الفهرس 
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Abstract
Deltas are coastal and nearshore depositional features formed by accumulations
of riverborne sediments at the confluence of rivers with large water bodies, like the
sea. The term delta (~) was first applied by the Greek historian Herodotus about 450
BCto the triangular alluvial deposits at the mouths of the Nile River.
Since ancient times, deltas have been of fundamental importance to civilization.
Most of the world’s deltas are focal points for the trade, agriculture and fisheries of
coastal communities. Therefore, they are vital food-producing areas and population
centers. Moreover, the ancient deltas are favoured sites and prime sources for the
generation and accumulation of fossil fuels including coal, gas and oil.
from sedimentological point of view, deltas also accept unique attention; they
are probably the most complex of all depositional systems. Each delta consists of
varietyof environments and interplay of sediments that are never accumulated by any
other system. They are loci of maximum sediment deposition and form greatly
thickened successions relative to time-equivalent nondeltaic strata (Friedman et al.,
1992).
For these obvious reasons, geologists are vitally concerned with the ancient
deltaic facies and processes of deltaic sedimentation. The criteria needed for
recognizing facies in ancient deltas and for resolving the many complexities
resulting from deltaic sedimentation are best determined by study of modern deltas,
whereinthe facies can be related directly, in both time and space, to local depositional
environments and their geographic distribution.