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

The Sorbas basin of SE Spain contains one of the most complete sedimentary successions of the Mediterranean reflecting 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-opalrich 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

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

One of the most striking aspects of the Mediterranean "Messinian Salinity Crisis" as observed in landbased sections, is the basin-wide synchronicity in facies change (Krijgsman et al., 1999a). The Messinian succession of the Caltanisetta Basin on Sicily serves as the classical standard for these facies changes, which can also be recognised elsewhere in the Mediterranean, i.e. on Cyprus, Crete, northern Italy and southern Spain. It starts with an alternation of open marine marls and sapropels, passes via diatomites into evaporitic limestones, gypsum and halite of the "Lower Evaporites" (of marine origin) and, following an erosional unconformity, ends with the "Upper Evaporites" and associated fresh to brackish water deposits of the Lago Mare that are essentially of non-marine origin and contain a caspi-brackish ostracode fauna. The erosional unconformity between the "Lower and Upper Evaporites" is assumed to reflect the phase of most extreme sea level drawdown in the Mediterranean that caused significant erosion and localised channel entrenchment on the continental shelves and slopes

The Abad composite (SE Spain): a Messinian reference section for the Mediterranean and the APTS

A high-resolution integrated stratigraphy is presented for the Abad marls of the Sorbas and Nijar basins in SE Spain (preevaporitic Messinian of the Western Mediterranean). Detailed cyclostratigraphic and biostratigraphic analyses of partially overlapping subsections were needed to overcome stratigraphic problems in particular encountered at the complex transition from the Lower to the Upper Abad. The resulting Abad composite section contains a continuous stratigraphic record from the Tortonian/Messinian boundary up to the transition to the Messinian evaporites of the Yesares Member. All together, 18 calcareous plankton events were recognized which were shown to be synchronous throughout the Mediterranean by means of detailed (bed-to-bed) cyclostratigraphic correlations. The magnetostratigraphy allowed the identification of the four magnetic reversals of chron C3An in the Upper Abad. Details in the sedimentary cycle patterns allowed the Abad composite to be astronomically calibrated. This calibration to the 658N summer insolation curve of solution La90(1,1) yielded astronomical ages for all sedimentary cycles, calcareous plankton bioevents, ash layers and paleomagnetic reversals. Up to now, the Abad composite is the only astronomically well-calibrated section that provided a reliable cyclostratigraphy, magnetostratigraphy and calcareous plankton biostratigraphy. As such it will serve as a reference section both for the pre-evaporite Messinian in the Mediterranean as well as for the Messinian interval in the Astronomical Polarity Time Scale

Chronology, causes and progression of the Messinian salinity crisis

The Messinian salinity crisis is widely regarded as one of the most dramatic episodes of oceanic change of the past 20 or so million years (refs 1±3). Earliest explanations were that extremely thick evaporites were deposited in a deep and desiccated Mediterranean basin that had been repeatedly isolated from the Atlantic Ocean, but elucidation of the causes of the isolation--whether driven largely by glacio-eustatic or tectonic processes--have been ham pered by the absence of an accurate time frame. Here we present an astronomically calibrated chronology for the Mediterranean Messinian age based on an integrated high-resolution stratigraphy and `tuning' of sedimentary cycle patterns to variations in the Earth's orbital parameters. We show that the onset of the Messinian salinity crisis is synchronous over the entire Mediterranean basin, dated at 5:96 ± 0:02 million years ago. Isolation from the Atlantic Ocean was established between 5.59 and 5.33 million years ago, causing a large fall in Mediterranean water level followed by erosion (5.59±5.50 million years ago) and deposition (5.5-05.33 million years ago) of non-marine sediments in a large `Lago Mare' (Lake Sea) basin. Cyclic evaporite deposition is almost entirely related to circum-Mediterranean climate changes driven by changes in the Earth's precession, and not to obliquity-induced glacio-eustatic sea-level changes. We argue in favour of a dominantly tectonic origin for the Messinian salinity crisis, although its exact timing may well have been controlled by the ~400-kyr component of the Earth's eccentricity cycle

Evolution of the gulf of Cadiz margin and southwest Portugal contourite depositional system : Tectonic, sedimentary and paleoceanographic implications from IODP expedition 339

