Using Mesoproterozoic sedimentary geochemistry to reconstruct basin tectonic geography and link organic carbon productivity to nutrient flux from a Northern Australian large igneous Province

The Beetaloo Sub-basin, northern Australia, is considered the main depocentre of the 1,000-km scale Mesoproterozoic Wilton package of the greater McArthur Basin – the host to one of the oldest hydrocarbon global resources. The ca. 1.40–1.31 Ga upper Roper Group and the latest Mesoproterozoic to early Neoproterozoic unnamed group of the Beetaloo Sub-basin, together, record ca. 500 million years of depositional history within the North Australia Craton. Whole-rock shale Sm–Nd and Pb isotope data from these sediments reveal sedimentary provenance and their evolution from ca. 1.35 to 0.85 Ga. Furthermore, these data, together with shale major/trace elements data from this study and pyrolysis data from previous publications, are used to develop a dynamic tectonic geography model that links the organic carbon production and burial to an enhanced weathering of nutrients from a large igneous province. The ca. 1.35–1.31 Ga Kyalla Formation of the upper Roper Group is composed of isotopically evolved sedimentary detritus that passes up, into more isotopically juvenile Pb values towards the top of the formation. The increase in juvenile compositions coincides with elevated total organic carbon (TOC) contents of these sediments. The coherently enriched juvenile compositions and TOC the upper portions of the Kyalla Formation are interpreted to reflect an increase in nutrient supply associated with the weathering of basaltic sources (e.g. phosphorous). Possible, relatively juvenile, basaltic sources include the Wankanki Supersuite in the western Musgraves and the Derim Derim–Galiwinku large igneous province (LIP). The transition into juvenile, basaltic sources directly before a supersequence-bounding unconformity is here interpreted to reflect uplift and erosion of the Derim Derim–Galiwinku LIP, rather than an influx of southern Musgrave sources. A new baddeleyite crystallisation age of 1,312.9 ± 0.7 Ma provides both a tight constraint on the age of this LIP, along with its associated magmatic uplift, as well as providing a minimum age constraint for Roper Group deposition. The unconformably overlying lower and upper Jamison sandstones are at least 300 million years younger than the Kyalla Formation and were sourced from the Musgrave Province. An up-section increase in isotopically juvenile compositions seen in these rocks is interpreted to document the progressive exhumation of the western Musgrave Province. The overlying Hayfield mudstone received detritus from both the Musgrave and Arunta regions, and its isotopic geochemistry reveals affinities with other early Neoproterozoic basins (e.g. Amadeus, Victoria and Officer basins), indicating the potential for inter-basin correlations.     

Unique achondrite Northwest Africa 11042: Exploring the melting and breakup of the L chondrite parent body

Northwest Africa (NWA) 11042 is a heavily shocked achondrite with medium‐grained cumulate textures. Its olivine and pyroxene compositions, oxygen isotopic composition, and chromium isotopic composition are consistent with L chondrites. Sm‐Nd dating of its primary phases shows a crystallization age of 4100 ± 160 Ma. Ar‐Ar dating of its shocked mineral maskelynite reveals an age of 484.0 ± 1.5 Ma. This age coincides roughly with the breakup event of the L chondrite parent body evident in the shock ages of many L chondrites and the terrestrial record of fossil L chondritic chromite. NWA 11042 shows large depletions in siderophile elements (<0.01×CI) suggestive of a complex igneous history involving extraction of a Fe‐Ni‐S liquid on the L chondrite parent body. Due to its relatively young crystallization age, the heat source for such an igneous process is most likely impact. Because its mineralogy, petrology, and O isotopes are similar to the ungrouped achondrite NWA 4284 (this work), the two meteorites are likely paired and derived from the same parent body.     

A middle–late Ediacaran volcano‐sedimentary record from the eastern Arabian‐Nubian shield

The Ediacaran Jibalah Group comprises volcano‐sedimentary successions that filled small fault‐bound basins along the NW–SE‐trending Najd fault system in the eastern Arabian‐Nubian Shield. Like several other Jibalah basins, the Antaq basin contains exquisitely preserved sedimentary structures and felsic tuffs, and hence is an excellent candidate for calibrating late Ediacaran Earth history. Shallow‐marine strata from the upper Jibalah Group (Muraykhah Formation) contain a diversity of load structures and intimately related textured organic (microbial) surfaces, along with a fragment of a structure closely resembling an Ediacaran frond fossil and a possible specimen of Aspidella. Interspersed carbonate beds through the Muraykhah Formation record a positive δ¹³C shift from ?6 to 0‰. U‐Pb zircon geochronology indicates a maximum depositional age of ~570 Ma for the upper Jibalah Group, consistent with previous age estimates. Although this age overlaps with that of the upper Huqf Supergroup in nearby Oman, these sequences were deposited in contrasting tectonic settings on opposite sides of the final suture of the East African Orogen.     

Correction to: Predicting surf zone injuries along the Delaware coast using a Bayesian network

Natural Hazards - The article was published with errors.     

Geoarchaeological Investigations in Mesoamerica Move into the 21st Century: A Review

Over the past thirty years, geoarchaeology has moved from the fringe to mainstream status within Mesoamerican archaeological investigations. This review focuses on works published since the year 2000. Five themes are identified as central to recent studies: (1) the correlation of environmental change and cultural history; (2) anthropogenic environmental impacts; (3) ancient land cover, land use, and diet; (4) archaeological prospection; and (5) provenance studies. These themes are often interwoven in the application of complex systems approaches that allow scientists to more accurately model the intricacies of ancient human–environment interactions.