Conference Agenda

While the effects of OAEs are well known for the pelagic successions of the Tethys Ocean, little is known about their impact on the Peri-Tethyan shallow-water carbonate systems. We present the preliminary results of a study related to the realisation of the Geological Map of Italy (CARG Project), focussed on the identification and description of the perturbation induced in the Lower Cretaceous shallow-water carbonate succession of the Latium-Abruzzi Carbonate Platform by the well-known Early Cretaceous OAEs. Two stratigraphic sections were studied in the Ernici Mts. (central Apennines, Italy) "calcari ciclotemici a gasteropodi" fm. (CCG - Berriasian p.p. - lower Aptian p.p.). A layer of black dolostone, about ten centimetres thick, has been observed in several outcrops of the dolomitic lithofacies (CCGa) of CCG. SEM images, along with EDS and WDS analysis indicated the presence of siderite and pyrite aggregates starting from the basal part of the blackish dolostone and gently decrease towards the upper part of the study interval. TOC and sulphates show similar trends. In situ analyses using the LA-ICP-MS facility at Roma Tre University shows a significant increase in elemental concentration of redox-sensitive elements as well as in the Fe/Al ratio in the blackish dolostones. Biostratigraphic calibration performed on the collected samples has established a Hauterivian p.p. age. A preliminary attempt for U-Pb dating of the CCGa black dolostone was carried out through LA-ICP-MS investigations providing a lower intercept age of 125.7± 1.8 Ma. These promising results suggest that the perturbations were induced by the Faraoni OAE.

Mudurnu-Göynük basin, Central Pontides (NW Turkey) and Central Taurides (S Turkey) and Arabian Platform include records of Cretaceous oceanic anoxic events in Mid-Barremian, Aptian, Albian, Cenomanian-Turonian, Campanian intervals of the Cretaceous successions as presence of black shale intervals and or their representatives respectively.

The Mid-Barremian black shales (MBE) have been recorded within pelagic succession in central Sakarya zone of Pontides after the drowning of the platform. The carbon isotope curve displays a 2 ‰ shifts. Eu, Ce, V, Cu, Zn, Fe, Ba, P, and S values display a relative enrichment. The Aptian black shales (OAE1a) are recorded in pelagic carbonates in central and north of Sakarya zone negative carbon shift of 2 ‰, and TOC around 2%. In Sakarya zone of Pontides, OAE2 is recorded in pelagic carbonates with more than 1 ‰ carbon positive shift and >2 % TOC. This interval is relatively rich in S, Mo, Ba, Cd, Ni, V, Zn, Pb, Cr, Co. Another OAE2 wasrecorded in Antalya Nappes of Taurides without carbon isotope curve but TOC >20%.

Mid-Late Campanian OAE is recorded in Pontides and Arabian Platform. It displays relative enrichment of S, Mo, Cd, Fe, Ni, V, Zn, Cr, Co, U.

The OAE1a and OAE2 levels recorded in Turkey are correlated with European examples controlled by sealevel and tectonics in large-scale and climate and oceanographic changes in small-scale. The most extensive OAE records in Turkey belong to OAE1a and OAE2, and display potential for source rocks for hydrocarbon and sedimentary strategic element exploration.

A carbon cycle disturbance occurred in the mid Cretaceous, within the upper Albian-lower Cenomanian interval, described as the Albian-Cenomanian Boundary Event (ACBE). This anoxic event is seen as a global one, being identified in both Tethyan and Boreal realms. For pointing out changes related to the ACBE, we investigated two successions of the Tethyan Realm: (i) Lepşa section, Eastern Carpathians, placed at 34°N palaeolatitude during mid Cretaceous times and (ii) Youxia section, S Tibet, situated at 21°S palaeolatitude. Both successions contain nannofossil events characterizing the Albian-Cenomanian Boundary Interval, i.e., the successive LO (last occurrence) of Crucicribrum anglicum and Hayesites albiensis, followed by the successive FO (first occurrence) of Gartnerago chiasta, Calculites anfractus, and Corollithion kennedyi, spanning the UC0 and UC1 zones. In the Youxia section, a few nannofossils confined to high palaeolatitudes were identified in the UC0a subzone. In both sections four successive peaks (A, B, C and D) of d¹³C isotope were observed, where A, B, and C are late Albian in age and peak C is early Cenomanian. The boundary between the Albian and Cenomanian falls, as globally identified, between peaks C and D, just above the FO of Calculites anfractus. Additionally, the lower part of Youxia section (UC0a subzone) shows increased values of d¹⁸O, accompanied by increased productivity of the nannofossils, possibly linked to temperature decrease in the surface waters. These changes might reflect ocean circulation modifications in the Southern Hemisphere, resulting from the enhanced connection among different oceanic basins during the mid Cretaceous times.

