Abstract Recent ichnological analysis conducted in two sections (Rodiles and Lastres) of the Asturian Basin revealed the presence of Halimedides Lorenz von Liburnau 1902 , which occurs just above the black shales related to the end of the Toarcian Oceanic Anoxic Event (T-OAE). Halimedides is associated with recovery of the trace-maker community after the re-establishment of favourable, oxic, conditions. The appearance of Halimedides after the T-OAE event, previously not registered, supports the close relationship of the trace maker with oxygen conditions, as occurs in other anoxic events including the Cretaceous OAE-1a and OAE-2. Also, a relationship between morphometric and palaeoenvironmental parameters is observed: occurring larger and densely chambered specimens in darker, weakly oxygenated facies, while smaller and sparsely chambered forms are registered in lighter, better oxygenated sediments.

Abstract The Early Jurassic was marked by several episodes of rapid climate change and environmental perturbation. These changes culminated during the Toarcian Oceanic Anoxic Event (T-OAE), an episode of global warming that led to the widespread deposition of organic-rich shales. The Toarcian shales of NW Europe have also yielded exceptionally preserved fossils of marine vertebrates and invertebrates, but the potential links between the occurrences of these exceptionally preserved fossils and the T-OAE remain poorly investigated. Palaeontological excavations realized in Toarcian strata near Lodève (Hérault, southern France) have yielded several specimens of marine vertebrates and abundant invertebrate fauna. We have developed a multiproxy approach (ammonite biostratigraphy, X-ray diffraction-bulk mineralogy, Rock-Eval pyrolysis, stable isotopes, trace element, phosphorus and mercury contents) to place these findings in a well-defined temporal and palaeoenvironmental context, and hence constrain the factors that led to their remarkable preservation. The Jenkyns Event interval, unambiguously identified at the base of the Toarcian organic-rich shales by a 5‰ negative carbon isotope excursion, records higher mercury fluxes, which suggest a causal link with intense volcanic activity of the Karoo–Ferrar large igneous province. This interval is very condensed and unfossiliferous, and might have been deposited under abnormally low-salinity conditions. Our data show that the deposition of the vertebrate-yielding horizons post-dated the T-OAE by several hundreds of ka, and took place during a prolonged period of widespread oxygen-deficiency and elevated carbon burial. Our results indicate that the unusual richness in vertebrates of the studied site can be explained by a combination of regional factors such as warming-induced, prolonged seafloor anoxia, and more local factors, such as extreme condensation owing to reduced dilution by carbonate and detrital input.

Abstract The study of past climate changes is pivotal for understanding the complex biogeochemical interactions through time between the geosphere, atmosphere, hydrosphere and biosphere, which are critical for predicting future global changes. The Toarcian Oceanic Anoxic Event, also known as the Jenkyns Event, was a hyperthermal episode that occurred during the early Toarcian ( c. 183 Ma; Early Jurassic) and resulted in numerous collateral effects including global warming, enhanced weathering, sea-level change, carbonate crisis, marine anoxia–dysoxia and biotic crisis. The IGCP-655 project of the IUGS–UNESCO has constituted an international network of researchers with different disciplinary skills who have collaborated and shared conceptual advances on uncovering drivers of the environmental changes and ecosystem responses. This volume, Carbon Cycle and Ecosystem Response to the Jenkyns Event in the Early Toarcian (Jurassic) , presents 16 works that investigate the early Toarcian environmental changes related to the global warming, sea-level rise, carbon cycle perturbation and second-order mass extinction through biostratigraphy, micropalaeontology, palaeontology, ichnology, palaeoecology, sedimentology, integrated stratigraphy, inorganic, organic and isotopic geochemistry, and cyclostratigraphy.

Abstract Central Lebanon provides some of the best exposed and most readily accessible Upper Jurassic (Kimmeridgian-Tithonian) sections in the Middle East, and is one of the few places where lateral equivalents of the prolific Arab Formation (Kimmeridgian-Tithonian) reservoirs of Peninsular Arabia can be studied at outcrop. At the Bikfaya outcrop section (35 km ENE of Beirut), the uppermost Jurassic comprises at least two disconformity-bounded third-order depositional sequences. Sequence 1 (“Falaise de Bikfaya”) is 61 m+ thick and comprises a progradational succession (highstand systems tract) of foreshoal micropeloid packstones, shoal-crest stromatoporoid floatstones, back-shoal Permocalculus wackestones, and (?attached mainland-) shoreface facies culminating in tidal-flat deposits. This interval is of Early to Middle Tithonian age. Sequence 2 (“Calcaire de Salima”) is ca. 63 m thick, and commences with an abrupt transgressive surface and an associated influx of calcareous dinocysts. The lower part of this sequence comprises strongly argillaceous micropeloidal packstones and occasional peloid-intraclast packstones, interpreted as an offshore transition zone facies association. The initial marine flooding event is of late Middle Tithonian (upper fallauxi-ponti Zone) age. A candidate maximum flooding surface (MFS) is recognized within the late Middle Tithonian ponti Zone, coincident with calcareous dinocyst species and abundance maximum. (A ponti Zone MFS has also been identified elsewhere in the Middle East.) The recessive middle part of Sequence 2 is largely unexposed, whereas the upper cliff-forming part comprises ca. 22 m of Upper Tithonian ooid-skeletal grainstones that coarsen and thicken up-section. These grainstones are characterized by pronounced planar cross-stratification with set heights of up to 3.6 m, and are interpreted as a wave-dominated shoal complex culminating in emergent foreshore facies. Sequence 2 is terminated by a prominent paleo-karst (Type 1 sequence boundary) corresponding to the Jurassic-Cretaceous boundary, and is overlain by basal Cretaceous wacke-ironstones that form the lower part of the Chouf Sandstone Formation. The lower part of the Chouf Sandstone Formation lacks age-diagnostic fossils. The timing of initial Cretaceous onlap is thus only poorly constrained by the presence of Late Tithonian taxa in the underlying “Calcaire de Salima” and the presence of Barremian spores in the upper part of the Chouf Sandstone Formation.