Isotope composition (δ34S, δ18O) of the Middle Triassic-Early Jurassic sulfates in eastern Iberia

This study combines published isotope data (223 samples) with new data (153 samples) on the delta S-34 and delta O-18 composition of Ca-sulfate rocks (anhydrite and secondary gypsum) accumulated in eastern Iberia during the Middle Triassic to Early Jurassic. The delta S-34 mean values of the evaporite units reveal the following trends: a decrease from the lower Anisian (similar to 18 parts per thousand) to the Carnian-Norian interval (similar to 15 parts per thousand); an increase at the Rhaetian (similar to 16 parts per thousand); a decrease in the Hettangian-Sinemurian interval (-14 parts per thousand); and finally an increasing trend from the Sinemurian-Pliensbachian (similar to 16 parts per thousand) to the Pliensbachian-Toarcian (similar to 19 parts per thousand). This delta S-34 isotope assemblage together with the generalized low standard deviations observed for the different evaporite units is consistent, and suggests that the isotope composition of these Ca-sulfates are primary signatures related to feeding marine water sulfate. Depending on the evaporite units, these delta S-34 mean values are, nevertheless, similar to 1 parts per thousand to similar to 3 parts per thousand lower than those reported for coeval Triassic evaporites of the Germanic basin and the Alp-Apennine domains. In eastern Iberia, the delta O-18 values are more variable and also display wider scatters than the corresponding delta S-34 values. Of particular interest in our study are: (i) the low delta S-34 values for the Anisian in comparison with those in the Germanic basin; (ii) the shift to heavier values in the Rhaetian, recorded for first time in the evaporites of eastern Iberia; (iii) the low values observed for the Hettangian, which suggest that the change to the heavier values of the Jurassic (similar to 19 parts per thousand) occurred after the end-Hettangian in eastern Iberia; and (iv) the affinity of the delta S-34 values recorded for the Hettangian-Sinemurian interval to those known for the Canadian domain. (C) 2022 Elsevier B.V. All rights reserved.