THE ATCHAFALAYA DELTA
Delta ID # 60.
Air temperature range: oC to oC
Mean wave height:
Drainage Basin area:
Contributed by Professor George F. Hart.
The modern depositional environments of the Louisiana Deltaic Plain are part of the most recent highstand systems tract. Studies of this high stand system tract show switching has taken place about every 1,500 years. Each of the deltaic complexes, formed by a river switch, covers an average area of 30,000 sq km and has an average thickness of some 35 meters. The Atchafalaya delta is the youngest of the four major delta complexes presently existing over coastal Louisiana. Within this complex at least 12 individual sub-deltas have formed during the last 4,000 years.
The Atchafalaya delta is a modern Bay Head Delta [Van Heerden and Roberts, 1988], which became a sub-aqueous delta in 1952 [Morgan et all, 1953; Shlemon, 1972] and developed subaerial expression in 1973. Current activity involves distributary channel elongation and bifurcation and channel abandonment with associated obfusion. Small crevassing in the form of narrow overbank channels supply sediment to the interior of the sediment lobes formed between second order channels. The present depositional environments are similar to those present in a sub-delta and include distributary mouth bars, distal bars, distributary channels, levees, and algal flats. An oyster reef forms the delta front.