--> Abstract: Rethinking Controls on the Mechanics of Deep-Water Thrusting – Interaction of Structure and Sedimentation, by Ana Krueger and Ed Gilbert; #90072 (2007)

Datapages, Inc.Print this page

Rethinking Controls on the Mechanics of Deep-Water Thrusting – Interaction of Structure and Sedimentation

Ana Krueger and Ed Gilbert
Devon Energy, Houston, TX

Critical taper models for the initiation and propagation of thrusts were developed in foreland FTBs, and accretionary wedges at convergent margins. These models generally assume that the controlling factors - basal and surficial slopes - are functions of purely tectonic processes, primarily load-induced down-bending of the sub-thrust “basement”, and construction of a forward surface slope by thrust uplift. A secondary effect may be exerted by surface erosion of the uplifted wedge. In submarine gravity-driven thrust belts sedimentation becomes the critical controlling factor on surface slope. Sediment-wedge progradation during basinward shifts of deposition has the capability to construct a surface slope far more rapidly than thrust uplift. Thrusting can thus be initiated when sea level falls and the sediment wedge progrades rapidly into the basin, increasing the effective surface slope independently of the basal slope. Thrusting can then be “turned off” when the effective surface slope is reduced by (1) ponding of sediment behind rising thrust fronts, or (2) a sea level rise which halts progradation. This process can give rise to cycles of episodic thrusting, and the abandonment of existing structures by burial within the ponded basins. Such structures are then isolated in small translational basins as active thrusting shifts basinward. In any case the primary locus of active thrusting will be at the boundary between the toe of the sediment slope and the basin floor, where the slope break marks a boundary between domains of pure versus simple shear within the sediment pile.

 

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece