ERTH 2401 Lecture : Lecture19-KTextinction.doc

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95% of all extinction are accounted for by background extinctions. Many dinosaurs have been victims to background extinction. Mass extinction: large numbers of species go extinct, many types of species go extinct, effect must take place on a global scale, happens over a short period of geological time. Times of mass extinction (know very important: late ordovician (438 ma, late devonian ( 380 ma, permian (245 ma) largest mass extinction 96% of all species, late triassic (208 ma, cretaceous/ tertiary ( 65 ma, manicouagan extinction. Study of extinctions-problems: incompleteness of fossil record, incompleteness of sedimentary record, resolution. Time resolution: 50-90% of the rock record not preserved, 9 out of 10 hours of earth history not preserved, either erosion or non-deposition, only 20 localities of k/t boundary. Effect of sampling: biostratigraphic ranges, last appearance datums, species disappear at different levels in different areas, signor-lipps effect.

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