Showing papers on "Gondwana published in 2008"

The magnitude of late paleozoic glacioeustatic fluctuations: A synthesis

Abstract: A comprehensive literature review shows that the magnitude of eustatic fluctuations varied throughout the Carboniferous and Permian and that at least eight distinct phases can be recognized. Facies juxtapositions in carbonate successions and erosional relief in clastic successions indicate that glacioeustatic fluctuations of 20–25 m, and occasionally as much as 60 m, took place throughout the early Mississippian (Tournaisian)—a widely recognized glacial period. Middle Mississippian (mid-Chadian through Holkerian) shallow marine carbonate and clastic successions indicate that eustatic fluctuations were 10–25 m, a decrease that matches well with the paucity of coeval glacial deposits. Late Visean (Asbian through mid-Brigantian) glacioeustatic fluctuations of 10–50 m record the initial phases of ice accumulation in advance of the widespread mid-Carboniferous glacial event. The latest Mississippian–earliest Pennsylvanian (mid-Brigantian through Langsettian) was a time of widespread glaciation, and strata of this age commonly exhibit evidence of glacioeustatic fluctuations of as much as 40–100 m. Although middle Pennsylvanian (Duckmantian through Asturian) glacial deposits are present in eastern Australia, paleovalley depths suggest that coeval glacioeustatic fluctuations were less than 40 m. Glacioeustatic fluctuations of as much as 100–120 m have been widely reported from late Pennsylvanian–earliest Permian (Stephanian through mid-Sakmarian) successions in North America, an increase that corresponds to the growth of large ice sheets across much of Gondwana and the accumulation of ice in the northern hemisphere. Incision and facies juxtaposition in Early–middle Permian (mid-Sakmarian through Kungurian) successions in eastern Australia indicate that glacioeustatic fluctuations of 30–70 m occurred during the waning stages of major glaciation. Erosional relief in paleoequatorial carbonates and the presence of coeval glacial deposits in Australia suggests that eustatic fluctuations of 10–60 m occurred during the final stages of glaciation in the middle to Late Permian (Roadian through Capitanian), but the modest size of most of these fluctuations makes it difficult to isolate the glacioeustatic signature. This review demonstrates that far-field cyclic successions record changing glacial conditions in Gondwana, that the magnitude of glacioeustatic fluctuations was directly related to the volume of glacial ice, that Carboniferous–Permian glacioeustasy was more variable than previously recognized, and that generalizations from short temporal intervals are probably not representative of the late Paleozoic ice age as a whole. Although any attempt to quantify the magnitude of ancient eustatic changes is based on caveats and assumptions, this review incorporates the results of over 100 published papers on the topic in an attempt to minimize the errors inherent in any one study.

Neoproterozoic-early Palaeozoic tectonostratigraphy and palaeogeography of the peri-Gondwanan terranes: Amazonian v. West African connections

