|
Jotnian
In north European geology, Jotnian sediments are a group of Precambrian rocks more specifically assigned to the Mesoproterozoic Era ( Riphean), albeit some might be younger. Jotnian sediments include the oldest known sediments in the Baltic area that have not been subject to metamorphism. Stratigraphically, Jotnian sediments overlie the rapakivi granites and other igneous and metamorphic rocks and are often intruded by younger diabases. Overview Jotnian sediments include quartz-rich sandstones, siltstones, arkose, shale and conglomerates. The characteristic red colour of Jotnian sediments is due to their deposition in subaerial (e.g. non-marine) conditions. Jotnian sediments are the oldest known sediments in the Baltic area that have not been subject to metamorphism. Their age is poorly constrained, but generally they are younger than the rapakivi granites and older than ''Postjotnian'' diabases that intrude the sediments. This means that Jotnian sediments were deposited ap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wilhelm Ramsay
Wilhelm Ramsay (20 January 1865 – 6 January 1928) was a Finland Swede geologist. He became a member of the Royal Swedish Academy of Sciences in 1914 and in 1915 was accepted into the Royal Physiographic Society in Lund. He coined the terms Fennoscandia (1900) and Postjotnian (1909). Ramsay also coined the term ijolite. Together with Jakob Sederholm, Ramsay was a student of Fredrik Johan Wiik. Pentti Eskola Pentti Elias Eskola (8 January 1883 – 6 December 1964) was a Finnish geologist who specialised in the petrology of granites and developed the concept of metamorphic facies. He won the Wollaston Medal in 1958, the Vetlesen Prize in 1964, a ... was a student of Ramsay. References 1865 births 1928 deaths Finnish geologists Tectonicists Members of the Royal Swedish Academy of Sciences Members of the Royal Physiographic Society in Lund Swedish-speaking Finns {{geologist-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rapakivi Granite
Rapakivi granite is a hornblende-biotite granite containing large round crystals of orthoclase each with a rim of oligoclase (a variety of plagioclase). The name has come to be used most frequently as a textural term where it implies plagioclase rims around orthoclase in plutonic rocks. Rapakivi is a Finnish compound of "rapa" (meaning "mud" or "sand") and "kivi" (meaning "rock"), because the different heat expansion coefficients of the component minerals make exposed rapakivi crumble easily into sand. Rapakivi was first described by Finnish petrologist Jakob Sederholm in 1891. Since then, southern Finland's rapakivi granite intrusions have been the type locality of this variety of granite. Occurrence Rapakivi is a fairly uncommon type of granite, but has been described from localities in North and South America ( Illescas Batholith, Uruguay, Rondônia, Brazil) parts of the Baltic Shield, southern Greenland, southern Africa, India and China. Most of these examples are found wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arvid Högbom
Arvid Gustaf Högbom was a Swedish geologist. He was a professor of mineralogy and geology at Uppsala University. Biography Arvid Högbom was born at Vännäs in Västerbotten County, Sweden. Högbom was a student at Uppsala University earning a Bachelor of Philosophy in 1880 and a Licentiate in philosophy in 1884. In 1885, he defended his doctorate thesis; '' Iakttagelser rörande Jemtlands glaciala geologi med inledande öfversigt af berggrunden'' ( Stockholm. 1885). He appointed lecturer at Uppsala in 1885. In 1891 he joined the staff of the University of Stockholm, but returned to Uppsala University in 1896 as professor of geology and mineralogy, occupying the chair until his retirement in 1922. He became a member of the Royal Society of Sciences in Uppsala in 1898, of the Royal Swedish Academy of Agriculture and Forestry in 1913 and of the Royal Society of Arts and Sciences in Gothenburg in 1921. He became a member of the Royal Swedish Academy of Sciences in 1905 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geology Of The Baltic Sea
The geology of the Baltic Sea is characterized by having areas located both at the Baltic Shield of the East European Craton and in the Danish-North German-Polish Caledonides. Historical geologists make a distinction between the current Baltic Sea depression, formed in the Cenozoic era, and the much older sedimentary basins whose sediments are preserved in the zone. Although glacial erosion has contributed to shape the present depression, the Baltic trough is largely a depression of tectonic origin that existed long before the Quaternary glaciation. Ancient sedimentary basin Tectonic evolution The Baltic Sea sedimentary basin was formed on top of the East European Craton millions of years after it consolidated. This occurred during the Late Ediacaran and the Early Cambrian when the weakest part of the craton was reactivated. Since then the basin has been deepened mainly through subsidence caused by extensional tectonics. In the northern part of the Baltic Sea basin, inclu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hogland Series
The Hogland Series are a series of Subjotnian sedimentary rocks exposed in the island of Gogland ( sv, Hogland), the Sommer Islands and the nearby sea bottom in the Gulf of Finland. The series encompass quartz-rich conglomerates and breccias plus some volcanic rocks of mafic composition in the form of lava flows and some more silica-rich igneous rocks including quartz-porphyry. The porphyries, which lie at the top the pile, share their origin with the rapakivi granites found nearby. An exhumed Subjotnian erosion surface In geology and geomorphology, an erosion surface is a surface of rock or regolith that was formed by erosion and not by construction (e.g. lava flows, sediment deposition) nor fault displacement. Erosional surfaces within the stratigraphic reco ... is exposed on the island. References {{russia-stub Geology of European Russia Mesoproterozoic Stratigraphy of Europe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jakob Sederholm
