Mass‐transport complexes (MTCs) document subsidence patterns in a northern Gulf of Mexico salt minibasin

Mass‐transport complexes (MTCs) dominate the stratigraphic record of many salt‐influenced sedimentary basins. Commonly in such settings, halokinesis is invoked as a primary trigger for MTC emplacement, although the link between specific phases of salt movement, and related minibasin dynamics, remains unclear. Here, we use high‐quality 3D seismic reflection and well data to constrain the composition, geometry and distribution (in time and space) of six MTCs preserved in a salt‐confined, supra‐canopy minibasin in the northern Gulf of Mexico, and to assess how their emplacement relate to regional and local controls. We define three main tectono‐sedimentary phases in the development of the minibasin: (a) initial minibasin subsidence and passive diapirism, during which time deposition was dominated by relatively large‐volume MTCs (c. 25 km3) derived from the shelf‐edge or upper slope; (b) minibasin margin uplift and steepening, during which time small‐volume MTCs (c. 20 km3) derived from the shelf‐edge or upper slope were emplaced; and (c) active diapirism, during which time very small volume MTCs (c. 1 km3) were emplaced, locally derived from the diapir flanks or roofs. We present a generic model that emphasizes the dynamic nature of minibasin evolution, and how MTC emplacement relates to halokinetic sequence development. Although based on a single data‐rich case study, our model may be applicable to other MTC‐rich, salt‐influenced sedimentary basins

Tectonic and oceanographic process interactions archived in Late Cretaceous to Present deep‐marine stratigraphy on the Exmouth Plateau, offshore NW Australia

Deep‐marine deposits provide a valuable archive of process interactions between sediment gravity flows, pelagic sedimentation and thermohaline bottom‐currents. Stratigraphic successions can also record plate‐scale tectonic processes (e.g. continental breakup and shortening) that impact long‐term ocean circulation patterns, including changes in climate and biodiversity. One such setting is the Exmouth Plateau, offshore NW Australia, which has been a relatively stable, fine‐grained carbonate‐dominated continental margin from the Late Cretaceous to Present. We combine extensive 2D (~40,000 km) and 3D (3,627 km2) seismic reflection data with lithologic and biostratigraphic information from wells to reconstruct the tectonic and oceanographic evolution of this margin. We identified three large‐scale seismic units (SUs): (a) SU‐1 (Late Cretaceous)—500 m‐thick, and characterised by NE‐SW‐trending, slope‐normal elongate depocentres (c. 200 km long and 70 km wide), with erosional surfaces at their bases and tops, which are interpreted as the result of contour‐parallel bottom‐currents, coeval with the onset of opening of the Southern Ocean; (b) SU‐2 (Palaeocene—Late Miocene)—800 m‐thick and characterised by: (a) very large (amplitude, c. 40 m and wavelength, c. 3 km), SW‐migrating, NW‐SE‐trending sediment waves, (b) large (4 km‐wide, 100 m‐deep), NE‐trending scours that flank the sediment waves and (c) NW‐trending, 4 km‐wide and 80 m‐deep turbidite channel, infilled by NE‐dipping reflectors, which together may reflect an intensification of NE‐flowing bottom currents during a relative sea‐level fall following the establishment of circumpolar‐ocean current around Antarctica; and (c) SU‐3 (Late Miocene—Present)—1,000 m‐thick and is dominated by large (up to 100 km3) mass‐transport complexes (MTCs) derived from the continental margin (to the east) and the Exmouth Plateau Arch (to the west), and accumulated mainly in the adjacent Kangaroo Syncline. This change in depositional style may be linked to tectonically‐induced seabed tilting and folding caused by collision and subduction along the northern margin of the Australian plate. Hence, the stratigraphic record of the Exmouth Plateau provides a rich archive of plate‐scale regional geological events occurring along the distant southern (2,000 km away) and northern (1,500 km away) margins of the Australian plate

Diagenetic priming of submarine landslides in ooze-rich substrates

Oozes are the most widespread deep-sea sediment in the global ocean, but very little is known about how changes in their physical properties during burial impact slope stability and related geohazards. We used three-dimensional seismic reflection, geochemical, and petrophysical data acquired both within and adjacent to 13 large (in total ~6330 km2) submarine slides on the Exmouth Plateau, North West Shelf, Australia, to investigate how the pre-slide physical properties of oozes control slope failure and emplacement processes. Our integrated data set allows potential slide surfaces to be detected within ooze successions, a crucial advance for improved submarine geohazard assessment. Moreover, we demonstrate that the interplay of tectonics, ocean current activity, and silica diagenesis can prime multiple slides on very low-gradient slopes in tropical oceanic basins. Therefore, the diagenetic state of silica-rich sediments should be considered in future studies to improve slope stability assessments