Abstract: Within the Appalachian–Variscan orogen of North America and southern Europe lie a collection of terranes that were distributed along the northern margin of West Gondwana in the late Neoproterozoic and early Palaeozoic. These peri-Gondwanan terranes are characterized by voluminous late Neoproterozoic (c. 640–570 Ma) arc magmatism and cogenetic basins, and their tectonothermal histories provide fundamental constraints on the palaeogeography of this margin and on palaeocontinental reconstructions for this important period in Earth history. Field and geochemical studies indicate that arc magmatism generally terminated diachronously with the formation of a transform margin, leading by the Early–Middle Cambrian to the development of a shallow-marine platform–passive margin characterized by Gondwanan fauna. However, important differences exist between these terranes that constrain their relative palaeogeography in the late Neoproterozoic and permit changes in the geometry of the margin from the late Neoproterozoic to the Early Cambrian to be reconstructed. On the basis of basement isotopic composition, the terranes can be subdivided into: (1) Avalonian-type (e.g. West Avalonia, East Avalonia, Meguma, Carolinia, Moravia–Silesia), which developed on juvenile, c. 1.3–1.0 Ga crust originating within the Panthalassa-like Mirovoi Ocean surrounding Rodinia, and which were accreted to the northern Gondwanan margin by c. 650 Ma; (2) Cadomian-type (e.g. North Armorican Massif, Ossa–Morena, Saxo-Thuringia, Moldanubia), which formed along the West African margin by recycling ancient (c. 2.0–2.2 Ga) West African crust; (3) Ganderian-type (e.g. Ganderia, Florida, the Maya terrane and possible the NW Iberian domain and South Armorican Massif), which formed along the Amazonian margin of Gondwana by recycling Avalonian and older Amazonian basement; and (4) cratonic terranes (e.g. Oaxaquia and the Chortis block), which represent displaced Amazonian portions of cratonic Gondwana. These contrasts imply the existence of fundamental sutures between these terranes prior to c. 650 Ma. Derivation of the Cadomian-type terranes from the West African craton is further supported by detrital zircon data from their Neoproterozoic–Ediacaran clastic rocks, which contrast with such data from the Avalonian- and Ganderian-type terranes that suggest derivation from the Amazonian craton. Differences in Neoproterozoic and Ediacaran palaeogeography are also matched in some terranes by contrasts in Cambrian faunal and sedimentary provenance data. Platformal assemblages in certain Avalonian-type terranes (e.g. West Avalonia and East Avalonia) have cool-water, high-latitude fauna and detrital zircon signatures consistent with proximity to the Amazonian craton. Conversely, platformal assemblages in certain Cadomian-type terranes (e.g. North Armorican Massif, Ossa–Morena) show a transition from tropical to temperate waters and detrital zircon signatures that suggest continuing proximity to the West African craton. Other terranes (e.g. NW Iberian domain, Meguma) show Avalonian-type basement and/or detrital zircon signatures in the Neoproterozoic, but develop Cadomian-type signatures in the Cambrian. This change suggests tectonic slivering and lateral transport of terranes along the northern margin of West Gondwana consistent with the transform termination of arc magmatism. In the early Palaeozoic, several peri-Gondwanan terranes (e.g. Avalonia, Carolinia, Ganderia, Meguma) separated from West Gondwana, either separately or together, and had accreted to Laurentia by the Silurian–Devonian. Others (e.g. Cadomian-type terranes, Florida, Maya terrane, Oaxaquia, Chortis block) remained attached to Gondwana and were transferred to Laurussia only with the closure of the Rheic Ocean in the late Palaeozoic.

The Basement of the Central Andes: The Arequipa and Related Terranes

Abstract: The basement of the Central Andes provides insights for the dispersal of Rodinia, the reconstruction of Gondwana, and the dynamics of terrane accretion along the Pacific. The Paleoproterozoic Arequipa terrane was trapped during collision between Laurentia and Amazonia in the Mesoproterozoic. Ultrahigh-temperature metamorphism correlates with the collapse of the Sunsas-Grenville orogen after ∼1000 Ma and is related to slab break-off and dispersal of Rodinia. The Antofalla terrane separated in the Neoproterozoic, forming the Puncoviscana basin. Its closure was coeval with the collision of the eastern Sierras Pampeanas. The rift-drift transitions of the early Paleozoic clastic platform showed a gradual younging to the north, in agreement with counterclockwise rotation based on paleomagnetic data of Antofalla. North of Arequipa arc magmatism and high-grade metamorphism are linked to collision of the Paracas terrane in the Ordovician, during the Famatinian orogeny in the Sierras Pampeanas. The early Paleozoic ...

