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Denver Formation
The Denver Formation is a geological formation that is present within the central part of the Denver Basin that underlies the Denver, Colorado, area. It ranges in age from latest Cretaceous (Maastrichtian) to early Paleocene, and includes sediments that were deposited before, during and after the Cretaceous-Paleogene boundary event.Tweto, O. 1979. Geologic map of Colorado. U.S. Geological Survey, Map G77115. The formation is known for its paleontological resources, including dinosaur remains that are found in the Late Cretaceous part of the formation, and it includes aquifers that are important sources of water for the area. Stratigraphy The Denver Formation rests on the Arapahoe Formation, and its base is marked by the first appearance of tuffaceous sediments. It is overlain by the Dawson Arkose. In 2002 the Denver Formation was included as part of a larger unconformity-bounded unit named the D1 sequence, in order to facilitate basin-wide studies and avoid confusion arising ... [...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 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 Abraham Gottlob Wer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maastrichtian
The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from . The Maastrichtian was preceded by the Campanian and succeeded by the Danian (part of the Paleogene and Paleocene). The Cretaceous–Paleogene extinction event (formerly known as the Cretaceous–Tertiary extinction event) occurred at the end of this age. In this mass extinction, many commonly recognized groups such as non-avian dinosaurs, plesiosaurs and mosasaurs, as well as many other lesser-known groups, died out. The cause of the extinction is most commonly linked to an asteroid about wide colliding with Earth, ending the Cretaceous. Stratigraphic definitions Definition The Maastrichtian was introduced into scientific literature by Belgian geologist André Hubert Dumont in 1849, after studying rock strata of the Chalk Group c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bedding (geology)
In geology, a bed is a layer of sediment, sedimentary rock, or pyroclastic material "bounded above and below by more or less well-defined bedding surfaces".Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds., 2005. ''Glossary of Geology'' (5th ed.). Alexandria, Virginia; American Geological Institute. p 61. Specifically in sedimentology, a bed can be defined in one of two major ways.Davies, N.S., and Shillito, A.P. 2021, ''True substrates: the exceptional resolution and unexceptional preservation of deep time snapshots on bedding surfaces.'' ''Sedimentology.'' published online 22 May 2021, doi: 10.1111/sed.12900. First, Campbell and Reineck and SinghReineck, H.E., and Singh, I.B., 1980. ''Depositional Sedimentary Environments'', (2nd ed.) Berlin, Germany: Springer-Verlag, 504 pp. use the term ''bed'' to refer to a thickness-independent layer comprising a coherent layer of sedimentary rock, sediment, or pyroclastic material bounded above and below by surfaces known as beddi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lenticular (geology)
In geology, a lens or lentil is a body of ore or rock that is thick in the middle and thin at the edges, resembling a convex lens in cross-section. To thin out in all directions is to "lens out", also known as "lensing". The adjectives "lenticular" and "lentiform" are used to describe lens-like formations. Lenticle is a synonym for lentil, but may also refer to a fragment of rock that is lens-shaped. "Lenticule" is used for small lentil. A lentil may also refer a minor unit in a formation of rock, similar to a member but not generally spread out over a large geographical area. In this usage, the lentil thins out towards its edges. Lenticular bedding is a special form of rock interbedded mudrock and cross-laminated rippled 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) . ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Andesite
Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende. Andesite is the extrusive equivalent of plutonic diorite. Characteristic of subduction zones, andesite represents the dominant rock type in island arcs. The average composition of the continental crust is andesitic. Along with basalts, andesites are a component of the Martian crust. The name ''andesite'' is derived from the Andes mountain range, where this rock type is found in abundance. It was first applied by Christian Leopold von Buch in 1826. Description Andesite is an aphanitic (fine-grained) igneous rock that is intermediate in its content of silica and low in alkali metals. It has less than 20% quartz and 10% feldspathoid by volume, with at least 65% of the fe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paludal
Paludal is derived from the Latin word ''palus'' ("marsh"). *Paludal, in geology, refers to sediments that accumulated in a marsh environment. *Paludal, in ecology Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps wi ..., refers to the environment of a marsh. Sedimentology {{Geology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluvial
