Changes

  | part    = Predicting the occurrence of oil and gas traps

  | part    = Predicting the occurrence of oil and gas traps

  | chapter = Applied paleontology

  | chapter = Applied paleontology

  | frompg  = 17-1

  | frompg  = 17-25

  | topg    = 17-65

  | topg    = 17-25

  | author  = Robert L. Fleisher, H. Richard Lane

  | author  = Robert L. Fleisher, H. Richard Lane

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch17/ch17.htm

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch17/ch17.htm

==Definition==

==Definition==

Paleoclimate can be operationally defined as those factors of climate, weather, and atmospheric and oceanic circulation that influence biotic distribution and the rate and locus of clastic, evaporite, and carbonate deposition.

Paleoclimate can be operationally defined as those factors of climate, weather, and atmospheric and oceanic circulation that influence biotic distribution and the rate and locus of [http://www.merriam-webster.com/dictionary/clastic clastic], [[evaporite]], and [[carbonate]] deposition.

==Utility of fossils in paleoclimatology==

==Utility of fossils in paleoclimatology==

Fossils have been used in an ''ad hoc'' manner to interpret climate since the beginnings of geology as a science, but a systematic methodology for using fossils to assess climate is still lacking. The following elements can contribute to such a methodology:

Fossils have been used in an ''ad hoc'' manner to interpret climate since the beginnings of geology as a science, but a systematic methodology for using fossils to assess climate is still lacking. The following elements can contribute to such a methodology:

* Biostratigraphic correlation

* [[Biostratigraphic correlation and age determination|Biostratigraphic correlation]]

* Adaptive morphology of animals and plants

* Adaptive morphology of animals and plants

* Isotopic “paleothermometers”

* Isotopic “paleothermometers”

==Biostratigraphic correlation==

==Biostratigraphic correlation==

Because climate is a global phenomenon, the various lithofacies and biofacies that reflect climate in the time interval of interest must be correlated accurately. Climates may change abruptly, and biostratigraphy provides the only practical means to demonstrate the contemporaneity, or lack of it, of contrasting climates.

Because climate is a global phenomenon, the various [[lithofacies]] and [[Fossil assemblage|biofacies]] that reflect climate in the time interval of interest must be correlated accurately. Climates may change abruptly, and [[Biostratigraphic correlation and age determination|biostratigraphy]] provides the only practical means to demonstrate the contemporaneity, or lack of it, of contrasting climates.

==Adaptive morphology==

==Adaptive morphology==

For example, many plants of the tropical rain forest have drip points on their leaves to facilitate rainwater drainage; similar features on fossil leaves can be taken to suggest a similar paleoenvironment.

For example, many plants of the tropical rain forest have drip points on their leaves to facilitate rainwater drainage; similar features on fossil leaves can be taken to suggest a similar paleoenvironment.

This approach can be used even when the significance of the adaptive form is unclear; Wolfe<ref name=ch17r96>Wolfe, J. A., 1979, Temperature parameters of humid to mesic forests of eastern Asia and relation to forests of other regions of the northern hemisphere and Australia: U., S. Geological Survey Professional Paper 1106-K, 37 p.</ref> for example, suggests that quantification of angiosperm leaf characteristics (i.e., the percentage of entire-margined leaves) helps us determine [[Tertiary]] temperatures to within [[temperature::1&deg;C]].

This approach can be used even when the significance of the adaptive form is unclear; Wolfe<ref name=ch17r96>Wolfe, J. A., 1979, Temperature parameters of humid to mesic forests of eastern Asia and relation to forests of other regions of the northern hemisphere and Australia: U.S. Geological Survey Professional Paper 1106-K, 37 p.</ref> for example, suggests that quantification of angiosperm leaf characteristics (i.e., the percentage of entire-margined leaves) helps us determine [[Tertiary]] temperatures to within [[temperature::1&deg;C]].

==Isotopic paleo-temperature==

==Isotopic paleotemperature==

An analysis of the ratios of oxygen isotopes in fossil shell material yields estimates of ancient temperatures. Oceanic paleotemperatures based on analysis of fossil calcareous foraminiferal tests are widely used to interpret Cenozoic paleoclimate and paleoceanography (see [[Stable isotope stratigraphy]]).

An analysis of the ratios of oxygen isotopes in fossil shell material yields estimates of ancient temperatures. Oceanic paleotemperatures based on analysis of fossil calcareous [http://www.ucmp.berkeley.edu/foram/foramintro.html foraminiferal] tests are widely used to interpret [[Cenozoic]] paleoclimate and [[Paleobathymetry|paleoceanography]] (see [[Stable isotope stratigraphy]]).

==Quantitative paleoclimate models==

==Quantitative paleoclimate models==

Quantitative paleoclimate models often produce unique solutions to the paleoclimatic interpretation of geologic and paleontologic data.

Quantitative paleoclimate models often produce unique solutions to the paleoclimatic interpretation of geologic and paleontologic data.

A quantitative community climate model (CCM₁) at the National Center for Atmospheric Research was used by Amoco Production Research to investigate possible causes of Late Devonian extinctions. The results<ref name=ch17r69>Ormiston, A., R., Klapper, G., 1992, Paleoclimate, controls on Upper Devonian source rock sequences and stacked extinctions (abs.), in Lidgard, S., Crane, P., R., eds., Fifth North American Paleontological Convention Abstracts and Programs: Paleontological Society Special Publication 6, p. 227.</ref> suggest two things:

A quantitative community climate model (CCM₁) at the National Center for Atmospheric Research was used by Amoco Production Research to investigate possible causes of [[Late Devonian]] extinctions. The results suggest two things:

* There was no perennial snow cover and, hence, no glaciation in the Austral regions.

* There was no perennial snow cover and, hence, no glaciation in the austral regions.<ref name=ch17r69>Ormiston, A. R., and G. Klapper, 1992, Paleoclimate, controls on Upper Devonian source rock sequences and stacked extinctions (abs.), in S. Lidgard, and P. R. Crane, eds., Fifth North American Paleontological Convention Abstracts and Programs: Paleontological Society Special Publication 6, p. 227.</ref>

* Simulated sea-surface temperatures in the tropics ranged from [[temperature::27&deg;C]] to [[temperature::34&deg;C]]—high enough to kill reefs.<ref name=ch17r84>Thompson, J., Newton, C., 1989, Late Devonian mass extinction: episodic cooling or warming?, in McMillan, N., Embry, A., Glass, D., eds., Devonian of the World: Canadian Petroleum Society Memoir 14, vol. 3, p. 29–34.</ref>

* Simulated sea-surface temperatures in the tropics ranged from [[temperature::27&deg;C]] to [[temperature::34&deg;C]]—high enough to kill reefs.<ref name=ch17r84>Thompson, J., and C. Newton, 1989, Late Devonian mass extinction: episodic cooling or warming?, in N. McMillan, A. Embry, and D. Glass, eds., Devonian of the World: Canadian Petroleum Society Memoir 14, vol. 3, p. 29–34.</ref>

These results support a climatic cause for the extinctions.

These results support a climatic cause for the extinctions.

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Applied paleontology]]

[[Category:Applied paleontology]]