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Sources of sulphur in gypsiferous sediments and crusts and pathways of gypsum redistribution in southern Tunisia
Author(s) -
Drake Nick A.,
Eckardt Frank D.,
White Kevin, H.
Publication year - 2004
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.1133
Subject(s) - bedrock , evaporite , gypsum , geology , aeolian processes , geochemistry , crust , weathering , groundwater , halite , sedimentary rock , geomorphology , earth science , paleontology , geotechnical engineering
Southern Tunisia contains one of the most extensive gypsum accumulations in Africa comprising Triassic, Cretaceous, Eocene and Mio‐Pliocene marine evaporites, spring deposits, playa sediments, aeolian sands and gypsum crusts. Sulphur isotope analysis ( δ 34 S) of bedrock samples, groundwater, playa brines, playa sediments, and gypsiferous crusts provides insight into the sources of gypsum in the region and sheds light on the processes that lead to gypsum crust formation. Results suggest that recycling of marine gypsum is the most likely source of the sulphate in the groundwater, playa sediments and crusts. The low δ 34 S values found in Eocene and Mio‐Pliocene samples suggest that this recycling has been going on for millions of years. Though bedrock appears to be the ultimate source of the gypsum in the crusts, transport of this sulphate to playas, concentration therein, and subsequent dispersal across the landscape by aeolian processes provides the most likely pathway for surcial gypsum crust formation. Comparison of these results with those from Australia, Chile and Namibia suggests that, although the source of the sulphur varies from region to region, the processes of surcial crust formation appear to be similar. Copyright © 2004 John Wiley & Sons, Ltd.