The Early Cretaceous of the Umbria-Marche Basin is marked by three Oceanic Anoxic Events (OAEs) within the Marne a Fucoidi Formation, which is composed of multicolour marlstones and marly limestones interbedded with organic-rich black shale layers. These events are associated to the development of anoxic conditions at the sea floor. Some of these occurred on a global scale—such as the early Aptian OAE1a—while others were regional, such as the early Albian OAE1b. In the present study, the microfloristic content from the Fiume Bosso, Roccaccia, and Bottaccione sections was analysed for the first time, along with data from the Poggio le Guaine section. The palynological assemblage of OAE1b is characterized by sporomorphs as Cyathidites spp. and Afropollis spp., and dinocysts as Florentinia mantellii. The dinoflagellate cyst species Litosphaeridium conispinum was recorded in all studied sections. Its first occurrence marks the late Albian in the Tethyan domain. The occurrence of Elaterosporites klaszii and E. verrucatus—typical of the Albian to Cenomanian—was also recorded. These taxa were found in association with L. conispinum in the Fiume Bosso section, and below its first occurrence in the Bottaccione section. The distribution of dinoflagellate cysts provides valuable insights into the palaeobiogeographic dynamics of the Tethyan realm during the Early Cretaceous, highlighting patterns of ecological response to regional and global anoxic events and reinforcing their utility as biostratigraphical and palaeoenvironmental markers.

This study provides data from a 15-meter-thick section located within the outermost thrust sheet of the Eastern Carpathians. The lower part contains deep-sea black shales, silts, and black radiolarites, whereas the upper section consists of cm-thick radiolarites-green shale couplets, and rarely, thin sandstones, clastic radiolarites and black shales. Based on calcareous nannofossil biostratigraphy, the analyzed sequence corresponds to the UC3 and UC4a zones/subzones. The succession of the nannofossil event is the LO (last occurrence) of Gartnerago theta (base of the UC3b subzone), followed by the LO of Staurolithes gausorhethium (base of the UC3c) and the LO of Corollithion kennedyi (base of UC3d). The youngest event recorded in the studied succession is the FO (first occurrence) of Cylindralithus biarcus which marks the base of the UC4 biozone. As Lithraphidites acutus and Cretarhabdus striatus are present from the base to the top of the succession, we consider that the youngest nannofossil subzone is UC4a.In the base of the sequence, two peaks of the isotope δ¹³C_org were identified: i) the oldest reaches the value of -23.7‰, being accompanied by the highest values of TOC (total organic carbon) in the studied section (5.9%), and (ii) the youngest, up to -23.9‰, keeping high TOC values, i.e., up to 1.8%. These peaks, positioned in the UC3a nannofossil zone, likely represent the distinct characteristics of the Mid-Cenomanian Event (MCE), with the oldest significant positive excursion attributed to MCE Ia while the youngest to MCE Ib.

Since the Permian/Triassic boundary, significant atmospheric and oceanic carbon cycle perturbations repeatedly occurred in the Mesozoic. One well-documented perturbation is Oceanic Anoxic Event 2, which occurred at the Cenomanian/Turonian boundary. Integrated Ocean Drilling Program, Expedition 342 recovered a relatively expanded Cretaceous sequence, including the Cenomanian/Turonian boundary interval in the northwestern Atlantic, off Newfoundland. We examined planktic foraminiferal assemblages, planktic foraminiferal mass accumulation rate (PFAR), and organic carbon isotope stratigraphy across the Cenomanian/Turonian boundary sequence from Site U1407. At around 269 mCCSF. a distinctive and typical organic carbon isotope excursion is identified within an approximately 40 cm-thick black shale layer. The development of this black shale indicates that the subsurface and/or deep-water column became anoxic in this interval. On the other hand, the coarse fraction and planktic foraminiferal accumulation rates began to decrease at 270 mCCSF and returned to the pre-event level at approximately 267 mCCSF. The carbonate production rate was depressed for a 3 m-thick interval, which is significantly thicker/longer than the thickness of the black shale. If we assume that the decline in PFAR represents surface-ocean acidification, this acidification, hence an increase in pCO₂, started significantly earlier than the observed water-column anoxia.