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Abstract: Flexural Wedges - A Model from Lower Valanginian Outcrops of Southeastern Spain

Bruno Granier

In the Alicante area (SE Spain), Lower Valanginian deposits take place in a distally steepened ramp setting. At the shelf edge (e.g. Sierra de Cabezon de Oro), they consist of storm-dominated facies (with HCS and SCS) arranged in a coarsening-, shallowing-upward calcarenitic sequence. This wedge thins rapidly landward whereas, on the opposite side, it thickens and forms at the slope bottom (e.g. between Busot and Sierra de Fontcalent) a huge depocenter; then in turn it thins basinward. It is overlained by a condensed section (ferruginous oolite, glauconite-rich levels, etc.) representing the remaining part of the Valanginian, the Hauterivian, the Barremian, and part of Aptian. Its base corresponds to a tectonically enhanced, flexural unconformity marked by abrupt facies c anges, i.e., on the platform from shallow-water carbonates to outer shelf storm-dominated facies, and in the basin from pelagic facies to turbidites.

In conclusion, it is suggested that such peculiar wedges are possibly not restricted to tectonic events but that they may occur in most of the transgressive phases due to the major and hydrodynamic changes enhanced at those periods.

The same unconformity is reported from the Central Atlantic in a by-pass margin setting. There the flexural wedge consists of the basin depocenter alone; it has been previously misinterpreted as a lowstand systems tract.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France