Shoreface stratigraphy: evolution and morphology observations from southern Mozambique.

Abstract

Shoreface morphology and stratigraphy are poorly documented but are acknowledged to be important influences on shoreline behaviour during changing sea level. A wide, low gradient wave-dominated shoreface off Xai-Xai in southern Mozambique is developed on the Holocene wave ravinement surface cut into deltaic sands punctuated by lithified aeolianite ridges. The 2 km-wide mobile shoreface sand body extends to -23 m depth and averages 10 m in thickness. Seismic stratigraphic analysis accompanied by seabed cores, reveals the shoreface to be underlain by a deltaic sedimentary sequence. The modern shoreface mimics the wave ravinement surface and this, in turn is influenced by the presence of aeolianite ridges that create a pronounced break in slope that defines the base of the modern shoreface. Comparison with theoretical shoreface profiles reveals contrasting interpretations depending upon the model chosen and emphasizes the acknowledged but still little understood role of geologic inheritance on shoreface morphology and evolution.