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25-660: Sarmatia is made up of several once-independent Archaean land masses that formed respectively at 3.7–2.9, 3.6–2.8, 3.2–3.0, and 2.7–2.6 Ga. These are separated by a series of 2.2–2.1 Ga orogenic belts . Sarmatia's northwestern margin has an extensive continental magmatic arc dating back to 2.0–1.95 Ga. The Ukrainian Shield and Voronezh Massif are the exposed areas of the Sarmatian Craton. The craton can be divided into Archaean ( c. 3.7–2.7  Ga ) terranes separated by Palaeoproterozoic (c. 2.2–2.1 Ga and 2.0–1.9 Ga) belts . The Osnitsk-Mikashevichi Belt in

50-515: A large load on the Earth's crust, causing flexural depressions in adjacent lithospheric crust. These settings are not tectonically active, but still experience large-scale subsidence because of tectonic features of the crust. Intracontinental basins are large areal depressions that are tectonically inactive and not near any plate boundaries. Multiple hypotheses have been introduced to explain this slow, long-lived subsidence: long-term cooling since

75-453: A spreading center like a mid-ocean ridge, which moves progressively further from coastlines as oceanic lithosphere is produced. Due to this initial phase of rifting, the crust in a passive margin is thinner than adjacent crust and subsides to create an accommodation space. Accumulation of non-marine sediment forms alluvial fans in the accommodation space. As rifting proceeds, listric fault systems form and further subsidence occurs, resulting in

100-536: Is considered a microcontinent, though not a continental fragment. Other hotspot islands such as the Hawaiian Islands and Iceland are considered neither microcontinents nor continental fragments. Not all islands can be considered microcontinents: Borneo , the British Isles , Newfoundland , and Sri Lanka , for example, are each within the continental shelf of an adjacent continent, separated from

125-423: Is controlled by load migration and corresponding sedimentation rates. The broader a basin is, the greater the subsidence is in magnitude. Subsidence is increased in the adjacent basin as the load migrates further into the foreland, causing subsidence. Sediment eroded from the fold thrust is deposited in the basin, with thickening layers toward the thrust belt and thinning layers away from the thrust belt; this feature

150-399: Is known as "thermal subsidence". The adding of weight by sedimentation from erosion or orogenic processes, or loading, causes crustal depression and subsidence. Sediments accumulate at the lowest elevation possible, in accommodation spaces. The rate and magnitude of sedimentation controls the rate at which subsidence occurs. By contrast, in orogenic processes, mountain building creates

175-424: Is the sinking of the Earth's crust on a large scale, relative to crustal-scale features or the geoid . The movement of crustal plates and accommodation spaces produced by faulting brought about subsidence on a large scale in a variety of environments, including passive margins , aulacogens , fore-arc basins , foreland basins , intercontinental basins and pull-apart basins . Three mechanisms are common in

200-425: Is very similar to that of typical continental crust. Strike-slip fault zones cause the fragmentation of microcontinents. The zones link the extensional zones where continental pieces are already isolated through the remaining continental bridges. Additionally, they facilitate quick crustal thinning across narrow zones and near-vertical strike-slip-dominated faults . They develop fault-block patterns that slice

225-554: The Buru - Seram - Ambon complex ( Maluku ), Obi , Sumba , and Timor ( Nusa Tenggara ) [REDACTED] Africa [REDACTED] Antarctica [REDACTED] Asia [REDACTED] Australia [REDACTED] Europe [REDACTED] North America [REDACTED] South America [REDACTED] Afro-Eurasia [REDACTED] Americas [REDACTED] Eurasia [REDACTED] Oceania Tectonic subsidence Tectonic subsidence

250-469: The Caribbean Sea , are composed largely of granitic rock as well, but all continents contain both granitic and basaltic crust, and there is no clear dividing line between islands and microcontinents under such a definition. The Kerguelen Plateau is a large igneous province formed by a volcanic hotspot ; however, it was associated with the breakup of Gondwana and was for a time above water, so it

275-677: The Korosten pluton is not made of mantle-derived igneous material but from the lower crust of the Osnitsk-Mikashevichi Belt extruded in the Central Belarus Suture Zone. The Podolian Domain in southern Sarmantia is made mostly of Archaean-Palaeoproterozoic granulites (up to 3.7 Ga) and divided by major faults into the Vinnitsa and Gayvoron regions. Archaean charnockite intrusions are common in

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300-499: The Osnitsk-Mikashevichi Belt formed at an Andes -type active margin along which 2.0–1.95 Ga-old oceanic crust subducted. This subduction was followed by a calm period after which Sarmantia and Fennoscandia collided c. 1.84–1.82 Ga. The Palaeoproterozoic Volyn Domain is made of 2.06–2.02 Ga-old granitoids emplaced within the 2.2 Ga-old, strongly deformed rocks of the Teterev–Belaya Tserkov belt. The area

325-418: The accretionary prism and the volcanic arc may occur. Abnormal cooling effects due to the cold, water-laden downgoing plate as well as crustal thinning due to underplating may also be at work. [REDACTED] Foreland basins are flexural depressions created by large fold thrust sheets that form toward the undeformed continental crust. They form as an isostatic response to an orogenic load. Basin growth

