Sr ions and isotopes in groundwater Campeche, Mexico: Insight into development of Edzna Valley

Strontium isotope chemistry, combined with previously obtained groundwater ion chemistry elucidates the stratigraphy of buried sedimentary rocks of the southern Yucatan Peninsula, Mexico. Whereas in groundwater of the northern Peninsula, ion chemistry is dominated by contact with a saline intrusion, the groundwater of southern Campeche and southern Quintana Roo has high SO₄/Cl and Sr/Cl indicating extensive contact with beds of dissolving gypsum (and celestite) in the subsurface. The newly-obtained strontium isotope data strengthen a conclusion of previous research, namely that, in marked contrast with the north, there is no saline intrusion in the southern Peninsula.⁸⁷Sr/⁸⁶Sr measurements confirm that much of the evaporite that is contributing ions to southern Peninsula groundwater has a Kt-Eocene seawater isotope signature. A key conclusion from combined study of Sr, Sr isotopes, Cl, and SO₄ is that a large geomorphic feature in western Campeche, the Valley of Edzna polje, was once occupied by a post-Eocene seawater incursion.