Patrick Grunert

Onset of Mediterranean outflow into the North Atlantic

The when of Mediterranean water outflow The trickle of water that began to flow from the Mediterranean Sea into the Atlantic Ocean after the opening of the Strait of Gibraltar turned into a veritable flood by the end of the Pliocene 2 to 3 million years ago. It then began to influence large-scale ocean circulation in earnest. Hernández-Molina et al. describe marine sediment cores collected by an ocean drilling expedition (see the Perspective by Filippelli). The results reveal a detailed history of the timing of Mediterranean outflow water activity and show how the addition of that warm saline water to the cooler less-salty waters of the Atlantic was related to climate changes, deep ocean circulation, and plate tectonics. Science, this issue p. 1244; see also p. 1228 Mediterranean outflow water began to enter the Atlantic and influence global ocean circulation by the late Pliocene. [Also see Perspective by Filippelli] Sediments cored along the southwestern Iberian margin during Integrated Ocean Drilling Program Expedition 339 provide constraints on Mediterranean Outflow Water (MOW) circulation patterns from the Pliocene epoch to the present day. After the Strait of Gibraltar opened (5.33 million years ago), a limited volume of MOW entered the Atlantic. Depositional hiatuses indicate erosion by bottom currents related to higher volumes of MOW circulating into the North Atlantic, beginning in the late Pliocene. The hiatuses coincide with regional tectonic events and changes in global thermohaline circulation (THC). This suggests that MOW influenced Atlantic Meridional Overturning Circulation (AMOC), THC, and climatic shifts by contributing a component of warm, saline water to northern latitudes while in turn being influenced by plate tectonics.

Deciphering bottom current velocity and paleoclimate signals from contourite deposits in the Gulf of Cádiz during the last 140 kyr: An inorganic geochemical approach

Contourites in the Gulf of Cadiz (GC) preserve a unique archive of Mediterranean Outflow Water (MOW) variability over the past 5.3 Ma. In our study, we investigate the potential of geochemical data obtained by XRF scanning to decipher bottom current processes and paleoclimatic evolution at two different sites drilled during IODP Expedition 339 through contourites in the northern GC: Site U1387, which is bathed by the upper MOW core, and Site U1389, located more proximal to the Strait of Gibraltar. The lack of major downslope transport during the Pleistocene makes both locations ideally suited for our study. The results indicate that the Zr/Al ratio, representing the relative enrichment of heavy minerals (zircon) over less dense alumnosilicates under fast bottom current flow, is the most useful indicator for a semiquantitative assessment of current velocity. Although most elements are biased by current-related processes, the bromine (Br) record, representing organic content, preserves the most pristine climate signal rather independent of grain-size changes. Hence, Br can be used for chronostratigraphy and site-to-site correlation in addition to stable isotope stratigraphy. Based on these findings, we reconstructed MOW variability for Marine Isotope Stages (MIS) 1–5 using the Zr/Al ratio from Site U1387. The results reveal abrupt, millennial-scale variations of MOW strength during Greenland Stadials (GS) and Interstadials (GI) with strong MOW during GS and glacial Terminations and a complex behavior during Heinrich Stadials. Millennial-scale variability persisting during periods of poorly expressed GS/GI cyclicities implies a strong internal oscillation of the Mediterranean/North Atlantic climate system.

Integrated high-resolution stratigraphy of a Middle to Late Miocene sedimentary sequence in the central part of the Vienna Basin

Integrated high-resolution stratigraphy of a Middle to Late Miocene sedimentary sequence in the central part of the Vienna Basin In order to determine the relative contributions of tectonics and eustasy to the sedimentary infill of the Vienna Basin a high-resolution stratigraphic record of a Middle to Late Miocene sedimentary sequence was established for a well (Spannberg-21) in the central part of the Vienna Basin. The well is located on an intrabasinal high, the Spannberg Ridge, a location that is relatively protected from local depocentre shifts. Downhole magnetostratigraphic measurements and biostratigraphical analysis form the basis for the chronostratigraphic framework. Temporal gaps in the sedimentary sequence were quantified from seismic data, well correlations and high-resolution electrical borehole images. Stratigraphic control with this integrated approach was good in the Sarmatian and Pannonian, but difficult in the Badenian. The resulting sedimentation rates show an increase towards the Upper Sarmatian from 0.43 m/kyr to > 1.2 m/kyr, followed by a decrease to relatively constant values around 0.3 m/kyr in the Pannonian. The sequence reflects the creation of accommodation space during the pull-apart phase of the basin and the subsequent slowing of the tectonic activity. The retreat of the Paratethys from the North Alpine Foreland Basin during the Early Sarmatian temporarily increased the influx of coarsergrained sediment, but eventually the basin acted mostly as a by-pass zone of sediment towards the Pannonian Basin. At a finer scale, the sequence exhibits correlations with global eustasy indicators, notably during the Sarmatian, the time of greatest basin subsidence and full connectivity with the Paratethyan system. In the Pannonian the eustatic signals become weaker due to an increased isolation of the Vienna Basin from Lake Pannon.

Upwelling conditions in the Early Miocene Central Paratethys Sea

Upwelling conditions in the Early Miocene Central Paratethys Sea Evidence for regional upwelling conditions in the Central Paratethys Sea is presented for mid-Burdigalian (early Ottnangian) times. The oceanographic phenomenon is detected in clay-diatomite successions along the steep escarpment of the Bohemian Massif in the eastern North Alpine Foreland Basin. Interpretations are based on a multiproxy data-set including published sedimentological and paleontological data, newly performed stable isotope measurements (δ18O, δ13C) of foraminifers and bulk sediment samples, and analyses of dinoflagellate cyst assemblages. The revealed stable isotope values of planktonic foraminifers point to upwelling: low δ13C values indicate strong mixing of surface waters with rising nutrient-rich waters, high δ18O values reflect cool sea surface temperatures (SST). Temperature calculations give SSTs ranging from 10-14 °C. Cool SSTs and high productivity are additionally supported by bulk sediment analyses. Assemblages of dinoflagellate cysts indicate a distal-shelf environment with nutrient-rich waters. Westerly winds and tidal currents are discussed as potential driving forces behind the local upwelling event. As mid-Burdigalian geography favoured strong current patterns in the Central Paratethys as documented in the sedimentary record from the Rhône Basin to Hungary upwelling might have been a more common phenomenon in this epicontinental sea than currently known.

