The Limón Fold-and-Thrust Belt, Costa Rica, Central America: Structural Evolution and Thermal Modeling

Brandes, Christian¹, Allan Astorga², Stefan Back³, Peter Blisniuk⁴, Ralf Littke⁵, Jutta Winsemann¹ (1) University Hannover, Hannover, Germany (2) Escuela Centroamericana de Geología, San José, Costa Rica (3) RWTH Aachen, Aachen, Germany (4) Universität Potsdam, Potsdam, Germany (5) Technical University of Aachen (RWTH), Aachen, Germany

The Limón Back-arc Basin extends along the east coast of Costa Rica and belongs to the southern Central American arc-trench system. Basin evolution started in Late Cretaceous times. The Limón Basin is subdivided into a northern and a southern sub-basin, separated by the E-W striking “Trans Isthmic Fault System”. A grid of 2D seismic reflection lines par­allel and perpendicular to the basin-axis allows a detailed reconstruction of basin-fill archi­tecture and deformation style in both sub-basins. The northern basin is undeformed. The southern sub-basin has been affected by a northeastward propagating deformation result­ing in the development of a fold-and-thrust belt, characterized by concentric hangingwall anticlines and southwestward dipping listric thrusts. Seismic interpretation was carried out with the software Kingdom Suite. Well data was incorporated to get stratigraphic control. Thickness variations across the thrust faults were used to date the deformation. In the off­shore part of the Limón Fault-and–Thrust belt deformation started in Pliocene times. Special emphasis was laid on detailed mapping of a basement structure at the boundary between the northern and southern basin. This structure acted as an obstacle that probably led to the strong bending of the northern edge of the Limón Fault-and-Thrust belt. Additionally 1D and 2D basin modelling studies were carried out focussing on temperature and burial history. First results point towards a 15°C higher mean heat-flow in the northern sub-basin than in the southern sub-basin. Reasons for this might be found in lithosphere thickening due to fold-belt formation and in the lack of volcanic activity.