Constraints on intraplate mountain building stages in central Patagonia determined from the analysis of 2-D and 3-D seismic and borehole data: San Bernardo Fold and Thrust Belt

FACUNDO PAGÁN; GUIDO GIANNI

Congreso; Adapted from poster presentation given at 2019 International Conference and Exhibition, Buenos Aires, Argentina, August 27-30, 2019; 2019

Intraplate belts are considered among the most enigmatic features in plate tectonic theory. Their origin remains not completely understood aswell as their episodic character, usually concentrating long lasting uplift and deformational activity. In this work we analyze borehole, 2D and3D seismic data in an intraplate belt crossing the Patagonian region with the aim of revealing its multi-episodic character. Seismic data tied toborehole and surface data show internal unconformities affecting synrift deposits of the Neocomian and lower D-129 Formation associatedwith initial stages of the Pangea break up. Above these erosional features a first canyon incision and important thickness variations characterizethe upper D-129 Formation and the Matasiete Formation in association with contractional structures and strike slip faults, interpreted assynorogenic strata. Then an erosive unconformity separates Cretaceous from Paleogene strata, being these in turn incised by deep canyonfeatures. Horizons slices performed at different time intervals allow deciphering variable sediment supply and structural control, through theidentification of distributary fluvial and deltaic morphologies, with a nearly constant source in the northwest.These features indicate that the San Bernardo fold and thrust belt uplifted and structured through the Late Early Cretaceous times throughisolated uplifts in a context of highly oblique convergence, and Late Cretaceous to the Cenozoic in a context of more orthogonal convergence,showing that Central Patagonia has absorbed variable amounts of shortening and strike slip deformation, which constitutes valuableinformation for biota and paleogeographic reconstructions as well as for oil exploration.