Wave Effects on Fan Delta Deposits of the Western Gulf of California, Mexico

• Published in: Journal of coastal research 1998-04, p.312-319
• Main Authors: Nava-Sanchez, E.H., Troyo-Dieguez, S., Gorsline, D.S.
• Format: Article
• Language: English
• Subjects: Alluvial fans; Bathymetry; Beaches; Boulders; Coasts; Cobbles; Gulfs; River deltas; Sediments; Storms
• ISSN: 0749-0208; 1551-5036

The Gulf of California is a marginal sea, bordered by high relief coasts, where cliffs are common and beaches are scarece. Fan deltas are common at the canyon mouths, which contain sediments of a large range of grain sizes, and are fed by torrential currents during the summer tropical storms. Six wave-dominated fan deltas were studied, which are of a variety of sizes and affected by different degrees of wave energy. The dominant waves are formed by winter northwesterly winds and generate a north-to-south longshore current as they reach the coast. The zones of the fan deltas most affected by waves are the transitional zone, dominated by beaches, and the delta front. The lower limit of the delta front, the wave-base, is defined by an increase in slope, observed on bathymetric profiles. The beach and delta front of the northern portion of the fan deltas, facing the littoral drift, have finer sediments (sandy gravel), gentle slopes and delta plains with flood plains and dunes; the southern portions have very steep ramparts of coarser sediments (boulders and cobbles). On the central portions, beaches are composed of the coarsest sediments and the gradient is the steepest. On the delta front, a morphology of bars and troughs has been developed, which is more typical of shallow-water fan deltas. The flashy fluvial discharges take place during the short summer storm season and are followed by a long period of starvation when waves redistribute the sediments and erase or mask the fluvial morphology.