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Lookingglass Formation
The Lookingglass Formation is a geologic formation in Oregon. It preserves fossils dating back to the Paleogene period. Geologically, it spans a time frame from the Tertiary period to the middle Eocene. It was named for the Lookingglass Valley. It overlies the Roseburg Formation, and is divided into three geologic members: the Bushnell Rock Member, the Tenmile Member, and the Olalla Creek Member. The Bushnell Rock Member is a basal conglomerate, mostly made of 1-2 inch diameter pebbles embedded in a sandstone matrix, deposited by an onlapping (advancing) sea. The Tenmile Member is composed of rhymthically bedded layers of sandstone and siltstone, indicating deposition in quiet water not close to the shore. The Olalla Creek member is composed in some places of conglomerate and pebbly sandstone, and in other places of thinner bedded sandstone and silt, and, where the silt layer is absent, is hard to distinguish from the Bushnell Rock Member. See also * List of fossilife ... [...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] |
Lookingglass, Oregon
Lookingglass is an unincorporated community and census-designated place in the Lookingglass Valley of Douglas County, Oregon, United States, about southwest of Roseburg. As of the 2010 census it had a population of 855. Lookingglass is considered a suburb of Roseburg. History The valley was named in 1846 by surveyor Hoy Flournoy, who said the beautiful green grass of the valley reflected light almost as well as a mirror. Flournoy later returned to settle in the area. The Lookingglass Store, built in 1852, was once the terminus for the Oakland to Lookingglass stage and freight road. It was also the beginning of the Coos Bay Wagon Road. Today the store continues to serve as the hub of the community and is the oldest business in Douglas County. Lookingglass also has a school, a grange hall, a church and a fire station. Lookingglass post office closed in 1942. In the 1970s, Lookingglass, population 40 at the time, received national media attention for installing a two-horse pa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleontology In Oregon
The location of the state of Oregon Paleontology in Oregon refers to paleontological research occurring within or conducted by people from the U.S. state of Oregon. Oregon's geologic record extends back approximately 400 million years ago to the Devonian period, before which time the state's landmass was likely submerged under water. Sediment records show that Oregon remained mostly submerged until the Paleocene period. The state's earliest fossil record includes plants, corals, and conodonts. Oregon was covered by seaways and volcanic islands during the Mesozoic era. Fossils from this period include marine plants, invertebrates, ichthyosaurs, pterosaurs, and Trace fossil, traces such as invertebrate Burrow (animal), burrows. During the Cenozoic, Oregon's climate gradually cooled and eventually yielded the environments now found in the state. The era's fossils include marine and terrestrial plants, invertebrates, fish, amphibians, turtles, birds, mammals, and traces such as Egg fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Fossiliferous Stratigraphic Units In Oregon
This article contains a list of fossil-bearing stratigraphic units in the state of Oregon, U.S. Lists of fossiliferous stratigraphic units Cenozoic Mesozoic Paleozoic See also * Paleontology in Oregon * Lists of Oregon-related topics References {{DEFAULTSORT:Fossiliferous stratigraphic units in Oregon Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ... Stratigraphy of Oregon Oregon geography-related lists United States geology-related lists ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Siltstone
Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, pp.381-382 Although its permeability and porosity is relatively low, siltstone is sometimes a tight gas reservoir rock, an unconventional reservoir for natural gas that requires hydraulic fracturing for economic gas production. Siltstone was prized in ancient Egypt for manufacturing statuary and cosmetic palettes. The siltstone quarried at Wadi Hammamat was a hard, fine-grained siltstone that resisted flaking and was almost ideal for such uses. Description There is not complete agreement on the definition of siltstone. One definition is that siltstone is mudrock ( clastic sedimentary rock containing at least 50% clay and silt) in which at least 2/3 of the clay and silt fraction is composed of silt-sized particles. Silt is defi ... [...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 r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclic Sediments
