UH GEOL 1376 - Lecture 4 (3 pages)

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Lecture 4



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Lecture 4

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Pages:
3
School:
University of Houston
Course:
Geol 1376 - Historical Geology
Historical Geology Documents

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9 4 14 Chapter 4 Stratigraphic principles Humans classify things classification of phenomena is inherent necessary for reasoning 4 kinds of strata graphic classification lithostratigraphic rocks by lithology biostratigraphic rocks by fossils chronostratigraphic rocks by age geochronologic time abstract Lithostratigraphy lithostratigraphic unit local unit of rock defined by lithology color composition texture stratification genesis origin formation is basic unit boundaries may be sharp transitional or arbitrary group formation member bed large to small named for geographic feature Diachronous cutting across time time transgressive not exactly the same age everywhere upper and lower boundaries are not time horizons lithographic units never correspond exactly to chronostratigraphic units because a local environment occupies just a small area at any time migrates across a much larger area through time sediment deposited in this environment is of different ages in different places it is not important to distinguish lithographic and chronostratigraphic units Biostratigraphy basic unit bio zone fossil zone unit of rock defined by fossils includes all rocks in which an index fossil occurs named for that fossil examples named for Cretaceous oysters Texas Exogyra ponderosa zone Exogyra cancellata zone Index fossils lived only short time Purpose of biostratigraphy is to provide evidence for chronostratigraphy Good index fossils evolve rapidly diverse many species short stratigraphic ranges planktonic float at surface independent of sea floor environment regional to global distribution large population good for long distance correlation Facies environmental aspect of a rock Good facies fossils conservative evolve slowly not diverse long strata graphic ranges Benthic live on sea floor environmentally restricted local to global distribution useless for long distance correlation useful for recognizing environments of deposits Chronostratigraphy chronostratigraphic unit by any



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