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.

Regional Geological Framework of South Island, New Zealand, and its Significance for Understanding the Active Plate Boundary

Abstract: New Zealand basement is composed of distinct volcano-sedimentary terranes, intruded by batholiths and overprinted by metamorphism, that were accreted to the Pacific margin of Gondwana during the Paleozoic and Mesozoic. Extension and sea floor spreading during the Cretaceous and Paleogene thinned and isolated a large fragment of Gondwana, most of which still remains submerged. A sedimentary section comprising rifted (oldest), passive and convergent (youngest) margin episodes was deposited unconformably on basement, changing locally in character as the Australian-Pacific plate boundary developed during the Neogene. Terranes were offset by up to 470 km on the Alpine Fault, bent dextrally by distributed deformation, and now constrain the maximum plate motion to be around 850 km. Displacement of the basal unconformity (Waipounamu erosion surface) and laterally offset Tertiary sediments constrain long-term plate boundary deformation. New Zealand's landscape evolved during the Pleistocene, and has been profoundly affected by asymmetric rainfall and erosion. This has affected geomorphology, glaciation and glacial cycles, uplift, exhumation and rock distribution across the Southern Alps, controlled the first order shape of the orogen, and probably the distribution of deformation. Pleistocene glacial cycles shaped the landscape and left a fragmentary record of moraines, outwash surfaces, alluvial terraces and fans. Fluvio-glacial landforms have been offset by active faults and constrain the rate and location of much late Quaternary deformation, but evidence of active deformation is absent from the most mountainous region, and the geological record Australian-Pacific plate motion during the late Quaternary is incomplete.

Overthrust terranes in the Lachlan fold belt, southeastern Australia

Abstract: The Paleozoic history of the Lachlan fold belt involves terrane translation and accretion of discrete allochthonous fragments. Four major terranes developed adjacent to the Gondwana continental margin and were overthrust in the Middle Devonian to form a partly composite crust for southeastern Australia.

Evolution of the late Paleozoic accretionary complex and overlying forearc‐magmatic arc, south central Chile (38°–41°S): Constraints for the tectonic setting along the southwestern margin of Gondwana

Abstract: Stratigraphic, structural, metamorphic, and geochronologic studies of basement rocks in the Andean foothills and Coast Ranges of south central Chile (39°–41°S) suggest a protracted late Paleozoic to middle Mesozoic deformational and metamorphic history that imposes important constraints on the tectonic development of the southwestern Gondwana margin. In the study area the late Paleozoic paired metamorphic belt, coeval magmatic arc, and overlying Triassic sedimentary units preserve a record of Late Carboniferous to Early Permian subduction and arc magmatism, subsequent deep exhumation of the Western Series subduction complex, and diminished uplift and erosion of the Eastern Series arc-forearc region by the Late Triassic. Late Paleozoic structural elements and metamorphic assemblages formed during early subduction and arc magmatism, collectively referred to as Dl, are largely erased in the Western Series by the dominant D2 schistosity and lower greenschist grade metamorphism. D1 structural features, as well as original sedimentary textures, are relatively well preserved in the less penetratively deformed Eastern Series. The regional distribution of late Paleozoic arc magmatism suggests that the late Paleozoic convergent margin deviated from a N–S trend north of this area to a NW–SE trend near this latitude and faced an open marine environment to the southwest. A transition from F2 isoclinal folding to more open, larger-scale F3 folds, interpreted as change in ductility during differential uplift of the Western Series, is not apparent in the Eastern Series. Despite a lesser degree of uplift during the main exhumational D2 event, delineation of unconformities and U-Pb dating of detrital zircons and intrusions into the Eastern Series allow tighter constraints to be placed on timing of uplift and denudation of the Eastern Series than on that in the Western Series. A regional unconformity exposed in the Lake District that separates more highly deformed Eastern Series lithologies from Late Triassic shallow marine to continental deposits suggests that substantial uplift also affected the inner forearc and magmatic arc region during the D2 event. We propose that dextral-oblique convergence, initiated during the middle Permian along this segment of the Gondwana margin, resulted in the transpressional uplift and juxtaposition of high pressure/temperature (P/T) Western Series against low P/T Eastern Series lithologies and culminated with deposition of Late Triassic, continental to shallow marine, coarse clastic sedimentary rocks in fault-bounded strike-slip basins adjacent to the exhumed Western Series. Large-scale dextral transpression and northward displacement of the accretionary complex during Late Permian to Late Triassic time along the Chilean margin of Gondwana are synchronous and kinematically compatible with widespread regional transpression, extension, and silicic magmatism inboard of the southern Gondwana margin at this time. We thank C. Mpodozis, M. Gardeweg, and J. Munoz of the Servicio de Geologia y Mineria de Chile (SERNAGEOMIN) for their support of this work. Fruitful discussions with N. Blanco, F. Herve, H. Moreno, C. Mpodozis, and F. Munizaga have aided in our understanding of the geology of the region. The hard work by the staff of SERNAGEOMIN’s Puerto Varas office is graciously appreciated. We thank J.D. Walker and W.R. Van Schmus at the University of Kansas for allowing MWM use of their U-Pb and mass spectrometer facilities and J. Vargas and the staff of SERNAGEOMIN’s geochemistry laboratory for their assistance in this project. F. Munizaga allowed us to cite an unpublished 40Ar-39Ar date. We thank G. Ya˜nez for access to aeromagnetic data. T. Kato wishes to thank W. G. Ernst. Comments by I. Dalziel, S. Kay, and V. Ramos helped clarify ideas presented in this paper and are greatly appreciated. This work is dedicated to our friend and colleague Alberto Campos C., who died in a climbing accident on Calbuco Volcano, 1996.