Deep structure and isostasy of the central Scotia Sea.

Autor: Teterin, D., Dubinin, E., Udintsev, G.
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Zdroj: Izvestiya, Physics of the Solid Earth; Jul2015, Vol. 51 Issue 4, p469-479, 11p
Abstrakt: About 30 Ma ago in the Early Oligocene, the Drake Passage started to open and the Scotia lithospheric plate started to form. Although extensively studied during the past decade, the tectonic structure and evolution of the plate are still largely unclear. According to present-day notions, three large blocks-western, central, and eastern-are distinguished within the plate by the morphological features of undersea topography and anomalous geophysical fields in different reductions. From the standpoint of the origin and evolution, the central block is most interesting. In this work, we have studied the peculiar features of the deep structure and mechanism of isostatic equilibration for the central part of this plate using density modeling and cross-spectral analyzing. The density model has been constructed along the free-air gravity profile that intersects the central part of the Scotia Sea from the southeast to the northwest. The model estimates of crustal density are slightly lower than the average density of the oceanic crust and vary within 2.65 to 2.75 g/cm. The transfer functions between the bathymetry and free-air gravity anomalies (gravitational admittance) have been calculated. By comparing the predicted and empirical transfer functions, we determined the mechanism of isostatic compensation and estimated the depths of the compensating boundaries. Together with the results of morphological analysis on undersea topography and geophysical fields (Teterin et al., 2015), these estimates suggest that the central Scotia Sea probably followed a different evolution scenario than the commonly accepted spreading model. This part of the Scotia Sea is probably a large fragment of the continental bridge that connected the South America with Antarctic and sank due to the heating and extension of the continental lithosphere. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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