No abstract

Sr isotope records from marginal marine basins track the mixing between seawater and local continental runoff, potentially recording the effects of sea level, tectonic, and climate forcing in marine fossils and sediments. Sr/ 86 Sr analyses from the astronomically tuned Lower Evaporites in the central Apennines (Italy) allow us to explore the effect of glacio-eustatic sea level and precipitation changes on 87 Sr/ 86 Sr. Most variation in our data can be explained by changes in sea level, with greatest negative excursions from global seawater values occurring during relative sea level lowstands, which generally coincided with arid conditions in the Mediterranean realm. We suggest that this greater sensitivity to lowered sea level compared with higher runoff could relate to the inverse relationship between Sr concentration and river discharge. Variations in the residence time of groundwater within the karst terrain of the circum-Mediterranean region during arid and wet phases may help to explain the single (robust) occurrence of a negative excursion during a sea level highstand, but this explanation remains speculative without more detailed paleoclimatic data for the region.

At the end of the Messinian salinity crisis, changes in the\ud palaeoceanography and palaeoclimate induced a transition\ud from hypersaline to hyposaline conditions in the Mediterranean\ud water body. Detailed investigation of natural radioactivity and\ud microfacies analyses of two early post-evaporitic Messinian\ud sections show that the transition occurred in poorly oxygenated\ud and well-stratified water masses. These transitional\ud deposits, which mainly consist of marls and CaCO3-rich\ud horizons, are generally well laminated and totally barren\ud in benthic and planktonic fauna. The presence of barite, small\ud (5–8 lm) authigenic framboidal pyrite, and high values of U\ud indicate persistent anoxic conditions during the early postevaporitic\ud Messinian stage in the Adriatic sub-basin of the\ud Mediterranean Sea. The presence of post-evaporitic welllaminated\ud barren deposits from both Mediterranean borderland\ud sections and ODP sites suggests that these anoxic\ud conditions extended to other sub-basins of the Mediterranean\ud region

No abstract

This paper is mainly based on field work carried out on the Messinian deposits of the Adana Basin (southern Turkey), as well as on the interpretation of seismic reflection profiles to understand 3D geometries of the basin filling. Chronostratigraphical constraints for the Messinian deposits are from micropaleontological studies on foraminifera, ostracods, and calcareous nannofossils, recently carried out on the Messinian deposits of the Adana Basin. Our results indicate that this basin developed in a marginal area strictly related to the Mediterranean realm. The Messinian deposits of the Adana Basin record all the main steps of the Messinian Salinity Crisis (MSC) that affected the Mediterranean area at the end of the Miocene. The new stratigraphical model for the Messinian deposits of the Adana Basin provided in this work gives new insights into both the MSC and the Taurus petroleum system. Despite their complete correspondence with the MSC, the Messinian deposits of the Adana Basin show some differences with respect to the current conceptual model for the MSC. For example, in the current conceptual model for the MSC, only one regional erosional surface (MES) characterizes the MSC deposits. In the Adana Basin, two regional erosional surfaces, named MES1 and MES2, separate the Messinian deposits related to the MSC in Lower Evaporites, Resedimented Lower Evaporites (RLE), and upper Messinian continental deposits containing a late Lago-Mare ostracod assemblage (mainly fluvial coarse-grained and fine-grained sediments). In some places, Brecciated Limestones lie just above the MES1 and beneath the RLE. In addition, the RLE are thought to be related to the same step that brought to the Messinian halite deposition throughout the Mediterranean, pointing to a hyperhaline environment. In contrast, the fine-grained deposits of the RLE of the Adana Basin show the occurrence of Parathetyan brakish ostracod fauna (early Lago-Mare ostracod assemblages), which defines an oligohaline depositional environment for the RLE.\ud In terms of hydrocarbon prospecting, the Messinian evaporites of the Adana Basin have been considered as a perfect seal for the active Taurus petroleum system. Our results show that due to the complex stratigraphical architecture of the basin filling and the occurrence of two regional erosional surfaces (MES1 and MES2), the Messinian evaporites are discontinuously present both in surface and in the subsurface of the Adana Basin. However, seal properties in the Adana Basin could be found in the Lower Pliocene deep marine clays of the Avadan Formation.\ud This work leads to suggest a new stratigraphical model for the Messinian deposits of the Adana Basin, allowing us to amend the classical scheme with respect to the Messinian, and to officially define some new formations within the stratigraphy of the Adana Basin