The Weissert Event ~133 million years ago marked a profound global cooling that punctuated the Early Cretaceous greenhouse. We present modelling, high-resolution bulk organic carbon isotopes and chronostratigraphically calibrated sea surface temperature (SSTs) based on an organic paleothermometer (the TEX86 proxy), which capture the Weissert Event in the semi-enclosed Weddell Sea basin, offshore Antarctica (paleolatitude ~54 °S; paleowater depth ~500 meters). We document a ~3–4 °C drop in SST coinciding with the Weissert cold end, and converge the Weddell Sea data, climate simulations and available worldwide multi-proxy based temperature data towards one unifying solution providing a best-fit between all lines of evidence. The outcome confirms a 3.0 °C ( ±1.7 °C) global mean surface cooling across the Weissert Event, which translates into a ~40% drop in atmospheric pCO2 over a period of ~700 thousand years. Consistent with geologic evidence, this pCO2 drop favoured the potential build-up of local polar ice.
HIGHLIGHTS• Biochar was evaluated for the biostimulation of hydrocarbon contaminated soils.• Amplicon sequence variants (ASVs) reveal specific soil microbial responses to oil.• Oil amplifies 13 ASVs -putative hydrocarbon degraders -to high relative abundance.• Standard biochars reduce soil diversity loss and are enriched in oil-selected ASVs.• Biochar enriched with endogenous microbes is a promising approach to bioremediation.
Mudrocks are highly heterogeneous in terms of both composition and fabric, with heterogeneities occurring at the submicron to centimetre plus scale. Such heterogeneities are relatively easy to visualise at the micron-scale through the use of modern scanning electron microscopy (SEM) techniques, but due to their inherent fine grain size, can be difficult to place within the greater context of the mudrock as a whole, or to visualise variation when viewed at a centimetre scale. The utilisation of SEM to collect automated high-resolution backscattered (BSE) images (tiles) over whole, polished thin-sections presents a potential large data bank on compositional and fabric changes that can be further processed using simple image analysis techniques to extract data on compositional variation. This can then be plotted graphically in 2D as colour contoured distribution maps to illustrate any observed variability. This method enables the easy visualisation of micron-scale heterogeneity present in mudrock, which are here illustrated and discussed for pyrite and organic content at the larger (thin-section) centimetre scale. This does not require the use of other techniques such as energy dispersive x-ray (EDX) mapping to identify phases present, but instead utilizes BSE images that may already have been collected for textural fabric studies. The technique can also be applied to other phases in mudrocks, such as carbonates and silicates, as well as porosity. Data can also be extracted and used in a similar fashion to bulk compositional analytical techniques such as inductively coupled plasma-atomic emission microscopy (ICP-AES) and carbon, nitrogen and sulphur (CNS) analysis, for average organic carbon and percentage pyrite.
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