ENVIRSC 1G03 Lecture Notes - Lecture 17: Geologic Time Scale, Anthropocene, Hadean
7 Dec 2016
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An unconformity is a gap in the sedimentary record: since not all layers have been deposited continuously over time. Three types: disconformity: sedimentary rocks above and below are parallel, angular unconformity: folded, uplifted, eroded, nonconformity: such as metamorphic or igneous rocks underneath sedimentary strata. The (cid:710)time(cid:711) gap (cid:697)missing rock(cid:698) can only be measured by: Oldest to youngest: precambrian (4600 ma) Hadean period between formation of earth and oldest known rocks. Proterozoic multi-cellular organisms: paleozoic (541 ma 252. 2 ma) Sediments contain shelled marine organisms, primitive fish, amphibians, reptiles, plants: mesozoic (252. 2 ma 66 ma) Sediments contain remnants of reptiles, dinosaurs, and ammonites: cenozoic (66 ma present) Mammals and flowering plants, among others: anthropocene (present future?) Potential new time unit holocene or part of it has ended and. Based on geological evidence of human-induced environmental changes. Plastiglomerate: new type of rock cobbled together from plastic, volcanic rock, beach sand, seashells, and corals has begun forming on the shores of hawaii.
