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Little is known about the impact of the mid-Cretaceous Oceanic Anoxic Events (OAEs) on the neritic carbonate systems in South America. In order to fill this knowledge gap, the present paper reports on the record of environmental changes in the Albian–Turonian neritic carbonates from the western South American domain in Peru. Owing to the very expanded and well-exposed sections in the Oyon region of central Peru, the OAE 1d and 2 intervals were sampled at high temporal resolution for both bulk micrite and bulk organic matter carbon isotopes, allowing us to compare the fingerprint of these two events between the northern and central Peruvian regions. This suggests the installation of two marked depositional modes: 1) the Albian–Turonian formation of a regional facies belt constituted by oyster-rich mixed siliciclastic-carbonate deposition along the western South America platform; 2) a restricted oligotrophic environment, characterized by the mass occurrence of Perouvianella peruviana and associated miliolids in central Peru during the late Cenomanian–Turonian. These observations advocate for the following scenario: Global warming during the late Albian–early Turonian resulted in humid climate on the western platform. This in turn caused enhanced chemical weathering rates on the Brazilian Shield, resulting in high runoff of nutrients onto the western platform. Nutrient runoff promoted the diversification of benthic oyster communities. Due to the uplift of the Marañon Massif and the installation of the Huarmey Trough, central Peru was isolated from the Pacific and from eastern deltaic influx of the Brazilian continental basement, allowing the local development of oligotrophic conditions during OAE 2. Furthermore, an increased influx of argillaceous sediment and reduced carbonate production is recorded in northern Peru at the onset of OAE 2, marked by a prominent negative shift in δ 13 C. This negative carbon-isotope excursion has also been identified in other sections in the Pacific domain and can be linked to an increase in isotopically light pCO 2 induced by the formation of the Caribbean large igneous province. [ABSTRACT FROM AUTHOR]

Abstract: Large scale channel systems are commonly imaged using seismic data and classified hierarchically. Where exposed at outcrop, similar scale ancient channel systems provide an opportunity to investigate subseismic scale architectures, produced for example through short duration autocyclic processes, and assess how they contribute to larger seismic scale architectures. In this study, a seismic scale slope-confined channel system from the Numidian Flysch Formation of northern Sicily is described using a hierarchical classification scheme. The channel system is 5.7 km wide and is organised within 3 hierarchical levels, comprising; 2 channel complex sets, 16 channel complexes, and >30 channel elements. channel complexes are mappable bodies and reach 500 m wide and 90 m thick. Slope confined sinuous channel complexes contain stacked channel elements which show a progression of incision and bypass to fill with massive sandstones interspersed with graded turbidite deposits. Flows are interpreted to predominantly deposit during quasi-steady flow conditions although flow non-uniformity produced beds with complex grading patterns. Lateral expansion of channel elements produced terracing within the complex margin and had the capacity to alter flow rheology through incorporation of large mud volumes. Sinuosity of channel element thalwegs and offset stacking produced asymmetric channel complexes with heterogeneous internal architectures and lithofacies distributions. Both channel complexes and channel elements thicken with younging indicating increased entrenchment through allocyclic forcing. The frequency distribution of channel-element thicknesses also shows a positive skew centred around 12 m as with published data global datasets. We question whether this distribution similarity may result from a fundamental process at the channel-element scale such as substrate armouring through coarse grained sedimentary deposits exceeding the capacity limits of transiting flows. The use of a hierarchical classification scheme therefore highlights the importance of subseismic scale processes on mappable architectures. The quantification of specific hierarchical elements also allows the role of allocyclic forcing to be investigated in an area of complex palaeogeography. [Copyright &y& Elsevier]

Abstract: The Early Toarcian is marked by a global perturbation of the carbon cycle and major marine biological changes. These coincide with a general decrease in calcium carbonate production and an increase in organic carbon burial, and culminate in the so-called Toarcian Oceanic Anoxic Event. It is believed that the environmental crisis was triggered by the activity of the Karoo–Ferrar large igneous province. In order to further document the Early Toarcian palaeoenvironmental perturbations, carbon isotope, total organic matter, calcareous nannofossils and phosphorus content of the Amellago section in the High Atlas rift basin of Morocco were investigated. This section is extremely expanded compared to the well-studied European sections. Its position along the northern margin of the Gondwana continent is of critical importance because it enables an assessment of changes of river nutrient input into the western Tethyan realm. The carbon isotope curve shows two negative excursions of equal thickness and amplitude, at the Pliensbachian–Toarcian boundary and at the transition from the Polymorphum to the Levisoni Zone. This confirms the supra-regional nature of these shifts and highlights the possible condensation of the first “boundary” shift in European sections. Phosphorus content is used to trace palaeo-nutrient changes and shows that the two negative carbon isotope shifts are associated with increased nutrient levels, confirming that these episodes are related to enhanced continental weathering, probably due to elevated greenhouse gases in the atmosphere. In the High Atlas Basin, the increase in nutrient levels at the Pliensbachian–Toarcian boundary is moreover likely to be the main factor responsible for the coeval demise of the Saharan carbonate platform. A middle Toarcian event, centered on the boundary between the Bifrons and Gradata Zones, characterized by a positive carbon isotope excursion and nutrient level rise, is documented in the Amellago section. [Copyright &y& Elsevier]

