In geology , an aulacogen is a failed arm of a triple junction of a plate tectonics rift geology rift system. A triple junction beneath a continental plate initiates a three way breakup of the continental plate. As the continental break up develops one of the three spreading ridges typically fails or stops spreading. The resulting failed rift is called an aulacogen and becomes a filled graben system within the continent. The term aulacogen is derived from the Greek aulax furrow and was suggested by the Soviet geologist Nicholas Shatski in 1946. ref name Shatski Nicholas S. Shatski, 1946, The Great Donets basin and the Wichita System comparative tectonics of ancient platforms Akademiia Nauk SSSR Doklady, Geology Series, No. 6, p. 57 90. ref ref http arjournals.annualreviews.org doi abs 10.1146 annurev.ea.05.050177.002103 Aulacogens and Continental Breakup ref The crust in an aulacogen region remains weakened by previous rifting activity and thus seismic activity and, occasionally, volcanic activity may re occur subsequently from time to time. As aulacogens remain places of weakness, given the appropriate conditions, they can reactivate into active rift valleys again, as had happened to the Ottawa Bonnechere Graben in Ontario and Quebec , Canada , an ancient aulacogen that reactivated during the breakup of Pangaea . The Mississippi embayment with the associated New Madrid Seismic Zone is an example of an ancient aulacogen that dates back to the breakup of the ancient continent, Rodinia . This ancient rift was the site of 1812 New Madrid earthquake extreme earthquakes in the early 19th century in the region. The Southern Oklahoma Aulogen, exposed in the Wichita Mountains , is an Cambrian Eocambrian rift system formed as a product of intracontinetal rifting during the breakup of Pannotia . The Rio Grande Rift is another example. Located on the Southwestern European margin ... it Aulacogeno he ka kk sw Aulakogenia nl Aulacogen ja nn Aulakogen ... more details
The Nipigon Embayment is an inactive continental rift zone in Northwestern Ontario , Canada , centered on Lake Nipigon . It represents an aulacogen of the much larger Midcontinent Rift System , which formed some 1,100 million years ago when the North American craton began to split apart during the Proterozoic eon. ref http gizmo.geotop.uqam.ca mareschalJC Perry et al GRL 2004.pdf Heat flow in the Nipigon arm of the Keweenawan rift, northwestern Ontario, Canada ref References reflist coord 50.07 N 88.64 W display title Category Geology of Ontario Category Aulacogens Category Proterozoic Ontario geo stub Canada geology stub ... more details
File MLIP igneous figures.png thumb right 250px alt An image showing a zone with related features. Tectonic and magmatic features associated with the Mackenzie Large Igneous Province, including the rifting that created the Poseidon Ocean. Red star shows the initial Mackenzie plume zone relative to the lithosphere. The Poseidon Ocean is a supposed ocean that existed in the Mesoproterozoic period of the geologic timescale between 1600 and 1000 million years ago . It began to form when a hotspot geology hotspot collided with lithosphere that was already in an extensional regime that allowed rifting to occur at the onset of hotspot volcanism that created the Mackenzie Large Igneous Province . This hotspot, known as the Mackenzie hotspot , produced passive rifting to form a triple junction . As two of the rift arms continued to grow, they created the Poseidon Ocean basin. The third rift arm failed to open fully, creating an aulacogen . ref cite book last Ernst first Richard E. coauthors Buchan, Kenneth L. title Mantle plumes their identification through time publisher Geological Society of America year 2001 pages 148 url http books.google.ca books?id X4W9aGXDa9cC&pg PA261&lpg PA261&dq anahim hotspot&source bl&ots BQnqvzgq9K&sig 7gRnMRoyzaBGkyl1 M26gfYVu38&hl en&ei AtVPS8KJApD2NZnmjZcJ&sa X&oi book result&ct result&resnum 7&ved 0CBYQ6AEwBjgU v onepage&q anahim 20hotspot&f false isbn 0 8137 2352 3 accessdate 2009 04 11 ref References reflist Paleo geo stub Category Historical oceans Category Proterozoic ... more details