A Damara orogen perspective on the assembly of southwestern Gondwana

Abstract: The Pan-African Damara orogenic system records Gondwana amalgamation involving serial suturing of the Congo-Sao Francisco and Ro ´o de la Plata cratons (North Gondwana) from 580 to 550 Ma, before amalgamation with the Kalahari - Antarctic cratons (South Gondwana) as part of the 530 Ma Kuunga-Damara orogeny. Closure of the Adamastor Ocean was diachronous from the Aracuao ´ Belt southwards, with peak sinistral transpressional deformation followed by craton overthrusting and foreland basin development at 580- 550 Ma in the Kaoko Belt and at 545-530 Ma in the Gariep Belt. Peak deformation/metamorphism in the Damara Belt was at 530-500 Ma, with thrusting onto the Kalahari Craton from 495 Ma through to 480 Ma. Coupling of the Congo and Ro ´o de la Plata cratons occurred before final closure of the Mozambique and Khomas (Damara Belt) oceans with the consequence that the Kuunga suture extends into Africa as the Damara Belt, and the Lufilian Arc and Zambezi Belt of Zambia. Palaeomagnetic data indicate that the Gondwana cratonic components were in close proximity by c. 550 Ma, so the last stages of the Damara-Kuunga orogeny were intracratonic, and led to eventual out- stepping of deformation/metamorphism to the Ross-Delamerian orogen (c. 520-500 Ma) along the leading edge of the Gondwana supercontinental margin.

Hikurangi Plateau: Crustal structure, rifted formation, and Gondwana subduction history

Abstract: Seismic reflection profiles across the Hikurangi Plateau Large Igneous Province and adjacent margins reveal the faulted volcanic basement and overlying Mesozoic-Cenozoic sedimentary units as well as the structure of the paleoconvergent Gondwana margin at the southern plateau limit. The Hikurangi Plateau crust can be traced 50–100 km southward beneath the Chatham Rise where subduction cessation timing and geometry are interpreted to be variable along the margin. A model fit of the Hikurangi Plateau back against the Manihiki Plateau aligns the Manihiki Scarp with the eastern margin of the Rekohu Embayment. Extensional and rotated block faults which formed during the breakup of the combined Manihiki-Hikurangi plateau are interpreted in seismic sections of the Hikurangi Plateau basement. Guyots and ridge-like seamounts which are widely scattered across the Hikurangi Plateau are interpreted to have formed at 99–89 Ma immediately following Hikurangi Plateau jamming of the Gondwana convergent margin at ∼100 Ma. Volcanism from this period cannot be separately resolved in the seismic reflection data from basement volcanism; hence seamount formation during Manihiki-Hikurangi Plateau emplacement and breakup (125–120 Ma) cannot be ruled out. Seismic reflection data and gravity modeling suggest the 20-Ma-old Hikurangi Plateau choked the Cretaceous Gondwana convergent margin within 5 Ma of entry. Subsequent uplift of the Chatham Rise and slab detachment has led to the deposition of a Mesozoic sedimentary unit that thins from ∼1 km thickness northward across the plateau. The contrast with the present Hikurangi Plateau subduction beneath North Island, New Zealand, suggests a possible buoyancy cutoff range for LIP subduction consistent with earlier modeling.

The Rheic Ocean: Origin, Evolution, and Significance

Abstract: The Rheic Ocean, which separated Laurussia from Gondwana after the closure of Iapetus, was one of the principal oceans of the Paleozoic Its suture extends over 10,000 km from Middle America to Eastern Europe, and its closure assembled the greater part of Pangea with the formation of the Ouachita-Alleghanian-Variscan orogen The Rheic Ocean opened in the Early Ordovician, following protracted Cambrian rifting that represented a continuum of Neoproterozoic orogenic processes, with the separation of several Neoproterozoic arc terranes from the continental margin of northern Gondwana Separation likely occurred along a former Neoproterozoic suture in response to slab pull in the outboard Iapetus Ocean The Rheic Ocean broadened at the expense of Iapetus and attained its greatest width (>4000 km) in the Silurian, by which time Baltica had sutured to Laurentia and the Neoproterozoic arc terranes had accreted to Laurussia, closing Iapetus in the process Closure of the Rheic Ocean began in the Devonian and was largely complete by the Mississippian as Gondwana and Laurussia sutured to build Pangea In this process, North Africa collided with southern Europe to create the Variscan orogen in the Devono-Carboniferous, and West Africa and South America sutured to North America to form the Alleghanian and Ouachita orogens, respectively, during the Permo-Carboniferous The Rheic Ocean has long been recognized as the major Paleozoic ocean in southern Europe, where its history dominates the basement geology In North America, however, the Rheic has historically received less attention than Iapetus because its suture is not exposed Yet, it was the Rheic Ocean that played the dominant role in creating the AppalachianOuachita orogen, and an important record of its history may be preserved in Mexico

