|Exploring for Oil and Gas Traps|
|Series||Treatise in Petroleum Geology|
|Part||Predicting the occurrence of oil and gas traps|
|Author||Robert L. Fleisher, H. Richard Lane|
Agglutinated, or arenaceous, microfossils have tests (shells) constructed from sedimentary particles bound together by organic, calcareous, siliceous, or ferruginous cement. There is only one type of stratigraphically significant agglutinated microfossil: agglutinated, or arenaceous, foraminifera.
Agglutinated foraminifera are benthic microfossils found in rocks of Cambrian through Holocene age and in most marine and brackish environments, particularly in clastic facies. They construct their tests by gluing sedimentary grains together, in contrast to the other types of foraminifera, which secrete their tests. The sedimentary particles used by these forms may include silt or sand grains, glauconite, sponge spicules, or even other foraminiferal tests. Some species are highly selective in the material used and in its arrangement.
Although they are sometimes useful in age determination, agglutinated foraminifera are especially valuable as paleoenvironmental indicators because they are particularly characteristic of very shallow marine to brackish environments and very deep marine environments. Recent studies by Alve and Murray and Kaminski and Kuhnt suggest they may be useful in interpreting other paleoenvironments as well. Agglutinated foraminifera are the dominant and distinctive microfauna in Cretaceous and Tertiary flysch facies.
The color of agglutinated foraminifera has recently been shown to alter irreversibly with heating, both naturally within buried sediments and experimentally.
Figure 1 shows some typical agglutinated foraminifera.
- Microfossils in exploration
- Calcareous microfossils
- Siliceous microfossils
- Phosphatic microfossils
- Palynomorphs (organic-walled microfossils)
- Alve, E., and J. W. Murray, 1995, Experiments to determine the origin and palaeoenviron-mental significance of agglutinated foraminiferal assemblages, in M. A. Kaminski, S. Geroch, and M. A. Gasiński, eds., Proceedings of the Fourth International Workshop on Agglutinated Foraminifera: Grzybowski Foundation Special Publication 3, p. 1–11.
- Kaminski, M. A., and W. Kuhnt, 1995, Tubular agglutinated foraminifera as indicators of organic carbon flux, in M. A. Kaminski, S Geroch, and M. A. Gasiński, eds., Proceedings of the Fourth International Workshop on Agglutinated Foraminifera: Grzybowski Foundation Special Publication 3, p. 141–144.