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AbstractDual‐energy X‐ray computed tomography consists of imaging objects using two incident X‐ray beams of different energy to distinguish the different compounds within a sample based on their density (electron density, ρe) and elemental composition (effective atomic number, Zeff). The stoichiometric calibration for dual‐energy X‐ray computed tomography was already successfully implemented to identify single and homogeneous minerals easily and non‐destructively. It is here applied for the first time to a more complex and heterogeneous sample, a varved sediment core with three distinct facies. The output of dual‐energy X‐ray computed tomography was compared against elemental geochemistry obtained at the same resolution using a micro‐XRF core scanner. The three individual facies can be successfully differentiated using dual‐energy X‐ray computed tomography because their range of ρe and Zeff values allow their discrimination. Correlations with elemental geochemistry are also discussed but are less conclusive, probably because of variations in grain size and porosity, and because these high resolution analyses were not performed at the exact same location. The paper not only eventually discusses the limitations when using dual‐energy X‐ray computed tomography on sediments but also demonstrates its potential to quantitatively study sediment cores in a non‐destructive way.

ABSTRACTOxygen concentration in the ocean is vital for sustaining marine ecosystems. While the potential impacts of deoxygenation on modern oceans are hard to predict, lessons can be learned from better characterizing past geological intervals formed under a greenhouse climate. The greenhouse Cretaceous containing several oceanic anoxic events characterized by widespread oxygen‐deficient water is ideal in this regard. The Austin Chalk Group in south Texas (USA) shows organic‐rich intervals that can be linked to oxygen depletion in the ocean, but the exact bottom water oxygenation conditions have not been estimated. This study aims to reconstruct both sediment interstitial and bottom water oxygenation history during Austin Chalk Group deposition by integrating detailed ichnological, sedimentological and geochemical (X‐ray fluorescence and X‐ray diffraction) analyses, thereby providing a consistent model that may be applicable across a range of marine shelf settings. The 141.12 m Gise #1 core contains a continuous record of the Austin Chalk Group, providing an opportunity for unravelling oxygenation and deoxygenation events. Whereas the anaerobic–exaerobic deposits are essentially nonbioturbated, four oxygen‐related ichnocoenoses are defined, further refining the transition of aerobic to dysaerobic conditions in the sediment interstitial water. Omission surfaces and glauconitic grains, products of current‐induced scouring and condensation, suggest sporadic high‐energy events in the Austin Chalk Group ramp that drove elevated terrestrial inputs. Geochemical data further help to identify anoxic bottom water conditions within the anaerobic facies. Additionally, the lowermost part of the Austin Chalk Group illustrates redox cycles, whereas dilution events characterized by elevated terrestrial input are identified throughout the rest of the Austin Chalk Group. The evolution of oxygenation levels in sediment interstitial water and bottom water disputes the existence of a long‐lasting oxygen‐deficient sea in south Texas. The refined depositional model may be applicable to coeval shelfal settings. Moreover, the results provide insights into variable, evolving palaeoclimatic and palaeoceanographic conditions of the greenhouse Late Cretaceous.

With increased concerns about data protection and privacy over the past several years, and concomitant introduction of regulations restricting access to personal information (PI), archivists in many jurisdictions now must undertake ‘sensitivity reviews’ of archival documents to determine whether they can make those documents accessible to researchers. Such reviews are onerous given increasing volume of records and complex due to how difficult it can be for archivists to identify whether records contain PI under the provisions of various laws. Despite research into the application of tools and techniques to automate sensitivity reviews, effective solutions remain elusive. Not yet explored as a solution to the challenge of enabling access to archival holdings subject to privacy restrictions is the application of privacy-enhancing technologies (PETs) —a class of emerging technologies that rest on the assumption that a body of documents is confidential or private and must remain so. While seemingly being counterintuitive to apply PETs to making archives more accessible, we argue that PETs could provide an opportunity to protect PI in archival holdings whilst still enabling research on those holdings. In this article, to lay a foundation for archival experimentation with use of PETs, we contribute an overview of these technologies based on a scoping review and discuss possible use cases and future research directions.

ABSTRACTSedimentological and ichnological descriptions of fluvio‐tidal translating point bars are rare, and complex physico‐chemical processes make highly detailed but concise facies descriptions challenging. Herein, mesofacies are defined to describe and interpret three ancient translating point bars from the Lower Cretaceous McMurray Formation, Alberta, Canada. Twenty‐three mesofacies are defined, based on their recurring sedimentological and ichnological characteristics. These mesofacies form the building blocks of beds and bedsets that make up three depositional facies. Facies 1 reflects sand dune migration at the channel base, which grades into inclined heterolithic stratification of Facies 2 and 3. Facies 2 occurs in the centre and seaward portions of the translating point bars and records tide‐dominated deposition of sand and muddy sand during periods of reduced river discharge. Ichnological suites and bioturbation intensities in these beds reflect persistent but variable brackish‐water conditions, fluctuating deposition rates and the deposition of mud. Mud beds are derived from flows with high suspended‐sediment concentrations. Tidally derived mud beds are typically bioturbated with trace fossil suites indicative of slow deposition rates and brackish‐water conditions. Mud deposited during elevated river discharge is burrowed after the dewatering of the bed. Facies 3 occurs at the landward apex of the translating point bar and is marked by sand‐rich and mud‐rich dune deposits with abundant soft‐sediment deformation, indicative of elevated flow velocities and deposition rates. Bioturbation is rare and sporadically distributed owing to unstable substrates. The distribution of the facies reflect the hydrodynamic variations that occurred vertically and laterally across the bar in response to temporal variations in fluvial and tidal flow interaction, as recorded by their mesofacies. The detailed facies analysis strongly suggests that deposition of the three McMurray Formation translating point bars occurred in proximity to the turbidity maximum zone of a fluvio‐tidal channel system.

AbstractSeafloor topography can affect turbidity current dynamics on deep‐water slopes, significantly influencing the dispersal of sediment. Despite the common occurrence of topographic complexity, there are few detailed investigations of topographic interactions and their effect on downslope flow evolution in intraslope environments. In this study, the sedimentology and architecture of an Upper Cretaceous intraslope fan succession deposited within an extensional, fault‐bound minibasin are described from a rare, well‐exposed, near‐continuous, oblique depositional‐dip outcrop of the Tres Pasos Formation, Chile. The 2 to 8 m thick studied interval transitions downslope from high‐energy heterolithic strata, including metre‐scale steep‐faced scours, to non‐amalgamated thick‐bedded sandstones. Abrupt increases in sandstone percentage, sandstone bed thickness and grain size occur on the hangingwall blocks of south‐east and north‐east‐dipping normal faults that bound the minibasin. Sandstone beds are dominated by backset or wavy low‐angle stratification proximally, contain compositional banding near faults, and are characterised by increased proportions of planar laminated and structureless turbidite divisions downslope along the transect. Experimental observations of turbidity current interactions with topography are synthesised into a qualitative framework, which is used to interpret flow processes and characteristics from deposit trends. The results reconstruct the response of Froude‐supercritical, stratified turbidity currents with denser basal layers when encountering metre‐scale fault scarps. The analysis shows that metre‐scale topographic features can substantially alter the flow properties of stratified turbidity currents, and their downslope flow evolution to include the development of transitional, depositional and flow‐stripped sediment gravity currents. However, in comparison to base‐of‐slope settings, overall flow conditions are interpreted to be more uniform over slope breaks and zones of flow expansion in a partially confined intraslope environment. These findings have considerable implications for understanding flow response to similar scale morphological features on the seafloor and the potential for flow transformations in intraslope settings.