Dr Howard D. Johnson, c/o The British National Oil Corporation, 150 St Vincent Street, Glasgow G2 5LJ, Scotland.
Sandstone mounds and associated facies sequences in some Late Precambrian and Cambro-Ordovician inshore tidal flat/lagoonal deposits
Article first published online: 14 JUN 2006
Volume 24, Issue 6, pages 801–818, December 1977
How to Cite
BALDWIN, C. T. and JOHNSON, H. D. (1977), Sandstone mounds and associated facies sequences in some Late Precambrian and Cambro-Ordovician inshore tidal flat/lagoonal deposits. Sedimentology, 24: 801–818. doi: 10.1111/j.1365-3091.1977.tb01916.x
- Issue published online: 14 JUN 2006
- Article first published online: 14 JUN 2006
- Manuscript received 21 March 1977; revision received 20 June 1977
Sandstone mounds occur in some shallow marine heterolithic deposits from the Late Precambrian Stangenes Formation (N. Norway) and the Cambro-Ordovician Crozon Formation (N. W. France) and Cabos Series (N.W. Spain). The sediments displaying the mounds accumulated in partially protected tidal flat/ lagoonal environments immediately before and during major transgressions.
The mounds are erosional features typically occurring on the tops of sheet sandstones (ca. 50–500 mm thick) some of which may have a storm washover origin. Mound genesis related to periodic emergence and late stage run-off is supported by their intimate association with mudcracks and other very shallow water features (e.g. bidirectional current-formed structures, wave ripples, ladder and interference patterns, mudflakes, etc.). Variation in mound morphology suggests that post-depositional dissection began as elongate ridge-gully couplets with secondary erosion of the ridge flanks leading to the development of more characteristic hemispherical geometries. Emergence may have been a function of tidal fluctuations and/or subsidence of storm surge events.
Facies sequences point to the repeated filling of these inshore environments by storm washovers superimposed on ambient tidal conditions which possibly resulted from the progressive decay of beach barriers during transgression.