Chemostratigraphy (CaCO3, TOC, δ13Corg) of Sinemurian (Lower Jurassic) black shales from the Wessex Basin, Dorset and palaeoenvironmental implications

A study of the Dorset and East Devon Coast, specifically focusing on the Sinemurian (Lower Jurassic) black shales from the Wessex Basin, reveals significant stratigraphic variations in carbonate, organic carbon, and organic-carbon isotopes. These variations, particularly in total organic carbon (TOC), indicate periods of deoxygenation likely driven by basin stratification due to freshwater influx, which enhanced organic matter preservation. The organic-carbon isotope curve (δ13Corg) shows positive excursions that do not correlate with TOC stratigraphy, suggesting long-term changes in seawater isotopic composition, potentially linked to marine organic-carbon burial on the margins of the proto-Atlantic. While detailed correlation with sea-level curves is challenging, significant transgressive pulses in the turneri and late raricostatum Zones align with positive δ13Corg excursions.

Jenkyns, H. C., & Weedon, G. P. (2013). Chemostratigraphy (CaCO3, TOC, δ13Corg) of Sinemurian (Lower Jurassic) black shales from the Wessex Basin, Dorset and palaeoenvironmental implications. Newsletters on Stratigraphy, 46(1), 1–21. https://doi.org/10.1127/0078-0421/2013/0029