Thierry Nalpas¹, Laurie Barrier¹, Sebastien Castelltort¹, François Guillocheau¹, Cécile Robin², Delphine Rouby¹

(1) University of Rennes, Rennes, France
(2) University of Paris VI, Paris, France

ABSTRACT: Interaction between the Couple Sedimentation/Erosion and the Evolution of Growth Structures from Field, 3-D Seismic Examples and Analogue Modeling

Several parameters can control the evolution and the geometry of growth structures: (1) the occurrence of décollement layer(s), (2) the initial thickness of sediment involved in the deformation, (3) the amount of strike-slip associated with shortening or stretching and (4) the rate of sedimentation or erosion during deformation.

Among these parameters, we have studied the influence of the couple sedimentation/erosion on the kinematics of several growth systems: (1) growth folds, (2) growth reverse faults, (3) graben inversion and (4) extensional raft tectonics. We then studied the influence of the growth of these structures on the associated sedimentary systems. To do so, we used field examples (the Southern Pyrenees and the Iberique Chain), 3-D seismic examples (the Broad Fourteens Basin in the North Sea and the offshore Congo margin), and analogue modeling.

Experiments were made of silicone putty (representing décollement layers) overlain by sand (representing sediments). For each experiment, rate and amount of deformation were kept constant with varying rate of erosion/sedimentation. Experiments show that variations of sedimentation/erosion rate systematically modified the initial location, the period during which structures were active and their final geometry. From field and seismic examples, we study the consequences of the modified structure geometry on the deposition profile. This study further suggests that a fundamental parameter of synsedimentary deformation processes is the ratio between rate of deformation and rate of erosion/sedimentation.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado