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Tomas Villamil - One of the best experts on this subject based on the ideXlab platform.
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campanian miocene Tectonostratigraphy depocenter evolution and basin development of colombia and western venezuela
Palaeogeography Palaeoclimatology Palaeoecology, 1999Co-Authors: Tomas VillamilAbstract:Abstract The position of the central axis of deposition over Colombian and Venezuelan continental crust has varied markedly through time. The axis migrated from west to east from Late Cretaceous to Oligocene but at times, secondary drainage divides were established by local uplift events. In Oligocene times with initial inversion of the Eastern Cordillera the central axis of deposition was divided into two main axes, the proto-Magdalena and the proto-Orinoco systems. The west to east migration of the central axis of deposition had a tectonic origin and it occurred in combination with tectonically driven changes in accommodation space. Depocenter evolution can be divided as follows. (1) The axis of the Campanian and early Maastrichtian depocenter was located few km east of the present position of the Central Cordillera of Colombia; it migrated east with gradual uplift of the Central Cordillera. (2) The central axis of late Maastrichtian deposition is positioned approximately over the present-day western foothills of the Eastern Cordillera, possibly crosses the Eastern Cordillera over the Santander Massif and continues into the Maracaibo Lake in western Venezuela. Accommodation space decreased from Campanian to Maastrichtian times. In Cretaceous–Tertiary boundary times parts of the eastern margin of the Eastern Cordillera were uplifted by an initial phase of inversion of deeply rooted Jurassic and Early Cretaceous normal faults. (3) In Paleocene times the central axis of deposition was located along the spine of the Eastern Cordillera and extended into the Maracaibo Basin, and accommodation space continued to decrease. (4) In latest Paleocene times the central axis of deposition shifted to eastern regions of the Eastern Cordillera and accommodation space decreased. (5) The Early Eocene central axis of deposition was located along the present-day eastern foothills of the Eastern Cordillera; accommodation space continued to decrease and the regional Middle Eocene unconformity began to develop. In Middle Eocene times a regional unconformity developed, marking the climax of the pre-Andean Orogeny. Deposition during these times was dominant in the Maracaibo Basin area where large amounts of sediment derived from vast exposed areas accumulated. (6) The Late Eocene central axis of deposition was confined to the present position of the Llanos foothills. Late Eocene deposition reflects a regional increase in accommodation space. In Oligocene times the initial uplift of the Eastern Cordillera divided the main depocenter into two central axes. Accommodation space diminished in uplifted regions but continued to increase in the depocenters allowing sporadic marine ingressions into the present position of the Llanos foothills. As uplift of the Eastern Cordillera continued, the eastern depocenter axis (proto-Orinoco) migrated east and the western depocenter axis (proto-Magdalena) migrated west. This process continued through the rest of the Cenozoic.
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Campanian–Miocene Tectonostratigraphy, depocenter evolution and basin development of Colombia and western Venezuela
Palaeogeography Palaeoclimatology Palaeoecology, 1999Co-Authors: Tomas VillamilAbstract:Abstract The position of the central axis of deposition over Colombian and Venezuelan continental crust has varied markedly through time. The axis migrated from west to east from Late Cretaceous to Oligocene but at times, secondary drainage divides were established by local uplift events. In Oligocene times with initial inversion of the Eastern Cordillera the central axis of deposition was divided into two main axes, the proto-Magdalena and the proto-Orinoco systems. The west to east migration of the central axis of deposition had a tectonic origin and it occurred in combination with tectonically driven changes in accommodation space. Depocenter evolution can be divided as follows. (1) The axis of the Campanian and early Maastrichtian depocenter was located few km east of the present position of the Central Cordillera of Colombia; it migrated east with gradual uplift of the Central Cordillera. (2) The central axis of late Maastrichtian deposition is positioned approximately over the present-day western foothills of the Eastern Cordillera, possibly crosses the Eastern Cordillera over the Santander Massif and continues into the Maracaibo Lake in western Venezuela. Accommodation space decreased from Campanian to Maastrichtian times. In Cretaceous–Tertiary boundary times parts of the eastern margin of the Eastern Cordillera were uplifted by an initial phase of inversion of deeply rooted Jurassic and Early Cretaceous normal faults. (3) In Paleocene times the central axis of deposition was located along the spine of the Eastern Cordillera and extended into the Maracaibo Basin, and accommodation space continued to decrease. (4) In latest Paleocene times the central axis of deposition shifted to eastern regions of the Eastern Cordillera and accommodation space decreased. (5) The Early Eocene central axis of deposition was located along the present-day eastern foothills of the Eastern Cordillera; accommodation space continued to decrease and the regional Middle Eocene unconformity began to develop. In Middle Eocene times a regional unconformity developed, marking the climax of the pre-Andean Orogeny. Deposition during these times was dominant in the Maracaibo Basin area where large amounts of sediment derived from vast exposed areas accumulated. (6) The Late Eocene central axis of deposition was confined to the present position of the Llanos foothills. Late Eocene deposition reflects a regional increase in accommodation space. In Oligocene times the initial uplift of the Eastern Cordillera divided the main depocenter into two central axes. Accommodation space diminished in uplifted regions but continued to increase in the depocenters allowing sporadic marine ingressions into the present position of the Llanos foothills. As uplift of the Eastern Cordillera continued, the eastern depocenter axis (proto-Orinoco) migrated east and the western depocenter axis (proto-Magdalena) migrated west. This process continued through the rest of the Cenozoic.