File Ukraine geology.png 250px thumb 10. Sarmatian craton Sarmatian craton is a geology geological and tectonics term for the southern segment region of the East European craton also known as Scythian plateau . The craton contains Archaean rocks 2.8 to 3.7 billion years old. During the Carboniferous Period the craton was rift ed apart by the Dneiper Donets rift . As a result, geomorphologically the cratonic area is split by the Donbass Fold Belt, also known as a part of the large Pripyat Dniepr Donets aulacogen , which transects Sarmatia, dividing it into the Ukrainian Massif or shield on the southwest and the Voronezh Massif to the northeast. Sarmatia is made up of several once independent Archaen land masses that developed at 3.7 2.9, 3.2 3.0, and 2.7 Ga. 2.3 2.1 Ga orogenic belts now separate these land masses. Sarmatia s northwestern margin has an extensive continental magmatic arc dating back to 2.0 Ga. At 200 Ma Sarmatia collided with Fennoscandia. References Bogdanova, Svetlana V. 2005 The East European Craton Some Aspects of the Proterozoic Evolution in its South West. Polskie Towarzystwo Mineralogiczne Prace Specjalne Mineralogical Society of Poland Special Papers, Zeszyt 26, 2005 Vol. 26. Online http www.geo.uw.edu.pl PTMINSP 2005 018.pdf http www.geofys.uu.se eprobe Projects ebridge ep eubr.pdf Svetlana Bogdanova Lund and EUROBRIDGE, Palaeoproterozoic Accretion of Sarmatia and Fennoscandia http www.geol.uniovi.es TDG Volumen25 TG25 06.PDF Dmitry A. Ruban and Shoichi Yoshioka, Late Paleozoic Early Mesozoic Tectonic Activity within the Donbass Russian Platform Category Cratons Category Geography of Ukraine Category Landforms of Europe geology stub kk no Sarmatiske skjold pl Kraton sarmacki ru uk ... more details
File Central African Rifts.svg thumb 300px Central African rifts Anza trough to the southeast. The Anza trough is a rift in Kenya that was formed in the Jurassic Period of the Mesozoic Era. The trough runs inland from the coast in the northwest direction. The trough appears to be an aulacogen , a failed arm of a triple junction of a plate tectonics rift system, formed during the initial stretching phase when Gondwana was breaking up. ref cite book url http books.google.ca books?id H0UwWlOKAHYC&pg PA230 page 230 title Flow and creep in the solar system observations, modeling, and theory author David B. Stone, S. K. Runcorn publisher Springer year 1993 ISBN 0792321480 ref The rift was formed by the same forces that created the rift system in South Sudan , and connects those rifts to the Lamu embayment further to the south. The separation of the other two arms of the junction allowed Indian Plate India Madagascar to separate from Africa . ref cite journal url http www.mendeley.com research crustal structure tectonic evolution anza rift northern kenya title Crustal structure and tectonic evolution of the Anza rift, northern Kenya author L C Greene, D R Richards, R A Johnson journal Tectonophysics year 1991 volume 197 issue 2 4 pages 203 211 accessdate 2010 12 20 bibcode 1991Tectp.197..203G doi 10.1016 0040 1951 91 90041 P ref The trough is now hidden by a cover of Quaternary sediments and volcanic rocks. ref cite journal title Geophysical evidence for a failed Jurassic rift and triple junction in Kenya author C.V. Reeves, F.M. Karanja and I.N. MacLeod journal Earth and Planetary Science Letters volume 81 issue 2 3 month January year 1987 pages 299 311 accessdate 2010 12 20 doi 10.1016 0012 821X 87 90166 X bibcode 1987E&PSL..81..299R ref References reflist 1 refs Major African geological formations coord missing Kenya Category Aulacogens Category Landforms of Kenya ... more details
For the Miles Davis album Panthalassa The Music of Miles Davis 1969 1974 unreferenced date September 2011 Image Pangaea.png right 250px thumb The blue ocean surrounding Pangaea is Panthalassa Panthalassa Ancient Greek Greek , meaning all sea , also known as the Panthalassic Ocean , was the vast global ocean that surrounded the supercontinent Pangaea , during the late Paleozoic and the early Mesozoic years. It included the Pacific Ocean to the west and north and the Tethys Ocean to the southeast. It became the Pacific Ocean, following the closing of the Tethys basin and the breakup of Pangaea, which created the Atlantic Ocean Atlantic , Arctic Ocean Arctic , and Indian Ocean basins. The Panthalassic is often called the Paleo Pacific old Pacific because the Pacific Ocean evolved from it. In the map on the right, the Earth s equator was a line that roughly crossed the spot where Spain , Casablanca Morocco and Boston United States U.S. met. South of that line, the land mass is referred to as Gondwana . North of the line, it is referred to as Laurasia . Formation By 900 million years ago in the early Neoproterozoic a triple junction formed as the supercontinent Rodinia started to rift apart. Between about 800 million and 700 million years ago, it split in half. This was one of the most significant rifting events of all time, because it opened up the Panthalassic Ocean to the west of Laurentia , a continent that became North America . In western Laurentia North America , tectonic episodes that preceded this rifting produced Aulacogen failed rift s that harbored large depositional basins in Western Laurentia. The global ocean of Mirovia , an ocean that surrounded Rodinia, started to shrink because the Pan African ocean and Panthalassa were expanding. Between 650 million and 550 million years ago, another supercontinent was forming, Pannotia , which was shaped like a V . Inside the V was Panthalassa, outside of the V was the Pan African Ocean and remnants of the M ... more details
