Gondwana

About: Gondwana is a research topic. Over the lifetime, 6078 publications have been published within this topic receiving 263050 citations. The topic is also known as: Gondwanaland.

Multicyclic History of the Northern India Continental Margin (Northwestern Himalaya) (1)

Abstract: The geologic evolution of northern India is best recorded in the stratigraphic succession of the Zanskar Range (northwestern Himalaya), which represents the most complete transect through this ancient continental margin. Sedimentary history began in the late Proterozoic, and recorded a late Pan-African orogenic event around the Cambrian-Ordovician boundary, when the Gondwana supercontinent was eventually assembled. The following long period of epicontinental deposition in shallow seas linked to palaeo-Tethys lasted until the Early Permian, when a neo-Tethyan rift began to open between paleo-India and the Cimmerian microcontinents. Neo-Tethyan history can be subdivided into two sedimentary megasequences, both recording a major tectonic and magmatic event in the lower part. The first one began with breakup in the Late Permian and lasted until the end of the Jurassic. The second one started in the Early Cretaceous with the final detachment of India from Gondwana and the opening of the Indian Ocean, and ended with the India-Eurasia collision in the Early Eocene. The two megasequences can be in turn subdivided into six transgressive/regressive supersequences bounded by tectonically enhanced unconformities. Basal sandstone units of Early Permian, Late Permian, Norian, Callovian, Early Cretaceous, and Paleocene age are invariably associated with oolitic ironstones or reworked glauco-phosphorites, and mark the transgre sive part of each supersequence. Next, condensed nodular carbonates or shales with pelagic fauna are typically overlain by thick shallowing-upward marly units capped by regressive platformal carbonates. The six tectono-eustatic supercycles reflect successive rifting episodes which punctuated the progressive separation of India from the rest of Gondwana, and document the combination of plate/microplate reorganizations and eustatic, climatic, and oceanographic changes in the Tethyan domain. After the onset of collision between India and Asia close to the Paleocene/Eocene boundary, obduction of the remnants of the neo-Tethys ocean floor onto the Indian margin began, and the latter underwent multiphase deformation with fold-thrust shortening followed by heating and extension. After the main metamorphic event, ophiolitic nappes were re-thrusted and finally emplaced with their sedimentary sole on top of the passive-margin succession.

The Pampean Orogeny of the southern proto-Andes: Cambrian continental collision in the Sierras de Cordoba

Abstract: A detailed study of the pre-Silurian geology of the Sierras de Cordoba, Eastern Sierras Pampeanas, is used to define the sequence of magmatic and metamorphic events during the Pampean orogeny. This primarily involved Early to Mid-Cambrian subduction and terrane collision at the western margin of Gondwana during the amalgamation of the super-continent. Evidence for this is based principally on new information concerning (a) regional mapping and field relations, (b) analysis of the structures, deformational history and meta-morphic evolution and (c) geochronology and geochemistry of the igneous and metamorphic rocks. The main events recognized are (1) Late Proterozoic break-up of Rodinia (Nd model ages of 1500 ± 200 Ma, inherited zircons 800–1400 Ma), (2) development of an Early Cam-brian passive margin sequence (Puncoviscana Formation and equivalents), (3) emplacement of metaluminous calc-alkaline granitoids (G1a, dated at 530 ± 3 Ma) as a result of NE-directed subduction, (4) crustal thickening, ophiolite obduction, compression and high-grade metamorphism (M2: 8.6±0.8 kbar, 810 ± 50°C, c.525 Ma) related to collision, and culmina-ting in (5) isothermal uplift and widespread low-P anatexis (M3, 4.0±0.5 kbar, 715 ± 15°C, c.520 Ma). The last event is responsible for the linked generation of highly peraluminous granites (G1b) and cordieritites. Subsequent emplacement into the accreted terrane of Ordovician trondhjemite-tonalites (500-470 Ma) and dextral wrench shear are interpreted as inner cordilleran counterparts of the Famatinian arc, which developed to the west along the newly-formed proto-Andean margin.

