Saline Lakes and their Deposits: A Sedimentological Approach

Abstract

Saline lakes (lakes with >5000 ppm dissolved solutes) are common throughout the arid regions of the world. Their distribution is controlled by tectonic setting and climate, and thus their deposits take on an importance beyond their size and abundance in the geological column. To exploit this aspect of saline lakes an understanding is needed of their sedimentary record. Saline lakes occupy the hydrographically lowest areas of closed drainage basins and are surrounded by a complex of interrelated depositional subenvironments that result mainly from the characteristics of the inflow. Our approach is to identify distinctive subenvironments, each subject to a distinctive set of hydrological, biological, chemical and sedimentological processes and hence each with a diagnostic set of sedimentary features in their deposits, as follows: (1) alluvial fan; coarse gravelly wedges composed of braid channel deposits, incised channel fills, sieve deposits and debris flows; (2) sandflat; flat unchannelled sandy apron at base of fan; planar and wavy laminated coarse sand (upper flow regime bedforms); (3) dry mudflats; exposed plain of mudcracked muddy sediment fringing the saline lake, covered with thin saline efflorescent crusts; sediment laminated but disrupted by mudcracks, sheetcracks, and saline mineral growth; (4) ephemeral saline lake consisting of an inner salt pan (thin beds of crystalline salts with mud partings) and an outer saline mudflat (massive mud crowded with salt crystals that have destroyed layering); (5) perennial saline lake; bottom sediment of laminated carbonates, gypsum, etc., or, if very saline, thin-bedded halite, etc.; (6) dune field (aeolian deposits); (7) perennial stream floodplain (braid or meander deposits); (8) ephemeral stream floodplain (braid deposits); (9) springs; travertine and tufa mounds and sheets; (10) shoreline features (deltas, beach ridges, spits, etc.). By recognizing from the sedimentary record which subenvironments were present and how they were arranged in space and time, we can interpret the history of a saline lake basin, either modern or ancient.