A novel single nucleotide polymorphism within the NOD2 gene is associated with pulmonary tuberculosis in the Chinese Han, Uygur and Kazak populations

<p>Abstract</p> <p>Background</p> <p>The present study aimed to investigate the genetic polymorphisms in exon 4 of the <it>NOD2 </it>gene in tuberculosis patients and healthy controls, in order to clarify whether polymorphisms in the <it>NOD2 </it>gene is associated with tuberculosis.</p> <p>Methods</p> <p>A case-control study was performed on the Chinese Han, Uygur and Kazak populations. Exon 4 of the <it>NOD2 </it>gene was sequenced in 425 TB patients and 380 healthy controls to identify SNPs.</p> <p>Results</p> <p>The frequency of T/G genotypes for the Arg587Arg (CGT → CGG) single nucleotide polymorphism (SNP) in <it>NOD2 </it>was found to be significantly higher in the Uygur (34.9%) and Kazak (37.1%) populations than the Han population (18.6%). Also, the frequency of G/G genotypes for the Arg587Arg SNP was significantly higher in the Uyghur (8.3%) and Kazak (5.4%) populations than the Han population (0.9%). Meanwhile, no significant difference was found in the Arg587Arg polymorphism between the tuberculosis patients and healthy controls in the Uyghur and Kazak populations (<it>P </it>> 0.05) whereas, a significant difference was observed in the Arg587Arg polymorphism between the tuberculosis patients and healthy controls in the Han population (<it>P </it>< 0.01). The odd ratio of 2.16 (95% CI = 1.31-3.58; <it>P </it>< 0.01) indicated that the Arg587Arg SNP in <it>NOD2 </it>may be associated with susceptibility to tuberculosis in the Chinese Han population.</p> <p>Conclusions</p> <p>Our study is the first to demonstrate that the Arg587Arg SNP in <it>NOD2 </it>is a new possible risk factor for tuberculosis in the Chinese Han population, but not in the Uyghur and Kazak populations. Our results may reflect racial differences in genetic susceptibility to tuberculosis.</p

Mass‐transport complexes (MTCs) document subsidence patterns in a northern Gulf of Mexico salt minibasin

Mass‐transport complexes (MTCs) dominate the stratigraphic record of many salt‐influenced sedimentary basins. Commonly in such settings, halokinesis is invoked as a primary trigger for MTC emplacement, although the link between specific phases of salt movement, and related minibasin dynamics, remains unclear. Here, we use high‐quality 3D seismic reflection and well data to constrain the composition, geometry and distribution (in time and space) of six MTCs preserved in a salt‐confined, supra‐canopy minibasin in the northern Gulf of Mexico, and to assess how their emplacement relate to regional and local controls. We define three main tectono‐sedimentary phases in the development of the minibasin: (a) initial minibasin subsidence and passive diapirism, during which time deposition was dominated by relatively large‐volume MTCs (c. 25 km3) derived from the shelf‐edge or upper slope; (b) minibasin margin uplift and steepening, during which time small‐volume MTCs (c. 20 km3) derived from the shelf‐edge or upper slope were emplaced; and (c) active diapirism, during which time very small volume MTCs (c. 1 km3) were emplaced, locally derived from the diapir flanks or roofs. We present a generic model that emphasizes the dynamic nature of minibasin evolution, and how MTC emplacement relates to halokinetic sequence development. Although based on a single data‐rich case study, our model may be applicable to other MTC‐rich, salt‐influenced sedimentary basins

Extreme erosion by submarine slides

Submarine slides (including slides, slumps, and debris flows) pose major geohazards by triggering tsunami and damaging essential submarine infrastructure. Slide volume, a key parameter in hazard assessments, can increase markedly through substrate and/or water entrainment. However, the erosive potential of slides is uncertain. We quantified slide erosivity by determining the ratio of deposited (Vd) to initially evacuated (Ve) sediment volumes; i.e., slides that gain volume through erosion have a Vd/Ve ratio >1. We applied this method to the Gorgon slide, a large (500 km3), seismically imaged slide offshore northwestern Australia, and reviewed Vd/Ve ratios for 11 other large slides worldwide. Nine of the 11 slides have Vd/Ve >1 (median value = 2), showing emplaced volumes increased after initial failure. The Gorgon slide is the most erosive slide currently documented (Vd/Ve = 13), possibly reflecting its passage across a highly erodible carbonate ooze substrate. Our new approach to quantifying erosion is important for hazard assessments given substrate-flow interactions control slide speed and runout distance. The variations in slide volume also have important implications for submarine infrastructure impact assessments, including more robust tsunami modeling