Harald Fritz - One of the best experts on this subject based on the ideXlab platform.
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Internal structural geometry of the Paleozoic of Graz
International Journal of Earth Sciences, 2009Co-Authors: Deta Gasser, Kurt Stuwe, Harald FritzAbstract:The Paleozoic of Graz is an isolated nappe complex of about 1,500 km2 size and belongs to the Austroalpine units of the eastern European Alps. Despite more than 500 publications on stratigraphy, paleontology and local structure, many aspects of the internal geometry of this complex as a whole remained unclear. In this contribution, we present integrated geological profiles through the entire nappe complex. Based on these profiles, we present (1) a simplified lithological subdivision into 13 rock associations, (2) a modified Tectonostratigraphy where we consider only two major tectonic units: an upper and a lower nappe system and in which we abandon the traditionally used facies nappe concept, and (3) a modified paleogeography for the whole complex. Finally, we discuss whether the internal deformation of the Paleozoic of Graz is of Variscan or Eo-Alpine age and which of the published models best explain the tectonic evolution of the Paleozoic of Graz.
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Geodynamic and tectonic evolution of the southeastern Bohemian Massif: The Thaya section (Austria)
Mineralogy and Petrology, 1996Co-Authors: Harald FritzAbstract:The Tectonostratigraphy within eastern sections of the Bohemian Massif includes two different terranes. A Proterozoic terrane is composed of the Moravo-Silesian parautochthon, the Moravian nappe complex and the Moldanubian Variegated and Monotonous complexes. A Paleozoic terrane includes the Gfohl Gneiss and the granulite klippen. Both terranes are separated by an oceanic suture zone which is represented by the Letovice ophiolite complex (Czech Republic) and the Raabs complex in Austria. The Raabs structural unit is interpreted to represent a tectonic melange of a dismembered ophiolite complex and metaandesites.
Richard Armstrong - One of the best experts on this subject based on the ideXlab platform.
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Detrital zircon constraints on the Tectonostratigraphy of the Paleoproterozoic Pretoria Group, South Africa
Precambrian Research, 2016Co-Authors: Stefan Schröder, Nicholas J. Beukes, Richard ArmstrongAbstract:Abstract Absolute age constraints are a key requirement to understand links between global tectonics, sedimentation and changing surface environments in the Neoarchean and Paleoproterozoic, in particular oxygenation of the ocean–atmosphere system (the Great Oxidation Event, GOE) or increased carbon burial during the Lomagundi δ13C excursion. This paper presents new detrital zircon U–Pb dates from the 2.4 to 2.1 Ga Pretoria Group (Transvaal Supergroup, South Africa), a clastic-dominated succession spanning surface oxidation and the δ13C excursion. Zircon ages cover all major igneous source terrains on the Kaapvaal craton and thus constitute a representative cross section of craton structure. Maximum depositional ages have been determined for the Duitschland Formation (2424 ± 12 Ma – youngest single grain age), Timeball Hill Formation (2324 ± 17 Ma – youngest single grain age), Hekpoort Formation (2247 ± 10 Ma – weighed mean peak age), Daspoort Formation (2265 ± 20 Ma – weighed mean peak age), and Magaliesberg Formation (2214 ± 11 Ma – youngest 2-grain cluster). These ages are consistent with previously published age constraints, but represent the first direct age constraints for the Daspoort and Magaliesberg formations. Maximum depositional ages and zircon populations show clear younging trends up through the succession that reflect a progressively thicker sedimentary cover and increasing internal recycling. The lower Pretoria Group (Duitschland to Hekpoort formations) contains a prominent ∼2575–2410 Ma zircon population that likely derived from Pilbara craton volcanic rocks, but its equivalent was probably eroded from the Kaapvaal craton. Major disconformities exist at the base of Duitschland, Hekpoort and Daspoort formations. The Duitschland Formation represents significant tectonic uplift and renewed clastic input across the craton. The Duitschland/Timeball Hill contact is reconsidered as a conformable contact to paraconformity with a minor time gap on the basis of sedimentary observations and similar zircon signatures, thus placing the top of the Duitschland Formation at about 2320 Ma. Although no age constraints were obtained for the basal Duitschland glacial period, it was likely associated with tectonic activity between ∼2420 Ma and sometime before 2320 Ma. The Pretoria Group tectonostratigraphic record is largely consistent with global supercontinent assembly and rifting in the interval ∼2.4–2.1 Ga. It includes possible crustal uplift and tectonic activity between deposition of iron formation and the upper Duitschland Formation, and two potential rifting events in the Bushy Bend lavas and Hekpoort basalts. Only two glacial intervals are confirmed for South Africa (Makganyene–Rietfontein diamictite ∼2250–2220 Ma, basal Duitschland diamictite ∼2420–2320 Ma), with a third possibly represented by a cryptic glacial surface in the Duitschland Formation.
