SEDIMENTOLOGY AND STRATIGRAPHY OF MODERN HALITE SEQUENCE FORMED UNDER DEAD SEA LEVEL FALL

Many halite sequences in the geological record accumulated in deep hypersaline basins. However, modern analogs of active halite deposition were studied in shallow hypersaline environments and then applied in interpreting halite sequences. Recently, halite deposition in the deep, hypersaline Dead Sea has been studied together with its coeval environmental and limnogeological forcing; which is the closest modern analog for the deep environments. Therefore, stratigraphy, sedimentology, and petrography of a well-dated, high-resolution modern Dead Sea halite sequence are explored. The sequence was deposited during a ~30-m lake-level decline since the onset of modern halite deposition in 1980, and was compared with sub-annual lake levels, precipitation, and flood records. The sedimentology of the sequence documents the trend of shallowing water depth, including individual, short-term events. The base of the sequence is composed of alternating bottom growth-cumulate halite annual couplets, typical of deep hypolimnetic water deposition. The annual couplets disappear up-sequence and the upper part of the sequence is composed of cumulate layers with dissolution features, typical of shallow epilimnetic water deposition. As a result, halite deposition rate is reduced by 60% at the shallow lakefloor compared with the deep lakefloor. The top of the sequence contains shoreline deposits, halolites (halite ooids) and polygonal surface cracks, indicating subaerial exposure. We show petrographic indicators for summer thermal dissolution )partially dissolved crystals), which are distinct from dissolution features by winter floods that generate a regional truncation surface. We also observed spatial variations in halite thickness and facies, indicate much thinner and spatially limited halite unit compared to the modeled halite unit based on mass balance considerations. Our observations provide criteria for, (a) recognizing water depths and shallowing lake level trend from halite sequences throughout the geological record, and (b) interpretating paleolimnology and water column structure.