Jakob Johannes Sederholm (20 July 1863 – 26 June 1934) was a Finnish petrologist most associated with his studies of migmatites. Troubled by illness throughout his life, Sederholm originally chose to study geology to allow him to work outdoors. After studying first in Helsinki (where he was a student of Fredrik Johan Wiik), then in Stockholm and Heidelberg, Sederholm returned to Finland to work for the Geological Survey of Finland. In 1893 he assumed the role of director of this institution, a post he occupied until his death forty years later. Working on local Precambrian basement rocks, Sederholm instigated a map-making programme that, between 1899 and 1925, published many maps and descriptions of their geological history. Gneisses in the areas he studied (the so-called Baltic Shield) were often of mixed composition, with layers of granitic rock being interleaved with metamorphic rock. Sederholm termed these as migmatites, and viewed them as the product of the intrusio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mesoproterozoic
The Mesoproterozoic Era is a geologic era that occurred from . The Mesoproterozoic was the first era of Earth's history for which a fairly definitive geological record survives. Continents existed during the preceding era (the Paleoproterozoic), but little is known about them. The continental masses of the Mesoproterozoic were more or less the same ones that exist today, although their arrangement on the Earth's surface was different. Major events and characteristics The major events of this era are the breakup of the Columbia supercontinent, the formation of the Rodinia supercontinent, and the evolution of sexual reproduction. This era is marked by the further development of continental plates and plate tectonics. The supercontinent of Columbia broke up between 1500 and 1350 million years ago, and the fragments reassembled into the supercontinent of Rodinia around 1100 to 900 million years ago, on the time boundary between the Mesoproterozoic and the subsequent Neoproterozoi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Riphean (stage)
The Riphean is a stage or age of the geologic timescale from . The name Riphean is used in the Proterozoic stratigraphy of Russia and the Fennoscandian Shield in Finland. It was also used in a number of older international geologic timescales but, in the most recent timescales of the ICS, it is replaced by the Calymmian, Ectasian, Stenian, Tonian and Cryogenian periods of the Neoproterozoic and Mesoproterozoic eras. During the Riphean, there was a great increase in stromatolite diversity, possibly related to the appearance of eukaryotes. The word 'Riphean' comes from the ancient Riphean Mountains, sometimes identified with the Ural Mountains. The Riphean has been divided by geologists into the Early Riphean (1600–1400 Ma), Middle Riphean (1400–1000 Ma) and Late Riphean (1000–600 Ma) subdivisions. Proterozoic (Russian stratigraphic scale in English).png, Russian timescale for Proterozoic. Riphean and its subdivisions are in brown. See also *Jotnian In north European geol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arkose
Arkose () or arkosic sandstone is a detrital sedimentary rock, specifically a type of sandstone containing at least 25% feldspar. Arkosic sand is sand that is similarly rich in feldspar, and thus the potential precursor of arkose. Quartz is commonly the dominant mineral component, and some mica is often present. Apart from the mineral content, rock fragments may also be a significant component. Arkose usually contains small amounts of calcite cement, which causes it to effervesce (fizz) slightly in dilute hydrochloric acid; sometimes the cement also contains iron oxide. Arkose is typically grey to reddish in colour. The sand grains making up an arkose may range from fine to very coarse, but tend toward the coarser end of the scale. Fossils are rare in arkose, due to the depositional processes that form it, although bedding is frequently visible. Arkose is generally formed from the weathering of feldspar-rich igneous or metamorphic, most commonly granitic, rocks, which are p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shale
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite.Blatt, Harvey and Robert J. Tracy (1996) ''Petrology: Igneous, Sedimentary and Metamorphic'', 2nd ed., Freeman, pp. 281–292 Shale is characterized by its tendency to split into thin layers ( laminae) less than one centimeter in thickness. This property is called '' fissility''. Shale is the most common sedimentary rock. The term ''shale'' is sometimes applied more broadly, as essentially a synonym for mudrock, rather than in the more narrow sense of clay-rich fissile mudrock. Texture Shale typically exhibits varying degrees of fissility. Because of the parallel orientation of clay mineral flakes in shale, it breaks into thin layers, often splintery and usually parallel to the otherwise indistinguishable beddin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conglomerate (geology)
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 G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth-Science Reviews
''Earth-Science Reviews'' is a monthly peer-reviewed scientific journal published by Elsevier. It covers all aspects of Earth sciences. The editors-in-chief for this journal are A. Chin, C. Doglioni, J.L. Florsheim, M.F.J. Flower, G.R. Foulger, A. Gómez-Tuena, S. Khan, S. Marriott, A.D. Miall, G.F. Panza, J.A. Sanchez-Cabeza, M. Strecker, E.S. Takle, M. Widdowson, and P.B. Wignall. Abstracting and indexing This journal is abstracted and indexed by: According to the ''Journal Citation Reports'', the journal has a 2012 impact factor The impact factor (IF) or journal impact factor (JIF) of an academic journal is a scientometric index calculated by Clarivate that reflects the yearly mean number of citations of articles published in the last two years in a given journal, as i ... of 7.339. References External links {{Authority control Earth and atmospheric sciences journals Elsevier academic journals English-language journals Monthly journals Publications established ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
