating back to the Paleozoic era can be found in the state of Indiana. It was close to the equator during the Pangea and lay in a shallow sea of water. Later as the land changed, sand from the Acadian Mountains washed over the rocks and land in the sea. Mollusks, Crinoids, bryozoans, brachiopods, gastropods, bivalves, which are two half shelled filter-feeders, gastropods (snails) and trace fossils can be found as remnants of that time period in the state.

Much of the large amounts of plants from the delta are where the large amount of coal originated from. Plants included ferns, seed ferns, moss and many types of swamp plants which also contributed to the large deposits of coal. Plant fossils from the late Paleozoic era include Lepidodendron, Sigillaria, Calamites, Pecopteris, Annularia and Asterphyllities. (Polly, David 2007) Currently, Indiana is rich in limestone, aggregates (crushed limestone dolomite, sand and gravel), aglime (agricultural lime) and other minerals and rock forms.

It also has siliciclastic (made from broken pieces of silica rocks) and carbonate rocks (sedimentary rocks made up of mostly carbonate minerals) and coal. These rocks have all evolved from the Paleozoic era through the rock cycle of erosion, deposition, temperature and pressure. Older rocks are altered and become slightly different and newer younger versions.

Lingulella © 2003 Milwaukee Public Museum Works Cited Collins, Allen (1994) last updated in 1999 The Paleozoic Era Web Geological Time Machine Accessed on May 31, 2010 <http://www.ucmp. berkeley. edu/help/timeform. html> Polly, David (2007) Historical Geology Paleozoic Fossils II Accessed on May 31, 2010 <http://www. indiana. edu/~g112/Lab%2011%20Handout. pdf> Freebee, M. J. (2002) Paleobiology: The Early Paleozoic Accessed on June1, 2010 <http://www. emc. maricopa. edu/faculty/farabee/biobk/BioBookPaleo3. html> UCMP The Paleontology Portal Indiana, U. S. Accessed on May 31, 2010 <http://www. paleoportal. org/index. php? globalnav=time_space&sectionnav=state&name=Indiana>


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