Anatomy and global context of the Andes: Main geologic features and the Andean orogenic cycle

Abstract: The Andes make up the largest orogenic system developed by subduction of oceanic crust along a continental margin Subduction began soon after the breakup of Rodinia in Late Proterozoic times, and since that time, it has been intermittently active up to the present The evolution of the Pacifi c margin of South America during the Paleozoic occurred in the following stages: (1) initial Proterozoic rifting followed by subduction and fi nal re-amalgamation of the margin in Early Cambrian times, as depicted by the Puncoviscana and Tucavaca Basins and related granitoids in southern Bolivia and northern Argentina; (2) a later phase of rifting in the Middle Cambrian, and subsequent collisions in Middle Ordovician times of parautochthonous terranes derived from Gondwana, such as Paracas, Arequipa, and Antofalla, and exotic terranes originating in Laurentia, such as Cuyania, Chilenia and Chibcha; (3) fi nal Permian collision between South America and North America to form Pangea during the Alleghanides orogeny, leaving behind rifted pieces of Laurentia as the Tahami and Tahuin terranes in the Northern Andes and other poorly known orthogneisses in the Cordillera Real of Ecuador in the Late Permian–Early Triassic; and (4) amalgamation of the Mejillonia and Patagonia terranes in Early Permian times, representing the last convergence episodes recorded in the margin during the Gondwanides orogeny These rifting episodes and subsequent collisions along the continental margin were the result of changes of the absolute motion of Gondwana related to global plate reorganizations during Proterozoic to Paleozoic times Generalized rifting during Pangea breakup in the Triassic concentrated extension in the hanging wall of the sutures that amalgamated the Paleozoic terranes The opening of the Indian Ocean in Early Jurassic times was associated with a new phase of subduction along the continental margin The northeastward absolute motion of western Gondwana produced a negative trench roll-back velocity that controlled subduction under an extensional regime until late Early Cretaceous times The Northern Andes of Venezuela, Colombia, and Ecuador record a series of collisions of island arcs and oceanic plateaus from the Early Cretaceous to the middle Miocene as a result of interaction with the Caribbean plate The remaining Central and Southern Andes record periods of orogenesis and mountain building alternating with periods of quiescence and absence of deformation as recorded in parts of the Oligocene Based on the generalized occurrence of fl at-slab subduction episodes through time, as recorded in most Ramos, VA, 2009, Anatomy and global context of the Andes: Main geologic features and the Andean orogenic cycle, in Kay, SM, Ramos, VA, and Dickinson, WR, eds, Backbone of the Americas: Shallow Subduction, Plateau Uplift, and Ridge and Terrane Collision: Geological Society of America Memoir 204, p 31–65, doi: 101130/20091204(02) For permission to copy, contact editing@geosocietyorg ©2009 The Geological Society of America All rights reserved

Locating South China in Rodinia and Gondwana: A fragment of Greater India Lithosphere? (Invited)

Abstract: From the formation of Rodinia at the end of the Mesoproterozoic to the commencement of Pangea breakup at the end of the Paleozoic, the South China craton fi rst formed and then occupied a position adjacent to Western Australia and northern India. Early Neoproterozoic suprasubduction zone magmatic arc-backarc assemblages in the craton range in age from ca. 1000 Ma to 820 Ma and display a sequential northwest decrease in age. These relations suggest formation and closure of arc systems through southeast-directed subduction, resulting in progressive northwestward accretion onto the periphery of an already assembled Rodinia. Siliciclastic units within an early Paleozoic succession that transgresses across the craton were derived from the southeast and include detritus from beyond the current limits of the craton. Detrital zircon age spectra require an East Gondwana source and are very similar to the Tethyan Himalaya and younger Paleozoic successions from Western Australia, suggesting derivation from a common source and by inference accumulation in linked basins along the northern margin of Gondwana, a situation that continued until rifting and breakup of the craton in the late Paleozoic.