--> Abstract: The Unusual Seismic Architecture of the Var Deep-sea Fan (French Riviera), by B. Savoye, D. J. W. Piper, and L. Droz; #90987 (1993).

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SAVOYE, BRUNO, IFREMER DRO/GM, Brest, France; DAVID J. W. PIPER, Atlantic Geoscience Center, Dartmouth, Nova Scotia; and LAURENCE DROZ, CNRS, Brest, France

ABSTRACT: The Unusual Seismic Architecture of the Var Deep-sea Fan (French Riviera)

The Var fan has been deposited during the Pliocene and Quaternary. Except during the early Pliocene when coarse sediment was trapped in the Var ria, coarse fluvial or reworked sediments have been supplied to the fan even during sea-level highstands.

During the Pliocene, the Var fan consisted of a single, leveed fan valley that trended southward from the Var canyon to the Ligurian abyssal plain. Several discrete fan valleys of various ages are recognized and suggest changes of fan valley course periodically occured through avulsion. Some stratigraphic levels lack a prominent fan valley, suggesting that sea-level change may have controlled sediment supply at some times.

Avulsion occurred to the east at about the beginning of the Quaternary and the resulting new west-east levee prograded rapidly downslope and aggraded upward through the growth of fine sediment waves. Since that time, progressive leftward migration of channels occurred, largely through formation of multiple channels and filling of the southern channels with fine sediment.

Other western Mediterranean deep-sea fans, such as the Rhone and Ebro, that evolved in a similar post-Messinian basin setting, present a completely different Quaternary growth pattern and morphology.

The unusual architecture of the Var fan is a consequence of the continuous supply of coarse material to the fan. The Laurentian Fan shows a similar architecture; in contrast, the Rhone, Amazon or Mississippi fans, which received predominantly fine sand and mud, grew through fan valley aggradation. This contrast is similar to the high-sand efficient and low-sand inefficient models of Mutti (1979).

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.