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the Tectonostratigraphy granitoid geochronology and geological evolution of the precambrian of southern ethiopia
Journal of African Earth Sciences, 2002Co-Authors: B Yibas, Wolf Uwe Reimold, Richard Armstrong, Christian Koeberl, C R Anhaeusser, David PhillipsAbstract:Abstract Two distinct tectonostratigraphic terranes, separated by repeatedly reactivated deformation zones, are recognised in the Precambrian of southern Ethiopia: (1) granite-gneiss terrane, which is classified into sub-terranes and complexes, and (2) ophiolitic fold and thrust belts. The granite-gneiss terrane consists of para- and orthoquartzofeldspathic gneisses and granitoids, intercalated with amphibolites and sillimanite–kyanite-bearing schists. The paragneisses resemble gneisses from northern Kenya that were derived from sediments that filled the Kenyan sector of the “Mozambique Belt basin” between 1200 and 820 Ma. The volume of sediments formed during this period is comparatively small in southern Ethiopia, implying that the “Mozambique Belt basin” became progressively narrower northwards. The granitoid rocks in the study area vary from granitic gneisses to undeformed granites and range compositionally from diorites to granites. The granitoid gneisses form an integral part of the granite-gneiss terrane, but are rare in the ophiolitic fold and thrust belts. The ophiolitic fold and thrust belts are composed of mafic, ultramafic and metasedimentary rocks in various proportions. Undeformed granitoids are also developed in these belts. Eight granitoids from southern Ethiopia have been dated by U–Pb single zircon SHRIMP and laser probe 40Ar–39Ar dating. The SHRIMP ages range from ∼880 to 526 Ma, and are interpreted as close approximations of the respective magmatic emplacement ages. The 40Ar–39Ar data range from 550 to 500 Ma. The available geochronological data and field studies allowed classification of the granitoids of the Precambrian of southern Ethiopia into seven generations: Gt1 (>880 Ma); Gt2 (800–770 Ma); Gt3 (770–720 Ma); Gt4 (720–700 Ma); Gt5 (700–600 Ma); Gt6 (580–550 Ma); and Gt7 (550–500 Ma). The period 550–500 Ma (Gt7) is marked by emplacement of late- to post-tectonic and post-orogenic granitoids and presumably represents the latest tectonothermal event marking the end of the East African Orogen. Five tectonothermal events belonging to the East African Orogen are recognised in the Precambrian of southern Ethiopia: (1) Adola (1157±2 to 1030±40 Ma); (2) Bulbul–Awata (∼876±5 Ma); (3) Megado (800–750 Ma); (4) Moyale (700–550 Ma); and (5) Berguda (550–500 Ma).
Chuanshan Wang - One of the best experts on this subject based on the ideXlab platform.
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the jinshajiang ailaoshan suture zone china Tectonostratigraphy age and evolution
Journal of Asian Earth Sciences, 2000Co-Authors: Xiaofeng Wang, Ian Metcalfe, Ping Jian, Chuanshan WangAbstract:Abstract The Jinshajiang Suture Zone is important for enhancing our understanding of the evolution of the Paleo-Tethys and its age, tectonic setting and relationship to the Ailaoshan Suture Zone have long been controversial. Based on integrated tectonic, biostratigraphic, chemostratigraphic and isotope geochronological studies, four tectono-stratigraphic units can be recognized in the Jinshajiang Suture Zone: the Eaqing Complex, the Jinshajiang Ophiolitic Melange, the Gajinxueshan “Group” and the Zhongxinrong “Group”. Isotope geochronology indicates that the redefined Eaqing Complex, composed of high-grade-metamorphic rocks, might represent the metamorphic basement of the Jinshajiang area or a remnant micro-continental fragment. Eaqing Complex protolith rocks are pre-Devonian and probably of Early–Middle Proterozoic age and are correlated with those of the Ailaoshan Complex. Two zircon U–Pb ages of 340±3 and 294±3 Ma , separately dated from the Shusong and Xuitui plagiogranites within the ophiolitic assemblage, indicate that the Jinshajiang oceanic lithosphere formed in latest Devonian to earliest Carboniferous times. The oceanic lithosphere was formed in association with the opening and spreading of the Jinshajiang oceanic basin, and was contiguous and equivalent to the Ailaoshan oceanic lithosphere preserved in the Shuanggou Ophiolitic Melange in the Ailaoshan Suture Zone; the latter yielded a U–Pb age of 362±41 Ma from plagiogranite. The re-defined Gajinxueshan and Zhongxinrong “groups” are dated as Carboniferous to Permian, and latest Permian to Middle Triassic respectively, on the basis of fossils and U–Pb dating of basic volcanic interbeds. The Gajinxueshan “Group” formed in bathyal slope to neritic shelf environments, and the Zhongxinrong “Group” as bathyal to abyssal turbidites in the Jinshajiang–Ailaoshan back-arc basin. Latest Permian–earliest Middle Triassic synorogenic granitoids, with ages of 238±18 and 227±5–255±8 Ma , respectively, and an Upper Triassic overlap molasse sequence, indicate a Middle Triassic age for the Jinshajiang–Ailaoshan Suture, formed by collision of the Changdu-Simao Block with South China.
