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Sediment Partitioning across Tertiary Continental Slopes

Prather, Bradford 1; O'Byrne, Ciaran 1; Pirmez, Carlos 1; Sylvester, Zoltan 1
1 Shell International E&P, Houston, TX.

An ability to predict the behavior of source-to-sink systems is important for a variety of reasons including energy resource assessment. Process-based conceptual understanding encoded in numerical models is one means to predict stratal geometries useful for the oil and gas exploration and production. Judging the validity of both the conceptual framework and numerical code used in these forward models requires ground-truth. We propose a conceptual framework for quantifying sediment partitioning along three Tertiary continental slope profile types as a means of benchmarking these models.

The distribution of environments of deposition across slope systems varies as a function of accommodation, sediment flux rates, substrate mobility and sand-mud content. Most sediment on slopes is partitioned into five environments of deposition: 1) aprons, 2) valleys, 3) mass-transport, 4) unconfined slope and 5) slope drape deposits. Unconfined slope and drape deposits include muddy turbidites, hemipelagic, pelagic and mud-belt deposits. Aprons include environments previously classified as fan aprons, ponded basin and healed-slope deposits, perched-slope fills, healed-slope aprons and transient fans. Valleys include incisional and outer levee-confined channel complexes with their associated inner levee and lobe deposits. Stacks of channel storeys in the axis of the valley characterize this depositional environment. High percentages of MTDs, valleys and few apron deposits reflect sediment partitioning controlled by down-slope transport on graded slopes. Abundant aprons suggest topography affects partitioning of sediment on above-grade slopes, differentiating them from graded slopes. Higher percentage of sand partitioned into aprons on ponded above-grade slopes further differentiates them from stepped above-grade and graded slopes.

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009