Deformation style and basin-fill architecture of the offshore Limón back-arc basin (Costa Rica)

Abstract

The Limón back-arc basin, located at the eastern coast of Costa Rica, is part of the southern Central American arc-trench system. Basin evolution started in Late Cretaceous times as response to the onset of the subduction of the Farallón Plate below the Caribbean Plate. The Limón Basin can be subdivided into a northern and a southern sub-basin separated by the E–W trending Trans Isthmic Fault System. A regional grid of offshore seismic lines allows the comparative analysis of the basin-fill architecture and the deformation style in both sub-basins. The northern sub-basin shows exclusively normal faults. The basin-fill architecture resembles a passive continental margin setting showing a distinct wedge-shaped geometry and seaward propagating depositional units. The area of the Rio San Juan Delta is characterized by gravity-driven, deltaic deformation exhibiting a series of listric growth faults both on the shelf and in slope areas. In contrast to the northern basin, the southern sub-basin is characterized by the development of thin-skinned fold-and-thrust belt tectonics best recorded in concentric or asymmetric hangingwall anticlines separated by listric or planar southwestward dipping thrust faults. Due to the pronounced NE-propagating of folding the shelf is broader and the slopes are steeper in the southern sub-basin, compared with the northern sub-basin. Thus both sub-basins show a very different tectonic style. In the North Limón Basin an extensional regime established, whereas in the South Limón Basin compression dominated. However, in both sub-basins the basal detachment is probably controlled by a lithological change from limestone to shale.