In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluvioglacial is used. Fluvial processes Fluvial processes include the motion of sediment and erosion or deposition on the river bed. The movement of water across the stream bed exerts a shear stress directly onto the bed. If the cohesive strength of the substrate is lower than the shear exerted, or the bed is composed of loose sediment which can be mobilized by such stresses, then the bed will be lowered purely by clearwater flow. In addition, if the river carries significant quantities of sediment, this material can act as tools to enhance wear of the bed ( abrasion). At the same time the fragments themselves are ground down, becoming smaller and more rounded (attrition). Sediment in rivers is transported as either bedload (the coarser fr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alluvial Fan
An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to semiarid climates, but are also found in more humid environments subject to intense rainfall and in areas of modern glaciation. They range in area from less than to almost . Alluvial fans typically form where flow emerges from a confined channel and is free to spread out and infiltrate the surface. This reduces the carrying capacity of the flow and results in deposition of sediments. The flow can take the form of infrequent debris flows or one or more ephemeral or perennial streams. Alluvial fans are common in the geologic record, such as in the Triassic basins of eastern North America and the New Red Sandstone of south Devon. Such fan deposits likely contain the largest accumulations of gravel in the geologic record. Alluvial fans have also been found on Mars ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North Table Mountain
North Table Mountain is a mesa on the eastern flank of the Front Range of the Rocky Mountains of North America. The mesa summit is located in North Table Mountain Park, north by east ( bearing 9°) of downtown Golden, Colorado, United States, in Jefferson County. Mesa The most distinctive feature of the mesa is its nearly flat cap that was formed by ancient Paleocene lava flows. It is separated from companion South Table Mountain, which consists of the same geologic formation, by Clear Creek. North Table Mountain is a popular scenic and recreational destination in the Denver metro area, and it is preserved as public open space by Jefferson County and the Access Fund. Recent and ongoing projects by Jefferson County Open Space have resulted in the construction of several new trails and eliminated large numbers of unofficial trails. Geology North Table Mountain is underlain by sedimentary rocks of the Denver Formation, which spans the interval from latest Cretaceous t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleosol
In the geosciences, paleosol (''palaeosol'' in Great Britain and Australia) is an ancient soil that formed in the past. The precise definition of the term in geology and paleontology is slightly different from its use in soil science. In geology and paleontology, a paleosol is a former soil preserved by burial underneath either sediments (alluvium or loess) or volcanic deposits (volcanic ash), which in the case of older deposits have lithified into rock. In Quaternary geology, sedimentology, paleoclimatology, and geology in general, it is the typical and accepted practice to use the term "paleosol" to designate such "''fossil soils''" found buried within sedimentary and volcanic deposits exposed in all continents. In soil science the definition differs only slightly: ''paleosols'' are soils formed long ago that have no relationship in their chemical and physical characteristics to the present-day climate or vegetation. Such soils are found within extremely old continental cra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Facies
In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with specified characteristics, which can be any observable attribute of rocks (such as their overall appearance, composition, or condition of formation), and the changes that may occur in those attributes over a geographic area. A facies encompasses all of the characteristics of a rock including its chemical, physical, and biological features that distinguish it from adjacent rock. The term facies was introduced by the Swiss geologist Amanz Gressly in 1838 and was part of his significant contribution to the foundations of modern stratigraphy, which replaced the earlier notions of Neptunism. Types of facies Sedimentary facies Ideally, a Sedimentary structures, sedimentary facies is a distinctive rock unit that forms under certain conditions of sedimentation, reflecting a particular process or environment. Sedimentary facies are either descriptive or interpretative. Sedimentary facies ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aquifers
An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characteristics. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include aquitard, which is a bed of low permeability along an aquifer, and aquiclude (or ''aquifuge''), which is a solid, impermeable area underlying or overlying an aquifer, the pressure of which could create a confined aquifer. The classification of aquifers is as follows: Saturated versus unsaturated; aquifers versus aquitards; confined versus unconfined; isotropic versus anisotropic; porous, karst, or fractured; transboundary aquifer. Challenges for using groundwater include: overdrafting (extracting groundwater beyond the equilibrium yield of the aquifer), groundwater-related subsidence of land, groundwater becoming sa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
