Changes

Thermal maturity is the extent of heat-driven reactions that alter the composition of organic matter (e.g., conversion of sedimentary organic matter to [[petroleum]] or [[cracking]] of oil to [[gas]].) Different geochemical scales, such as [[vitrinite reflectance]], [[pyrolysis]] T_max, and [[biomarker]] maturity ratios can be used to indicate the level of thermal maturity of organic matter.<ref name=Petersetal_2012>Peters, Kenneth E., David J. Curry, and Marek Kacewicz, 2012, [http://archives.datapages.com/data/specpubs/hedberg4/INTRODUCTION/INTRODUCTION.HTM An overview of basin and petroleum system modeling: Definitions and concepts], ''in'' Peters, Kenneth E., David J. Curry, and Marek Kacewicz, eds., Basin modeling: New horizons in research and applications: [http://store.aapg.org/detail.aspx?id=1106 AAPG Hedberg Series no. 4], p. 1-16.</ref>

Thermal maturity is the extent of heat-driven reactions that alter the composition of organic matter (e.g., conversion of sedimentary organic matter to [[petroleum]] or [[cracking]] of oil to [[gas]].) Different geochemical scales, such as [[vitrinite reflectance]], [[pyrolysis]] T_max, and [[biomarker]] maturity ratios can be used to indicate the level of thermal maturity of organic matter.<ref name=Petersetal_2012>Peters, Kenneth E., David J. Curry, and Marek Kacewicz, 2012, [http://archives.datapages.com/data/specpubs/hedberg4/INTRODUCTION/INTRODUCTION.HTM An overview of basin and petroleum system modeling: Definitions and concepts], ''in'' Peters, Kenneth E., David J. Curry, and Marek Kacewicz, eds., Basin modeling: New horizons in research and applications: [http://store.aapg.org/detail.aspx?id=1106 AAPG Hedberg Series no. 4], p. 1-16.</ref>

Many of the elements of basin modeling programs—maturation of source rocks, reservoir diagenesis, and [[porosity]] evolution—are affected by thermal and burial history.<ref name=ch17r91>van Gizjel, P., 1980, Characterization and identification of kerogen and bitumen and determination of thermal maturation by means of qualitative and quantitative microscopical techniques, in How to Assess Maturation and Paleotemperatures: SEPM Short Course Notes, p. 1–56.</ref><ref name=ch17r70>Pradier, B., Bertrand, P., Martinez, L., Laggoun-Defarge, F., 1991, Fluorescence of organic matter and thermal maturity assessment: Organic Geochemistry, vol. 17, no. 4, p. 511–524, DOI: 10.1016/0146-6380(91)90115-Z.</ref> Thermal maturation data used to model these parameters are usually derived from fossils.

Many of the elements of basin modeling programs—maturation of source rocks, reservoir [[diagenesis]], and [[porosity]] evolution—are affected by thermal and burial history.<ref name=ch17r91>van Gizjel, P., 1980, Characterization and identification of kerogen and bitumen and determination of thermal maturation by means of qualitative and quantitative microscopical techniques, in How to Assess Maturation and Paleotemperatures: SEPM Short Course Notes, p. 1–56.</ref><ref name=ch17r70>Pradier, B., Bertrand, P., Martinez, L., Laggoun-Defarge, F., 1991, Fluorescence of organic matter and thermal maturity assessment: Organic Geochemistry, vol. 17, no. 4, p. 511–524, DOI: 10.1016/0146-6380(91)90115-Z.</ref> Thermal maturation data used to model these parameters are usually derived from fossils.

The following table shows which fossil material changes appearance due to thermal stress and therefore can be used as organic geothermometers.

The following table shows which fossil material changes appearance due to thermal stress and therefore can be used as organic geothermometers.

==Pollen and spores==

==Pollen and spores==

Pollen and spores are the organic-walled microfossils most commonly used for gauging paleotemperature. Fossil color, which changes with heating, is used to estimate a [[thermal alteration index]], or TAI.<ref name=ch17r82>Staplin, F., L., 1969, Sedimentary organic matter, organic metamorphism, and oil and gas occurrence: Bulletin of Canadian Petroleum Geology, vol. 17, no. 1, p. 47–66.</ref><ref name=ch17r56>Lerche, I., McKenna, T., C., 1991, Pollen translucency as a thermal maturation indicator: Journal of Petroleum Geology, vol. 14, no. 1, p. 19–36, DOI: 10.1111/jpg.1991.14.issue-1</ref><ref name=ch17r62>Marshall, J., E., A., 1991, Quantitative spore colour: Journal of the Geological Society of London, vol. 148, p. 223–233, DOI: 10.1144/gsjgs.148.2.0223</ref> The use of pollen and spores lets us examine in situ fossils rather than evaluate an aggregate “kerogen soup.” Other organic-walled fossils—acritarchs, chitinozoans, graptolites, scolecodonts (annelid worm jaws), and dinoflagellates—have been examined for their visual and reflected values, but these fossil groups have not been rigorously calibrated to the standard vitrinite reflectance scale.<ref name=ch17r16>Bertrand, R., Heroux, Y., 1987, [http://archives.datapages.com/data/bulletns/1986-87/data/pg/0071/0008/0950/0951.htm Chitinozoan, graptolite and scolecodont reflectance as an alternative to vitrinite and pyrobitumen reflectance in Ordovician and Silurian strata, Anticosti Island, Quebec, Canada]: AAPG Bulletin, vol. 41, p. 951–957.</ref>

Pollen and spores are the organic-walled microfossils most commonly used for gauging paleotemperature. Fossil color, which changes with heating, is used to estimate a [[thermal alteration index]], or TAI.<ref name=ch17r82>Staplin, F., L., 1969, Sedimentary organic matter, organic metamorphism, and oil and gas occurrence: Bulletin of Canadian Petroleum Geology, vol. 17, no. 1, p. 47–66.</ref><ref name=ch17r56>Lerche, I., McKenna, T., C., 1991, Pollen translucency as a thermal maturation indicator: Journal of Petroleum Geology, vol. 14, no. 1, p. 19–36, DOI: 10.1111/jpg.1991.14.issue-1</ref><ref name=ch17r62>Marshall, J., E., A., 1991, Quantitative spore colour: Journal of the Geological Society of London, vol. 148, p. 223–233, DOI: 10.1144/gsjgs.148.2.0223</ref> The use of pollen and spores lets us examine in situ fossils rather than evaluate an aggregate “[[kerogen]] soup.” Other organic-walled fossils—acritarchs, chitinozoans, graptolites, scolecodonts (annelid worm jaws), and dinoflagellates—have been examined for their visual and reflected values, but these fossil groups have not been rigorously calibrated to the standard vitrinite reflectance scale.<ref name=ch17r16>Bertrand, R., Heroux, Y., 1987, [http://archives.datapages.com/data/bulletns/1986-87/data/pg/0071/0008/0950/0951.htm Chitinozoan, graptolite and scolecodont reflectance as an alternative to vitrinite and pyrobitumen reflectance in Ordovician and Silurian strata, Anticosti Island, Quebec, Canada]: AAPG Bulletin, vol. 41, p. 951–957.</ref>

==Other microfossils==

==Other microfossils==

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

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

[[Category:Applied paleontology]]

[[Category:Applied paleontology]]