Founders of Historical Geology Charles Darwin 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 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 Produced the first geologic map of the US

Founders of Historical Geology North American Notables Amos Eaton 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 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 First director of NY State Geological Survey

Founders of Historical Geology North American Notables James D. Dana 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

Founders of Historical Geology North American Notables Othniel C. Marsh Yale Edwin D. Cope 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 Colby graduate, 1893

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 Subdivisions of Time Phanerozoic Eon byBP – present Includes most sedimentary rocks and history of life Proterozoic Eon byBP Mostly crystalline rocks Archean Eon byBP Oldest preserved rocks Hadean Eon 4.6–3.9 billion years before present (byBP) No geologic record Precambrian

Time and Geology Subdivisions of Time Phanerozoic Eon Three major subdivisions: ERA Cenozoic Era (recent life) 65 myBP-present Mesozoic Era (middle life) myBP Paleozoic Era (ancient life) myBP

Time and Geology Subdivisions of Time Paleozoic Era 7 major subdivisions: PERIODS Permian Pennsylvanian Mississippian Devonian Silurian Ordovician Cambrian Carboniferous PALEOZOIC

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 UnitsChronostratigraphic Units Eon Eonathem Era Erathem Period System Epoch Series Age Stage Chron 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