This document discusses how fossils found in different layers of the geologic column can be used to determine the relative ages of the strata. It explains that each fossil is from a different era in earth's history, and they are deposited in sediments as time passes. The document also analyzes four specific fossils found in a location, identifying the fossils and the periods they are from, ranging from the oldest Cambrian period fossil to the youngest Pennsylvanian period fossil. It determines that the area shows exposures from several periods but not others, indicating periods where no life was preserved in the rock strata.

1. Fossils and the Geologic Column<br />Carol Rene Green<br />SCI/245 Physical Geology<br />April 16, 2011<br />Heather Hill<br />Fossils and the Geologic Column<br />Fossils are important to determining the relative age of the strata. Each fossil found is from a different era in time. Theses fossils are deposited in the sediments of the strata as time evolved. The different types of fossils found in different strata layers can help determine a time period for which the fossilized animal or plant existed. The three localities in figure 3.6 on p. 68 of the text look to be around the same age for the fossil assemblages seem to be the same or similar. The fossils from figure 3.6 are from the Paleozoic Era (age of ancient life). There are basically four fossils the oldest being from the Cambrian period and called Paradoxides pinus. The next fossil in succession is from the Ordovician period and is called the Bathyurus extans. The third fossil in succession is from the Mississippi period and is called the Prolecanites gurleyi. The fourth fossil and the youngest of the four is from the Pennsylvanian period called the Dictyoclostus americanus. The area of rock exposed is evident from the Pennsylvanian, Mississippi, Ordovician, and the Cambrian period. It shows to me that during the Silurian and the Devonian period there was no exposed rock layer for plant or animal life to become fossilized in.<br />