Only core subjects that are of interest to all geologists should be listed here. Consider the subjects that are covered in secondary school or undergraduate Introduction to geology courses before geology majors start to specialize. See the Talk Page. Please develop a list of subtopics here before moving articles from the main list into them, so that we know what categories we have to choose from. This is a list of all articles related to geology that cannot be readily placed on the following subtopic pages col begin col 3 Geologic time scale List of compounds List of earthquakes List of elements by name Geology of the English counties col 3 List of geologists List of fluvial topics List of landform s List of minerals List of oil fields col 3 List of plate tectonics topics List of rock types List of tectonic plates List of volcanoes col end compactTOC8 side yes top yes num yes A Asthenosphere Astrogeology Aulacogen B Batholith Beach Bolide C Calcium Canyon Cave Cement Cementation Cenozoic Coast Concretion Conglomerate geology Conglomerate Continent Convergent boundary Crag and tail Crust geology Crust D Datum geodesy Deposition sediment Deposition Dike geology Dike Divergent boundary Drumlin E Earth science Eustasy Environmental engineering Environmental geography Eon geology Eon Epigenesis Epoch geology Epoch Era geology Era F Falls line Felsic G Geologic age Fault geology Geologic fault Geologic modeling Geologic period Geologic time scale Geological phenomenon Geologist Geology of the Alps Geomorphology Geostatistics Geyser Glaciation Graben H Horst geology Hotspot geology I Igneous rock Isostasy J Karst L Laccolith List of geologists List of tectonic plates List of rock types Lithosphere M Mafic Mantle geology Mass wasting Matrix geology Metamorphic rock Meteorite Mineral Mining engineering Mud pot Mud volcano N Empty section date July 2010 O Orogeny P Paleontology Pedology soil study Permeability fluid Petroleum engineering Phosphate Piercement structure Plate t ... more details
Other uses Rift Valley disambiguation Image RiftValleyLakes.JPG 250px thumb African Rift Valley . From left to right Lake Upemba , Lake Mweru , Lake Tanganyika largest , and Lake Rukwa . Image Browncanyonquilotoa.jpg 250px thumb caption A rift valley near Quilotoa , Ecuador . Image Ottawabonnecheregrabenmap.png thumb right 250px The Ottawa Bonnechere Graben A rift valley is a linear shaped lowland between highlands or mountain ranges created by the action of a geologic rift or fault geology fault . This action is manifest as crustal extension, a spreading apart of the surface which is subsequently further deepened by the forces of erosion. When the tensional forces are strong enough to cause the plate to split apart it will do so such that a center block will drop down relative to its flanking blocks, forming a graben . This creates the nearly parallel steeply dipping walls. This feature is the beginning of the rift valley. As this process continues, the valley gets wider and wider until it becomes a large basin that fills with sediment from the rift walls and the surrounding area. One of the better long term examples of this process is the Basin and Range province in Nevada and Utah. Rifts can occur at all elevations, from the sea floor to plateaus and mountain ranges. They can occur in continental crust or in oceanic crust . Rift valleys are often associated with a number of adjoining subsidiary or co extensive valleys which are typically considered geologically part of the principal rift valley. The most extensive rift valley is located along the crest of the mid ocean ridge system and is the result of sea floor spreading . Examples of this type of rift include the Mid Atlantic Ridge and the East Pacific Rise . Many existing continental rift valleys are the result of a failed arm aulacogen of a triple junction , although there are two, the East African Rift and the Baikal Rift Zone , which are currently active, as well as a third which may be, the West Antarctic ... more details
