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Boquillas Formation
The Boquillas Formation is a geologic Formation (geology), formation deposited during the Late Cretaceous in modern-day West Texas. It is typically composed of alternating marls and limestones with thin volcanic ash beds (bentonites). It was named for outcrops near the former Boquillas post office in Big Bend National Park. The term Boquillas Formation has been used for rocks that outcrop from Del Rio, Texas to as far west as Doña Ana County, New Mexico. Vertebrate fossils found in the Boquillas Formation include mosasaurs, fish bones, and shark's teeth.Gorden L. Bell, Jr., Kenneth R. Barnes and Michael J. Polcyn (2013) Late Cretaceous mosasauroids (Reptilia, Squamata) of the BigBend region in Texas, USA. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, Available onCJO 2013 doi:10.1017/S1755691013000406Hunt, ReBecca K., Vincent L. Santucci and Jason Kenworthy (2006) A preliminary inventory of fossil fish from National Park Service units, ''in'' S. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Formation (stratigraphy)
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the stratigraphic column). It is the fundamental unit of lithostratigraphy, the study of strata or rock layers. A formation must be large enough that it can be mapped at the surface or traced in the subsurface. Formations are otherwise not defined by the thickness (geology), thickness of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock. The concept of a geologic formation goes back to the beginnings of modern scientific geology. The term was used by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