Abstract: The Jeffara escarpment spans 400km from southeastern Tunisia to sorthwestern Libya, and marks the northern edge of the Berkine–Ghadames Basin. Its horseshoe shape provides a good 3D control of regional-scale depositional architecture. Historically, the political border between Tunisia and Libya hindered the integration of studies over its entirety, which led to the establishment of separate litho-biostratigraphic frameworks. Field-work undertaken on both sides of the border has allowed the unification of lithostratigraphic schemes developed in both countries. Published stratigraphic ages of the different formations and members are compared and integrated in order to propose a unified bio-lithostratigraphic framework. The correlation of serial sections along the Jeffara escarpment shows that two major tectonic unconformities divide the Early Cretaceous sedimentary pattern. The first one is dated as Late Aptian and is commonly associated with the European “Austrian” tectonic phase. The second, which has previously not been recognized as a regional significant surface in Libya, occurs during the Middle Albian and marks moreover the transition from a siliciclastic to a carbonate-dominated sedimentation regime. These two important regional unconformities form the lower and upper boundaries of the Kiklah–Aïn el Guettar Formations, and can be associated with intra-plate deformation linked with the opening of the central segment of the South Atlantic and the Equatorial Atlantic oceans. [ABSTRACT FROM AUTHOR]

In the fluid catalytic cracking process, a standpipe system transfers solids from the low-pressure regenerator to the high-pressure riser bottom. The standpipe system consists of a regenerator withdrawal means, either a hopper or a well where solids can be refluidized and entrained bubbles can escape, a conical transition from the well to a smaller diameter standpipe and a standpipe which builds pressure. The present study is the first to address the withdrawal well vessel and the conical transition to the standpipe.The withdrawal well should be fluidized with a coarse sparger which forms large bubbles which are not easily entrained downward into the conical transition. A theoretical equation predicts the minimum well aeration flowrate. Compression which occurs in the conical transition may cause defluidization. A model quantifies this compression and evaluates the aeration flowrate required to compensate for it. A conical transition with a small included angle maximizes the range of aeration flowrates over which stable operation without slugs can be achieved. [Copyright &y& Elsevier]

Standard sequence stratigraphy interpretations are commonly built upon the premise of fairly constant sediment supply, leaving vast uncertainties about sequence architecture and sea-level change recorded during major paleoenvironmental disturbances, usually associated with carbonate productivity collapse and increased siliciclastic sediments supply. During relative sea-level rise, this process is referred to as drowning event. However, drastic collapse of carbonate productivity during relative sea-level drop remains poorly documented. The Pliensbachian/Toarcian boundary in Morocco provides an outstanding example of such a case, referred here to as poisoning event. Using bio-, chemo- and high-resolution sequence stratigraphic approaches on horizontal seismic-scale outcrop data, we characterize the architecture of vertically and laterally mixed siliciclastic/carbonate systems. During poisoning event, the standard sequence Lowstand-Transgressive-Highstand system tracts is altered into Highstand-Transgressive-Falling Stage system tracts with little or no evidence for Highstand deposits. Noteworthy, it is important to note that poisoning and drowning events can be confused together in sedimentary records where the shoreline trajectory cannot be clearly tracked, as it has often been the case in previous Pliensbachian/Toarcian studies. The outcome of this study calls thus for a closer re-examination of other carbonate factory collapse event attributed to drowning events without an unambiguous knowledge of their coeval shoreline trajectory. • Carbonate productivity collapse induced by increased runoff during relative sea-level drop referred to as "poisoning" event. • Novel sequence stratigraphic model describing the stratigraphic architecture of poisoning events. • Introduction of a new type of surface: SB type-4. • The Pliensbachian/Toarcian event, one of the most drastic Mesozoic carbonate crises, is associated with a poisoning event. • The T-OAE is fundamentally different from the Pliensbachian/Toarcian event, and corresponds to a drowning event. [ABSTRACT FROM AUTHOR]