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Geology Of Illinois
The geology of Illinois includes extensive deposits of marine sedimentary rocks from the Palaeozoic, as well as relatively minor contributions from the Mesozoic and Cenozoic. Ice age glaciation left a wealth of glacial topographic features throughout the state. Precambrian Geology Precambrian rocks of Illinois are deeply buried by 2000–13000 feet (610–3960 m) of later sediments. Drilling has revealed these rocks to be primarily intrusive felsic igneous rocks, though some extrusive felsic rocks have also been recovered from boreholes. Precambrian rocks of Illinois are highly faulted; tectonic extension and related thermal subsidence have led to the formation of two major sedimentary basins. These basins, termed the Illinois Basin and Michigan Basin, allowed for extensive deposition of sedimentary rock during the Palaeozoic Era. The Illinois Basin is a northwest-southeast asymmetrical structural basin that is filled with more than 4000 meters of Paleozoic sedimentary rocks. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Precambrian
The Precambrian (or Pre-Cambrian, sometimes abbreviated pêž’, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic Eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time. The Precambrian is an informal unit of geologic time, subdivided into three eons ( Hadean, Archean, Proterozoic) of the geologic time scale. It spans from the formation of Earth about 4.6 billion years ago ( Ga) to the beginning of the Cambrian Period, about million years ago ( Ma), when hard-shelled creatures first appeared in abundance. Overview Relatively little is known about the Precambrian, despite it making up roughly seven-eighths of the Earth's history, and what is known has largely been discovered from the 1960s onwards. The Precambrian fossil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mudcrack
Mudcracks (also known as mud cracks, desiccation cracks or cracked mud) are sedimentary structures formed as muddy sediment Desiccation, dries and contracts.Jackson, J.A., 1997, ''Glossary of Geology'' (4th ed.), American Geological Institute, Alexandria, VA, 769 p.Stow, D.A., 2005, ''Sedimentary Rocks in the Field'', Academic Press, London, 320 p. Crack formation also occurs in clay-bearing soils as a result of a reduction in water content. Formation of mudcrack Naturally forming mudcracks start as wet, muddy sediment desiccation, dries up and contracts. A strain is developed because the top layer shrinks while the material below stays the same size. When this strain becomes large enough, channel cracks form in the dried-up surface to relieve the strain. Individual cracks spread and join up, forming a polygonal, interconnected network of forms called "tesselations." If the strain continues to build the polygon start to curled upward. This characteristic can be used in geology t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gastropoda
The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. There are many thousands of species of sea snails and slugs, as well as freshwater snails, freshwater limpets, and land snails and slugs. The class Gastropoda contains a vast total of named species, second only to the insects in overall number. The fossil history of this class goes back to the Late Cambrian. , 721 families of gastropods are known, of which 245 are extinct and appear only in the fossil record, while 476 are currently extant with or without a fossil record. Gastropoda (previously known as univalves and sometimes spelled "Gasteropoda") are a major part of the phylum Mollusca, and are the most highly diversified class in the phylum, with 65,000 to 80,000 living snail and slug species. The anatomy, behavior, feeding, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brachiopod
Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection. Two major categories are traditionally recognized, articulate and inarticulate brachiopods. The word "articulate" is used to describe the tooth-and-groove structures of the valve-hinge which is present in the articulate group, and absent from the inarticulate group. This is the leading diagnostic skeletal feature, by which the two main groups can be readily distinguished as fossils. Articulate brachiopods have toothed hinges and simple, vertically-oriented opening and closing muscles. Conversely, inarticulate brachiopods have weak, untoothed hinges and a more complex system of vertical and oblique (diagonal) muscles used to keep the two valves aligned. In many brachiopods, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trilobite
Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period () and they flourished throughout the lower Paleozoic before slipping into a long decline, when, during the Devonian, all trilobite orders except the Proetida died out. The last extant trilobites finally disappeared in the mass extinction at the end of the Permian about 252 million years ago. Trilobites were among the most successful of all early animals, existing in oceans for almost 270 million years, with over 22,000 species having been described. By the time trilobites first appeared in the fossil record, they were already highly diversified and geographically dispersed. Because trilobites had wide diversity and an easily fossilized exoskeleton, they left an extensive fossil record. The stu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lee County, Illinois
