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Guanling Formation
The Guanling Formation is a Middle Triassic (Anisian or Pelsonian in the regional chronostratigraphy) geologic Formation (geology), formation in southwestern China. Geology The formation encompasses two members. The first member is primarily calcareous mudstone and dolomite (rock), dolomite, indicative of a coastal environment. The second member is a thicker marine sequence of dark Micrite, micritic limestone with some dolomite. Two distinct fossil assemblages are found in the second member. The older Luoping biota preserves abundant arthropods (including Isopoda, isopods, decapods, mysidaceans and thylacocephalans) along with fossils from other invertebrates and vertebrates, which are rare but well-preserved. The slightly younger Panxian fauna has a more diverse and common assortment of marine reptiles such as sauropterygians. A tuff bed in the Luoping biota has been dated to 244.5 ± 2.2 Ma via Uranium–lead dating, U-Pb Sensitive high-resolution ion microprobe, SHRIMP ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geological Formation
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] |
