Description: Biological activity introduces variability in element incorporation during calcification and thereby decreases the precision and accuracy when using foraminifera as geochemical proxies in paleoceanography. This so-called 'vital effect' consists of organismal and environmental components. Whereas organismal effects include uptake of ions from seawater and subsequent processing upon calcification, environmental effects include migration- and seasonality-induced differences. Triggering asexual reproduction and culturing juveniles of the benthic foraminifer Ammonia tepida under constant, controlled conditions allow environmental and genetic variability to be removed and the effect of cell-physiological controls on element incorporation to be quantified. Three groups of clones were cultured under constant conditions while determining their growth rates, size-normalized weights and single-chamber Mg/Ca and Sr/Ca using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Results show no detectable ontogenetic control on the incorporation of these elements in the species studied here. Despite constant culturing conditions, Mg/Ca varies by a factor of similar to 4 within an individual foraminifer while intra-individual Sr/Ca varies by only a factor of 1.6. Differences between clone groups were similar to the intra-clone group variability in element composition, suggesting that any genetic differences between the clone-groups studied here do not affect trace element partitioning. Instead, variability in Mg/Ca appears to be inherent to the process of bio-calcification itself. The variability in Mg/Ca between chambers shows that measurements of at least 6 different chambers are required to determine the mean Mg/Ca value for a cultured foraminiferal test with a precision of 〈= 10%

Description: Highlights • Sub-basalt imaging improvement on the Vøring Margin • Definition of a new seismic facies unit: the Lower Series Flows • Significant organic carbon content within the melting crustal segment • Apectodinium augustum marker for the PETM is reworked into the Lower Series Flows • The Lower Series Flows, early Eocene in age, predate the Vøring Margin breakup Abstract Improvements in sub-basalt imaging combined with petrological and geochemical observations from the Ocean Drilling Program (ODP) Hole 642E core provide new constraints on the initial breakup processes at the Vøring Margin. New and reprocessed high quality seismic data allow us to identify a new seismic facies unit which we define as the Lower Series Flows. This facies unit is seismically characterized by wavy to continuous subparallel reflections with an internal disrupted and hummocky shape. Drilled lithologies, which we correlate to this facies unit, have been interpreted as subaqueous flows extruding and intruding into wet sediments. Locally, the top boundary of this facies unit is defined as a negative in polarity reflection, and referred as the K-Reflection. This reflection can be correlated with the spatial extent of pyroclastic deposits, emplaced during transitional shallow marine to subaerial volcanic activities during the rift to drift transition. The drilled Lower Series Flows consist of peraluminous, cordierite bearing peperitic basaltic andesitic to dacitic flows interbedded with thick volcano-sedimentary deposits and intruded sills. The peraluminous geochemistry combined with available C (from calcite which fills vesicles and fractures), Sr, Nd, and Pb isotopes data point towards upper crustal rock-mantle magma interactions with a significant contribution of organic carbon rich pelagic sedimentary material during crustal anatexis. From biostratigraphic analyses, Apectodinium augustum was found in the The Lower Series Flows. This species is a marker for the Paleocene – Eocene Thermal Maximum (PETM). However, the absence of very low carbon isotope values (from bulk organic matter), that characterize the PETM, imply that A.augustum was reworked into the early Eocene sediments of this facies unit which predate the breakup time of the Vøring Margin. Finally, a plausible conceptual emplacement model for the Lower Series Flows facies unit is proposed. This model comprises several stages: (1) the emplacement of subaqueous peperitic basaltic andesitic flows intruding and/or extruding wet sediments; (2) a subaerial to shallow marine volcanism and extrusion of dacitic flows; (3) a proto-breakup phase with intense shallow marine to subaerial explosive volcanism responsible for pyroclastic flow deposits which can be correlated with the seismic K-Reflection and (4) the main breakup stage with intense transitional tholeiitic MORB-type volcanism and large subsidence concomitant with the buildup of the Seaward Dipping Reflector wedge.

Description: Early diagenetic features are noticed in the vicinity of carbonate platforms. Planktonic foraminifera of two tropical Atlantic deep-sea sediment cores show the strict relation between micro-scale euhydral crystallites of inorganic precipitates, higher oxygen isotope values and Mg/Ca ratios, and lower Sr/Ca ratios than expected for their pelagic environment in the time interval of ~100 000–550 000 calendar years before present. Laser ablation Mg/Ca (Sr/Ca) of crystallite-bearing foraminiferal chamber walls revealed 4–6 times elevated (2–3 times depleted) ratios, when ablating the diagenetic overgrowth. Crystalline overgrowth in proportion of 10–20% are estimated to cause the observed geochemical alteration. The extent of foraminiferal Mg/Ca alteration, moreover, seems to be controlled by the composition of the bulk sediment, especially the content of high-magnesium calcite. Anomalous ratios of 〉6 mmol/mol only occur, when high-magnesium calcite has dissolved within the sediment. The older parts (back to ~800 kyrs) of the records are characterized by similar trends of Mg/Ca and Sr/Ca. We discuss possible scenarios to accommodate the obtained geochemical information.

Description: The late Miocene Messinian Salinity Crisis (MSC) was an extraordinary geologic event in the Mediterranean Basin marked by massive salt accumulation and presumably basin desiccation as a consequence of the reduced water exchange with the Atlantic Ocean. The discovery of a desiccation deposit in the Black Sea, the so-called Pebbly Breccia unit, was used to claim that the Black Sea also became desiccated during the MSC. Erosional features interpreted from seismic profiles of the Black Sea margin, correlated by some to the Pebbly Breccia unit, were used to support this hypothesis. However, the age of the Pebbly Breccia is poorly constrained, and its origin and relevance to the MSC subject to controversy. Here we present new biostratigraphic (dinoflagellate cyst) data from two key sedimentary successions located in a deep and a marginal setting of the Black Sea Basin. These records demonstrate that the Pebbly Breccia predates the Mediterranean water-level drop during the MSC. We argue that the presumed erosional features in the Black Sea Basin are not related to the MSC and likely represent an older Miocene event.

