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Turbidites and Debris Flows: Sea-Level Variations Versus Tectonic Processes

John J. Reijmer1, Pauline Palmieri2, Marc Floquet2, Ralph Groen1, and Sebastiaan Kerkvliet1
1FALW-S&MG, VU University Amsterdam, Amsterdam, Netherlands
2Géologie des Systèmes Carbonatés, Université de Provence (Aix-Marseille 1), Marseille, France

Compositional variations, skeletal and non-skeletal components, were point-counted in carbonate gravity deposits from Exuma Sound (Pleistocene, Bahamas) and the Southern Provence Basin (Turonian-Coniacian, SE France). The Bahamian gravity deposits were deposited in an environment in which sedimentation was controlled by eustatic sea-level variations while in contrast the Southern Provence Basin (SPB) sedimentation was strongly influenced by tectonic processes.

Earlier studies have shown that compositional variations of gravity deposits can be linked to different sources on the carbonate margin, i.e. platform interior, edge, and slope. In the Bahamian cores (ODP Leg 101, Site 632A) two types of deposits, calciturbidites and debris flows were present. The calciturbidites show variations in their skeletal and non-skeletal components that depend on the position of sea level; highstand (platform top flooded) versus lowstand (platform top exposed). In contrast, the composition of the debris flows remains unaltered through time and shows a dominance of platform edge derived sediments. In addition, it was noted that the debris flows were deposited during regressions in sea level.

Gravity flow deposits in the SPB were deposited during a sea-level rise associated with a series of earthquakes related to the opening of the SPB. They show a mix of sediments with components derived from the platform interior, the platform edge as well as the upper slope.

The study shows that the composition of calciturbidites and debris flows can be used to determine which process, eustatic sea-level variations or tectonic processes, triggered sediment redeposition. The results will not only help to understand the origin of redeposited sediments in sedimentary basins, but will also aid to differentiate between tectonic and sea level induced time lines along carbonate platform to basin transects.

 

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas