The surfaces of saline lakes are shrinking at a threatening rate worldwide. Likewise, the Uchhali complex (formed by three saltwater lakes located in the Salt Range, Pakistan) that serves as a major regional source of water for humans and as a habitat for water birds must be monitored. With this objective in mind, we conducted a study coupling hydrochemistry and stable isotope compositions (δ³⁷Cl, δ¹⁸O and δD) in order to characterize its hydrochemical properties and the main processes controlling them. Results showed that the Uchhali complex salinity has dramatically increased compared to other similar lakes in the world. While the Uchhali (UL) and Khabbeki (KL) lakes present a sodium-chloride hydrofacies, the Jahlar (JL) is of a sodium-bicarbonate type. Hydrochemistry parameters indicate that the weathering of surrounding rocks is the major vector for the increase of total dissolved solids in the water. On the other hand, the observed enrichment in heavy isotopes of the water stable isotope compositions implies that the different lakes are undergoing a long history of intense evaporation. The study of the corresponding δ³⁷Cl isotope compositions supports the conclusion that evaporation, along with weathering, are the main driving processes. Besides climate effects that result in the decrease of annual precipitation and the increase of evaporation, water consumption for domestic purposes (household and agriculture) aggravates the rise of the lakes’ salinity.

In this study, the ion concentrations (K⁺, Na⁺, Ca²⁺, Mg²⁺, Cl⁻, SO₄²⁻, Br⁻, NO₃⁻, and B³⁺) and boron isotope compositions (δ¹¹B) of 34 halite and brines samples from the Neoproterozoic Salt Range Formation, Punjab, Pakistan were studied. Relation among B³⁺ vs. Mg²⁺, B³⁺ vs. SO₄²⁻, δ¹¹B vs. B³⁺, and δ¹¹B vs K⁺ were observed, they indicated that these elements originate from multiple sources and the end members were identified as seawater, B desorption from clays, and meteoric precipitation. Halite samples of the area under study displayed a Na-HCO₃-type to Ca-Cl type sedimentary basin of deposition, on δ¹¹B vs. 1/B plot. Molar ratios of B/Cl vs. δ¹¹B revealed the addition of B in some of the studied samples from desorption of clay minerals. This type of diagenetic desorption of B from clays is the consequence of a stress driven mechanism, generated in the proximity of a decollement zone. Results confirm that the number of B stable isotopes that fractionate between the brine and the halite is low. The halite δ¹¹B from the Salt Range Formation vary from +2.1 to +24.4‰, compared to +17.3 to +26.1‰ in the salt pool brines, and suggest that boron isotope compositions are controlled by the δ¹¹B of the B sources. The positive relationship between the boron content and the corresponding δ¹¹B indicates a higher salinity and drier paleoclimate conditions during the formation process, associated with a high evaporation rate in the Late Neoproterozoic time. Presence of elevated δ¹¹B in the present study, demonstrate compatibility with other marine basins of the world, arising the need for further investigations to better characterize the ¹¹B-enriching processes.