Plateau collapse model for the Transantarctic Mountains–West Antarctic Rift System: Insights from numerical experiments (original) (raw)
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Tectonics, 1995
Brittle fault arrays mapped along the structural boundary between the Transantarctic Mountains and the West Antarctic rift system are oriented obliquely to the axis of the mountains and offshore rift basins. The north to northwest trending regional rift boundary is thus not controlled by continuous rift border faults. Instead, the rift margin trend must be imposed by inherited lithospheric weaknesses along the ancestral East Antarctic craton margin. Fault kinematic solutions indicate that a dextral transtensional regime characterized the rift boundary in the Cenozoic and that dominantly transcurrent motion occurred during the most recent faulting episode. The Transantarctic Mountains are considered to be a rift-flank uplift, yet no substantial isostatic uplift is expected in a transtensional setting, and the mechanism of large-magnitude Cenozoic uplift of the mountains remains problematical. Regional deformation patterns in Victoria Land and the Ross Sea can be explained by a transtensional model and are not compatible with largemagnitude crustal stretching within the West Antarctic rift system in the Cenozoic. The crustal thinning across the rift system more likely took place in the Mesozoic, when major West Antarctic crustal block motions occurred. The Cenozoic intracontinenml deformation can be related to plate interaction resulting from the global Eocene plate reorganization, prior to the final separation between Antarctica and a narrow salient of the southeastern Australian margin. Displacement magnitude was probably minor, and thus early Tertiary east-west Antarctic motion is unlikely to account for discrepancies in global plate motion circuits. embayment, which is underlain by the Mesozoic-Cenozoic West Antarctic rift system. This association has led to the widely accepted model that the TM form an uplifted rift shoulder, possibly analogous to the Colorado Plateau-Basin and Range boundary or the flanks of the East African rift system [Fitzgerald et al., 1986; Tessensohn and WOrner, 1991]. In comparison to other rift flanks, however, the TM
2008
s (part 1), 32nd International Geological Congress, Florence, Italy, 2004, Abstract 86-9, p. 423. Scott, J. M., and A. F. Cooper. 2006. Early Cretaceous extensional exhumation of the lower crust of a magmatic arc: Evidence from the Mount Irene Shear Zone, Fiordland, New Zealand. Tectonics 25, doi.10.1029/2005TC001890. Siddoway, C. S., S. Baldwin, G. Fitzgerald, C. M. Fanning, and B. P. Luyendyk. 2004a. Ross Sea mylonites and the timing of intracontinental extension within the West Antarctic rift system. Geology 32:57-60. Siddoway, C. S., S. M. Richard, C. M. Fanning, and B. P. Luyendyk. 2004b. Origin and emplacement of a middle Cretaceous gneiss dome, Fosdick Mountains, West Antarctica. In Gneiss Domes in Orogeny, eds. D. L. Whitney, C. Teyssier, and C. S. Siddoway, Geological Society of America Special Paper 380:267-294. Siddoway, C. S., L. C. Sass III, and R. Esser. 2005. Kinematic history of Marie Byrd Land terrane, West Antarctica: Direct evidence from Cretaceous mafic dykes. In...
Geodynamic models of the tectonomagmatic evolution of the West Antarctic Rift System
2007
Finite element geodynamic models of the West Antarctic Rift System reproduce the transition from prolonged diffuse extension throughout the rift system during the Cretaceous and early Cenozoic to later focused extension in the Victoria Land Basin during the middle Paleogene. The change in the style of rifting is due to intraplate processes, and does not require changes in plate motions or impingement of a mantle plume. The models are consistent with the Paleogene onset of magmatism in the West Antarctic Rift System under normal mantle thermal conditions. However, the preliminary models indicate that spatially widespread magmatism may require mantle temperatures elevated approximately 100 °C above normal, supporting arguments favoring the presence of a plume.
Two distinct stages of extension are recognized in the West Antarctic Rift system (WARS). During the first stage, beginning in the Late Cretaceous, extension was broadly distributed throughout much of West Antarctica. A second stage of extension in the late Paleogene was focused primarily in the Victoria Land Basin, near the boundary with the East Antarctic craton. The transition to focused extension was roughly coeval with volcanic activity and strike-slip faulting in the adjacent Transantarctic Mountains. This spatial and temporal correspondence suggests that the transition in extensional style could be the result of a change in plate motions or impingement of a plume.
2007
The West Antarctic rift system (WARS) is largely buried beneath 1-4 km of ice, obscuring vast areas that could provide clues about the potential for active volcanism beneath the ice sheet, and whether significant tectonic extension has taken place in Cenozoic time. This study explores the consequences of viewing the ice as basin fill, and of approximating the mass equivalent of ice as unconsolidated sediment. It then compares the results with active rift systems elsewhere in the world. The results suggest (1) that the interior rift trough is relatively cool and volcanically inactive, (2) that extension and over-deepening of interior basins, like the Bentley Subglacial Trench, has taken place beneath the ice sheet in late Cenozoic time, and (3) that dome uplift and the growth of large central volcanoes along the Marie Byrd Land coast, together with subsidence of interior basins, have significantly increased the relief within the rift system in Neogene time.
