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Geo-Mar Lett (2011) 31:163174 DOI 10.1007/s00367-010-0222-y
ORIGINAL
Morphology and structure of the Camarinal Sillfrom high-resolution bathymetry: evidence of fault zones in the Gibraltar Strait
Mara Lujn & Ana Crespo-Blanc & Menchu Comas
Received: 9 June 2010 /Accepted: 26 October 2010 /Published online: 13 November 2010 # Springer-Verlag 2010
Abstract The Gibraltar Strait is the very narrow neck which connects the Atlantic Ocean and the Mediterranean Sea. The causes and mode of its opening at the end of the Messinian Salinity Crisis are still a matter of debate, and models based on eustatic rise and/or topographic lowering due to either erosion or faulting are generally evoked. We investigated the presence of faults based on a morphological and structural analysis of the Camarinal Sill, the shallowest passage in the Gibraltar Strait (<100 m water depth in places). This sill connects the Spanish and Moroccan shelves, and probably represents a structural high inherited from the Miocene compressive tectonics which took place in the external zones of the Betic-Rif orogenic arc. Our high-resolution bathymetric data enabled us to identify and interpret the origin of major morphological features in the area, including canyons, channels and a landslide, which we name the Tarifa landslide. Topographic arguments suggest that the Camarinal Sill is crossed by two main E-W- to ENE-WSW-directed fault zones which bound areas with different distribution, orientation and slopes of both scarps and crests. We name these the Hercules and Tarik fault zones, north and south of the sill respectively. The Hercules fault zone probably incorporates a normal
movement component, whereas kinematic indicators are poor along the Tarik fault zone. The age of faulting is poorly constrained in both cases. Together with existing evidence of faults onland, the presence of these fault zones implies that they could be responsible for, or have contributed to, the opening of the Gibraltar Strait.
Introduction
The Gibraltar Strait is a very narrow, ENE-WSW-directed and shallow-marine neck between southern Europe and northern Africa which today connects the Atlantic Ocean and the Mediterranean Sea (Fig. 1). It straddles and erodes the Betic and Rif mountains, an arcuate orogenic system which includes the extensional Alboran back-arc basin to the east and an accretionary prism in the Gulf of Cadiz to the west.
The causes and mode of...