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A typical shale is composed of about 58% clay minerals, 28% quartz, 6% feldspar, 5% carbonate minerals, and 2% iron oxides. [8] Most of the quartz is detrital (part of the original sediments that formed the shale) rather than authigenic (crystallized within the shale after deposition). [9]
Oil shale geology is a branch of geologic sciences which studies the formation and composition of oil shales–fine-grained sedimentary rocks containing significant amounts of kerogen, and belonging to the group of sapropel fuels. [1] Oil shale formation takes place in a number of depositional settings and has considerable compositional variation.
The shale layers often contain calcareous and phosphatic lenses, and also liesegang rings. The depositional environment is considered to have been deep marine within a basin-plain or outer basin-floor fan. The presence of tuff layers indicates that volcanic activity took place during the time of deposition.
[4] [11] Finally, the lack of acritarchs in the shales, the dominant lithology of the formation is regarded as evidence for minimal marine influence during their deposition. [12] Isolated shale beds within the Bright Angel Shale that contain a well preserved and diverse fauna of trilobites, brachiopods and others fossils likely represent ...
A diagram of various depositional environments. In geology, depositional environment or sedimentary environment describes the combination of physical, chemical, and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be formed after lithification, if the sediment is preserved in the rock record.
Eagle Ford stratigraphic column Outcrop of the Eagle Ford and Austin Chalk Contact off Kiest Blvd, 1/2 mile east of Patriot Pky in Dallas County. The Eagle Ford Group (also called the Eagle Ford Shale) is a sedimentary rock formation deposited during the Cenomanian and Turonian ages of the Late Cretaceous over much of the modern-day state of Texas.
The Juniata is defined as a grayish-red to greenish-gray, thin- to thick-bedded siltstone, shale, and very fine to medium-grained crossbedded sandstone or subgraywacke and protoquartzite with interbedded conglomerate. [3] [4] The Juniata is a lateral equivalent of the Queenston Shale in western Pennsylvania.
The Martinsburg is defined as a gray to dark gray, and infrequently tan and purple shale and slate.Local members of impure sandstone; thin, argillaceous limestone or phyllitic shale are present in the Cumberland Valley and the Lehigh Valley.