Lee County is a county located in the U.S. state of Illinois. According to the 2010 census, it has a population of 36,031. Its county seat is Dixon. The Dixon, IL Micropolitan Statistical Area includes all of Lee County. History The area's first non-native settlers were mostly from the six New England states. The early nineteenth century saw a wave of westward movement from New England, due largely to completion of the Erie Canal and the end of the Black Hawk War. The area that included present-day Lee County was delineated as St. Clair County in 1809. In 1823, a large section of northern St. Clair County was partitioned off as Fulton County. In 1825, the northwestern portion of that county was partitioned off as Putnam County. In 1831, the area was further partitioned into Jo Daviess County. A section of that county was partitioned off in 1836 as Ogle County, and in 1839 the bottom half of Ogle County was split off as Lee County. It is largely understood that the county's ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ogle County, Illinois
Ogle County is a county in the northern part of the U.S. state of Illinois. According to the 2010 United States Census, it had a population of 53,497. Its county seat is Oregon, and its largest city is Rochelle. Ogle County comprises Rochelle, IL Micropolitan Statistical Area, which is also included in the Rockford- Freeport-Rochelle, IL Combined Statistical Area. History Ogle County was formed in 1836 out of Jo Daviess and LaSalle counties, and named in honor of Captain Joseph Ogle, a veteran of the Revolutionary War who settled in Illinois in 1785. Ogle County government was organized in 1837; before that time it remained assigned to Jo Daviess County for legislative, taxation, and judicial matters. In 1839, part of Ogle County was partitioned off to form Lee County. Ogle County was a New England settlement. The founders of Oregon and Rochelle arrived from New England; they were "Yankees", descendants of English Puritans who had settled New England in the 1600s. They ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jordan Sandstone
The Jordan Sandstone is a Formation (geology), geologic formation in Wisconsin. It preserves fossils dating back to the Cambrian Period (geology), period. See also * List of fossiliferous stratigraphic units in Wisconsin * Paleontology in Wisconsin References * Cambrian geology of Wisconsin {{Wisconsin-geologic-formation-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eminence Formation
The Eminence Formation or Eminence Dolomite is a geologic formation in Missouri. It preserves fossils dating back to the Cambrian period. Paleofauna Monoplacophora * '' Biloboconus'' : ''B. frizzelli'' * '' Potosiplina'' : ''P. delorensis'' See also * List of fossiliferous stratigraphic units in Missouri * Paleontology in Missouri Paleontology in Missouri refers to paleontological research occurring within or conducted by people from the U.S. state of Missouri. The geologic column of Missouri spans all of geologic history from the Precambrian to present with the exception ... References * Cambrian Missouri Dolomite formations Landforms of Shannon County, Missouri Geologic formations of Missouri Cambrian southern paleotropical deposits {{ShannonCountyMO-geo-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Potosi Dolomite
The Potosi Formation is a geologic formation in Missouri, Illinois and Indiana. It preserves fossils dating back to the Cambrian period. Paleofauna Monoplacophora Monoplacophora , meaning "bearing one plate", is a polyphyletic superclass of molluscs with a cap-like shell inhabiting deep sea environments . Extant representatives were not recognized as such until 1952; previously they were known only from ... * '' Gayneoconus'' : ''G. echolsi'' See also * List of fossiliferous stratigraphic units in Missouri * Paleontology in Missouri References * Cambrian Missouri Dolomite formations Geography of St. Francois County, Missouri Cambrian System of North America Geologic formations of Missouri Cambrian southern paleotropical deposits {{Missouri-geologic-formation-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Franconia Formation
The Franconia Formation is a Formation (geology), geologic formation in the upper mid-western United States, with outcroppings found in Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio, and Wisconsin. It preserves fossils dating back to the Cambrian Period (geology), period. It was named the Franconia Formation due to the first published documentation of exposures in vicinity of Franconia, Minnesota, Franconia, Minnesota in the 1897 Ph.D. dissertation by Charles P. Berkley at the University of Minnesota titled Geology of the St. Croix Dalles. The Franconian (stage), Franconian Stage (stratigraphy), stratigraphic stage was named after this formation. The formation consists of fine-grained dolomitic sandstone with interbedded shaly zones, becoming more dolomitic towards the east and south of its extent. See also * List of fossiliferous stratigraphic units in Wisconsin * Paleontology in Wisconsin References * USGS National Geologic Map Database Unit Summary for "Franco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galesville Sandstone
The Galesville Sandstone is a geologic 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 exp ... in Indiana. References Generalized Stratigraphic Column of Indiana Bedrock Geology of Indiana {{Indiana-geologic-formation-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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