Solid sediment load history of the Zambezi Delta

摘要

We calculate the solid sediment load history of the Zambezi River for the last 120 Ma (i.e. Middle Cretaceous-Recent times). Our starting point is a detailed grid of two-dimensional seismic reflection profiles, calibrated by well-log information. After conversion from two-way travel time to depth, we made simple assumptions about the compaction history in order to construct isochore maps of solid sediment load and yield as a function of geological time. Our results show that solid sediment load has varied by similar to 1 order of magnitude over the last 120 Ma. There have been three periods of elevated flux. The first period occurred in Late Cretaceous times (90-65 Ma) and was synchronous with the rapid denudation of southern Africa recognised by, for example, apatite fission track modelling. The second period occurred in Oligocene times (34-24 Ma) during proposed rapid regional uplift of Southern Africa. The youngest phase of elevated flux started in Late Miocene times (10 Ma) and has continued to increase rapidly through to the present day. A large proportion of this increase can be attributed to a doubling of the size of the Zambezi catchment during the Pliocene. At other times, we suggest that load variations can be used to bound the uplift history of the region, which encompasses the catchment. Finally, changes in the shape of the Zambezi Delta through time suggest that the Mozambique current, which sweeps through the Mozambique Channel from northeast to southwest, initiated at the start of the Miocene. (c) 2005 Elsevier B.V. All rights reserved.