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Evolutionary Mass-Flow Megaturbidites in Interplate Basin: Example of the North Pyrenean Basin

Robert Bourrouilh

The Cretaceous North Pyrenean interplate basin develops in close relationship with the opening of the Bay of Biscay. The basin margins and its gravity sedimentary filling are related to differential movements of Iberian and European plates.

Optimal climatic and morphologic conditions allow large amounts of carbonates to be deposited on its margins, major factors provoked the sedimentary and tectonic instability of the basin shelf and slope, particularly by reactivating a deep, ancient fault network.

These events generated a single event or a series of successive autosuspended mass flows, which differentiate into megaturbidites, spreading over large areas of the basin floor.

This large distribution of instantaneous evolutionary mass-flow megaturbidites, which pertain to the normal carbonate gravity sedimentation of the basin, allows us to determine: (1) paleoenvironments such as areas of paleoslopes; (2) the sedimentary and tectonic migration of the shelf break and of the basinal depocenter, and the relation of migration to regional plate tectonics; (3) evolution of local areas of special interest (petroleum geology), or evolution of the interplate basin, especially when it becomes a single trough (birth of first regional linear sequences); (4) interference of local centered transfer system (i.e., canyon fan or point-slope fan) and regional linear transfer system (i.e., shelf break and slope).

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.