S9 - Tectonic signals in the Messinian stratigraphy of the Sorbas basin (Almeria, SE Spaín)

Summary

Abstract

The Messinian (Late Miocene) stratigraphic record of the Sorbas basin (SE Spain) comprises two major sedimentary cycles that can be correlated with the TB 3.3 and TB 3.4 cycles of Haq et al. (1987). The lower cycle consists of a temperate-carbonate unit assigned to the Low-Systems Tract and bioherm and fringing reef units representing the Transgressive and High-Stand parts respectively. The upper cycle consists of a selenite–gypsum unit (Low-Stand), a marine, stromatolite-bearing unit corresponding to the Transgressive Systems Tract, and an alluvial, continental unit representing the High-Stand.

Tectonic movements were involved in the formation of the unconformities at the base of both major, third-order cycles as well as at the boundaries and interruptions of some high-order ones. The unconformity at the base of the lower cycle reflects the combined effects of the sea-level fall at the end of the last Tortonian cycle (TB 3.2 of Haq et ai, 1987) and a pulse of tectonic uplifting affecting the southern margin of the basin (Sierra Alhamilla). As a consequence of this, temperate, shallow-water carbonates lie directly on top of deep-water, submarine-fan deposits around the Sierra Alhamilla.

The unconformity separating both major Messinian cycles may be correlated with a global sea-level fall and may perhaps reflect the main evaporite event of the Mediterranean region.