Publication authorized by the Director, Bureau of Economic Geology, The University of Texas at Austin.
Large-scale rhomboid bed forms and sedimentary structures associated with hurricane washover*
Article first published online: 14 JUN 2006
Volume 25, Issue 2, pages 183–204, April 1978
How to Cite
MORTON, R. A. (1978), Large-scale rhomboid bed forms and sedimentary structures associated with hurricane washover. Sedimentology, 25: 183–204. doi: 10.1111/j.1365-3091.1978.tb00308.x
- Issue published online: 14 JUN 2006
- Article first published online: 14 JUN 2006
- Manuscript received 14 March 1977; revision received 14 July 1977
Hurricane washover fans from the Texas Gulf Coast exhibit large-scale rhomboid bed forms developed on washover deposits of fine sand with varying shell content. Washover processes inferred from aerial photographs, storm characteristics, and physical settings suggest that these bed forms are the product of (1) storm surge flooding or (2) high wind shear stress.
Multiple bed forms, including large-scale rhombs, are responsible for sedimentary structures preserved in washover deposits. Proximal channels exhibit scour and fill sequences capped by mud drapes. Mid-channel fan deposits also have scour bases marked by shell lags which are overlain by horizontal laminations and foreset and backset laminae. Distal fan sediments are relatively shell free and are interbedded with tidal flat deposits characterized by bioturbated, alternating sand and mud laminae.
Rhomboidal patterns can form on the free surface of water in response to five processes: (1) wave interference from two externally independent sources, (2) wave interference from refraction of a single set of wave fronts, (3) standing oblique waves caused by bed roughness elements, (4) standing oblique waves formed at channel boundaries and channel transitions, and (5) wind stress. Geologically, standing oblique waves from unidirectional nearly supercritical flow is probably the most important process in rhomboid bed form development.