Sedimentology and stratigraphy of a modern halite sequence formed under Dead Sea level fall. Issue 3 (28th November 2020)

• Record Type: Journal Article
• Authors: Sirota, Ido; Enzel, Yehouda; Mor, Ziv; Ben Moshe, Liran; Eyal, Haggai; Lowenstein, Tim K.; Lensky, Nadav G.
• Editors: Lokier, Stephen
• Is Part Of: Sedimentology. Volume 68:Issue 3(2021)
• Page Start: 1069
• Page End: 1090
• Publication Date: 2020-11-28
• Subjects: Dead Sea -- evaporites -- halite sedimentology -- hypersaline lakes -- limnogeology; Sedimentology -- Periodicals; 552.5
• DOI: 10.1111/sed.12814
• Languages: English
• ISSNs: 0037-0746

Abstract

Abstract: Halite sequences in the geological record accumulated in deep hypersaline basins. However, such halite sequences are interpreted based on modern analogues of halite deposition in shallow hypersaline environments. Recently, halite deposition in the deep, hypersaline Dead Sea has been studied together with its coeval environmental and limnogeological forcing. This is the closest modern analogue for 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 ca 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 floods. The sequence base is composed of alternating bottom growth‐cumulate halite annual couplets, typical of deep hypolimnetic water deposition. Up‐sequence, the annual couplets disappear and towards its top are composed of cumulate layers with dissolution features, typical of shallow epilimnetic water deposition. Halite deposition rate is reduced by 60% at the shallow lakefloor compared with the deep lakefloor, mainly due to the summer undersaturation that leads to depocentre 'halite focusing'. The top of the sequence contains shoreline deposits, halolites (halite ooids) and polygonal surface cracks, indicating subaerial exposure. This study shows petrographic indicators for summer thermal dissolution (partially dissolved crystals), which are distinct from dissolution features by winter floods that generate a regional truncation surface. Spatial variations in halite thickness and facies, indicating much thinner and spatially limited halite units compared to modelled halite units based on mass balance considerations were also observed. These observations provide criteria for: (i) recognizing water depths and shallowing lake‐level trends from halite sequences throughout the geological record; and (ii) interpreting palaeolimnology, water column structure and the relations between stratigraphic horizons and corresponding shorelines.