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The 420-m thick stratigraphic section of the Mural Formation that is exposed in the Cerro Pimas area of northern Sonora, Mexico, is composed of limestone lithofacies ranging from bioclastic wackestone to boundstone, whose biota is characterized by low diversity. Prominent age-diagnostic fossils are benthic foraminifera and long-ranging calcareous algae that indicate the Aptian/Albian boundary is close to the base of the Los Coyotes Member. The carbonates of this formation have negative to positive δ 13 C values (−4.63 to +2.6‰) and highly depleted δ 18 O values that range from −12.74 to −8.34‰. The absence of correlation between δ 13 C and δ 18 O values supports a primary marine origin for the δ 13 C values of these limestones. The carbon-isotopic curve of the Cerro Pimas stratigraphic section has well-defined δ 13 C segments (C8 – C15) that compare with published curves of similar age. In the lower part of the early Albian Los Coyotes Member, the presence of OAE 1b is indicated by an increase followed by a decrease in δ 13 C values, suggesting correlation with the Kilian Event. The middle part of the Los Coyotes Member has a significant negative carbon-isotope excursion correlated with the globally recognizable early Albian Paquier event. Moreover, another significant negative carbon-isotope shift is observed in the upper part of the Los Coyotes Member, which can be correlated with the Leenhardt Event. The occurrence of the Kilian, Paquier and Leenhardt Events (OAE 1b cluster) in the Cerro Pimas stratigraphy confirms the global nature of these early Albian disturbances of the carbon cycle. [ABSTRACT FROM AUTHOR]

Abstract: The Early Jurassic was characterized by a global disturbance of the carbon cycle known as the Toarcian Oceanic Anoxic Event (T-OAE). This event is recorded worldwide by a negative excursion in marine and terrestrial carbon-isotope ratios, typically interrupting an overarching positive trend attributed to large-scale burial of marine organic matter under oxygen-depleted conditions. The negative excursion is attributed to introduction of isotopically light carbon into the ocean–atmosphere system. Three sections from the Ionian Zone in Greece have been analysed in terms of biostratigraphy, Total Organic Carbon (TOC), CaCO3, δ13Ccarb, δ18Ocarb and δ13Corg. On the basis of bio- and chemostratigraphy, the age of Pliensbachian–Toarcian formations from the Ionian Zone in Greece has been refined and the geochemical signature of the T-OAE recognized. All sections illustrate the characteristic negative excursion in carbon isotopes from both carbonates and organic matter and, in only one locality, a positive excursion has also been recorded. The recognition of the T-OAE in this part of the Tethyan continental margin offers additional information on the global impact and amplitude of this important Jurassic palaeoceanographic event. [Copyright &y& Elsevier]

Abstract: In eastern Sicily, a series of highly organic-rich black shales occur as exotic blocks (~100 m across) floating in tectonized sediments (Argille Varicolori Unit containing olistoliths of Cretaceous–Palaeogene age). A 19-metre section, through one of these blocks near the town of Novara di Sicilia, includes cyclically bedded black shales, marlstones and claystones, which have been dated using planktonic foraminiferal and nannofossil biostratigraphy. On this basis, the section is assigned to the latest Cenomanian and clearly represents a manifestation of the Oceanic Anoxic Event characteristic of that interval. Total organic-carbon values range up to 23% and the relatively high hydrogen indices record the presence of marine organic matter of low thermal maturity. High-resolution carbonate and organic-carbon isotope curves are comparable with those recorded elsewhere in indicating a significant positive excursion and confirm that, in the Novara di Sicilia section, the black shales are latest Cenomanian in age. By comparison with Cenomanian–Turonian black shales exposed elsewhere in Italy (Calabianca section, western Sicily; Livello Bonarelli, Bottaccione Gorge, Gubbio, Marche–Umbria), the section of Novara di Sicilia is different in being more stratigraphically expanded. However, this section from eastern Sicily does resemble extremely closely coeval sediments cropping out in Tunisia and Morocco. This association is taken as evidence that the Argille Varicolori Unit includes elements that were initially deposited on the north African shelf during Cretaceous time. [Copyright &y& Elsevier]