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Trujillo Formation
The Trujillo Formation is a geologic formation in Texas and New Mexico. It preserves fossils dating back to the upper Triassic period. It is also known as the Trujillo Sandstone. Description The formation consists mostly of gray to brown or red sandstone, but with some conglomerate and mudstone. Conglomerate is more common in the middle beds while mudstone is more common in the middle and upper beds. The sandstone is typically crossbedded and is fine-grained in the lower beds and more coarse in the middle and upper beds. The lower sandstone beds tend to form a prominent cliff. The total thickness varies from . The formation overlies the Tecovas Formation. The Cuervo Sandstone Member is preempted by the Trujillo Formation. The formation crops out along Palo Duro Canyon and the Canadian River and their tributaries. It is also widespread in the Sangre de Cristo Mountains. The formation is interpreted as deposition in a braided stream system. The lower beds at Palo Duro Canyo ... [...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 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 W ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crossbedded
In geology, cross-bedding, also known as cross-stratification, is layering within a stratum and at an angle to the main bedding plane. The sedimentary structures which result are roughly horizontal units composed of inclined layers. The original depositional layering is tilted, such tilting not being the result of post-depositional deformation. Cross-beds or "sets" are the groups of inclined layers, which are known as cross-strata. Cross-bedding forms during deposition on the inclined surfaces of bedforms such as ripples and dunes; it indicates that the depositional environment contained a flowing medium (typically water or wind). Examples of these bedforms are ripples, dunes, anti-dunes, sand waves, hummocks, bars, and delta slopes.Collinson, J.D., Thompson, D.B., 1989, Sedimentary Structures (2nd ed): Academic Division of Unwin Hyman Ltd, Winchester, MA, XXX p. Environments in which water movement is fast enough and deep enough to develop large-scale bed forms fall into three ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleontology In Texas
Paleontology in Texas refers to paleontological research occurring within or conducted by people from the U.S. state of Texas. Author Marian Murray has remarked that "Texas is as big for fossils as it is for everything else." Some of the most important fossil finds in United States history have come from Texas. Fossils can be found throughout most of the state. The fossil record of Texas spans almost the entire geologic column from Precambrian to Pleistocene. Shark teeth are probably the state's most common fossil. During the early Paleozoic era Texas was covered by a sea that would later be home to creatures like brachiopods, cephalopods, graptolites, and trilobites. Little is known about the state's Devonian and early Carboniferous life. However, evidence indicates that during the late Carboniferous the state was home to marine life, land plants and early reptiles. During the Permian, the seas largely shrank away, but nevertheless coral reefs formed in the state. The rest of Texa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Fossiliferous Stratigraphic Units In Texas
This article contains a list of fossil-bearing stratigraphic units in the state of Texas, U.S. Sites See also * Paleontology in Texas References * * {{DEFAULTSORT:Fossiliferous stratigraphic units in Texas Fossil Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ... Texas geography-related lists United States geology-related lists Geology of Texas .Stratigraphic units ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sanmiguelia
''Sanmiguelia lewisi'' is an extinct plant genus, possibly of flowering plants. The fossil was first described from Late Triassic Chinle Formation in Colorado, and later in Lower Jurassic Moenave Formation in Utah. The species has been suggested to be one of the more primitive angiosperm fossils. References Prehistoric angiosperm genera Enigmatic angiosperm taxa Triassic plants Jurassic plants {{triassic-plant-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cycad
Cycads are seed plants that typically have a stout and woody (ligneous) trunk with a crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants of a species are either male or female. Cycads vary in size from having trunks only a few centimeters to several meters tall. They typically grow very slowly and live very long. Because of their superficial resemblance, they are sometimes mistaken for palms or ferns, but they are not closely related to either group. Cycads are gymnosperms (naked-seeded), meaning their unfertilized seeds are open to the air to be directly fertilized by pollination, as contrasted with angiosperms, which have enclosed seeds with more complex fertilization arrangements. Cycads have very specialized pollinators, usually a specific species of beetle. Both male and female cycads bear cones (strobili), somewhat similar to conifer cones. Cycads have been reported to fix nitrogen in association ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Typothorax
