Ben Kneller¹, Bill McCaffrey²

(1) University of California, Santa Barbara, CA
(2) University of Leeds, Leeds, United Kingdom

ABSTRACT: Flow Parameters and Stratigraphic Architecture in Turbidite Systems

The stratigraphic architecture of turbidite systems is determined not only by the nature of the receiving basin but also by the nature of the turbidity currents entering it. Using scaled laboratory experiments we have established relationships between flow type and the geometry of turbidite systems and their component beds. Variations in flow density, volume and proportion of fines affect the aspect ratios and cross-sectional geometries of the deposits in ways that may be identifiable in seismic data. Where changes in the starting conditions of the turbidity currents change with time, for example through a sea-level cycle, the external geometry and internal architecture of resulting turbidite sheet systems can be predicted.

We compare the results of our experiments with a turbidite complex in the western Gulf of Mexico that was deposited during the last glacial, about 80 ka to 10 ka ago, representing a single fourth order climate/sea-level cycle. It includes a number of temporally distinct turbidite systems, each with its own seismic character and geometry that can be related to changes in the grain-size mix, volume and density of the flows through the climate cycle. The sequence culminates in a small mud-rich fan, fed by a levéed channel, formed during the last stage of the glacial, as sand was sequestered on the shelf.

We generalize these results to suggest how other features of turbidite systems, such as retrogradational packages of beds and thinning/fining-upwards channel fills, can be related to externally-driven changes in flow parameters, directly or indirectly driven by climate.

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