The Relationships between Shelf-edge Trajectories and Slope-Facies Associations: Useful Predictors of Sand Delivery to Deepwater Areas

Gong, Chenglin; Wang, Yingmin; Zhu, Weilin; Xu, Qiang; Li, Dong; Li, Weiguo

The relationships between shelf-edge trajectories and slope-facies associations are the extremely important (but still poorly understood) issues, as they hold the potential for defining a method for the prediction of hydrocarbon reservoirs. The current study documents the relationships between shelf-edge trajectories and slope-facies associations and addresses the significance of shelf-edge trajectories for sand delivery to deepwater areas.

Four main types of shelf-edge trajectories are recognized in the study area, including descending, flat, low angle-ascending, and high angle-ascending shelf-edge trajectories. Descending and flat shelf-edge trajectories formed as a result of the interaction between falling and stable trends of sea level and low sediment input, whereas low angle-ascending and high angle-ascending shelf-edge trajectories resulted from the interplay of the rising and rapid rising trends of relative sea level and high sediment supply.

Descending shelf-edge trajectories suggest near-total bypass of sandy sediment across shelf edges, and record the development of submarine fans and sand-dominated depositional unit. Flat shelf-edge trajectories indicate less sediment bypass to the deep-water areas, and record the development of sand-rich depositional unit. Low angle-ascending shelf-edge trajectories, in contrast, are associated with mud-rich depositional unit, suggesting that a small amount of sediment was transported beyond shelf edges. High angle-ascending shelf-edge trajectories are directly linked to mud-dominated depositional unit, indicating that only very little sediment was carried seaward.

Our results will have great significance in predicting the potential for the presence of deep-water fans and how voluminous sandy slope facies are. Margins with descending shelf-edge trajectories holds the greatest potential for the occurrence of deep-water fans even under low sediment-supply conditions, the higher angle shelf-edge trajectory indicates the less potential for the presence of sandy deposits. Additionally, sandy deposits linked to lower angle shelf-edge trajectories tend to have much larger volumes than those associated with higher angle shelf-edge trajectories.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013