Sedimentology and microfacies of a mud-rich slope succession: in the Carboniferous Bowland Basin, NW England (UK)

A paucity of studies on mud-rich basin slope successions has resulted in a significant gap in our sedimentological understanding in these settings. Here, macro- and micro-scale analysis of mudstone composition, texture and organic matter was undertaken on a continuous core through a mud-dominated slope succession from the Marl Hill area in the Carboniferous Bowland Basin. Six lithofacies, all dominated by turbidites and debrites, combine into three basin slope facies associations: sediment-starved slope, slope dominated by low-density turbidites and slope dominated by debrites. Variation in slope sedimentation was a function of relative sea-level change, with the sediment-starved slope occurring during maximum flooding of the contemporaneous shelf, and the transition towards a slope dominated by turbidites and then debrites occurring during normal or forced shoreline progradation towards the shelf margin. The sediment-starved slope succession is dominated by Type II kerogen, whereas the slope dominated by low-density turbidites is dominated by Type III kerogen. This study suggests that mud-dominated lower slope settings are largely active depositional sites, with consistent evidence for sediment traction. Additionally, the composition and texture of basin slope mudstones, as well as organic content, vary predictably as a function of shelf processes linked to relative sea-level change

Terrestrial carbon isotope stratigraphy of the Eocene–Oligocene transition, Petrockstowe and Bovey basins, Devon, UK

The terrestrial sediments of the Petrockstowe and Bovey basins in Devon, UK were examined. Their age is considered to be Eocene and Oligocene. The sediments (kaolinitic clays, silts, sands, gravels, and lignites) from both basins were analysed for carbon isotopes of organic material, in conjunction with total organic carbon and palynological analyses used to unravel the type of and provenance of organic matter present. Within the Petrockstowe Basin, the lowermost interval examined shows a palynological distribution dominated by phytoclasts, whilst the upper part of the core is dominated by higher concentrations of palynomorphs (up to 90 %) and an increase in amorphous organic matter consistent (up to 37 %) with a change from sand-filled fluvial channels followed by an ephemeral lake or lake margin setting. Our palynological data from the South John Acres Lane Quarry section, Bovey Basin, show that within the lignites palynomorphs are high again (up to 95 %) consistent with them representing more ephemeral lakes or lake margins periodically exposed with mires. Our palynological data set further allows us to determine that isotope trends are not overly determined by the source of carbon in the basins. Our study suggests that the observed patterns were primarily produced by variations of the isotope ratios of terrestrial atmospheric carbon reservoirs. Even with our less than well constrained biostratigraphical control, the data indicate that the carbon isotope excursions seen in the Eocene and Oligocene could be associated with several transient carbon isotopic shifts (associated with the Paleocene–Eocene Thermal Maximum). Our findings therefore appear to lend support to the surface ocean and atmosphere behaving as coupled reservoirs at this time

Volcanism and carbon cycle perturbations in the High Arctic during the Late Jurassic – Early Cretaceous

Dataset for Vickers, M.L., Jelby, M.E., Śliwińska, K.K., Percival, L.M., Wang, F., Sanei, H., Price, G.D., Ullmann, C.V., Grasby, S.E., Reinhardt, L. and Mather, T.A., 2023. Volcanism and carbon cycle perturbations in the High Arctic during the Late Jurassic–Early Cretaceous. Palaeogeography, Palaeoclimatology, Palaeoecology, 613, p.111412