Stratigraphic re-evaluation of the stratotype for the regional Ottnangian stage (Central Paratethys, middle Burdigalian)

The Ottnangian stage represents the middle Burdigalian (c. 18.1-17.2 Ma) within the regional stratigraphic concept for the Central Paratethys. The section Ottnang-Schanze in the North Alpine Foreland Basin of Upper Austria has been defined as its stratotype by Rogl et al. (1973). We present an updated strati- graphic evaluation of the section based on biostratigraphy of foraminifers, dinoflagellate cysts and calcare- ous nannoplankton as well as magnetostratigraphy. In agreement with earlier studies, assemblages of benthic foraminifers (co-occurrence of Amphicoryna ott - nangensis and Sigmoilopsis ottnangensis, mass-occurrences of Lenticulina inornata) document a late early Ottnangian age. Dinoflagellate cyst Exochosphaeridium insigne is recorded for the first time in the early Ott- nangian and its occurrence together with Apteodinium spiridoides, Cordosphaeridium cantharellus and Glaphyrocysta reticulosa s. l. extends the regional dinoflagellate zone Ein from the middle to the early Ott - nangian. On a global scale, the revealed marker species indicate zone D17a (middle-late Burdigalian). Cal- careous nannoplankton assemblages with the very rare occurrence of Sphenolithus cf. belemnos and S. aff. heteromorphus show remarkable affinities to Mediterranean nannoplankton zone MNN3b. Together with the frequent occurrence of Helicosphaera ampliaperta and the absence of Triquetrorhabdulus carinatus an assignment to standard nannoplankton zone NN3 (early-middle Burdigalian) is indicated. Magnetostratigraphy revealed an inverse polarisation for the outcrop. In combination with the biostrati- graphic age constraints and the present correlation of the Ottnangian to the Bur3 sea-level cycle the section belongs to polarity chron C5Dr.2r. For the first time, an absolute age between 17.95-18.056 Ma for the stra- totype can be inferred.

A new Early Miocene barnacle lineage and the roots of sea-turtle fouling Chelonibiidae (Cirripedia, Balanomorpha)

The origin of the mainly sea-turtle fouling balanomorph family Chelonibiidae is still poorly documented. Aside from an Eocene erratic specimen assigned to an extinct subfamily, the extant subfamily Chelonibiinae did not appear in the fossil record before the Late Miocene. Protochelonibiinae Harzhauser & Newman subfam. nov. is here introduced as an extinct sister-group of Chelonibiinae. The subfamily is known so far only from the proto-Mediterranean and the Paratethys seas and ranged from Early Miocene to Late Pliocene. Members of the subfamily are characterized by large walls with tripartite rostra which display distinct sutures on the external surface. The tripartite rostrum, however, has evolved independently several times in the evolution of the balanomorphs and cannot be treated as synapomorphy. The subfamily comprises one new genus and two species. Protochelonibia Harzhauser & Newman gen. nov. is the type genus of Protochelonibiinae and Protochelonibia submersa Harzhauser & Newman sp. nov. is introduced as type species of this genus. Chelonobia Capellinii [sic] De Alessandri, 1895, from the Late Pliocene of Italy, reassigned as Protochelonibia capellinii (De Alessandri, 1895), is the youngest record of the subfamily. With the onset of the Pleistocene, Protochelonibiinae were fully replaced by Chelonibiinae, which had co-existed with Protochelonibiinae from the Late Miocene to the Pliocene. Surface imprints from the host substratum in one specimen of P. submersa are reminiscent of the sculpture of Caretta carapaces. Therefore, the Aquitanian Protochelonibia may be the earliest record of sea-turtle fouling in barnacles.

Middle and late Badenian palaeoenvironments in the northern Vienna Basin and their potential link to the Badenian Salinity Crisis

Abstract Hydrocarbon exploration in the Bernhardsthal and Bernhardsthal-Sued oil fields documents an up to 2000 m thick succession of middle and upper Badenian deposits in this part of the northern Vienna Basin (Austria). Based on palaeontological analyses of core-samples, well-log data and seismic surveys we propose an integrated stratigraphy and describe the depositional environments. As the middle/late Badenian boundary is correlated with the Langhian/Serravallian boundary, the cores capture the crucial phase of the Middle Miocene Climate Transition. The middle Badenian starts with a major transgression leading to outer neritic to upper bathyal conditions in the northern Vienna Basin, indicated by Bathysiphon-assemblages and glass-sponges. A strong palaeo-relief and rapid synsedimentary subsidence accentuated sedimentation during this phase. The middle/late Badenian boundary coincides with a major drop of relative sea level by about 200 m, resulting in a rapid shift from deeper marine depositional environments to coastal and freshwater swamps. In coeval marine settings, a more than 100 m thick unit of anhydrite-bearing clay formed. This is the first evidence of evaporite precipitation during the Badenian Salinity Crisis in the Vienna Basin. Shallow lagoonal environments with diverse and fully marine mollusc and fish assemblages were established during the subsequent late Badenian re-flooding. In composition, the mollusc fauna differs considerably from older ones and is characterized by the sudden appearance of species with eastern Paratethyan affinities.