Geochemistry of evaporitic deposits from the Cenomanian (Upper Cretaceous) Maha Sarakham Formation in the Khorat Basin, northeastern Thailand

The Cenomanian (Upper Cretaceous) Maha Sarakham Formation of the Khorat Basin, northeasternThailand consists of three evaporite units (Lower, Middle and Upper Salt) interbedded with clasticsediments and exhibits abundant deposits of potash. Although numerous studies have been carried outon the Khorat potash deposit, results are still equivocal with regard to the origin of the rock salt, whetherit was marine or non-marine (hydrothermal and/or mixedfluids). The purpose of this study is to examinethe origin of rock salt based on elemental compositions and boron isotope analyses in the southwesternpart of the Khorat Basin. A stratigraphic correlation offive boreholes (K-201e205) located in BamnetNarong and Chaturat districts, Chaiyaphum province, Thailand, revealed a salt dome structure. Theelemental composition andd11B values in the longest borehole K-203 indicate a precipitation of haliteand carnallite from seawater. Rare earth elements (REE) of claystone and siltstone fromfive boreholes (K-201e205) are comparable to the REE of sandstone from the Simao Basin in China, which suggest asimilar provenance. Stratigraphic comparisons and geochemical signatures are important for a betterunderstanding of the recharge models of paleoseawater. In agreement with some previous studies, weconclude that the Cenomanian evaporites within the Khorat Basin are marine deposits. (c) 2021 Elsevier Ltd. All rights reserved