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  = 17-31

  | topg    = 17-65

  | topg    = 17-35

  | 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

==Examples of data interpretation==

==Examples of data interpretation==

[[file:applied-paleontology_fig17-17.png|left|300px|thumb|{{figure number|1}}Biofacies associations reflect different and distinctive populations liv- ing in different paleoenvironments. Copyright: Lagoe, 1989; courtesy Palaios.]]

[[file:applied-paleontology_fig17-17.png|left|300px|thumb|{{figure number|1}}Biofacies associations reflect different and distinctive populations liv- ing in different paleoenvironments. Copyright: Lagoe;<ref name=ch17r54 /> courtesy Palaios.]]

 

==Species distribution and oxygen concentration==

==Species distribution and oxygen concentration==

Lagoe<ref name=ch17r54>Lagoe, M., B., 1987, The stratigraphic record of sea-level and climatic fluctuations in an active-margin basin: the Stevens Sandstone, Coles Levee area, California: Palaios, vol. 2, no. 1, p. 48–68., 10., 2307/3514572</ref> recognizes four [[Fossil assemblage|biofacies]] of benthic foraminiferal species in the upper Miocene [[Stevens Sandstone]] of the southern [[San Joaquin Valley]]. He demonstrates that the biofacies distribution was largely controlled by changes in oxygen concentration caused by fluctuations in the position and intensity of low-oxygen water within the oxygen minimum zone.

Lagoe<ref name=ch17r54>Lagoe, M. B., 1987, The stratigraphic record of sea-level and climatic fluctuations in an active-margin basin: the Stevens Sandstone, Coles Levee area, California: Palaios, vol. 2, no. 1, p. 48–68., 10., 2307/3514572</ref> recognizes four [[Fossil assemblage|biofacies]] of [[benthic]] foraminiferal species in the upper Miocene [[Stevens Sandstone]] of the southern [[San Joaquin Valley]]. He demonstrates that the biofacies distribution was largely controlled by changes in oxygen concentration caused by fluctuations in the position and intensity of low-oxygen water within the oxygen minimum zone.

In [[:file:applied-paleontology_fig17-17.png|Figure 1]], biofacies associations reflect different and distinctive populations living in different paleoenvironments. Biofacies are arranged from left to right in order of inferred increasing oxygen concentration. The stratigraphic distribution strongly suggests systematic shifts in oxygen concentration.

In [[:file:applied-paleontology_fig17-17.png|Figure 1]], biofacies associations reflect different and distinctive populations living in different paleoenvironments. Biofacies are arranged from left to right in order of inferred increasing oxygen concentration. The stratigraphic distribution strongly suggests systematic shifts in oxygen concentration.

[[file:applied-paleontology_fig17-18.png|300px|thumb|{{figure number|2}}Species inhabiting high-oxygen environments (e.g., shelf depth) are small, prolate forms; those in low-oxygen environments (e.g., basin depths) are large, lanceolate forms. Copyright: Douglas, 1979; courtesy SEPM.]]

==Test shape and oxygen concentration==

==Test shape and oxygen concentration==

[[file:applied-paleontology_fig17-18.png|300px|thumb|{{figure number|2}}Species inhabiting high-oxygen environments (e.g., shelf depth) are small, prolate forms; those in low-oxygen environments (e.g., basin depths) are large, lanceolate forms. Copyright: Douglas;<ref name=ch17r33 /> courtesy SEPM.]]

Test morphologies of some closely related species of the foraminiferal genus ''Bolivina'' differ in patterns apparently related to oxygen concentration<ref name=ch17r33>Douglas, R., G., 1979, Benthic foraminiferal ecology and paleoecology: a review of concepts and methods, in Lipps, J., H., ed., Foraminiferal Ecology and Paleoecology: SEPM Short Course 6, p. 21–53.</ref><ref name=ch17r34>Douglas, R., G., 1981, Paleoecology of continental margin basins: a modern case history from the borderland of southern California, in Depositional Systems of Active Continental Margin Basins: Pacific Section of Society of Economic Paleontologists and Mineralogists Short Course Notes, p. 121–156.</ref> in modern environments along the California continental margin. Compressed, relatively large species (''B. argentea'') are typical of low-oxygen environments.

 

Test morphologies of some closely related species of the foraminiferal genus ''Bolivina'' differ in patterns apparently related to oxygen concentration<ref name=ch17r33>Douglas, R., G., 1979, Benthic foraminiferal ecology and paleoecology: a review of concepts and methods, in Lipps, J., H., ed., Foraminiferal Ecology and Paleoecology: SEPM Short Course 6, p. 21–53.</ref><ref name=ch17r34>Douglas, R., G., 1981, Paleoecology of continental margin basins: a modern case history from the borderland of southern California, in Depositional Systems of Active Continental Margin Basins: Pacific Section of Society of Economic Paleontologists and Mineralogists Short Course Notes, p. 121–156.</ref> in modern environments along the California [[continental margin]]. Compressed, relatively large species (''B. argentea'') are typical of low-oxygen environments.

In [[:file:applied-paleontology_fig17-18.png|Figure 2]], species inhabiting high-oxygen environments (e.g., shelf depth) are small, prolate forms; those in low-oxygen environments (e.g., basin depths) are large, lanceolate forms.

In [[:file:applied-paleontology_fig17-18.png|Figure 2]], species inhabiting high-oxygen environments (e.g., shelf depth) are small, prolate forms; those in low-oxygen environments (e.g., basin depths) are large, lanceolate forms.

