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Gallup Sandstone
The Gallup Sandstone is a Formation (geology), geologic formation in the Gallup-Zuni basin of New Mexico. It preserves fossils dating back to the late Cretaceous Period (geology), period. Description The formation consists of uniform, very well sorted, fine-grained pink to buff sandstone with lesser amounts of shale and siltstone. It has a total thickness of . The sandstone is highly Bioturbation, bioturbated and in some place shows ripple marks and low-angle crossbedding. It overlies and intertongues with the Mancos Shale and is overlain and intertongues with the Crevasse Canyon Formation. The formation has few faunal fossils, but the age is likely late Turonian to early Coniacian. The formation is interpreted as an offshore marine transgression (geology), transgression-regression (geology), regression sequence. History of investigation The unit was first defined by J.D. Sears in 1925 as the Gallup Sandstone Member of the Mesaverde Formation and named after Gallup, New Mexico, w ... [...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] |
Period (geology)
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronology (scientific branch of geology that aims to determine the age of rocks). It is used primarily by Earth scientists (including geologists, paleontologists, geophysicists, geochemists, and paleoclimatologists) to describe the timing and relationships of events in geologic history. The time scale has been developed through the study of rock layers and the observation of their relationships and identifying features such as lithologies, paleomagnetic properties, and fossils. The definition of standardized international units of geologic time is the responsibility of the International Commission on Stratigraphy (ICS), a constituent body of the International Union of Geological Sciences (IUGS), whose primary objective is to precisely define ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Fossiliferous Stratigraphic Units In New Mexico
This article contains a list of fossil-bearing stratigraphic units in the state of New Mexico, U.S. Sites See also * Paleontology in New Mexico References * {{DEFAULTSORT:Fossiliferous stratigraphic units in New Mexico New Mexico Stratigraphic units A stratigraphic unit is a volume of Rock (geology), rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrology, petrographic, lithology, lithologic or paleontology, p ... Stratigraphy of New Mexico New Mexico geography-related lists United States geology-related lists ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Group (stratigraphy)
In geology, a group is a lithostratigraphic unit consisting of a series of related formations that have been classified together to form a group. Formations are the fundamental unit of stratigraphy. Groups may sometimes be combined into supergroups. Groups are useful for showing relationships between formations, and they are also useful for small-scale mapping or for studying the stratigraphy of large regions. Geologists exploring a new area have sometimes defined groups when they believe the strata within the groups can be divided into formations during subsequent investigations of the area. It is possible for only some of the strata making up a group to be divided into formations. An example of a group is the Glen Canyon Group, which includes (in ascending order) the Wingate Sandstone, the Moenave Formation, the Kayenta Formation, and the Navajo Sandstone. Each of the formations can be distinguished from its neighbor by its lithology, but all were deposited in the same vast ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesaverde Formation
The Mesaverde Group is a Late Cretaceous stratigraphic group found in areas of Colorado, New Mexico, Utah, and Wyoming, in the Western United States. History The Mesaverde Formation was first described by W.H.Holmes in 1877 during the Hayden Survey. Holmes described the formation in the northern San Juan Basin as consisting of three units, which were a "Lower Escarpment" consisting of 40 m of ledge- and cliff-forming massive sandstone; a "Middle Coal Group" consisting of up to 300 m of thick slope-forming sandstone, shale, marl, and lignite; and an "Upper Escarpment" consisting of 60 m of ledge- and cliff-forming sandstone. A.J. Collier redesignated these units in 1919 as the Point Lookout Sandstone, the Menefee Formation, and the Cliff House Sandstone, and raised the Mesaverde Formation to group rank. The group was later traced to the greater Green River Basin, the Uintah and Piceance Basins, the Bighorn Basin, the Front Range, the Zuni Basin, the Wasatch Plateau, Wind Riv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regression (geology)
A marine regression is a geological process occurring when areas of submerged seafloor are exposed above the sea level. The opposite event, marine transgression, occurs when flooding from the sea covers previously-exposed land. Evidence of marine regressions and transgressions occurs throughout the fossil record, and the fluctuations are thought to have caused or contributed to several mass extinctions, such as the Permian-Triassic extinction event (250 million years ago) and Cretaceous–Paleogene extinction event (66 Ma). During the Permian-Triassic extinction, the largest extinction event in the Earth's history, the global sea level fell 250 m (820 ft). A major regression could itself cause marine organisms in shallow seas to go extinct, but mass extinctions tend to involve both terrestrial and aquatic species, and it is harder to see how a marine regression could cause widespread extinctions of land animals. Regressions are, therefore, seen as correlates or symptoms of major ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transgression (geology)
