Growth Styles of Shelf-Margin Clinoforms: Prediction of Sand and Sediment-Budget Partitioning Into and Across Shelf Margins

Abstract

Growth styles of shelf-margin clinoforms are reliable but understudied predictors of Source-to Sink sand- and sediment-budget partitioning. Three discrete clinoform-growth styles were recognized, including strongly progradational clinoforms with low growth-trajectory angles (Gct), low aggradation/progradation ratios (A/P), low clinoform heights (Hc) and long clinoform length (Lc), mixed progradational and aggradational shelf-margin clinoforms are characterized by moderate Gct, moderate A/P, intermediate Hc and moderate Lc, and strongly aggradational clinoforms show high Gct, high A/P, high Hc and short Lc. In the South China Sea dataset considered, strongly progradational shelf-margin clinoforms exhibit flat progradational and at times a mildly aggrading stacking patterns, whereas mixed progradational and aggradational shelf-margin clinoforms display stacking patterns with significant progradation and aggradation. Strongly aggradational shelf-margin clinoforms are dominated by aggradational stacking patterns. Each clinoform-growth style therefore represents a specific stratal stacking pattern, providing an important tool for approaching a model-independent methodology in sequence stratigraphy. In the study dataset strongly progradational and strongly aggradational n clinoforms are fronted by sand-prone submarine fan systems with high sand-shale ratios and mud-dominated mass-transport systems with low sand-shale ratios, respectively. Mixed progradational and aggradational clinoforms are associated with mixed sand-mud submarine canyon systems with moderate sand-shale ratios. Additionally, strongly progradational shelf-margin clinoforms partitioned great volumes of sediment into deep-water areas, as reflected by high rates of shelf-edge progradation. Strongly aggradational clinoforms, in contrast, stored great volumes of sediment on the shelf itself, as indicated by high rates of shelf-edge aggradation and very thick clinoform topsets. Gct and Hc therefore increase linearly with sediment volumes partitioned into shelf margins, but decrease linearly with sand- and sediment-budget partitioning into deep-water areas, given a constant supply condition. Clinoforms growth styles are thus good predictors of sand- and sediment-volume partitioning into and across shelf margins, assisting greatly in developing a more dynamic stratigraphy.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015