Quantitative subsidence-uplift analysis of the Bajo Segura Basin (eastern Betic Cordillera, Spain): tectonic control on the stratigraphic architecture

The Bajo Segura Basin is located in the eastern Betic Cordillera, at presen t connected with the Mediterranean Sea to the east. It has a complete strat igraphic record from the Tortonian to the Quaternary, which has been separa ted into six units bounded by unconformities. This paper is concerned with the northern edge of the basin, controlled by a major strike-slip fault (th e Crevillente Fault Zone, CFZ), where the most complete stratigraphic succe ssions are found. The results obtained (summarised below) are based on an i ntegrated analysis of the sedimentary evolution and the subsidence-uplift m ovements. Unit I (Early Tortonian) is transgressive on the basin basement a nd is represented by ramp-type platform facies. organised in a shallowing u pward sequence related to tectonic uplift during the first stages of moveme nt along the CFZ. Unit II (lower Late Tortonian) consists of shallow platfo rm facies at bottom and pelagic basin facies at top, forming a deepening-up ward sequence associated with tectonic subsidence due to sinistral motion a long the CFZ. Unit III (middle Late Tortonian) is made up of exotic turbidi tic facies related to a stage of uplift and erosion of the southern edge of the basin. Unit IV (upper Late Tortonian) consists of pelagic basin facies at bottom and shallow platform facies at top, defining a shallowing-upward sequence related to tectonic uplift during continued sinistral movement on the basin-bounding fault. Units V (latest Tortonian-Messinian) and VI (Pli ocene-Pleistocene p.p.) consist of shallowing-upward sequences deposited du ring folding and uplift of the northern margin of the basin. No definitive evidence of any major eustatic sea-level fall, associated with the 'Messini an salinity crisis', has been recorded in the stratigraphic sections studie d. (C) 2001 Elsevier Science B.V. All rights reserved.