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Some of the highest density pockmark fields in the world have been observed on the northwest Australian continental shelf (>700/km2) where they occur in muddy, organic-rich sediment around carbonate banks and paleochannels. Here we developed a semi-automated method to map and quantify the form and density of these pockmark fields (~220,000 pockmarks) and characterise their geochemical, sedimentological and biological properties to provide insight into their formative processes. These data indicate that pockmarks formed due to the release of gas derived from the breakdown of near-surface organic material, with gas accumulation aided by the sealing properties of the sediments. Sources of organic matter include adjacent carbonate banks and buried paleochannels. Polychaetes biodiversity appears to be affected negatively by the conditions surrounding dense pockmark fields since higher biodiversity is associated with low density fields. While regional bi-directionality of pockmark scours corresponds to modelled tidal flow, localised scattering around banks suggests turbulence. This multi-scale information therefore suggests that pockmark scours can act as proxy for bottom currents, which could help to inform modelling of benthic biodiversity patterns.

Bathymetric and seismic surveys of the Florida Middle Ground area on the West Florida Shelf, aid in identifying the structure and origin of these unusual banks. Recent cores recovered from the area by other workers provide a useful context for interpreting geophysical data. Data indicate that high-relief banks may be largely biohermal, whereas low-relief banks are likely composed of clastic sediments with a vermetid gastropod carbonate caprock. The most seaward ridges reveal subtle internal aggradational stratal geometries indicating a possible origin as a subtidal shoal, or paleoshoreline, deposited during or immediately following the Younger Dryas. Bank locations appear to be related to the antecedent geology, specifically the occurrence of the highly weathered Miocene surface. High-resolution multibeam bathymetry and backscatter data reveal varied morphologies that suggest the influence of karst processes, linear trends suggestive of wave-reworked intertidal hardbottom, poorly lithified and benthic fauna-mantled beach ridges or sand waves, or perhaps surface-water flow patterns during lowstand exposure. Circular depressions on low banks are of the same scale and morphology as modern shallow karst features in the Everglades. An episodically active sand-wave field occurs in the northern study area, and provides sediment to the system. Scoured depressions surrounding carbonate banks also indicate intense, episodic current activity originating from shelf and wave currents. A partial modern analog for some of the morphology of this system may be the Ten Thousand Islands and portions of the Florida Everglades. Data indicate that the banks represent a brief period of reef growth (possibly mixed coral and vermetid) constrained by two rapid sea-level rise events, and impacted by changing water quality and trophic conditions. [ABSTRACT FROM AUTHOR]

Abstract: The early to middle Miocene Nullarbor Limestone forms the vast, karsted Nullarbor Plain in southern Australia, and may be the most extensive Miocene carbonate deposit described to date. These carbonates were deposited at southern paleolatitudes of ~40°S and are interpreted to be subtropical to warm-temperate in character because of the presence of certain genera of tropical coralline algae (rhodoliths and articulated types), large benthic foraminifera, tropical molluscs, zooxanthellate corals, and micrite envelopes. Facies are dominated by skeletal grainstones and floatstones that accumulated in three interpreted paleoenvironments: (1) seagrass banks (upper photic zone), (2) rhodolith pavements (lower photic zone), and (3) open seafloors (lower photic to subphotic zone). A decrease of tropical components from west to east across the platform implies that warm oceanic currents (possibly related to a proto-Leeuwin Current), as well as a period of warm climate (Miocene Climatic Optimum), resulted in subtropical deposition at southern latitudes. The Southern Ocean extended inboard ~450km from the shelf edge during Nullarbor Limestone deposition, but interpreted paleodepths did not extend much below the base of the photic zone. A small slope angle (~0.02°) over a wide shelf (~300,000km2) implies deposition on an epeiric platform or epeiric ramp. A Miocene barrier reef was likely coeval with Nullarbor Limestone deposition. Therefore, the inboard portion of the Nullarbor Limestone can be considered part of an extensive back-reef lagoon system on a rimmed epeiric platform, perhaps attaining a size similar to the modern Great Barrier Reef system. [Copyright &y& Elsevier]

Heavy oil extraction currently presents economic and environmental challenges due to low prices and costly energy usage for their exploitation and transport. The use of heavy oil as a sustainable source of energy requires novel and well-engineered technologies. In-Situ (in-reservoir) Upgrading Technology, ISUT, is an EOR-Upgrading process that combines the use of a hot dense fluid (i.e., vacuum distillation residue), hydrogen, and a nanocatalyst as upgrading agents. The operating control of this technology requires performance assessment and kinetic database for each application and each type of reservoir with specific rock-oil in place characteristics. In this work, a hydrocracking kinetic study is developed based on experiments carried out in a dolomite corepack using temperatures from 335 °C to 365 °C, residence times of 12 h–72 h under the constant pressure of 10 MPag, which are the typical ISUT's conditions for carbonate reservoirs. By using kinetic modeling, the operating temperatures were compared with a previous kinetic model, finding similar yields/reaction time performance results. Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray spectroscopy (EDX) techniques were used to analyze the nanocatalyst particles on the dolomite corepack's surface. The nanocatalysts deposited on the rock were in the range of 13 nm–1220 nm with two types, spherical- and agglomerated-shaped. The X-Ray Fluorescence Spectroscopy (XRF) was also used to determine metal content distributions along the corepack. Finally, ISUT's kinetic modeling studies so far, and this one, suggest the convenience of using the same model for the reservoirs studies, which include the effects of the conditions such as temperature, pressure or residence time used during ISUT's process application. • Catalytic reaction study is performed by using a five-lumps kinetic model. • Longer residence times produces higher quality products. • Ultradispersed nanocatalyst Ni–Mo is found in different sizes. • VR conversion was achieved by using different temperatures and residence times. [ABSTRACT FROM AUTHOR]

Some of the highest density pockmark fields in the world have been observed on the northwest Australian continental shelf (>700/km2) where they occur in muddy, organic-rich sediment around carbonate banks and paleochannels. Here we developed a semi-automated method to map and quantify the form and density of these pockmark fields (~220,000 pockmarks) and characterise their geochemical, sedimentological and biological properties to provide insight into their formative processes. These data indicate that pockmarks formed due to the release of gas derived from the breakdown of near-surface organic material, with gas accumulation aided by the sealing properties of the sediments. Sources of organic matter include adjacent carbonate banks and buried paleochannels. Polychaetes biodiversity appears to be affected negatively by the conditions surrounding dense pockmark fields since higher biodiversity is associated with low density fields. While regional bi-directionality of pockmark scours corresponds to modelled tidal flow, localised scattering around banks suggests turbulence. This multi-scale information therefore suggests that pockmark scours can act as proxy for bottom currents, which could help to inform modelling of benthic biodiversity patterns. [ABSTRACT FROM AUTHOR]