Relative contributions of tectonics and dynamic topography to the Mesozoic-Cenozoic subsidence of southern Patagonia

DÁVILA, F.M., AVILA, P., MARTINA, F., CANELO, H., NÓBILE, J.C, COLLO, G., SANCHEZ-NASSIF, F., EZPELETA, M.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2019 vol. 93 p. 412 - 423

0895-9811

Sedimentary basins result from a complex interaction between mantle, crustal and surficial erosional-drivenprocesses, which act at different time and spatial scales. While shortening and crustal loading drive flexuralsubsidence toward the foreland, stretching produces normal faulting and graben depocenters. In this contributionwe analyze the Mesozoic-Cenozoic subsidence history of southern Patagonia, using backstripping fromsixty eight oil well data and outcrops, distributed in the Santa Cruz and Chubut provinces, Argentina, in theGolfo San Jorge and Austral basins. These data are compared with three flexural analyses from six regionalbalanced cross sections along the southern Patagonian Cordillera, a stretching-thermal model (McKenzie) assuminglateral extension changes, five dynamic topography models localized in the core of the basins and apaleotopographic analysis derived from a paleolithospheric thickness approach (basalt geochemistry). Thecomparison between stratigraphic observations (backstripping in this case) and subsidence models provide us aresidual subsidence value in southern Patagonia. These values are compared with dynamic topography andpaleotopographic computations. No additional subcrustal forces are needed to explain the sedimentary accommodationduring the Jurassic-early Cretaceous (extensional basin stage). However, from the late Cretaceousto the early Neogene, the foreland stages do require additional processes to account for the subsidence or upliftevents. We reassert, like in our previous contributions, that subcrustal forces (lithospheric mantle thicknesschanges and asthenospheric flows) worked together with flexural accommodation to create a sedimentary basin,occasionally provoking drastic paleoenvironmental and landscape changes.