Upper Devonian block movements and sedimentation in the Asturo-Leonese Basin (Cantabrian Mountains, Spain)

The Upper Devonian shelf of the studied area was divided into two platforms separated by a significant break in the slope, related to the deep-seated fault system of the Sabero-Gordón Line. As differentiated block movements influenced the depositional history of the area, an External Zone, an Intermediate Zone and an Internal Zone can be distinguished. Each zone runs parallel to the east-west striking Upper Devonian coast and has a characteristic sedimentary succession. Due to upheaval, tilting and erosion of the area north of the Sabero-Gordón Line and intermitted subsidence south of this line, related to progradation of the linear shoreline from north to south, three regressive coarsening upward sequences were deposited in the External Zone. The first sequence is capped by a calcareous transgressive unit of minor importance. Based on these sequences the Nocedo Formation is divided into three members. The Gordon Member and the Millar Member are newly introduced in this paper. The Fueyo Member was already officially introduced by Evers (1967). After deposition of the three cycles epeirogenetic movements decreased and a levelling stage occurred in which coastal sands spread out over the whole area forming the transgressive upper part of the Ermita Formation.