''Typothorax'' is an extinct genus of typothoracine aetosaur that lived in the Late Triassic. Its remains have been found in North America. Two species are known: ''T. coccinarum'', the type species, and ''T. antiquum''. Description ''Typothorax'' was an aetosaur, a pseudosuchian distantly related to modern crocodilians. Unlike modern crocodilians, aetosaurs were herbivorous. ''Typothorax'' and other aetosaurs possess small, leaf-shaped teeth that were unsuited for a diet consisting of meat.Martz, J.W. 2002. The morphology and ontogeny of Typothorax coccinarum (Archosauria, Stagonolepididae) from the Upper Triassic of the American southwest. M.S. thesis, Geosciences, Texas Tech University, Lubbock, 279 pp. Unlike some aetosaurs such as ''Desmatosuchus'', ''Typothorax'' does not have large shoulder spikes. It does, however, have a pair of enlarged spikes on the neck projecting from the third row of scutes. It has lateral scutes that bear horns that are posteriorly hooked along ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vadose
The vadose zone, also termed the unsaturated zone, is the part of Earth between the land surface and the top of the phreatic zone, the position at which the groundwater (the water in the soil's pores) is at atmospheric pressure ("vadose" is from the Latin word for "shallow"). Hence, the vadose zone extends from the top of the ground surface to the water table. Water in the vadose zone has a pressure head less than atmospheric pressure, and is retained by a combination of adhesion (''funiculary groundwater''), and capillary action (''capillary groundwater''). If the vadose zone envelops soil, the water contained therein is termed soil moisture. In fine grained soils, capillary action can cause the pores of the soil to be fully saturated above the water table at a pressure less than atmospheric. The vadose zone does not include the area that is still saturated above the water table, often referred to as the capillary fringe. Freeze, R.A. and Cherry, J.A., 1979. Groundwater. Engle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Concretion
A concretion is a hard, compact mass of matter formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word 'concretion' is derived from the Latin "(act of) compacting, condensing, congealing, uniting", itself from ''con'' meaning 'together' and ''crescere'' meaning "to grow". Concretions form within layers of sedimentary strata that have already been deposited. They usually form early in the burial history of the sediment, before the rest of the sediment is hardened into rock. This concretionary cement often makes the concretion harder and more resistant to weathering than the host stratum. There is an important distinction to draw between concretions and nodules. Concretions are formed from mineral precipitation around some kind of nucleus while a nodule is a replacement body. Descriptions dating from the 18th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Braided Stream
A braided river, or braided channel, consists of a network of river channels separated by small, often temporary, islands called braid bars or, in English usage, '' aits'' or ''eyots''. Braided streams tend to occur in rivers with high sediment loads or coarse grain sizes, and in rivers with steeper slopes than typical rivers with straight or meandering channel patterns. They are also associated with rivers with rapid and frequent variation in the amount of water they carry, i.e., with "flashy" rivers, and with rivers with weak banks. Braided channels are found in a variety of environments all over the world, including gravelly mountain streams, sand bed rivers, on alluvial fans, on river deltas, and across depositional plains. Description A braided river consists of a network of multiple shallow channels that diverge and rejoin around ephemeral ''braid bars''. This gives the river a fancied resemblance to the interweaved strands of a braid. The braid bars, also known as channe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deposition (geology)
Deposition is the geological process in which sediments, soil and rocks are added to a landform or landmass. Wind, ice, water, and gravity transport previously weathered surface material, which, at the loss of enough kinetic energy in the fluid, is deposited, building up layers of sediment. Deposition occurs when the forces responsible for sediment transportation are no longer sufficient to overcome the forces of gravity and friction, creating a resistance to motion; this is known as the null-point hypothesis. Deposition can also refer to the buildup of sediment from organically derived matter or chemical processes. For example, chalk is made up partly of the microscopic calcium carbonate skeletons of marine plankton, the deposition of which has induced chemical processes (diagenesis) to deposit further calcium carbonate. Similarly, the formation of coal begins with the deposition of organic material, mainly from plants, in anaerobic conditions. Null-point hypothesis The n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sangre De Cristo Mountains
The Sangre de Cristo Mountains ( Spanish for "Blood of Christ") are the southernmost subrange of the Rocky Mountains. They are located in southern Colorado and northern New Mexico in the United States. The mountains run from Poncha Pass in South-Central Colorado, trending southeast and south, ending at Glorieta Pass, southeast of Santa Fe, New Mexico. The mountains contain a number of fourteen thousand foot peaks in the Colorado portion, as well as all the peaks in New Mexico which are over twelve thousand feet. The name of the mountains may refer to the occasional reddish hues observed during sunrise and sunset, and when alpenglow occurs, especially when the mountains are covered with snow. Although the particular origin of the name is unclear, it has been in use since the early 19th century. Before that time the terms "La Sierra Nevada", "La Sierra Madre", "La Sierra", and "The Snowies" (used by English speakers) were used.Robert Julyan, ''The Place Names of New Mexico'', Un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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