Lower Cantabrian basin margin deposits in NE Leon, Spain—a model for valley-fill sedimentation in a tectonically active, humid climatic setting

Basal Stephanian deposits of early Cantabrian age infill a deeply incised fossil topography at the western edge of the post-Leonian basin of NE Leon. Seven low sinuosity palaeovalleys, trending NNW–SSE range in depth of incision from 25 to 450 m. The fill is composed of: (i) Red bed succession: a proximal alluvial valley-fill association of debris flow and stream deposits in which seven mesosequences and two fining upwards megasequences are recognized on the basis of maximum clast sizes. (ii) Grey bed succession: two megasequences are distinguished. The lower megasequence comprises distal alluvial valley-fill deposits (sheet sandstone, lacustrine, swamp deposits). The upper megasequence comprises a mid-fan association of debris flow and interlobe/floodplain deposits. The palaeovalleys are considered in the context of previously described palaeovalleys and fill. These are categorized according to the degree of tectonic control and climatic setting. The lower Cantabrian examples may serve as a model for valley-fill sedimentation in a tectonically active area and a humid climatic setting.