Earth Science Quiz
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DEEP TIME AND EARTH HISTORY
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In a road cut, a geologist observes a sequence of parallel sedimentary layers. The lowest layer contains fossils of trilobites from the Ordovician period. The layer directly above it, with no evidence of an irregular contact, contains fossils of fish from the Devonian period. Fossils from the Silurian period, which is between the Ordovician and Devonian, are absent. This boundary represents a(n):
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