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

Christian Brandes, Institut für Geologie und Paläontologie, Universität Hannover, Callinstrasse 30, Hannover, 30167, Germany, phone: +49(0)5117624391, brandes@geowi.uni-hannover.de, Allan Astorga, Escuela Centroamericana de Geología, San José, Costa Rica, Stefan Back, Geologisches Institut, RWTH Aachen, Wüllnerstr. 2, Aachen, Peter Blisniuk, Institut für Geowissenschaften, Universität Potsdam, Postfach 601553, Potsdam, 14415, Germany, Ralf Littke, Institute of Geology and Geochemistry of Petroleum and Coal, Technical University of Aachen (RWTH), Lochnerstr. 4-20, D-52056 Aachen, Germany, and Jutta Winsemann, Institute for Geology/Palaeontology, University Hannover, Callinstraße 30, Hannover, 30167, 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.

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