1. You are a graduate student in paleontology, studying a fossil site below an a
ID: 288010 • Letter: 1
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1. You are a graduate student in paleontology, studying a fossil site below an ancient coastal lagoon. A simplified and exaggerated profile of the rocks and sediments at your site is shown here. The profile is not drawn to scale Formation 1 is composed of fine-grained sediments in which mammal fossils are abundant, but no dinosaurs are found (assume you would have found some dinosaurs had there been any present on Earth when this layer was formed) Formation 2 is a layer of red clay in which several theropod and mammal fossils are found Formation 3 is composed of gravelly sediments Formation 4 Chemical analysis of this layer and a few calculations reveal that of the 10,000 atoms you sample X atoms (see below) of the 4"K that was originally present in the sample (at the time the lava cooled) have decayed into the two daughter isotopes, Ar and Ca Formation 5 is rich in reef deposits where fossil fish are abundant. Formation 6 is another surface-deposited layer derived from a volcanic lava flow. Chemical analysis of a feldspar sample from this layer reveals that Y of the 0K originally in the sample at its formation have decayed into DAr and Ca Formation 7 is composed of fine-grained sediment Formation 8 is an igneous (granite) intrusion. Your chemical analyses of the granite crystals demonstrate that for every 100,000 atoms of "U in the sample, there are Z (see below) atoms of Pb present. A Based on stratigraphic analysis of the profile, list the order in which the formations (1-8) were formed, from most recent to most ancient. (1 point) Estimate the probably age (in terms of millions of years from the present) for each formation. For formations that can't be dated with radiolsotopes, give a maximum and minimum age estimate, if both carn be estimated from the data at hand. These estimates can be used to estimate the ages of fossils found in each formation. Based on your calculations (carry out all calculations to 5 significant digits), construct a table showing minimum and maximum age estimats for each formation. You will have to use outside information on known fossil ages and geological history to fill in a few of these maxima and minima! (10 points) Would it be surprising to also find fossils of dinosaurs in formation 5? Briefly justify your answer. (2 points) B) C) X 1689, Y = 19.85%, Z = 4357Explanation / Answer
A) formation 6 then formation 7 then formation8 and then formation 3 then formation 2 then formation 1 then formation 5 then formation 4
B) formation 6,7,3 are more or less recent in geological age
Formation4 is of Palaeocene(cenzoic)
Formation5 is mesozoic
Formation 4 Cambrian
Formation5 proterozoic
C) formation5 should have been formed in Devonian period as fishes fossils are found. We can't found dinasours fossils in the period because dinasours were found in mesozoic era
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