FAULT CONTROLS ON SEDIMENT DISTRIBUTION PATTERNS, LIMÓN BASIN, COSTA RICA

Abstract

The Limón back‐arc basin on the Caribbean Seaboard of Costa Rica is an excellent area in which to study the influence of fault activity on patterns of sediment dispersal. The basin can be divided into northern and southern sub‐basins which are characterized by different structural histories. Whereas the North Limón Basin is dominated by extension, the South Limón Basin has been deformed by northeastward directed compression. Data from a grid of seismic lines in the offshore parts of these two sub‐basins allowed us to map the basin‐fill architecture and the key tectonic elements. Sediment thickness maps were used to infer the sediment distribution during the Middle Miocene, Late Miocene, Pliocene and Quaternary.The results of this study show that the extensional North Limón Basin has the characteristics of a passive continental margin. A wide and structurally homogeneous depocentre developed in relative tectonic quiescence. Tectonic activity increased in Plio‐Pleistocene times and pronounced normal faulting led to the formation of structurally‐controlled depocentres. The configuration in the South Limón Basin is different, since compressional tectonics created a heterogeneous pattern of accommodation space and sediment thickness. In this region, a number of small depocentres have been active since the Middle Miocene and their location changed continuously through time. These changes are most obvious in the Plio‐Pleistocene, where a succession of piggy‐back basins evolved in response to offshore activity on the Limón fold‐and‐thrust belt. Today, ongoing thrust tectonics causes topographic breaks at the sea‐floor of the South Limón Basin. These morphological features control the position of recent submarine channels.The data and interpretations presented here document the influence of fault activity on depositional patterns in a sedimentary basin. This study shows that tectonically controlled depocentres can be highly variable in space and time.