The Geology of Central Europe - Volume 1 Precambrian and Palaeozoic

Abstract: This two-volume set provides the first comprehensive account in English of the geology of Central Europe. Written by more than 200 scientists from universities and research centres spread across Europe and North America, the 21 chapters are based on the main stratigraphic periods. Individual chapters outline the evolution of the region divided into a variety of sections which include overviews of the stratigraphic framework, climate, sea-level variations, palaeogeography and magmatic activity. These are followed by more detailed descriptions of the Central European succession, covering the main basins and magmatic provinces. Each chapter is thoroughly referenced, providing a unique and valuable information source. Volume 1 focuses on the evolution of Central Europe from the Precambrian to the Permian, a dynamic period which traces the formation of Central Europe from a series of microcontinents that separated from Gondwana through to the creation of Pangaea. Separate summary chapters on the Cadomian, Caledonian and Variscan orogenic events as well as on Palaeozoic magmatism provide an overview of the tectonic and magmatic evolution of the region. These descriptions sometimes extend beyond the borders of Central Europe to take in the Scottish and Irish Caledonides as well as the Palaeozoic successions in the Baltic region. Volume 2 provides an overview of the Mesozoic and Cenozoic evolution of Central Europe. This period commenced with the destruction of Pangaea and ended with the formation of the Alps and Carpathians and the subsequent Ice Ages. Separate summary chapters on the Permian to Cretaceous tectonics and the Alpine evolution are also included. The final chapter provides an overview of the fossil fuels, ore and industrial minerals in the region. The Geology of Central Europe is a key reference work suitable not only for libraries across the world, but of interest to all researchers, teachers and students of European Geology.

West Gondwana : pre-Cenozoic correlations across the South Atlantic Region

Abstract: Some 75 years after the visionary work of Wegener and du Toit, Neoproterozoic to Mesozoic geological correlations between South America and Africa are re-examined in the light of plate tectonics and modern geological investigation (structural and metamorphic studies, stratigraphic logging, geochemistry, geochronology and palaeomagnetism). The book presents both reviews and new research relating to the shared Gondwana origins of countries facing each other across the South Atlantic Ocean, especially Brazil, Argentina, Cameroon, Nigeria, Angola, Namibia and South Africa. This is the first comprehensive treatment to be readily available in book form. It covers the common elements of cratonic areas pre-dating Gondwana, and how they came together in late Precambrian and Cambrian times with the formation of the Pan-African/Brasiliano orogenic belts (Dom Feliciano, Brasilia, Ribeira, Damara, Gariep, Kaoko, etc.). The subsequent shared Palaeozoic and Mesozoic sedimentary record (Karoo system) prior to Gondwana break-up is also reviewed.

West Gondwana amalgamation based on detrital zircon ages from Neoproterozoic Ribeira and Dom Feliciano belts of South America and comparison with coeval sequences from SW Africa

Abstract: Abstract Neoproterozoic–Cambrian amalgamation of West Gondwana involved the collision of several terranes of older crust that are now in eastern South America and western Africa. U–Pb (SHRIMP) detrital zircon ages from representative metasedimentary units of the Ribeira and Dom Feliciano belts (South America) and Gariep and Damara belts (Africa) provide constraints on the possible sediment source areas across probable suture zones. Ribeira detrital zircons are Palaeoproterozoic and Archaean. For the Dom Feliciano Belt, a contribution of Meso- and Neoproterozoic zircons is present, which definitely indicate Neoproterozoic sedimentation. It is proposed that the inflow of material to the Ribeira basin was essentially derived from the Paranapanema and Rio de la Plata cratons, whereas for the Damara and Gariep–Rocha belts source areas were from the Namaqua Belt. The Dom Feliciano Belt received sediments from the South American side and to a lesser degree from African sources. These results highlight the differences in the detrital zircon signatures across a proposed West Gondwanan suture, with those in the west being derived from distinctive South American basement sources and those in the east from distinctive African sources.

