Messinian stratigraphy of the Nijar Basin (S.E. Spain) and the origin of its gypsum-ghost limestones

Abstract

The Middle Messinian of the Nijar-Carboneras area (S.E. Spain) shows common rapid lateral transitions from thick-bedded massive gypsum to brecciated or massive limestone with voids and pseudomorphs after gypsum crystals. These 'gypsum-ghost limestones' are underlain by, and interbedded with, laminated marly sediments that contain a restricted marine microfauna attesting to oxygen-deficient conditions. Oolite-rich series of the basin margin, which include gypsiferous stromatolite and a few restricted marine fauna levels, probably constitute a lateral equivalent. Upper Messinian fine-grained laminites of the central part of the basin contain brackish fossil assemblages and numerous tongues of coarse clastic material derived from the basin margins. The gypsum-ghost limestones are interpreted to be essentially the product of two phases and types of diagenesis. Microbial sulfate-reduction during oxygen-deficient periods of the Middle Messinian first played a role in their formation. An important fresh-water diagenetic phase took place later, probably in the Late Messinian.