Other uses Multijunction photovoltaic cell No footnotes date April 2009 A triple junction is the point where the boundaries of three tectonic plate s meet. At the triple junction a boundary will be one of 3 types a Mid ocean ridge ridge , oceanic trench trench or transform fault and triple junctions can be described according to the types of plate margin that meet at them. Of the many possible types of triple junction only a few are Triple junction stability stable through time stable in this context means that the geometrical configuration of the triple junction will not change through time . History The first scientific paper detailing the triple junction concept was published in 1969 by W. Jason Morgan , Dan McKenzie professor Dan McKenzie , and Tanya Atwater . ref http www.nature.com nature journal v224 n5215 abs 224125a0.html ref The term has traditionally been used for the intersection of three divergent boundaries or spreading ridges. These three divergent boundaries ideally meet at near 120 angles. In plate tectonics theory during the breakup of a continent, one of the divergent plate boundaries would fail see aulacogen and the other two would continue spreading to form an ocean. The Seafloor spreading opening of the south Atlantic Ocean started at the south of the South America n and African continents, reaching a triple junction in the present Gulf of Guinea , from where it continued to the west. The NE trending Benue Trough is the failed arm of this junction. ref name Petters1978 cite journal jstor 30061985 title Stratigraphic Evolution of the Benue Trough and Its Implications for the Upper Cretaceous Paleogeography of West Africa author S. W. Petters journal The Journal of Geology volume 86 issue 3 date May, 1978 pages 311 322 doi 10.1086 649693 bibcode 1978JG.....86..311P ref Examples Image EAfrica.gif thumb Map of East Africa showing some of the historically active volcanoes red triangles and the Afar Triangle shaded, center a triple junction where thr ... more details
The East European craton EEC is the core of the Baltica proto Tectonic plate plate and consists of three crustal regions segments Fennoscandia to the northwest, Volgo Uralia to the east, and Sarmatian craton Sarmatia to the south. Fennoscandia includes the Baltic Shield also referred to as the Fennoscandian Shield and has a diversified Accretion geology accretionary Archaean and Early Proterozoic Crust geology crust , while Sarmatia has an older Archaean crust. The Volgo Uralia region has a thick sedimentary cover, however deep drillings have revealed mostly Archaean crust. There are two shields in the East European Craton the Baltic Fennoscandian shield and the Ukrainian shield. The Ukrainian Shield and the Voronezh Massif consists of 3.2 3.8 Gya Ga Archaean crust in the southwest and east, and 2.3 2.1 Ga Early Proterozoic Orogeny orogenic belts . The Ural Mountains of central Russia is the eastern margin of the East European craton and marks the Late Paleozoic orogenic collision of the East European craton with the Siberia continent Siberian craton s. The southern margin of the craton is where Sarmatia is buried beneath thick Phanerozoic sediments and the Alpine orogen s. The intervening Late Palaeozoic Donbass Fold Belt, also known as part of the Pripyat River Pripyat Dniepr Donets aulacogen , transects Sarmatia, dividing it into the Ukrainian Shield and the Voronezh Massif. The southwestern boundary is known as the Trans European Suture Zone and separates the East European craton from the Phanerozoic orogen s of Western Europe eg. Carpathians . The northwestern margin of the craton is overlaid by the fold and thrust Early Paleozoic Caledonian orogen . Platform basement The most distinguishable physiographic aspect of the East European craton is the extensive 3 km and more thick Riphean stage Riphean middle to late Proterozoic sedimentary cover over its 3000 km wide Platform geology platform area East European Platform , EEP , also formerly known as the Russian P ... more details
