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Franciscan Formation
The Franciscan Complex or Franciscan Assemblage is a geologic term for a late Mesozoic terrane of heterogeneous rocks found throughout the California Coast Ranges, and particularly on the San Francisco Peninsula. It was named by geologist Andrew Lawson, who also named the San Andreas fault that defines the western extent of the assemblage. The Franciscan Complex is dominated by greywacke sandstones, shales and conglomerates which have experienced low-grade metamorphism. Other important lithologies include chert, basalt, limestone, serpentinite, and high-pressure, low-temperature metabasites (blueschists and eclogites) and meta-limestones. Fossils like radiolaria are found in chert beds of the Franciscan Complex. These fossils have been used to provide age constraints on the different terranes that constitute the Franciscan. The mining opportunities within the Franciscan are restricted to deposits of cinnabar and limestone. The outcrops of the formation have a very large ran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chert
Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a precipitation (chemistry), chemical precipitate or a diagenesis, diagenetic replacement, as in petrified wood. Chert is typically composed of the petrified remains of siliceous ooze, the biogenic sediment that covers large areas of the deep ocean floor, and which contains the silicon skeletal remains of diatoms, Dictyochales, silicoflagellates, and radiolarians. Precambrian cherts are notable for the presence of fossil cyanobacteria. In addition to Micropaleontology, microfossils, chert occasionally contains macrofossils. However, some chert is devoid of any fossils. Chert varies greatly in color (from white to black), but most often manifests as gray, brown, grayish brown and light green to rusty redW.L. Roberts, T.J. Campbell, G.R. Rapp Jr. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rock (geology)
In geology, rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition, and the way in which it is formed. Rocks form the Earth's outer solid layer, the crust, and most of its interior, except for the liquid outer core and pockets of magma in the asthenosphere. The study of rocks involves multiple subdisciplines of geology, including petrology and mineralogy. It may be limited to rocks found on Earth, or it may include planetary geology that studies the rocks of other celestial objects. Rocks are usually grouped into three main groups: igneous rocks, sedimentary rocks and metamorphic rocks. Igneous rocks are formed when magma cools in the Earth's crust, or lava cools on the ground surface or the seabed. Sedimentary rocks are formed by diagenesis and lithification of sediments, which in turn are formed by the weathering, transport, and deposition of existing ro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Santa Barbara County, California
Santa Barbara County, California, officially the County of Santa Barbara, is located in Southern California. As of the 2020 census, the population was 448,229. The county seat is Santa Barbara, and the largest city is Santa Maria. Santa Barbara County comprises the Santa Maria-Santa Barbara, CA Metropolitan Statistical Area. Most of the county is part of the California Central Coast. Mainstays of the county's economy include engineering, resource extraction (particularly petroleum extraction and diatomaceous earth mining), winemaking, agriculture, and education. The software development and tourism industries are important employers in the southern part of the county. Southern Santa Barbara County is sometimes considered the northern cultural boundary of Southern California. History The Santa Barbara County area, including the Northern Channel Islands, was first settled by Native Americans at least 13,000 years ago. Evidence for a Paleoindian presence has been found in the fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Douglas County, Oregon
Douglas County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 111,201. The county seat is Roseburg. The county is named after Stephen A. Douglas, an American politician who supported Oregon statehood. Douglas County comprises the Roseburg, OR Micropolitan Statistical Area. History The area originally was inhabited by the Umpqua Indians, a grouping of natives who spoke a variety of Penutian and Athabaskan languages. Following the Rogue River Indian War in 1856, most of the remaining natives were moved by the government to the Grand Ronde Indian Reservation. However, seven families of Umpqua hid in the hills, eluding capture for many decades. They are now federally recognized as the Cow Creek Band of Umpqua Tribe of Indians. The tribe manages a small reservation in Canyonville, Oregon, and has a Casino/Hotel named Seven Feathers to represent the seven families who refused forced removal to the Grand Ronde Reservation. Dou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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