Abrupt episode of mid-Cretaceous ocean acidification triggered by massive volcanism

Large igneous province volcanic activity during the mid-Cretaceous approximately 94.5 million years ago triggered a global-scale episode of reduced marine oxygen levels known as Oceanic Anoxic Event 2. It has been hypothesized that this geologically rapid degassing of volcanic carbon dioxide altered seawater carbonate chemistry, affecting marine ecosystems, geochemical cycles, and sedimentation. Here, we report on two sites drilled by the International Ocean Discovery Program offshore of southwest Australia that exhibit clear evidence for suppressed pelagic carbonate sedimentation in the form of a stratigraphic interval barren of carbonate, recording ocean acidification during the event. We then use the osmium isotopic composition of bulk sediments to directly link this protracted ~600- kiloyear shoaling of the marine calcite compensation depth to the onset of volcanic activity. This decrease in marine pH was prolonged by biogeochemical feedbacks in highly productive regions that elevated heterotrophic respiration of carbon dioxide to the water column. A compilation of mid- Cretaceous marine stratigraphic records reveals a contemporaneous decrease of sedimentary carbonate content at continental slope sites globally. Thus, we contend that changes in marine carbonate chemistry are a primary ecological stress and important consequence of rapid emission of carbon dioxide during many large igneous province eruptions in the geologic past

Expedition 369 methods

This chapter documents the procedures and methods used in the shipboard laboratories during International Ocean Discovery Program (IODP) Expedition 369. This introductory section in particular provides a rationale for the site locations and an overview of IODP depth conventions, curatorial procedures, and general core handling/analyses during Expedition 369. Subsequent sections describe specific laboratory procedures and instruments in more detail. This information only applies to shipboard work described in the Proceedings volume; methods used in shore-based analyses of Expedition 369 samples and/or data will be described in various scientific contributions in the open peer-reviewed literature and the Expedition Research Results chapters of this Proceedingsvolume

Late Cretaceous orbitally-paced carbon isotope stratigraphy from the Bottaccione Gorge (Italy)

A refined astronomical tuning of the upper Albian-lower Campanian is proposed from the Bottaccione reference section (Gubbio, central Italy). Long-term eccentricity cycles filtered from a high-resolution delta C-13 record were tuned to the highly stable 405 kyr cycles of the new La2010 astronomical solution for the Earth's orbital elements. The achieved orbital tuning provides a new precise, and accurate age model for dating biostratigraphic, magnetostratigraphic and carbon isotope events through a similar to 23 Myr long record. Cycles of similar to 8.0, 4.7, 3.4 and similar to 2.4 Myr modulate the entire delta C-13 record, thus extending their detection from the Cenozoic to similar to 100 Ma and represent primary and stable long-term oscillation modes of Earth's climate-ocean system. Although an ultimate driver of these long-term periodicities is lacking, we speculate that specifically the periodicity at 4.7 Myr, represents a homologue of the present eccentricity grand-cycles, evolved by the chaotic behaviour of solar system planets during the Mesozoic. The long-term periodicities potentially reflect an unexplored expression of the low-frequency response of the carbon cycle to global biogeochemical dynamics of major nutrients, particularly phosphorus, associated with modulation of inputs to the ocean in turn triggered by high-order marine transgressions and formation of highly productive shelf seas. This very long-term eccentricity control, modulated by periodic low-energy cycles, is suggested to play a crucial role in carbon cycling, controlling a chain of climate sensitive global biogeochemical processes on the Earth. Finally, these grand-cycles provide a potential tool for geological correlation and provide a robust constraint for accurate calculation of the orbital evolution of the Solar System. (C) 2013 Elsevier B.V. All rights reserved

Does large igneous province volcanism always perturb the mercury cycle? Comparing the records of Oceanic Anoxic Event 2 and the end-Cretaceous to other Mesozoic events

