Energy conditions at the seaward edge of deltas allow their division into fluvial-dominated, wave-dominated, and tide-dominated deltas. Each kind of delta has a distinct framework orientation and depositional pattern which results in a characteristic seismic reflection pattern. Fluvial-dominated deltas are characterized by clinoform seismic reflection patterns which include: oblique (tangential), complex oblique (tangential), sigmoid, and complex sigmoid-oblique. Seismic facies analysis can be used to define those facies which contain sand. Wave-dominated deltas are characterized by shingled seismic reflection patterns. Seismic facies analysis of this delta is not effective in identifying those facies which should be sand prone. Shingled reflections may be used in determi ing the possible location and depositional attitude of strandline sands. Tide-dominated deltas have not yet been identified using

End_Page 899------------------------------

seismic stratigraphic methods and therefore are not covered in this paper.

Turbidite fans are sequences of sands and shales deposited in conjunction with, and basinward of, deltas or submarine canyons. Turbidite sands can be generally classified into channel and suprafan sands. Certain seismic events and reflection patterns suggest the presence of turbidites. The interpreted events and reflection patterns include troughs, submarine canyons, mounds, a prograded fluvial-dominated delta reflection pattern and variations in its thickness, and onlap-offlap patterns on a depositional slope. Regional studies provide the best means of identifying and mapping depositional sequences. Examples from the North Sea, Gulf Coast, and Sacramento Valley illustrate the geologic and geophysical expression of delta and turbidite sequences, and their interrelation.

End_of_Article - Last_Page 900------------