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#1. Which is younger? Igneous intrusion A Unconformity X-Y Which fossil existed during the Devonian Period? Ctenocrinus Dicellograptus During which geologic time period did elliptocephala exist? Ordovician Cambrian. #1. #2. Which layer is a good key bed Volcanic Ash Conglomerate
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Which is younger? • Igneous intrusion A • Unconformity X-Y • Which fossil existed during the Devonian Period? • Ctenocrinus • Dicellograptus • During which geologic time period did elliptocephala exist? • Ordovician • Cambrian #1
Which layer is a good key bed • Volcanic Ash • Conglomerate • In outcrop C, which is older? • The igneous intrusion • Fault X-Y • In outcrop B, the unconformity between the red sandstone and gray siltstone was created by: • erosion • volcanism #2
If the parent material is U-238, how old is the sample? • 9.0 by • 4.5 by • How many white squares would be left after three half-lives? • 6 • 3 • What fraction of the original isotope will be left after one more half-life has passed? • 1/8 • 1/4 #3
What is the youngest layer in the outcrop? • Wind Blown Sand • Till • Which agent of erosion created feature A? • Glaciers • Rivers • Which way was the wind blowing to create feature B? • From the NE • From the SW #4
What is the oldest rock unit shown? • F • I • The metamorphic rock slate could form at which of the following locations? • Between F and H • Between A and C • Which feature in this cross section is younger? • Fault J • Unconformity G? #5
What fraction of the original mass was left after 4 half-lives? • 1/16 • 1/8 • If the undecayed isotope is U-238, what is the decayed? • Pb-206 • Ca-40 • Which radioactive isotope would take longer to undergo the change in the graph? • U-238 • Rb-87 #6
If shale was deposited during the Early Cretaceous and schist was lithified in the late Triassic, what is the most likely age of the intrusion? • Jurassic • Late Cretaceous • Which event is most recent? • Tilting of shale • Erosion of shale • Which rock layer would most likely contain a fossilized Eurypterid? • Schist • Shale #7
Which fossil is most likely to be found in Ithaca, NY? • Coelophysis • Bothriolepis • Which organism most likely became extinct at the end of the Cretaceous? • Cryptolithus • Ceolophysis • Which organism existed at the same time as the Taconian orogeny? • Cryptolithus • Mastodont #8
Which letter represents the best index fossil? • B • C • What is the name of the law that explains why limestone is younger than sandstone? • Original horizontality • Superposition • If fossil C represents Centroceras, fossil B could represent… • Naples tree • Elliptocephala #9