Pennsylvanian cyclothems in Midcontinent North America as far-field effects of waxing and waning of Gondwana ice sheets

Abstract: Pennsylvanian cyclothems of Midcontinent North America represent a repetitive succession of widespread marine beds, upon which widespread paleosols in the overlying terrestrial beds show that they resulted from extensive marine regressions as well as transgressions over a large land surface. Classic widespread late middle to late Pennsylvanian major cyclothems in this region consist of a thin transgressive limestone and thin offshore dark phosphatic shale (which contains the maximum fl ooding surface), followed upward by a thicker regressive shallowing-upward limestone and a variety of nearshore marine and terrestrial detrital facies as well as paleosols. Cyclothems of intermediate scale lack the black facies in the offshore shale and are less widespread, and those of minor scale lack much differentiation of facies. The greatest number of cyclothems of all scales is along the shelf-basin margin in the Kansas-Oklahoma border region, and the total number decreases as most minor cycles pinch out northward into Iowa, several intermediate cycles disappear eastward into Illinois, and only some of the major cycles extend farther into the shelfward Appalachian Basin. Cycles of all scales can be grouped around each major cyclothem to produce a succession of ~400-k.y.long groupings, which can be used to calibrate the Pennsylvanian time scale with the few radiometric dates that are available. Conodont-based biostratigraphic correlation of the Midcontinent cyclothems with those of the Illinois and Appalachian Basins and the north Texas shelf and Paradox Basin in Utah has been extended to the cyclothems now recognized on the Russian Platform and in the Donets Basin of Eastern Europe. This biostratigraphic zonation of the Pennsylvanian pantropical zone provides the framework for incorporating the radiometric dates now becoming available from fossiliferous marine successions that contain volcanics into the named units of the Pennsylvanian time scale. This framework ultimately should allow the Gondwana succession with entirely endemic biotas to be correlated more accurately with the pantropical zone. The current lack of apparent correlation of times of major cyclothem formation in the pantropical zone with widespread glacial deposits on Gondwana relates to the fact that only large-scale withdrawals of the sea off of the tropical shelves would correlate with widespread glacial deposits, whereas a succession of major cyclothems that are separated by regressions that only approached the edge of the shelf would appear to be simply a long-term interglacial episode in most of Gondwana.

Geology of the northern Borborema Province, NE Brazil and its correlation with Nigeria, NW Africa

Abstract: The Borborema and Benin–Nigeria provinces of NE Brazil and NW Africa, respectively, are key areas in the amalgamation of West Gondwana by continental collision during the Brasiliano/Pan-African orogenies. Both are underlain by complex basement: Nigeria has c. 3.05 Ga Archaean crust but no known Palaeoproterozoic rocks >2.0 Ga; in NE Brazil, 2.6–3.5 Ga Archaean rocks form small cores within Palaeoproterozoic gneiss terrains affected by plutonism at c. 2.17 Ga. Both regions exhibit Late Palaeoproterozoic (c. 1.8 Ga) rift-related magmatism and metasedimentary sequences overlying the basement. The Serido Group of NE Brazil (<0.65 Ga) is similar to the Igarra Sequence in SW Nigeria. The Ceara Group, which may date back to c. 0.85 Ga, is a passive margin deposit on crust thinned during initiation of an oceanic domain. In both provinces, basement and sedimentary cover were involved in tangential tectonics that resulted in crust-thickening by nappe-stacking associated with closure of this ocean. Frontal collision between c. 0.66 and 0.60 Ga later evolved to an oblique collision, generating north–south continental strike-slip shear zones at c. 0.59 Ga. In NE Brazil, the main Pan-African suture is probably buried beneath the Parnaiba Basin. The Transbrasiliano Lineament, interpreted as the prolongation of the Kandi–4°50 Lineament in Hoggar, may represent a cryptic suture.