Description: The Late Cretaceous Oceanic Anoxic Event 2 (OAE2; ca. 94 Ma) was one of the largest global carbon cycle perturbations during the Phanerozoic. OAE2 represents an important, although extreme, case study for modern trends because widespread anoxia and enhanced organic carbon burial during OAE2 were linked to exceptionally warm climates and high atmospheric CO 2 concentrations. However, the consequences of this warmth for the hydrological cycle remain poorly understood, hampering our understanding of its impact on biogeochemical cycles during this greenhouse episode. Here we show evidence for changes in the hydrological cycle during OAE2 based on combined geochemical and palynological data for the stratigraphically expanded coastal OAE2 succession at Bass River, located on the New Jersey shelf (Ocean Drilling Program Leg 174AX), eastern United States. Paleothermometry, based on TEX 86 , indicates sea-surface warming at the onset of OAE2 and a subsequent pronounced cooling event. Palynological data show that these changes in temperature were associated with strong variations in precipitation and runoff. We suggest that an acceleration of the hydrological cycle during OAE2 played a key role in supplying nutrients to coastal waters and enhancing stratification, thus contributing to the development of ocean anoxia.

Description: We present a Paleocene–Eocene (ca. 60–52 Ma) sea-surface temperature record from sediments deposited in the epicontinental West Siberian Sea. TEX 86 paleothermometry indicates long-term late Paleocene (~17 °C ca. 59 Ma) to early Eocene (26 °C at 52 Ma) sea-surface warming, consistent with trends previously observed for the Southern Ocean and deep oceans. Photic zone and seafloor anoxia developed as temperatures rose by 7 °C to ~27 °C during the Paleocene–Eocene Thermal Maximum (PETM). Based on paired palynological and TEX 86 data, we suggest that the minimum temperature for the proliferation of Paleocene and early Eocene members of the dinoflagellate family Wetzelielloideae, which includes the PETM marker taxon Apectodinium , was ~20 °C.

Description: The mode and vigor of the global oceanic circulation critically depend on the salinity of (sub)surface water masses advected to the loci of deep-water formation. Within the Atlantic meridional overturning circulation (AMOC), an important supplier of high-salinity waters is the Mediterranean Outflow Water (MOW), discharging into the North Atlantic via the Strait of Gibraltar. Despite its importance for the North Atlantic salinity budget, the long-term dynamics of MOW production have remained poorly understood. Here we present high-resolution records of bottom-current velocity from three drill sites within the Gulf of Cádiz that document a persistent low-latitude forcing of MOW flow speed over the past ~150 k.y. We demonstrate that the African monsoon is the predominant driver of orbital-scale MOW variability via its influence on the freshwater budget of the eastern Mediterranean Sea. Consequently, MOW formation fluctuates in concert with orbital precession overprinted by centennial-scale oscillations of high-latitude origin. We further document that Northern Hemisphere summer insolation minima stimulate maximal injection of MOW-derived salt into the North Atlantic, likely strengthening the intermediate AMOC branch. The direct coupling of MOW dynamics to low-latitude climate forcing represents a hitherto neglected process for propagating (sub)tropical climate signals into the high northern latitudes.

Description: Global ocean temperatures rapidly warmed by ~5°C during the Paleocene-Eocene Thermal Maximum (PETM; ~56 million years ago). Extratropical sea surface temperatures (SSTs) met or exceeded modern subtropical values. With these warm extratropical temperatures, climate models predict tropical SSTs 〉35°C—near upper physiological temperature limits for many organisms. However, few data are available to test these projected extreme tropical temperatures or their potential lethality. We identify the PETM in a shallow marine sedimentary section deposited in Nigeria. On the basis of planktonic foraminiferal Mg/Ca and oxygen isotope ratios and the molecular proxy TEX86H , latest Paleocene equatorial SSTs were ~33°C, and TEX86H indicates that SSTs rose to 〉36°C during the PETM. This confirms model predictions on the magnitude of polar amplification and refutes the tropical thermostat theory. We attribute a massive drop in dinoflagellate abundance and diversity at peak warmth to thermal stress, showing that the base of tropical food webs is vulnerable to rapid warming.

Description: During the Phanerozoic, Earth has experienced a number of transient global warming events associated with major carbon cycle perturbations. Paradoxically, many of these extreme greenhouse episodes are preceded or followed by cold climate, perhaps even glacial conditions, as inferred from the occurrence of glendonites in high latitudes. Glendonites are pseudomorphs of ikaite (CaCO 3 ·6H 2 O), a hydrated carbonate mineral increasingly stable at low temperatures. Here, we show that methane seepage and oxidation provide an overriding control on Mesozoic glendonite formation (i.e., ikaite fossilization). Geochemical and petrological analyses of 33 Early Jurassic to Early Cretaceous glendonites from five sections in Siberia (Russia) reveal that most of their infilling carbonate phases are reminiscent of methane-derived authigenic carbonates. Bulk glendonites and surrounding sediments exhibit exceptionally high and low carbon isotope values (+20 to –45 VPDB [Vienna Peedee belemnite]), typical for carbon sources linked to methane generation and oxidation. Gas inclusion data confirm the presence of methane and longer-chain hydrocarbon gases, suggesting a thermogenic source for the methane. Glendonite-bearing layers can be traced for hundreds of kilometers, suggesting widespread trapping of methane in the sub-seafloor during the Jurassic. As such, glendonites constitute an unexplored archive for detecting past episodes of methane release and oxidation in polar settings.