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Download Geological Time Scale [ B. Frueger – Colby ]
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Founders of Historical Geology Charles Darwin 1809-1882 Evolution – organisms changed through time Individuals with variations most favorable in existing environment had best chance of survival Passed these traits on to next generation Natural Selection Also recognized by Alfred Russell Wallace Neither knew the mechanism, do you? Founders of Historical Geology Charles Darwin 1809-1882 Origin of Species – 1859 Documented two things: 1. Evolution occurred 2. Natural selection was active & how it worked Organic evolution became the guiding principle of paleontological and biological research Founders of Historical Geology North American Notables William McClure 1763-1840 Produced the first geologic map of the US Founders of Historical Geology North American Notables Amos Eaton 1776-1842 Taught “hands on” geology at Rensselaer School (RPI) Took long field trips Father of American geology Studied New England region Founders of Historical Geology North American Notables Louis Agassiz 1807-1873 Recognized that massive ice sheets once covered North America First to hint at “ice ages” Stated that glacial deposits did not accumulate during Biblical flood Founders of Historical Geology North American Notables James Hall 1807-1873 First director of NY State Geological Survey Founders of Historical Geology North American Notables James D. Dana 1813-1895 Published Manual of Geology System of Mineralogy Founders of Historical Geology North American Notables John Wesley Powell Director of USGS First to traverse Grand Canyon by boat (1869) Union officer in Civil War Lost arm at Shiloh 1834-1905 Founders of Historical Geology North American Notables Othniel C. Marsh 1831-1899 Yale Edwin D. Cope 1850-1897 Penn Both vertebrate paleontologists Exploited fossil beds of western United States No cooperation between two Founders of Historical Geology North American Notables George Otis Smith Director of USGS 1907-1930 Colby graduate, 1893 1871-1944 Time and Geology The fundamental interest in geology is to put rocks in order time wise Geologists try to establish a GEOCHRONOLOGY Steno, Hutton, Smith etc tried by use of superposition, fossil succession As science advanced we used radiometric techniques. Time and Geology Smith and contemporaries used RELATIVE GEOLOGIC DATING techniques In relative dating, no reference to actual time Time and Geology ACTUAL OR NUMERICAL DATING tries to assign numbers in terms of years to events. Generally based on radiometric decay of unstable elements Expresses actual age of rocks or events Time and Geology GEOLOGIC TIME SCALE Subdivisions of Time Eons Eras Periods Epochs None last equal intervals of time. Based on events. Time and Geology Subdivisions of Time EON Largest subdivision of Geologic Time Scale Four Eons recognized Phanerozoic Proterozoic Archean Hadean Precambrian Time and Geology Precambrian Subdivisions of Time Phanerozoic Eon 0.544 byBP – present Includes most sedimentary rocks and history of life Proterozoic Eon 2.5-0.544 byBP Mostly crystalline rocks Archean Eon 3.9-2.5 byBP Oldest preserved rocks Hadean Eon 4.6–3.9 billion years before present (byBP) No geologic record Time and Geology Subdivisions of Time Phanerozoic Eon Three major subdivisions: ERA Cenozoic Era (recent life) 65 myBP-present Mesozoic Era (middle life) 250-65 myBP Paleozoic Era (ancient life) 544-250 myBP Time and Geology Subdivisions of Time Paleozoic Era 7 major subdivisions: PALEOZOIC PERIODS Permian Pennsylvanian Carboniferous Mississippian Devonian Silurian Ordovician Cambrian Time and Geology Subdivisions of Time EPOCH Periods are subdivided into EPOCHS Quaternary Period Holocene Epoch Pleistocene Epoch Tertiary Period Pliocene Epoch Miocene Epoch Oligocene Epoch Eocene Epoch Paleocene Epoch Time and Geology Subdivisions of Time Units on the Geologic Time Scale represent actual increments of time = GEOCHRONOLOGIC UNITS Actual rock units formed or deposited during these intervals are CHRONOSTRATIGRAPHIC UNITS Geochronologic Units Eon Era Period Epoch Age Chron Chronostratigraphic Units Eonathem Erathem System Series Stage Zone Time and Geology Subdivisions of Time Geochronologic units have the same names as Chronostratigraphic units Jurassic Period = Jurassic System Time and Geology Subdivisions of Time Geologic Time Scale Organized using fossil succession, superposition Then the units could be correlated Resolution of Geologic Time Scale still taking place today
