Fault Control On The Architecture Of Deepwater Channel-levee Systems In The Limón Back-arc Basin, Costa Rica

Brandes, Christian¹, Stefan Back², Ralf Littke³, Jutta Winsemann⁴ (1) Universität Hannover, Hannover, Germany (2) RWTH Aachen, Aachen, (3) Technical University of Aachen, Aachen, Germany (4) Universität Hannover, Hannover,

The Limón Back-arc Basin consists of two sub-basins. The extensional North Limón Basin has a narrow shelf and a broad slope, whereas in the compressional South Limón Basin, the shelf is broad and the slope is narrow. Seismic data allows a detailed assessment of the interplay of tectonics and sedimentation. Recent channel-levee systems in the North Limón Basin run parallel, forming channel-levee complexes. In the South Limón Basin there are only isolated channel-levee systems. A channel-levee system occurs in the south, which is directly controlled by active tectonics. The position and migration behaviour of the channel is influenced by a topographic break at the sea-floor. The channel runs parallel to the trend of the sea-floor break. The topographic break occurs above the tip of a thrust fault resulting from ongoing deformation. The thrust is associated with a hangingwall anticline. As a consequence of fault displacement and anticline formation, the sea-floor is elevated southeast of the tip line of the thrust. The proximal part of the channel is close to the topographic break and therefore a levee lacks at the southeastern channel margin, the northwestern margin in contrast shows a small levee. The more distal part of the channel has a greater distance to the sea-floor break and a levee is developed. The analysis of the channel architecture and deformation pattern shows that the active deformation probably limits the channel to migrate southeastward. The evolution of channel-levee complexes with parallel channels might be also limited by the active deformation.