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  = 17-9

  | topg    = 17-65

  | topg    = 17-10

  | 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

  | isbn    = 0-89181-602-X

  | isbn    = 0-89181-602-X

}}

}}

Siliceous microfossils are [http://www.biologycorner.com/lesson-plans/phyla/kingdom-protista/ protists] with shells constructed of opaline (amorphous) silica. There is no intense dissolution of siliceous remains in the deep ocean. Sediments deposited below the [http://geology.about.com/od/glossaryofgeology/fl/CCD.htm carbonate compensation depth] are commonly enriched in silica by removal of the carbonate, sometimes to the point of forming siliceous oozes. With subsequent remobilization of the silica, deep-sea [http://geology.com/rocks/chert.shtml cherts] may be formed. Siliceous microfossils are subject to burial [[diagenesis]] and become rare at great well depths except when recrystallized, preserved in nodules or concretions, or replaced by pyrite or calcite.

Siliceous microfossils are [http://www.biologycorner.com/lesson-plans/phyla/kingdom-protista/ protists] with shells constructed of opaline (amorphous) silica. There is no intense dissolution of siliceous remains in the deep ocean. Sediments deposited below the [http://geology.about.com/od/glossaryofgeology/fl/CCD.htm carbonate compensation depth] are commonly enriched in silica by removal of the carbonate, sometimes to the point of forming siliceous oozes. With subsequent remobilization of the silica, deep-sea [[chert]]s may be formed. Siliceous microfossils are subject to burial [[diagenesis]] and become rare at great well depths except when recrystallized, preserved in nodules or concretions, or replaced by pyrite or calcite.

There are three major groups of siliceous microfossils: radiolarians, diatoms, and silicoflagellates.

There are three major groups of siliceous microfossils: radiolarians, diatoms, and silicoflagellates.

[[file:applied-paleontology_fig17-6.png|300px|thumb|{{figure number|2}}Typical diatoms.]]

[[file:applied-paleontology_fig17-6.png|300px|thumb|{{figure number|2}}Typical diatoms.]]

Diatoms are [http://www.merriam-webster.com/medical/photosynthesis photosynthesizing] [http://www.thefreedictionary.com/planktonic protists] that occur in both marine and nonmarine environments. Marine diatoms range from [[Upper Jurassic]] or [[Lower Cretaceous]] to [[Holocene]] and are particularly useful for age and environmental determinations in the upper [[Cenozoic]]. Nonmarine diatoms range from [[Eocene]] to Holocene and also are useful in the upper [[Cenozoic]]. These microfossils can be a major rock-forming group, forming sedimentary rock (diatomites) consisting primarily of diatoms. Diatomaceous sediments, when altered by burial diagenesis, are converted to siliceous shale, [http://www.britannica.com/EBchecked/topic/470558/porcellanite porcellanite], and [http://geology.com/rocks/chert.shtml chert]. Such rocks can serve as sources and fractured reservoirs for hydrocarbons (e.g.,[[ Monterey Formation]] of California). The changes in rock properties associated with silica diagenesis permit seismic definition of [http://www.quartzpage.de/gen_mod.html silica phase transformation] zones in the subsurface (e.g., [http://wiki.seg.org/wiki/Dictionary:Bottom-simulating_reflector_%28BSR%29 bottom-simulating reflector]).

Diatoms are [http://www.merriam-webster.com/medical/photosynthesis photosynthesizing] [http://www.thefreedictionary.com/planktonic protists] that occur in both marine and nonmarine environments. Marine diatoms range from [[Upper Jurassic]] or [[Lower Cretaceous]] to [[Holocene]] and are particularly useful for age and environmental determinations in the upper [[Cenozoic]]. Nonmarine diatoms range from [[Eocene]] to Holocene and also are useful in the upper [[Cenozoic]]. These microfossils can be a major rock-forming group, forming sedimentary rock (diatomites) consisting primarily of diatoms. Diatomaceous sediments, when altered by burial diagenesis, are converted to siliceous shale, [http://www.britannica.com/EBchecked/topic/470558/porcellanite porcellanite], and [[chert]]. Such rocks can serve as sources and fractured reservoirs for hydrocarbons (e.g.,[[ Monterey Formation]] of California). The changes in rock properties associated with silica diagenesis permit seismic definition of [http://www.quartzpage.de/gen_mod.html silica phase transformation] zones in the subsurface (e.g., [http://wiki.seg.org/wiki/Dictionary:Bottom-simulating_reflector_%28BSR%29 bottom-simulating reflector]).

[[:file:applied-paleontology_fig17-6.png|Figure 2]] shows some typical diatoms.

[[:file:applied-paleontology_fig17-6.png|Figure 2]] shows some typical diatoms.

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

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

[[Category:Applied paleontology]]

[[Category:Applied paleontology]]