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Lecture 15 Lithostratigraphy. Lithostratigraphy Biostratigraphy Seismic stratigraphy. Magnetostratigraphy Geochemistry stable istopes radiometric dating. Stratigraphy: Putting together the whole picture (processes and history). I. “Facies” (Steno, 1669) “aspect” or “appearance” .
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Lithostratigraphy Biostratigraphy Seismic stratigraphy Magnetostratigraphy Geochemistry stable istopes radiometric dating Stratigraphy: Putting together the whole picture (processes and history)
I. “Facies” (Steno, 1669) “aspect” or “appearance” Can be genetic (fluvial facies) or descriptive (sandstone facies) Lithofacies = a consistent lithologic character within a formation. E.g. an evaporite lithofacies Walther’s law (1894) = facies that occur in conformable vertical successions of strata also occur in laterally adjacent environments.
II. Accumulation • Base level. Above sealevel, preservation is the exception rather than the rule • Sediment traps • tectonic • basin subsidence • sea-level rise
III. Gaps • Diastems = obscure, small gaps in the record. Barrell (1917) • Unconformities = larger gaps in the record.
IV. Correlation • Demonstrating the equivalence or correspondence of geographically separated parts of a geologic unit
Old (pre-1930) and new interpretations of units in the Devonian Catskills. Layer-cake versus concept of facies change.
An example of time-transgression of lithofacies from the Everglades
V. Sequences • Major unconformities representing Earth’s broad tectonic or eustatic events.
Time (geochronologic) units Eon Era Period Epoch Age VI. Time, Time-Rock and Rock Units • Time-rock chronostratigraphic) units • Eonothem • Erathem • System • Series • Stage • Zone
Time units Phanerozoic eon Cenozoic era Quaternary period Holocene epoch Wisconsinan age Examples • Time-rock units • Eonothem • Erathem • System • Series • Stage
Rock (lithostratigraphic) units • Supergroup • Group • FORMATION a mappable unit with distinctive lithic characteristics • Member • Bed