TYPES OF SHELF-MARGIN CLINOFORM AND THEIR ROLE IN BASIN FILLING

Examination of sediment volume partitioning, facies and trajectories within 20 shelf-margin clinoform sets in the Lower Eocene succession on Spitsbergen suggests that there are three main types of clinoforms: (1) clinoforms that show variably incised, river-dominated deltas on their outer-shelf segments, muddy slope segments with narrow channels and gullies in which coarse sands accumulated , and sand-prone basin-floor segments; (2) clinoforms with river-wave interaction deltas on the outer shelf, sheet turbidite-prone muddy slopes with sand thickening back up to the shelf edge, and muddy basin floors; (3) clinoforms that show strongly wave-influenced, sand-prone outer shelf segments, but muds on both slope and basin-floor segments.

These three clinoform types often form a clinoform set, developed during a cycle in which sandy shorelines regress to the pre-existing shelf edge, deliver sediment into deepwater, then transgress back across the shelf. This typically results in the sand budget being partitioned mainly into shelf and basin-floor segments. Another type of clinoform set is dominated by stacked Type 2 clinoforms (showing little or no fluvial incision at the shelf edge and no basin-floor sands). This resulted in sand partitioning mainly into the shelf and into substantial wedges on the slope.

Successive clinoform sets cause the shelf margin to prograde and aggrade. Sets dominated by Type 1 clinoforms produce a low-angle shelf-edge trajectory, whereas sets without Type 1 clinoforms have a more steep, aggrading trajectory. The basin fills by the irregular accretion of the shelf margin, aggradation of the coastal plain, and aggradation of the basin floor.