The Orange River, southern Africa: an extreme example of a wave-dominated sediment dispersal system in the South Atlantic Ocean

被引:51
作者
Bluck, B. J. [1 ]
Ward, J. D.
Cartwright, J.
Swart, Roger
机构
[1] Univ Glasgow, Dept Geog & Earthsci, Glasgow G12 8QQ, Lanark, Scotland
[2] Gem Diamonds Ltd, Johannesburg, South Africa
[3] Univ Cardiff, Dept Earth & Planetary Sci, Cardiff CF10 3YE, Wales
[4] NAMCOR, Windhoek, Namibia
关键词
D O I
10.1144/0016-76492005-189
中图分类号
P [天文学、地球科学];
学科分类号
07 ;
摘要
Sediments delivered to the South Atlantic Ocean by the Orange River are fractionated and dispersed northwards and westwards by a vigorous longshore drift system and a number of ocean currents. Gravels are accreted to the coastline for a distance > 300 km north from the Orange River mouth. Sands are transported alongshore for > 700 km but are, in places along this transport path, returned onshore by coastal winds to form the main Namib Sand Sea and other smaller dune fields. Mud is more widely dispersed westwards, northwards and southwards, probably by slow-moving, ocean-scale currents into basins on the shelf and onto the continental shelf edge. This dispersal system, operating since at least Eocene times, is believed to have originated during a time when there was a Late Cretaceous-Early Cenozoic uplift of southern Africa, which resulted in: (1) intensification of the existing southerly wind system; (2) incision of the Orange River, which, coupled with a shift in climate, resulted in a coarsening of its sediment load delivered to the coast; (3) a broad, weakly subsiding or mildly uplifting inner continental shelf with little accommodation space for the sediment load of the incising Orange River.
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页码:341 / 351
页数:11
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