350-426: The breakup of Pangea , interaction of deformation around the edge of the basin and deep earth dynamics. The Illinois basin and Michigan basin are examples of intracontinental basins. Extensive swamps are sometimes formed along the shorelines of these basins, leading to the burial of plant matter that later forms coal. Tectonic subsidence can occur in these environments as the crust thinning. Successful rifting forms

375-560: The continental fragments to form most likely impacts their layers and overall thickness along with the addition of mafic intrusions to the crust. Studies have determined that the average crustal thickness of continental fragments is approximately 24.8 ± 5.7 kilometres (15.4 ± 3.5 mi). The sedimentary layer of continental fragments can be up to 5 kilometres (3.1 mi) thick and can overlay two to three crustal layers. Continental fragments have an average crustal density of 2.81 g/cm (0.102 lb/cu in) which

400-546: The creation of an ocean basin. After the cessation of rifting, cooling causes the crust to further subside, and loading with sediment will cause further tectonic subsidence. Aulacogens occur at failed rifts, where continental crust does not completely split. Similar to the lithospheric heating that occurs during the formation of passive margins, subsidence occurs due to heated lithosphere sagging as spreading occurs. Once tensional forces cease, subsidence continues due to cooling. Tectonic subsidence can occur in these settings as

425-418: The crustal thinning via normal faulting. Forearc basins form in subduction zones as sedimentary material is scraped off the subducting oceanic plate, forming an accretionary prism between the subducting oceanic lithosphere and the overriding continental plate. Between this wedge and the associated volcanic arc is a zone of depression in the sea floor. Extensional faulting due to relative motion between

450-495: The lithosphere (the elevation of the upper surface decreases while the lower boundary rises). The underlying asthenosphere passively rises to replace the thinned mantle lithosphere. Subsequently, after the rifting/stretching period ends, this shallow asthenosphere gradually cools back into mantle lithosphere over a period of many tens of millions of years. Because mantle lithosphere is denser than asthenospheric mantle, this cooling causes subsidence. This gradual subsidence due to cooling

475-462: The mainland by inland seas flooding its margins. Several islands in the eastern Indonesian Archipelago are considered continental fragments, although this designation is controversial. The archipelago is home to numerous microcontinents with complex geology and tectonics. This makes it complicated to classify landmasses and determine causation for the formation of the landmass. These include southern Bacan , Banggai - Sulu Islands ( Sulawesi ),

500-852: The northwest is 150–200 km (93–124 mi)-wide and extends for more than 1,000 km (620 mi) from the Trans-European Suture Zone to Moscow. It is exposed only in the northwest corner of the Ukrainian Shield and in the Pripyat Trough (west of the Devonian Dniepr–Donets Aulacogen). Although mostly hidden beneath Phanerozoic sedimentary rocks the belt can be traced magnetically. The presence of granitic batholiths intruded by diorites and gabbros at c. 1.98–1.95 Ga and hypabbysal and metavolcanic rocks dated to 2.02 Ga indicate

525-439: The plates collide against or under each other. Pull-apart basins have short-lived subsidence that forms from transtensional strike-slip faults. Moderate strike-slip faults create extensional releasing bends and opposing walls pull apart from each other. Normal faults occur, inducing small scale subsidence in the area, which ceases once the fault stops propagating. Cooling occurs after the fault fails to propagate further following

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550-481: The portion of continent into detachable slivers. The continental fragments are located at various angles from their transform faults . Some microcontinents are fragments of Gondwana or other ancient cratonic continents; examples include Madagascar ; the northern Mascarene Plateau , which includes the Seychelles Microcontinent ; and the island of Timor . Other islands, such as several in

575-828: The southeast. Exposed rocks in western Sarmantia are 10–15 km (6.2–9.3 mi)-thick Archaean to Palaeoproterozoic crust. Granulites in southern Sarmantia were exhumed from a depth of at least 35 km (22 mi). The Golovanevsk Suture Zone in the east contains almost 3.0 Ga-old igneous rocks. The oldest rocks are probably derived from early Archaean oceanic crust. Continental fragment Continental crustal fragments , partly synonymous with microcontinents , are pieces of continents that have broken off from main continental masses to form distinct islands that are often several hundred kilometers from their place of origin. Continental fragments and microcontinent crustal compositions are very similar to those of regular continental crust . The rifting process that caused

600-572: The tectonic environments in which subsidence occurs: extension, cooling and loading. Where the lithosphere undergoes horizontal extension at a normal fault or rifting center , the crust will stretch until faulting occurs, either by a system of normal faults (which creates horsts and grabens ) or by a system of listric faults. These fault systems allow the region to stretch, while also decreasing its thickness. A thinner crust subsides relative to thicker, undeformed crust. Lithospheric stretching/thinning during rifting results in regional necking of

625-461: Was strongly deformed at 1.98–1.95 Ga but it can be interpreted as a setting of intense volcanism and sedimentation in a coastal-marine environment in which island arcs reused detritus from Archaean sources. The 1.80–1.74 Ga-old Korosten pluton in northern Ukraine formed from a succession of volcanism. It was originally believed to be an anorogenic process fueled by mantle underplating . More recently, however, it has been demonstrated that

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