Astrochronology for the Messinian Sorbas basin (SE Spain) and orbital (precessional) forcing for evaporite cyclicity

Abstract

The Sorbas basin of SE Spain contains one of the most complete sedimentary successions of the Mediterranean re¯ecting the increasing salinity during the Messinian salinity crisis. A detailed cyclostratigraphic study of these successions allows a correlation of the sedimentary cycle patterns to astronomical target curves. Here, we present an astrochronological framework for the Messinian of the central part of the Sorbas basin. This framework will form a solid basis for high-resolution correlations to the marginal carbonate facies and to the Central Mediterranean area.The early Messinian Abad Member contains 55 precession induced sedimentary cycles marked by homogeneous marl±opal-rich bed alternations in the`Lower Abad' and by homogeneous marl±sapropel alternations in the`Upper Abad'. Astronomical tuning results in an age of 5.96 Ma for the transition to the Yesares evaporites and thus for the onset of the`Messinian salinity crisis'. The marl±sapropel cycles of the`Upper Abad' are replaced by gypsum±sapropel cycles (14) in the Yesares Member, indicating that the evaporite cyclicity is related to precession controlled oscillations in (circum) Mediterranean climate as well. As a consequence, gypsum beds correspond to precession maxima (insolation minima) and relatively dry climate, sapropelitic marls to precession minima (insolation maxima) and relatively wet climate. An alternative (glacio-eustatic) obliquity control for evaporite cyclicity can be excluded because the number of sedimentary cycles with a reversed polarity is too high.Sedimentation during the Abad, Yesares, and the overlying coastal sequences of the Sorbas Member, took place in a continuously marine environment, indicating that marine conditions in the Sorbas basin prevailed at least until 5.60±5.54 Ma. According to our scenario, deposition of the Yesares and Sorbas Member took place synchronously with deposition of the`Lower Evaporites' in the Central Mediterranean. Finally, the continental Zorreras Member consists of 8 sedimentary cycles of alternating reddish silts (dry climate) and yellowish sands (wet climate) which correlates very well with the`Upper Evaporites' and Lago Mare facies of the Mediterranean. q

Late Miocene Mediterranean desiccation: topography and significance of the ‘Salinity Crisis’ erosion surface on-land in southeast Spain: Comment

“…Meanwhile, integrated stratigraphic research in the Sorbas basin (Sierro et al, 1999;Krijgsman et al, 1999aKrijgsman et al, , 2000 has revealed: (1) that the top of the Abad marls has exactly the same astrochronometric age as pre-evaporite successions elsewhere in the Mediterranean; (2) that the Yesares Gypsum contains 14 and the conformably overlying Sorbas unit 3 cycles ( 17 cycles); (3) that the Zorreras contains 8 cycles with caspi-brackish ostracode fauna's in the two distinct whitish limestone beds and (4) that all these units possess a reversed polarity. In our opinion, the conspicuous-integrated stratigraphic-similarities with the classical Mediterranean succession cannot be interpreted other than that the Sorbas basinal succession reflects essentially the same depositional history as other Mediterranean basins during the Messinian.…”

Modelling global-scale climate impacts of the late Miocene Messinian Salinity Crisis

“…This is carried out in the upper 13 ocean levels of the model, 0 to 1 km depth, which is an appropriate palaeobathymetry in the model for either side of the Messinian MediterraneanAtlantic seaways (e.g. van Assen et al, 2006;Fortuin and Krijgsman, 2003;Hilgen et al, 2000;Hodell et al, 1994;Krijgsman, 2001;Krijgsman et al, 2004;van der Laan et al, 2006). Although the continental seaways were probably not this deep, or at least not for the entire Messinian, because of the model's horizontal resolution constraints, the parameterisation also necessarily captures part of the mixing and flow that occurs above the continental shelf in the Gulf of Cadiz (Atlantic) and the Alboran Sea (Mediterranean).…”

The Status of Stratigraphy in the 21st Century

“…If true, the authors point out that the boundary would not coincide with a major deglaciation event and associated glacio-eustatic sea-level rise as generally believed; tectonics, rather, are thought to have played a significant role. Earlier, Krijgsman et al (2001) have shown that the initiation of the Messinian Salinity Crisis at -6 Ma was not related to a glacio-eustatic event either.…”