Geological map of the Miocene-Pleistocene successions of the Mejillones Peninsula, Northern Chile

The Mejillones Peninsula (northern Chile) has undergone a complex tectono-sedimentary history from the Miocene onward and is dissected by a network of normal faults that generated three asymmetric half-grabens located in a forearc position with respect to the Chile subduction system. A new 1:50,000-scale geological map of the peninsula, covering an area of ca 800 km2 and based on a detailed facies analysis and field mapping (1:20,000 scale) in conjunction with a comprehensive interpretation of aerial photographs (1:33,000 scale), gives new and updated information about the nature of marine sedimentation and deformation during the Miocene to Pleistocene and permits the geological history of the peninsula during this time period to be reconstructed. An important aspect of organising the Miocene to Pleistocene stratigraphy has been the recognition of three regional allostratigraphic units in the hangingwall basin-fill sediments (the Miocene Caleta Herradura, Pliocene La Portada, and Pleistocene Mejillones alloformations) and two major morphostratigraphic units (PlioMMU and PleiMMU) including extensive flights of Pliocene and Pleistocene marine terraces carved on crestal and flanking areas of adjacent footwall blocks.