Image New Madrid and Wabash seizmic zones USGS.png thumb right 350px Locations of quakes magnitude 2.5 or greater in the Wabash Valley upper right and New Madrid Seismic Zone New Madrid lower left Seismic Zones The Wabash Valley Seismic Zone also known as the Wabash Valley Fault System or Zone is a Plate tectonics tectonic region located in the Midwest of the United States , centered on the valley of the Lower Wabash River , along the state line between southeastern Southern Illinois Illinois and southwestern Indiana . Geology The Wabash Valley Seismic Zone consists largely of vertically oriented normal fault geology fault s deeply buried under layers of sediment. Although the tectonics of the region are still not fully understood and are the subject of ongoing research, these faults are thought by some to be associated with a branch of the New Madrid Seismic Zone New Madrid aulacogen , an old rift zone where the lithosphere actively began to pull apart at perhaps two separate times in the distant past.Present day GPS measurements show that the region deforms at about 1 2 mm yr with compression along the Wabash Valley Fault Zone, and extension in SW Indiana Hamburger et al., 2002 Galgana and Hamburger, 2010 . ref cite web url http www.cusec.org S zones Wabash fact 20sheet.htm title Seismicity of the Lower Wabash Valley Fact Sheet author Hill, John R. publisher Central United States Earthquake Consortium accessdate 2008 04 18 archiveurl http web.archive.org web 20080422001034 http cusec.org S zones Wabash fact sheet.htm Bot retrieved archive archivedate 2008 04 22 ref The Continental crust crust in the area has been weakened by the numerous faults, which remain active sites for continuing seismic activity as the motion of the North American Plate exerts both compressional and tensional forces. Earthquakes This zone has been proven to have had earthquake s for the last 20,000 years, with geologic evidence that they may have been as strong as 7.0 7.5 or greater on the ... more details
rift apart in an aulacogen during breakup of the Neoproterozoic continent, Pannotia. ref name McConnell ... Oklahoma Aulacogen , Tectonophysics, 174 p. 147 157. ref The exposed portion of this unit, named ... more details
Image Cratons West Gondwana.svg thumb right Approximate location of Mesoproterozoic older than 1.3 Ga craton s in South America and Africa The country of Paraguay lies geologically at the borderzone between several craton s being most of the country covered by Tertiary sediments and thick regolith . Due to thick Tertiary sediment and regolith development few outcrop s are available in Paraguay. ref name Fuldfa F lfaro V. J. http www.google.com books?hl sv&lr &id 0vxnCKlQOXMC&oi fnd&pg PA17&dq paraguay geology&ots vdBXx8P tQ&sig lNJbgDAOposlf8 EItxkJeL9YtI v onepage&q paraguay 20geology&f false Geology of Eastern Paraguay ref East of Paraguay River that Precambrian and Early Paleozoic crystalline basement crop out mainly in the heights of Caapuc and Apa. The geologial processes that have shaped Paraguay s bedrock and sedimentary basin s are diverse including Aulacogen rifting , marine sediment ation, metamorphic rock metamorphism , eruption of flood basalt s and alkaline potassic volcanism . Pre Silurian basement image Paisaje de Paraguari.jpg thumb right Serran as de Paraguar in Paraguar Department are made of Silurian sandstone of the Misiones Formation and alkaline rock alkaline intrusive rock intrusives of Creataceous Early Cretaceous age. Caapuc High Caapuc High formely called Prec mbrico Sur and Saliente del Pilar is the Northwesternmost outcrop of Rio de la Plata Craton . ref name Fuldfa The rocks found in the Caapuc High include porphyritic granitic rocks, orthogneiss es, paragneiss es, amphibolite s, migmatite s, talc schist s and rhyolite Dike geology dyke s. ref name Fuldfa During the Brasiliano Cycle 576 480 million years ago Ma ago the area of the Caapuc height suffered a major magma tic event. Apa High The formations at the Apa High include metamorphic rock metamorphosed limestone of Ediacaran Vendian Age and granites, metasediments, mafic gneiss es and granitoid Pegmatite pegmatititic intrusvies of Late Proterozoic age. ref name Fuldfa The ... more details
that spread toward the Las Vegas Valley . This embayment, called the Amargosa aulacogen , had highlands ... deposited from 1200 to 800 mya sfn Harris 1997 p 611 in the Amargosa aulacogen. sfn Collier 1990 p ... the area as the Amargosa aulacogen slowly subsided thick sequences of Lime mineral lime rich ooze ... Valley region once again rose above sea level, resulting in erosion. The Amargosa aulacogen then slowly ... Spring to erosion subsequent faster subsidence of the Amargosa aulacogen broke these formations into islands ... more details
the surface. The resulting rift system failed but has remained as an aulacogen a scar or zone of weakness ... zone is considered an aulacogen related to the New Madrid fault line. Citation needed date April ... more details
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