Homework 1

Homework 1 - SIO16 Homework 1 RELATIVE DATING Name Due From...

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SIO16 Name ______________________ Homework 1 Due: 4/8/11 RELATIVE DATING: From the lectures, you have already been introduced to several principles used in assigning relative ages to sedimentary rock formations (formation = a distinctive body of rock that serves as a convenient unit for mapping). These are: Principle of Faunal Succession : Groups of fossil plants and animals occur in the geologic record (in sediments) in a definite and determinable order. These groups can be associated with particular periods of geologic time. In applying this principle we use a global age range (below left), which is essentially a chart showing the geological times in which the species existed. This global age range must be constructed from many sedimentary sequences (no single sequence typically spans all of geologic time). We'll discuss later how the absolute ages are determined. The diagram below (left) shows that species A existed from 100 Ma to 75 Ma, species B existed from 90 to 65 and species C existed from 75 to 40 Ma. Once the sequence in which the fossils occur is established, the occurrence of particular fossils can be used to correlate (determine layers of the same age) between sedimentary sequences in different places. The sequence of fossils can also be used to recognize missing time. If there was continuous deposition of sediments in a basin then the geological section should successive layers having A, A+B, B+C, C from bottom to top. Absence of any of the assemblages would indicate a period of erosion or non-deposition (unconformity). In the diagram above (right) we suspect that time is missing between unit 1 and unit 2 because of the absence of a layer having fossils A+B. The approximate amount of missing time (~15 million years in the example above) can also be estimated from the
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global age range. Principle of Superposition
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This note was uploaded on 04/06/2011 for the course SIO 16 taught by Professor Gee,j during the Spring '08 term at UCSD.

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Homework 1 - SIO16 Homework 1 RELATIVE DATING Name Due From...

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