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The first record of the Early Toarcian Oceanic Anoxic Event (c. 183 Ma) from the Southern Hemisphere is described from the Neuquen Basin, Argentina, identified chemostratigraphically on the basis of a relative increase in marine organic carbon and a characteristic negative carbon-isotope excursion ([[delta].sup.13][C.sub.org]) in bulk rock and fossil wood. The negative excursion of -6 [per thousand] in bulk organic carbon (falling to -31.3 [per thousand]) crosses the boundary of the tenuicostatum--hoelderi Andean ammonite Zones, equivalent to the tenuicostatum--falciferum/serpentinum zones of Europe. These data indicate that the Early Toarcian Oceanic Anoxic Event was a global phenomenon. Supplementary material: A detailed stratigraphic log, chemostratigraphic data and nannofossil data are available at http:// www.geolsoc.org.uk/SUP18411. doi: 10.1144/0016-76492010-025.

We present new, detailed carbon-isotope records for bulk carbonate, total organic carbon (TOC) and phytane from three key sections spanning the Cenomanian--Turonian boundary, interval (Eastbourne, England; Gubbio, Italy; Tarfaya, Morocco), with the purpose of establishing a common chemostratigraphic framework for Oceanic Anoxic Event (OAE) 2. Isotope curves from all localities are characterized by a positive carbon-isotope excursion of c. 4[per thousand] for TOC and phytane and c. 2.5[per thousand] for carbonate, although diagenetic overprinting appears to have obliterated the primary carbonate carbon-isotope signal in at least part of the Tarfaya section. Stratigraphically, peak [[delta].sup.13]C values for all components are followed by intervals of high, near-constant [[delta].sup.13]C in the form of an isotopic plateau. Recognition of an unambiguous return to background [[delta].sup.13]C values above the plateau is, however, contentious in all sections, hence no firm chemostratigraphic marker for the end-point of the positive isotopic excursion can be established. The stratigraphically consistent first appearance of the calcarcous nannofossil Quadrum gartneri at or near the Cenomanian--Turonian boundary as established by ammonite stratigraphy, in conjunction with the end of the [[delta].sup.13]C maximum characteristic of the isotopic plateau, provides a potentially powerful tool for delimiting the stratigraphic extent and duration of OAE 2. This Oceanic Anoxic Event is demonstrated to be largely, if not wholly, confined to the latest part of the Cenomanian stage. Keywords: Oceanic Anoxic Event 2, Eastbourne, England, Gubbio, Italy, Tarfaya, Morocco, [sup.13]C.

Carbon- and oxygen-isotope stratigraphy of English Chalk and Italian Scaglia show similar trends in oxygen-isotope in various Chalk sections despite individual variation in values that are diagenesis-dependent. Warming till the Cenomanian-Turonian boundary interval and subsequent cooling are observed in the East Kent section. Climatic deterioration and CO2 drawdown result from regional organic-carbon burial.

A detailed isotopic profile is presented for a stratigraphically expanded Cenomanian-Turonian boundary section in Chalk facies exposed at Eastbourne, Sussex and compared with data from Pueblo, Colorado. In both sections macro- and micropalaeontological markers (first appearances and disappearances) are well-constrained, and their relative positions and relationship to the structure of the carbon-isotope curve are identical. This consistent relationship between two independent phenomena, one geochemical, the other biostratigraphical, is taken as evidence for the likely synchroneity of both the biostratigraphical markers and the carbon-isotope excursion in these two areas. This interpretation contrasts with suggestions made recently by other authors whose data have been taken to imply a lack of correlation between the carbon-isotope excursion in Europe and North America.

Presents data from the Belemnite Marls, Dorset, southern England, using cyclostratigraphy and the early Jurassic timescale. Sedimentology and diagenesis; Paleographic setting; Analysis of time series; Nature of bundle cycles and paleoclimatic variations in early Jurassic time.

The Sogno Core represents one of the deepest pelagic records of the Toarcian Oceanic Anoxic Event (T-OAE) in the Alpine-Mediterranean Tethys. New sedimentological, elemental, Rock-Eval, and biomarker data are presented here, with the aim of reconstructing the depositional conditions that characterized the sedimentation of this succession during the broad positive carbon-isotope excursion of the T-OAE, and its negative isotopic anomaly (Jenkyns Event). Higher Mn xs concentrations, inversely correlated with the δ18O curve, were observed starting slightly below the onset level of the Jenkyns Event up to the lowermost part of the negative carbon-isotope anomaly, reflecting a combination of a gradual warming and a progressive increase in fresh waters delivered by runoff. Increased weathering intensity was accompanied by enhanced detrital input with higher concentrations in lithogenic elements, and by a relative increase in palaeoproductivity, consistently with higher Si xs concentrations and changes in calcareous nannoplankton assemblages. The enhanced fresh-water input favored water-column stratification, less efficient deep-water circulation and oxygen depletion. Except for two discrete black shales characterized by anoxic pore waters, redox conditions at Sogno turned at maximum suboxic, as indicated by rare to absent bioturbation, limited enrichments in redox-sensitive elements, and molecular biomarkers. The Sogno Core record shows that dominant oxic–suboxic conditions were present also at bathyal depths in the Alpine-Mediterranean Tethys during the Jenkyns Event, thereby contrasting with the anoxic–euxinic environments present both in the shallower water basins and sub-basins of epicontinental northern Europe and, locally, in the relatively deep-water areas of the Alpine Tethys. • In the Lombardy Basin suboxic to oxic conditions prevailed during the Toarcian Oceanic Anoxic Event. • Water stratification caused by enhanced runoff and warmer conditions favoured the onset of bottom-water suboxia. • Reducing conditions became generally more severe around the lowest point in the δ13C trough that defines the Jenkyns Event. • The Alpine-Mediterranean Tethys was mainly characterized by suboxic conditions during the Toarcian Oceanic Anoxic Event. [ABSTRACT FROM AUTHOR]