Antarctica at the Close of …
The West Antarctic Rift System dominates the lithospheric structure of the Ross Sea sector of West Antarctica. A suite of aerogeophysical data has been used to compile a complete Bouguer anomaly map and to reveal the crustal architecture of a major portion of the rift system between Marie Byrd Land and the Whitmore Mountains. Three major crustal segments are proposed. The Whitmore Mountains crustal block, a segment of transitional crust between the Whitmore Mountains and the Bentley Subglacial Trench, and a unit of stretched crust towards the rift centre. The crustal thickness has been estimated from power spectral analysis and forward modelling of the gravity data. Beneath the Whitmore Mountains, a crustal thickness of 34 km has been estimated, which thins to 26 km beneath the Bentley Subglacial Trench. The distinct changes in Bouguer gravity from the transitional crust, the Bentley Subglacial Trench, and the stretched crust possibly represent the differential crustal extension during the Mesozoic. The lower boundary for the amount of extension has been estimated as b = 1.3. The influence of rifting for the crustal evolution seems to be weaker in the region between Marie Byrd Land and the Whitmore Mountains than in the Ross Sea. Similarities in the signature of the gravity anomalies and models between the Ross Sea and our study area suggest a possible early rift origin for the Bentley Subglacial Trench. The narrow basins along the rift shoulder close to the Whitmore Mountains block might have been reactivated during regional Cenozoic right-lateral strike-slip movements as well as a proposed en echelon sedimentary basin near Siple Dome.
Tectonophysics, 2018
The Transantarctic Mountains (TAM) are an imposing topographic feature, forming the western shoulder of the Meso-Cenozoic West Antarctic Rift System. Although the TAM topography is similar to other continental rifts, some aspects such as the high topography and the transition in the mode of crustal extension from orthogonal to oblique rifting during the Cenozoic makes the TAM an anomalous rift margin. Here, we present a topography analysis of a 600 km long transect along the TAM front in southern Victoria Land combined with a large available thermochronological data-set to decode the tectonic signals hidden in the topography. An alongstrike variability in tectonic, erosional and geomorphic characteristics is detected. We then focus our analysis on the Royal Society Range, where structural investigations were integrated with new fission track thermochronology in order to assess the morphotectonic evolution of the region. Fission-track data and topography of the Royal Society Range reveal remarkable differences with respect to the neighboring areas. Topography characteristics and thermal modeling suggest an increase in tectonic activity during late Eocene-early Oligocene times and structural analysis suggests that the Cenozoic rifting has been controlled by dextral transtension, as proposed for others
Geophysical studies of the West Antarctic Rift System
Tectonics, 1991
The West Antarctic rift system extends over a 3000 x 750 km, largely ice covered area from the Ross Sea to the base of the Antarctic Peninsula, comparable in area to the Basin and Range and the East African rift system. A spectacular rift shoulder scarp along which peaks reach 4-5 km maximum elevation marks one flank and extends from northern Victoria Land-Queen Maud Mountains to the Ellsworth-Whitmore-Horlick Mountains. The rift shoulder has maximum present physiographic relief of 5 km in the Ross Embayment and 7 km in the Ellsworth Mountains-Byrd Subglacial Basin area. The Transantarctic Mountains part of the rift shoulder (and probably the entire shoulder) has been interpreted as rising since about 60 Ma, at episodic rates of-• 1 km/m.y., most recently since mid-Pliocene time, rather than continuously at the mean rate of 100 m/m.y. The rift system is characterized by bimodal alkaline volcanic rocks ranging from at least Oligocene to the present. These are exposed asymmetrically along the rift flanks and at the south end of the Antarctic Peninsula. The trend of the Jurassic tholeiites (Ferrar dolerites, Kirkpatric basalts) marking the Jurassic Transantarctic rift is coincident with exposures of the late Cenozoic volcanic rocks along the section of the Transantarctic Mountains from northern Victoria Land to the Horlick Mountains. The Cenozoic rift shoulder diverges here from the Jurassic tholeiite trend, and the tholeiites are exposed continuously (including the Dufek intrusion) along the lower-elevation (1-2 kin) section of Transantarctic Mountains to the Weddell Sea. Widely spaced aeromagnetic profiles in West Antarctica indicate the absence of Cenozoic volcanic rocks in the ice covered part of the Whitmore-Ellsworth-Mountain block and suggest their widespread occurrence beneath the western part of the ice sheet overlying the Byrd Subglacial Basin.