Cyclic sediments (also called rhythmic sediments) are sequences of sedimentary rocks that are characterised by repetitive patterns of different rock types (strata) or facies within the sequence. Processes that generate sedimentary cyclicity can be either autocyclic or allocyclic, and can result in piles of sedimentary cycles hundreds or even thousands of metres thick. The study of sequence stratigraphy was developed from controversies over the causes of cyclic sedimentation. Processes leading to cyclic sedimentation Cyclic sedimentation occurs when the depositional environments change repeatedly. Changes in the environment of deposition influence the type and amount of sediments that are deposited, producing different sedimentary rock types. At least one rock type, which is regarded as the starting point, must be repeated. Based on the processes that generate the cyclic deposits, two types of sedimentary cyclic successions can be distinguished. Allocycles Allocycles are sedim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basal Conglomerate
Conglomerate () is a clastic sedimentary rock that is composed of a substantial fraction of rounded to subangular gravel-size clasts. A conglomerate typically contains a matrix of finer-grained sediments, such as sand, silt, or clay, which fills the interstices between the clasts. The clasts and matrix are typically cemented by calcium carbonate, iron oxide, silica, or hardened clay. Conglomerates form by the consolidation and lithification of gravel. They can be found in sedimentary rock sequences of all ages but probably make up less than 1 percent by weight of all sedimentary rocks. In terms of origin and depositional mechanisms, they are closely related to sandstones and exhibit many of the same types of sedimentary structures, e.g., tabular and trough cross-bedding and graded bedding.Boggs, S. (2006) ''Principles of Sedimentology and Stratigraphy.'', 2nd ed. Prentice Hall, New York. 662 pp. Friedman, G.M. (2003) ''Classification of sediments and sedimentary rocks.'' In Ger ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bushnell Rock Member
The Bushnell Rock Member is a geologic rock formation, named after an outcropping of an exposed portion of the member itself known as Bushnell Rock by University of Oregon Geologist Ewart M. Baldwin in 1974. This combined with Tenmile Member and Olalla Creek Member makeup the larger Lookingglass Formation lying beneath the Lookingglass Valley in Douglas County, Oregon. Lithology The Bushnell Rock Member is a basal conglomerate with sandstone beds occurring on a rarity. It was deposited by an onlapping sea that started during the Paleocene but the bulk of the formation was deposited during the early Eocene. The conglomerate is composed of 70% rock fragments (60% sedimentary, 30% metamorphic, 10% volcanic) 1 to 2 inches in diameter and a 30% percent matrix of medium to coarsegrained sands(66% quartz, 33% feldspar). Because the member is not well exposed other than a few limited areas, measurement for the overall stratigraphic thickness has not been achieved. It was determ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Member (geology)
A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features ( facies) that characterize it. Units must be ''mappable'' and ''distinct'' from one another, but the contact need not be particularly distinct. For instance, a unit may be defined by terms such as "when the sandstone component exceeds 75%". Lithostratigraphic units Sequences of sedimentary and volcanic rocks are subdivided the basis of their shared or associated lithology. Formally identified lithostratigraphic units are structured in a hierarchy of lithostratigraphic rank, higher rank units generally comprising two or more units of lower rank. Going from smaller to larger in rank, the main lithostratigraphic ranks are Bed, Member, Formation, Group and Supergroup. Formal names of lithostratigraphic units are assigned by geological surveys. Units of formation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Middle Eocene
The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "dawn") and (''kainós'', "new") and refers to the "dawn" of modern ('new') fauna that appeared during the epoch. The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a brief period in which the concentration of the carbon isotope 13C in the atmosphere was exceptionally low in comparison with the more common isotope 12C. The end is set at a major extinction event called the ''Grande Coupure'' (the "Great Break" in continuity) or the Eocene–Oligocene extinction event, which may be related to the impact of one or more large bolides in Siberia and in what is now Chesapeake Bay. As with other geologic periods, the strata that define the start and end ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleogene
The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago (Mya) to the beginning of the Neogene Period Mya. It is the beginning of the Cenozoic Era of the present Phanerozoic Eon. The earlier term Tertiary Period was used to define the span of time now covered by the Paleogene Period and subsequent Neogene Period; despite no longer being recognised as a formal stratigraphic term, 'Tertiary' is still widely found in earth science literature and remains in informal use. Paleogene is often abbreviated "Pg" (but the United States Geological Survey uses the abbreviation PE for the Paleogene on the Survey's geologic maps). During the Paleogene, mammals diversified from relatively small, simple forms into a large group of diverse animals in the wake of the Cretaceous–Paleogene extinction event that ended the preceding C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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