Stratigraphy, sedimentology and palaeogeography of Eifelian, Givetian and Frasnian strata between the river Porma and the Embalse de la Luna, Cantabrian Mountains, Spain

Abstract

The chronostratigraphy of the Middle-Upper Devonian Portilla Limestone Formation is discussed in three stratigraphic sections. Deposition of limestones occurred in a diachronous way. A discussion in four sections, of the sedimentology of the Huergas Formation, the Portilla Limestone Formation and the Nocedo Formation leads to a palaeogeographic picture of two shallow platforms in the west and in the east, resp., on which open marine subtidal to intertidal limestone sediments were deposited. The platforms were separated by a slightly deeper depositional environment into which a delta protruded, eventually filling up the basin. This delta was covered with limestones, similar to those present on the platforms but patchy, irregularly distributed and in smaller thicknesses. The limestone deposition ended with a new, strong pulse of siliciclastic sediments, presumably coming from the NE and spreading out gradually over the whole area. In these sediments, Lower Devonian ferrugenous San Pedro pebbles are present, indicating a deep erosion in the Northern Leonides