Biology 1001A Chapter Notes - Chapter 20.1 and 20.2: Paleogene, Phanerozoic, Neogene
Document Summary
Many fossils are found in sedimentary rock. Sediments found in any one place form distinctive strata (layers) that usually differ in colour, mineral composition, particle size, and thickness. If left undisturbed, the strata are arranged in the order on which the formed. Strata are sometimes uplifted, warped, or inverted by geological processes. Geologists deduced that fossils discovered in a particular sedimentary stratum, no matter where it was found, represent organisms that lived and died roughly the same time in the past. Because each stratum was formed at a specific time, the sequence of fossils from lowest (oldest) to highest (newest) strata reveals their relative ages. Geologists used the sequence of strata and their distinctive fossil assemblages to establish the geologic time scale that diagrams the history of life on earth. Angiosperm and mammals further diversify and dominate terrestrial habitats. Angiosperm and insects diversify; modern orders of mammals differentiate.
