Page 198 - Sedimentology and Stratigraphy

Variations in Delta Morphology and Facies 185

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Fig. 12.7 Differences in the grain size of the sediment supplied affect the form of a delta: (a) a high proportion of suspended
load results in a relatively small mouth bar deposited from bedload and extensive delta-front and prodelta deposits;
(b) a higher proportion of bedload results in a delta with a higher proportion of mouth bar gravels and sands.

and a large suspended load of silt and clay. Sand issues from the river mouth (Orton & Reading 1993;
deposition on the delta top is concentrated in the Bhattacharya 2003). The delta front may also be the
delta channels and on adjacent levees, while the site of mass flows: the wet, muddy sediment brought
bulk of the delta plain and any interdistributary bay down by the river may be transported by turbidity
areas are regions of mud accumulation (Fig. 12.7). currents to deposit as turbidites on the lower part of
The proximal mouth bars may also be sandy, but the the delta front, in the prodelta area and beyond.
rest of the delta slope and prodelta receive sediment Deltas can be the supply systems for large submarine
fall-out from the plume of suspended sediment that fan complexes (16.2). Muddy sediment deposited on