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The Jinshajiang–Ailaoshan Suture Zone, China: Tectonostratigraphy, age and evolution
Journal of Asian Earth Sciences, 2000Co-Authors: Xiaofeng Wang, Ian Metcalfe, Ping Jian, Chuanshan WangAbstract:Abstract The Jinshajiang Suture Zone is important for enhancing our understanding of the evolution of the Paleo-Tethys and its age, tectonic setting and relationship to the Ailaoshan Suture Zone have long been controversial. Based on integrated tectonic, biostratigraphic, chemostratigraphic and isotope geochronological studies, four tectono-stratigraphic units can be recognized in the Jinshajiang Suture Zone: the Eaqing Complex, the Jinshajiang Ophiolitic Melange, the Gajinxueshan “Group” and the Zhongxinrong “Group”. Isotope geochronology indicates that the redefined Eaqing Complex, composed of high-grade-metamorphic rocks, might represent the metamorphic basement of the Jinshajiang area or a remnant micro-continental fragment. Eaqing Complex protolith rocks are pre-Devonian and probably of Early–Middle Proterozoic age and are correlated with those of the Ailaoshan Complex. Two zircon U–Pb ages of 340±3 and 294±3 Ma , separately dated from the Shusong and Xuitui plagiogranites within the ophiolitic assemblage, indicate that the Jinshajiang oceanic lithosphere formed in latest Devonian to earliest Carboniferous times. The oceanic lithosphere was formed in association with the opening and spreading of the Jinshajiang oceanic basin, and was contiguous and equivalent to the Ailaoshan oceanic lithosphere preserved in the Shuanggou Ophiolitic Melange in the Ailaoshan Suture Zone; the latter yielded a U–Pb age of 362±41 Ma from plagiogranite. The re-defined Gajinxueshan and Zhongxinrong “groups” are dated as Carboniferous to Permian, and latest Permian to Middle Triassic respectively, on the basis of fossils and U–Pb dating of basic volcanic interbeds. The Gajinxueshan “Group” formed in bathyal slope to neritic shelf environments, and the Zhongxinrong “Group” as bathyal to abyssal turbidites in the Jinshajiang–Ailaoshan back-arc basin. Latest Permian–earliest Middle Triassic synorogenic granitoids, with ages of 238±18 and 227±5–255±8 Ma , respectively, and an Upper Triassic overlap molasse sequence, indicate a Middle Triassic age for the Jinshajiang–Ailaoshan Suture, formed by collision of the Changdu-Simao Block with South China.
Deta Gasser - One of the best experts on this subject based on the ideXlab platform.
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Internal structural geometry of the Paleozoic of Graz
International Journal of Earth Sciences, 2009Co-Authors: Deta Gasser, Kurt Stuwe, Harald FritzAbstract:The Paleozoic of Graz is an isolated nappe complex of about 1,500 km2 size and belongs to the Austroalpine units of the eastern European Alps. Despite more than 500 publications on stratigraphy, paleontology and local structure, many aspects of the internal geometry of this complex as a whole remained unclear. In this contribution, we present integrated geological profiles through the entire nappe complex. Based on these profiles, we present (1) a simplified lithological subdivision into 13 rock associations, (2) a modified Tectonostratigraphy where we consider only two major tectonic units: an upper and a lower nappe system and in which we abandon the traditionally used facies nappe concept, and (3) a modified paleogeography for the whole complex. Finally, we discuss whether the internal deformation of the Paleozoic of Graz is of Variscan or Eo-Alpine age and which of the published models best explain the tectonic evolution of the Paleozoic of Graz.