A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, which results in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling with water or decreasing in capacity. Transgressions and regressions may be caused by tectonic events such as orogenies, severe climate change such as ice ages or isostatic adjustments following removal of ice or sediment load. During the Cretaceous, seafloor spreading created a relatively shallow Atlantic basin at the expense of deeper Pacific basin. That reduced the world's ocean basin capacity and caused a rise in sea level worldwide. As a result of the sea level rise, the oceans transgressed completely across the central portion of North America and created the Western Interior Seaway from the Gulf of Mexico to the Arctic Ocean. The opposite of transgression is regression in which the sea level falls relative to the land and expo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coniacian
The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series and spans the time between 89.8 ± 1 Ma and 86.3 ± 0.7 Ma (million years ago). The Coniacian is preceded by the Turonian and followed by the Santonian. Stratigraphic definitions The Coniacian is named after the city of Cognac in the French region of Saintonge. It was first defined by French geologist Henri Coquand in 1857. The base of the Coniacian Stage is at the first appearance of the inoceramid bivalve species '' Cremnoceramus deformis erectus''. The official reference profile for the base (a GSSP) is located in Salzgitter-Salder, Lower Saxony, Germany. The top of the Coniacian (the base of the Santonian Stage) is defined by the appearance of the inoceramid bivalve ''Cladoceramus undulatoplicatus''. The Coniacian overlaps the regional Emscherian Stage of Germany, which is roughly coeval with the Coniacian and Santonian Stages. In magne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turonian
The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded by the Cenomanian Stage and underlies the Coniacian Stage. At the beginning of the Turonian an oceanic anoxic event (OAE 2) took place, also referred to as the Cenomanian-Turonian boundary event or the "Bonarelli Event". Stratigraphic definition The Turonian (French: ''Turonien'') was defined by the French paleontologist Alcide d'Orbigny (1802–1857) in 1842. Orbigny named it after the French city of Tours in the region of Touraine (department Indre-et-Loire), which is the original type locality. The base of the Turonian Stage is defined as the place where the ammonite species '' Watinoceras devonense'' first appears in the stratigraphic column. The official reference profile (the GSSP) for the base of the Turonian is located in the Roc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bioturbation
Bioturbation is defined as the reworking of soils and sediments by animals or plants. It includes burrowing, ingestion, and defecation of sediment grains. Bioturbating activities have a profound effect on the environment and are thought to be a primary driver of biodiversity. The formal study of bioturbation began in the 1800s by Charles Darwin experimenting in his garden. The disruption of aquatic sediments and terrestrial soils through bioturbating activities provides significant ecosystem services. These include the alteration of nutrients in aquatic sediment and overlying water, shelter to other species in the form of burrows in terrestrial and water ecosystems, and soil production on land.Shaler, N. S., 1891, The origin and nature of soils, in Powell, J. W., ed., USGS 12th Annual report 1890-1891: Washington, D.C., Government Printing Office, p. 213-45. Bioturbators are deemed ecosystem engineers because they alter resource availability to other species through the physical ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shale
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite.Blatt, Harvey and Robert J. Tracy (1996) ''Petrology: Igneous, Sedimentary and Metamorphic'', 2nd ed., Freeman, pp. 281–292 Shale is characterized by its tendency to split into thin layers ( laminae) less than one centimeter in thickness. This property is called '' fissility''. Shale is the most common sedimentary rock. The term ''shale'' is sometimes applied more broadly, as essentially a synonym for mudrock, rather than in the more narrow sense of clay-rich fissile mudrock. Texture Shale typically exhibits varying degrees of fissility. Because of the parallel orientation of clay mineral flakes in shale, it breaks into thin layers, often splintery and usually parallel to the otherwise indistinguishable beddin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) because they are the most resistant minerals to weathering processes at the Earth's surface. Like uncemented sand, sandstone may be any color due to impurities within the minerals, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Since sandstone beds often form highly visible cliffs and other topographic features, certain colors of sandstone have been strongly identified with certain regions. Rock formations that are primarily composed of sandstone usually allow the percolation of water and other fluids and are porous enough to store large quantities, making them valuable aquifers and petroleum reservoirs. Quartz-bearing sandstone can be changed into quartzite through metamorphism, usually related to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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