Changes

[[file:paleontology_fig1.png|left|300px|thumb|{{figure number|1}}Example of paleontological data from a well showing fossil assemblages and interbedded paleoecology. Abbreviations for bioevents (paleotops): Glob flex = ''Globorotalia flexuosa'', Trim A = ''Trimosina denticulata'', Hyal B = ''Hyalinea balthica'', Glob M = ''Globorotalia miocenica'', Glob alt = ''Globoquadrina altispira''. Paleoecological abbreviations: Bathy = bathyal, M = middle, U = upper, O = outer, I = inner. (From Armentrout.<ref name=pt05r20>Armentrout, J. M., 1987, Integration of biostratigraphy and seismic stratigraphy, Pliocene-Pleistocene, Gulf of Mexico: 8th Annual Research Conference, Gulf Coast Section, Society of Economic Paleontologists and Mineralogists Foundation, p. 6–14.</ref>)]]

[[file:paleontology_fig1.png|left|300px|thumb|{{figure number|1}}Example of paleontological data from a well showing fossil assemblages and interbedded paleoecology. Abbreviations for bioevents (paleotops): Glob flex = ''Globorotalia flexuosa'', Trim A = ''Trimosina denticulata'', Hyal B = ''Hyalinea balthica'', Glob M = ''Globorotalia miocenica'', Glob alt = ''Globoquadrina altispira''. Paleoecological abbreviations: Bathy = bathyal, M = middle, U = upper, O = outer, I = inner. (From Armentrout.<ref name=pt05r20>Armentrout, J. M., 1987, Integration of biostratigraphy and seismic stratigraphy, Pliocene-Pleistocene, Gulf of Mexico: 8th Annual Research Conference, Gulf Coast Section, Society of Economic Paleontologists and Mineralogists Foundation, p. 6–14.</ref>)]]

Because fossil species evolved through time in genetically related lineages and because extinction events were followed by new assemblages of species, fossils provide the best criteria for dividing the geological record into time intervals characterized by the first-appearance datums (FADs) and last-appearance datums (LADs) of key species ([[:file:paleontology_fig1.png|Figure 1]]). Fossil tops and bases may be synchronous in sections where the strata record continuous deposition and where suitable environmental conditions persisted.

Because fossil species evolved through time in genetically related lineages and because extinction events were followed by new assemblages of species, fossils provide the best criteria for dividing the geological record into time intervals characterized by the first-appearance datums (FADs) and last-appearance datums (LADs) of key species ([[:file:paleontology_fig1.png|Figure 1]]). Fossil tops and bases may be [http://en.wiktionary.org/wiki/isochronous synchronous] in sections where the strata record continuous deposition and where suitable environmental conditions persisted.

[[file:paleontology_fig2.png|thumb|300px|{{figure number|2}}Example of geological time using the stratigraphic column of Cook Inlet basin, Alaska. Geological time table modified after van Eysinga<ref name=pt05r158>van Eysinga, F. W. B., 1975, Geologic Time Table: Amsterdam, Elsevier (chart).</ref>. Tertiary stages are from Wolfe<ref name=pt05r172>Wolfe, J. A., 1977, Paleogene floras from the Gulf of Alaska region: U., S. Geological Survey Professional Paper 997, p. 108.</ref>. (From Magoon & Claypool.<ref name=pt05r108>Magoon, L. B., Claypool, G. E., 1981, [http://archives.datapages.com/data/bulletns/1980-81/data/pg/0065/0006/1000/1043.htm Petroleum geology of Cook Inlet Basin—an exploration model]: AAPG Bulletin, v. 65, p. 1043–1061.</ref>)]]

[[file:paleontology_fig2.png|thumb|300px|{{figure number|2}}Example of geological time using the stratigraphic column of Cook Inlet basin, Alaska. Geological time table modified after van Eysinga<ref name=pt05r158>van Eysinga, F. W. B., 1975, Geologic Time Table: Amsterdam, Elsevier (chart).</ref>. Tertiary stages are from Wolfe<ref name=pt05r172>Wolfe, J. A., 1977, Paleogene floras from the Gulf of Alaska region: U., S. Geological Survey Professional Paper 997, p. 108.</ref>. (From Magoon & Claypool.<ref name=pt05r108>Magoon, L. B., Claypool, G. E., 1981, [http://archives.datapages.com/data/bulletns/1980-81/data/pg/0065/0006/1000/1043.htm Petroleum geology of Cook Inlet Basin—an exploration model]: AAPG Bulletin, v. 65, p. 1043–1061.</ref>)]]