Lithofacies and water-body record of Messinian evaporites in Nijar Basin, SE Spain Feng H. Lu Stable Isotope Laboratory (Shaw Environmental), US EPA Groundwater and Ecosystem Research Center Shaw, Ada, OK 74820, USA Abstract The depositional lithofacies and fabrics of Messinian evaporites have been studied to evaluate the palaeodepth of water body in Nijar Basin, SE Spain. The Nijar Messinian strata consist of three formations: Abad marls, Yesares evaporites, and Feos rocks. Gypsum deposits dominate the Yesares Formation and the basal Feos Formation. Six gypsum lithofacies have been identified including coarse twinned selenite, grass-like selenite, hemiradial to radial selenite, turbidite selenite in the Yesares Formation; and gypsum conglomerate, laminated gypsum, and hemiradial to radial selenite in the Feos Formation. The size of Yesares selenites decreases upward while carbonate content and trace-element abundance increase in each selenite bed and the whole formation, suggesting a shallowing-up sequence. These gypsum lithofacies were deposited in subaqueous environments commonly at 10– 30 m and occasionally up to 100 m or deeper for the turbiditic selenites based on the interpretations of gypsum fabrics, marl intervals, basin configuration, and geochemistry. The sea level of Nijar Basin experienced two major drops with a magnitude of ∼ 40 m before and after the deposition of Yesares evaporites. However, the basin was never desiccated during the evaporite deposition and the change of sea level for the alternative deposition of gypsum beds and marl intervals was commonly around 50–80 m, probably resulting from the glacio-eustacy fluctuations. Feos gypsum reflects another evaporative event and is correlated to the “Upper Evaporite” while the Yesares selenite is correlated to the “Lower Evaporite” based on the interpretations of lithofacies, geochemistry, and sealevel change. As seawater in Nijar Basin was continuously supplied by the central Mediterranean basins and remained in subaqueous conditions during the Messinian salinity crisis, therefore, the desiccation theory needs to be reexamined. © 2006 Elsevier B.V. All rights reserved. Keywords: Evaporite; Water depth; Nijar Basin; Messinian salinity crisis; Mediterranean 1. Introduction Studies on the extensive dolomitization of the Late Miocene platform carbonates, Nijar, SE Spain propose that dolomitizing fluids were seawater-evaporated brines mixed with freshwater; and the brines derived from the adjacent basin (Meyers et al., 1997; Lu and Meyers, 1998). In addition, marine brines were believed to have dolomitized reef complex in Mallorca, NE Spain, 600 km away from Nijar (Oswald, 1992). The platform dolomite and basinal gypsum are further suggested to be cogenetic products of the Messinian salinity crisis (MSC). The initial goal of investigating Nijar evaporites was to understand the basin palaeoen- vironment and palaeohydrology in order to test the dolomitization hypothesis. This research of gypsum lithofacies can also help understand the MSC that is still under debate for its environmental interpretation (Hsü et al., 1973; Rouchy and Saint Martin, 1992; Sedimentary Geology 188–189 (2006) 115 – 130 www.elsevier.com/locate/sedgeo E-mail address: lu.feng@epa.gov . 0037-0738/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.sedgeo.2006.03.001