This is the author accepted manuscript. The final version is available via the DOI in this recordMercury (Hg) is increasingly being used as a sedimentary tracer of Large Igneous Province (LIP) volcanism, and supports hypotheses of a coincidence between the formation of several LIPs and episodes of mass extinction and major environmental perturbation. However, numerous important questions remain to be answered before Hg can be claimed as an unequivocal fingerprint of LIP volcanism, as well as an understanding of why some sedimentary records document clear Hg enrichment signals whilst others do not. Of particular importance is evaluating the impact of different volcanic styles on the global mercury cycle, as well as the role played by depositional processes in recording global Hg-cycle perturbations. Here, new mercury records of Cretaceous Oceanic Anoxic Event 2 (OAE 2: ~94 Ma) and the latest Cretaceous (~67 to 66.0 Ma) are presented. OAE 2 is associated with the emplacement of multiple, predominantly submarine, LIPs; the latest Cretaceous with subaerial volcanism of the Deccan Traps. Both of these connections are strongly supported by previously published trends towards unradiogenic osmium- (Os) isotope values in globally distributed sedimentary records. Hg data from both events show considerable variation between different locations, attributed to the effectiveness of different sediment types in registering the Hg signal, with lithologically homogeneous records documenting more clear Hg enrichments than sections with major changes in lithology such as limestones to claystones or organic-rich shales. Crucially, there is no geographically consistent signal of sedimentary Hg enrichment in stratigraphic records of either OAE 2 or the latest Cretaceous that matches Os-isotope evidence for LIP emplacement, indicating that volcanism did not cause a global Hg perturbation throughout the entire eruptive history of the LIPs formed at those times. It is suggested that the discrepancy between Os-isotope and Hg trends in records of OAE 2 is caused by the limited dispersal range of Hg emitted from submarine volcanoes compared to the global-scale distribution of Os. A similar lack of correlation between these two proxies in uppermost Cretaceous strata indicates that, although subaerial volcanism can perturb the global Hg cycle, not all subaerial eruptions will do so. These results highlight the variable impact of different volcanogenic processes on the efficiency of Hg dispersal across the globe. Factors that could influence the impact of LIP eruptions on the global mercury cycle include submarine versus subaerial volcanism, volcanic intensity or explosivity, and the potential contribution of thermogenic mercury from reactions between ascending magma and surrounding organic-rich sediments.We acknowledge the UK Natural Environment Research Council Grant NE/G01700X/1 (to Tamsin Mather), PhD studentship NE/L501530/1 (to Lawrence Percival), Grant NE/H020756/1 (to Ian Jarvis), the European Commission (FP7/2007–2013 grant number 215458), National Science Foundation Grant EAR0643290 (to Bradley Sageman and Jennifer McElwain), Shell International Exploration and Production Inc., and the Leverhulme Trust for funding

Specific coronary drug-eluting stents interfere with distal microvascular function after single stent implantation in pigs.

Objectives The aim of this study was to compare the effects of single drug-eluting stents (DES) on porcine coronary function distal to the stent in vivo and in vitro. Background The mechanism of endothelial dysfunction occurring in human coronary conduit arteries up to 9 months after DES implantation is unknown. Methods A sirolimus-eluting stent (SES), paclitaxel-eluting stent (PES), and a bare-metal stent (BMS) were implanted in the 3 coronary arteries of 11 pigs. After 5 weeks, in vivo responses in distal coronary flow to different doses of bradykinin (BK) and nitrates were measured. In vitro, vasodilation to BK and nitrates, as well as vasoconstriction to endothelin (ET)-1 were assessed in both distal coronary conduit and small arteries. In addition, contributions of nitric oxide (NO) and endothelium-derived hyperpolarizing factors (EDHFs) and cyclic guanosine monophosphate (cGMP) responses to BK-stimulation were determined in vitro. Results Both DES did not alter in vivo distal vasomotion. In vitro distal conduit and small arterial responses to BK were also unaltered; DES did not alter the BK-induced increase in cGMP. However, after NO synthase blockade, PES showed a reduced BK-response in distal small arteries as compared with BMS and SES (p <0.05). The ET-1–induced vasoconstriction and vascular smooth muscle cell function were unaltered. Conclusions In this study of single stenting in healthy porcine coronaries for 5 weeks, SES did not affect distal coronary vascular function, whereas PES altered distal endothelial function of small arteries under conditions of reduced NO bioavailability. Therefore, specifically the EDH-component of microvascular function seems affected by PES

Cyclostratigraphy and astronomical tuning of the Late Maastrichtian at Zumaia (Basque county, Northern Spain)

The standard Geological Time Scale for the Cretaceous is still largely based on seafloor anomaly profiles Combined with radio-isotopic tie-points. The astronomical tuned time scale with its much higher resolution and accuracy has recently been extended to the K/Pg-boundary and is being extended into the Cretaceous. To construct such a time scale for the Cretaceous, we selected the upper Maastrichtian of the Zumaia section in the Basque country (northern Spain) which contains a cyclic alternation of Limestones and marls deposited in a hemipelagic setting. The Paleogene portion of the Zumaia section has previously been studied for a joint cyclostratigraphic–radioisotopic intercalibration of the age of the K/Pg boundary. Here we present a high-resolution cyclostratigraphic framework for the upper Maastrichtian (Latest Cretaceous) of the Zumaia section in the Basque country (northern Spain), with new biostratigraphic and magnetostratigraphic data. Bed-to-bed correlation with the nearby Sopelana section provides additional bio-and magnetostratigraphic constraints. The stacking pattern of the lithologies shows a hierarchy that reflects the combined influence of the orbital parameters of precession and eccentricity. This is confirmed by time series analyses of lithological and geochemical data, indicating a strong influence of eccentricity-modulated precession on latest Cretaceous climate. The expression of the 405-kyr eccentricity cycle serves as primary signal for astronomical tuning. We provide two tuning options depending on absolute K/Pg-boundary ages of65.56 and 65.97 Ma. The logged part of the section encompasses nine and a half 405-kyr cycles in total and spans 3.9 Myr. The acquired cyclostratigraphic framework provides ages for characteristic planktonic foraminiferal events, magnetic reversals and carbon isotope excursions and resolves the late Maastrichtian time scale in unprecedented detail with relative age uncertainties <100 kyr.The high resolution and large amplitude of shifts in δ¹³C on the 405-kyr and 1.2-Myr scales allow for global correlation and may shed more light on the orbital pacing of Late Cretaceous climate