[[file:applied-paleontology_fig17-19.png|left|300px|thumb|{{figure number|3}}Nonmarine (fluvial and marsh), lagoon, barrier, and marine environments and the interpreted sediment transport direction (large arrow) during one time interval. Copyright: Whittaker et al.;<ref name=ch17r95 /> courtesy Geological Society.]]

Whittaker et al.<ref name=ch17r95>Whittaker, M. F., Giles, M., R., Cannon, S., J., C., 1992, Palynological review of the Brent Group, UK sector, North Sea, in Morton, A., C., Haszeldine, R., S., Giles, M., R., Brown, S., eds., Geology of the Brent Group: Geological Society Special Publication 61, p. 169–202.</ref> provide an industrial example in the [[Brent Group]] (Jurassic), [[North Sea]], in which the distribution of palynomorph types is used to infer the depositional environments and extent of delta [[Depocenter#Sediment_supply_rate_and_facies_patterns|progradation]] during brief intervals of the Jurassic. [[:file:applied-paleontology_fig17-19.png|Figure 3]] illustrates the nonmarine (fluvial and marsh), lagoon, barrier, and marine environments and the interpreted sediment transport direction (large arrow) during one time interval. This information can help identify regions of greater potential for fluvial reservoir sands.

Oboh<ref name=ch17r67>Oboh, F., E., 1992, Multivariate statistical analysis of palyno debris from the Middle Miocene of the Niger Delta and their environmental significance: Palaios, vol. 7, p. 559–573., 10., 2307/3514869</ref> develops a paleoenvironmental model of Middle Miocene reservoir units from the Niger Delta, which uses palynomorphs and organic matter to interpret more precisely the depositional environments. This improves the understanding of the lateral continuity of the reservoir and its susceptibility to diagenetic changes.

Whittaker et al.<ref name=ch17r95>Whittaker, M. F., Giles, M. R., Cannon, S. J. C., 1992, Palynological review of the Brent Group, UK sector, North Sea, in Morton, A., C., Haszeldine, R., S., Giles, M., R., Brown, S., eds., Geology of the Brent Group: Geological Society Special Publication 61, p. 169–202.</ref> provide an industrial example in the [[Brent Group]] (Jurassic), [[North Sea]], in which the distribution of palynomorph types is used to infer the depositional environments and extent of delta [[Depocenter#Sediment_supply_rate_and_facies_patterns|progradation]] during brief intervals of the Jurassic. [[:file:applied-paleontology_fig17-19.png|Figure 3]] illustrates the nonmarine (fluvial and marsh), lagoon, barrier, and marine environments and the interpreted sediment transport direction (large arrow) during one time interval. This information can help identify regions of greater potential for fluvial reservoir sands.

[[file:applied-paleontology_fig17-20.png|thumb|300px|{{figure number|4}}Integrated paleoenvironmental interpretation of the E2.0 reser- voir (Middle Miocene, Niger Delta). Copyright: Oboh, 1992; courtesy Palaios.]]

Oboh<ref name=ch17r67>Oboh, F. E., 1992, Multivariate statistical analysis of palyno debris from the Middle Miocene of the Niger Delta and their environmental significance: Palaios, vol. 7, p. 559–573., 10., 2307/3514869</ref> develops a paleoenvironmental model of Middle Miocene reservoir units from the Niger Delta, which uses palynomorphs and organic matter to interpret more precisely the depositional environments. This improves the understanding of the [[lateral]] continuity of the reservoir and its susceptibility to diagenetic changes.

==Integrated paleoenvironmental interpretation==

==Integrated paleoenvironmental interpretation==

[[:file:applied-paleontology_fig17-20.png|Figure 4]] shows an integrated paleoenvironmental interpretation of the E2.0 reservoir (Middle Miocene, [[Niger Delta]]). Lithofacies range from pebbly sandstones (S1) to mudstones (M2). The palynofacies are composed of the following substances:

[[:file:applied-paleontology_fig17-20.png|Figure 4]] shows an integrated paleoenvironmental interpretation of the E2.0 reservoir (Middle Miocene, [[Niger Delta]]). [[Lithofacies]] range from pebbly sandstones (S1) to mudstones (M2). The palynofacies are composed of the following substances:

 

* Wood and amorphous organic matter

* Wood and amorphous organic matter

The paleoenvironmental interpretation should be integrated with interpretations based on other data sources (e.g., sedimentology well log analysis, seismic) and plotted on wells or [[cross section]]s.

The paleoenvironmental interpretation should be integrated with interpretations based on other data sources (e.g., sedimentology well log analysis, seismic) and plotted on wells or [[cross section]]s.

 

===Limitations===

===Limitations===

Paleoenvironmental analysis can be limited by the ambiguity of the paleoecological significance of the fossils recorded. In general, reconstructions of paleoenvironment become less precise and less reliable with increasing geologic age as the affinities of ancient to modern forms become very distant.

Paleoenvironmental analysis can be limited by the ambiguity of the paleoecological significance of the fossils recorded. In general, reconstructions of paleoenvironment become less precise and less reliable with increasing geologic age as the affinities of ancient to modern forms become very distant.

* [[Thermal maturation]]

* [[Thermal maturation]]

* [[Biostratigraphy in sequence stratigraphy]]

* [[Biostratigraphy in sequence stratigraphy]]

==References==

==References==

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

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

[[Category:Applied paleontology]]

[[Category:Applied paleontology]]