Abstract

Decelerating turbidity currents commonly emplace sedimentary wedges. Here “sedimentary wedge” is used as a generic term for a sediment deposit, the thickness of which gradually decreases in the downdip direction. Examples of sedimentary wedges relevant to the research reported here include a) deposits in submarine minibasins, b) deposits on zones of lower slopes of stepped profiles, and c) deposits on the levees of submarine channels. In the present work, a generic configuration is used to study the flows that emplace sedimentary wedges. These flows consisted of a succession of sustained saline density underflows, which were used as surrogates for turbidity currents driven by fine-grained material (mud) that does not easily settle out. Although the flow naturally decelerated in the downstream direction, deceleration was ensured by the presence of a barrier to the flow at the downstream end of the study reach. The density underflows carried a load of lightweight plastic particles, from which the depositional wedge was constructed. The experiments were not designed to model any specific field configuration. This notwithstanding, the experimental configuration provides an analog for a) decelerating flows into confined minibasins, as well as b) levee-constructing overflows from submarine channels. This paper documents the nature of the flows that emplaced the wedge. The sedimentary wedge itself is documented in a companion paper.