Sandstone mounds and associated facies sequences in some Late Precambrian and Cambro‐Ordovician inshore tidal flat/lagoonal deposits

摘要: Sandstone mounds occur in some shallow marine heterolithic deposits from the Late Precambrian Stangenes Formation (N. Norway) and Cambro-Ordovician Crozon W. France) Cabos Series (N.W. Spain). The sediments displaying accumulated partially protected tidal flat/ lagoonal environments immediately before during major transgressions. The are erosional features typically occurring on tops of sheet sandstones (ca. 50–500 mm thick) which may have a storm washover origin. Mound genesis related to periodic emergence late stage run-off is supported by their intimate association with mudcracks other very water (e.g. bidirectional current-formed structures, wave ripples, ladder interference patterns, mudflakes, etc.). Variation mound morphology suggests that post-depositional dissection began as elongate ridge-gully couplets secondary erosion ridge flanks leading development more characteristic hemispherical geometries. Emergence been function fluctuations and/or subsidence surge events. Facies sequences point repeated filling these inshore washovers superimposed ambient conditions possibly resulted progressive decay beach barriers transgression.