Abstract

Growth styles of shelf-margin clinoforms are reliable but understudied predictors of sand- and sediment-budget partitioning into and across the shelf. Three discrete clinoform-growth styles were recognized, including (1) strongly progradational shelf-margin clinoforms with low growth-trajectory angles (G_ct,), low aggradation to progradation ratios (A/P), low clinoform heights (H_c), and long clinoform length (L_c); (2) mixed progradational and aggradational shelf-margin clinoforms with moderate G_ct, moderate A/P, intermediate H_c, and moderate L_c; and (3) strongly aggradational clinoforms with high G_ct, high A/P, high H_c, and short L_c.

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 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 shelf-margin 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 clinoforms partitioned great volumes of sediment into deep-water areas, as reflected by high rates of shelf-edge progradation and apparent toplap. 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. G_ct and H_c therefore increase linearly with sediment volumes partitioned into the shelf, but decrease linearly with sand- and sediment-budget partitioning into deep-water areas, given a constant sediment-supply condition. Growth styles of shelf-margin clinoforms are thus good predictors of source-to-sink sand- and sediment-volume partitioning into and across the shelf, assisting greatly in developing a more dynamic stratigraphy.