Acknowledgments This research used samples and data collected through the Integrated Ocean Drilling Program (IODP). The research was partially supported through the CTM 2008-06399-C04/MAR, CTM 2012-39599-C03, CGL2011-26493, CTM2012-38248, SA263U14, IGCP-619, INQUA 1204 and FWF P25831-N29 Projects. Some data were collected with 94-1090-C03-03 (FADO) and MAR-98-0209 (TASYO) Projects. Research was conducted in the framework of the Continental Margins Research Group of the Royal Holloway University of London, People and the Program (Marie Curie Actions) of the European Union's Seventh Framework Program FP7/2007-2013/ under REA Grant Agreement No. 290201 MEDGATE’. We are very grateful to REPSeOL, TGS–NOPEC, and the CSIC-Institut Jaume Almera (http://geodb.ictja.csic.es) for allowing us to use an unpublished seismic data from the Gulf of Cadiz. We thank J. Aguire (UGR, Spain) for comments and suggestions concerning the Pliocene and Quaternary outcrops, B. van den Berg (USAL) for organizing a thought-provoking field-trip to Cadiz, Spain in November, 2014, M. Ángel Caja, L. García Diego, and J. Tritlla (REPSOL) for provenance and diagenetic analysis of early Pliocene sandstones and debrites, and L.J. Lourens (Utrecht University) for providing us the eccentricity and 200-Kys glacio-eustatic sea-level curves included in the Figure 16. Both Prof. D.A.V. Stow (Heriot-Watt Univ., UK) and F.J. Hernández-Molina (RHUL, UK), as the main co-proponents of the IODP Proposal 644 and the co-chiefs of the IODP Exp. 339, thanks to IODP, Exp. IODP 339 Scientists; JR crew and technicians, as well as all people, institutions and companies involved in making IODP a success since 2003. Finally, we also thank the editor, Gert J. De Lange and the reviewers T. Mulder (Bourdeaux Univ.); D. Van Rooij (Ghent Univ) and J. Duarte (Monash Univ.) for their very positive and helpful feedback and discussions in publishing this research.Peer reviewedPublisher PD

Contourite depositional system after the exit of a strait: Case study from the late Miocene South Rifian Corridor, Morocco

Idealized facies of bottom current deposits (contourites) have been established for fine-grained contourite drifts in modern deep-marine sedimentary environments. Their equivalent facies in the ancient record however are only scarcely recognized due to the weathered nature of most fine-grained deposits in outcrop. Facies related to the erosional elements (i.e. contourite channels) of contourite depositional systems have not yet been properly established and related deposits in outcrop appear non-existent. To better understand the sedimentary facies and facies sequences of contourites, the upper Miocene contourite depositional systems of the South Rifian Corridor (Morocco) is investigated. This contourite depositional system formed by the dense palaeo-Mediterranean Outflow Water. Foraminifera assemblages were used for age-constraints (7.51 to 7.35 Ma) and to determine the continental slope depositional domains. Nine sedimentary facies have been recognized based on lithology, grain-size, sedimentary structures and biogenic structures. These facies were subsequently grouped into five facies associations related to the main interpreted depositional processes (hemipelagic settling, contour currents and gravity flows). The vertical sedimentary facies succession records the tectonically induced, southward migration of the contourite depositional systems and the intermittent behaviour of the palaeo-Mediterranean Outflow Water, which is mainly driven by precession and millennial-scale climate variations. Tides substantially modulated the palaeo-Mediterranean Outflow Water on a sub-annual scale. This work shows exceptional examples of muddy and sandy contourite deposits in outcrop by which a facies distribution model from the proximal continental slope, the contourite channel to its adjacent contourite drift, is proposed. This model serves as a reference for contourite recognition both in modern environments and the ancient record. Furthermore, by establishing the hydrodynamics of overflow behaviour a framework is provided that improves process-based interpretation of deep-water bottom current deposits

Evidence of early bottom water current flow after the Messinian Salinity Crisis in the Gulf of Cadiz

Highlights • Stratigraphic framework over the Miocene-Pliocene boundary at IODP Site U1387. • Abrupt sedimentary changes over the Miocene-Pliocene boundary. • Clear hints for onset of Mediterranean Outflow after the Messinian Salinity Crisis. • Evidence of bottom water currents in contouritic sedimentation and elevated Zr/Al. • Quiet, hemipelagic sediment deposition during the Messinian in the Gulf of Cadiz. Abstract Integrated Ocean Drilling Program (IODP) Expedition 339 cored multiple sites in the Gulf of Cadiz in order to study contourite deposition resulting from Mediterranean Outflow water (MOW). One hole, U1387C, was cored to a depth of 865.6 meters below seafloor (mbsf) with the goal of recovering the Latest Miocene to Pliocene transition in order to evaluate the history of MOW immediately after the end of the Messinian Salinity Crisis. To understand this history, an accurate age model for the succession is needed, but is challenging to construct, because the Miocene-Pliocene boundary is not marked by a clear biostratigraphic event in the Atlantic and coring gaps occur within the recovered stratigraphic record. These limitations are overcome by combining a variety of chronostratigraphic datasets to construct an age-model that fits the currently available age indicators and demonstrates that coring in Hole U1387C did indeed recover the Miocene-Pliocene boundary at around 826 mbsf. This boundary is associated with a distinct and abrupt change in depositional environment. During the latest Messinian, hemipelagic sediments exhibiting precession-induced climate variability were deposited. These are overlain by Pliocene sediments deposited at a much higher sedimentation rate, with much higher and more variable XRF-scanning Zr/Al ratios than the underlying sediment, and that show evidence of winnowing, particle sorting and increasing grain size, which we interpret to be related to the increasing flow of MOW. Pliocene sedimentary cyclicity is clearly visible in both the benthic δ18O record and the Zr/Al data and is probably also precessionally controlled. Two contouritic bigradational sandy-beds are revealed above the third sedimentary cycle of the Pliocene. On the basis of these results, we conclude that sedimentation associated with weak Mediterranean-Atlantic exchange, began in the Gulf of Cadiz virtually at or shortly after the Miocene-Pliocene boundary

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

The Sorbas basin of SE Spain contains one of the most complete sedimentary successions of the Mediterranean reflecting 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-opalrich 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