Spatial Variability in Triassic–Jurassic Boundary Proxy Records Across Nearshore Settings in the Northeast German Basin

The Triassic–Jurassic boundary (TJB) is globally marked by profound environmental change, including disruption of the carbon cycle, global warming, reorganization of sea level, and substantial turnover in marine and terrestrial ecosystems. A characteristic stratigraphic signal of this interval is a negative carbon isotope excursion (NCIE), which is widely correlated and commonly linked to volcanism associated with the Central Atlantic Magmatic Province (CAMP). However, in shallow epicontinental basins, the magnitude and continuity of this signal can be strongly influenced by depositional setting, complicating the distinction between global environmental forcing and local sedimentary overprints. To assess how nearshore environments modulate TJB proxy records, we examine three stratigraphically correlated Upper Triassic–Lower Jurassic nearshore successions spanning a proximal–distal transect across the northeastern Central European Epicontinental Sea (CEES; North German Basin). These archives comprise the delta-influenced Barth 10/65 core (proximal), the shallow-marine Schandelah core (intermediate), and the outer shallow-shelf Moseberg outcrop (distal). We integrate TOC and Rock-Eval data, δ^¹³C_org values, and major and trace element geochemistry to reconstruct carbon-cycle perturbations and depositional and redox conditions across the boundary.

All three successions record a NCIE that starts in the latest Rhaetian and reaches minimum values near the Triassic–Jurassic transition. This excursion coincides with a regressive–transgressive reversal and culminates in the earliest Hettangian flooding, linking the North German Basin records to the global end-Triassic carbon-cycle perturbation. Nevertheless, the expression of the NCIE varies systematically along the proximal–distal transect. The Barth 10/65 core exhibits strong siliciclastic dilution, dominantly oxidized Type III–IV kerogen, and a comparatively muted the NCIE (δ^¹³C_org ~3.6‰), consistent with high-energy deltaic settings and limited accommodation space. In contrast, the Schandelah and Moseberg sections preserve more pronounced excursions of approximately 5‰ in δ^¹³C_org. At Schandelah, the maximum isotope shift occurs during early transgression, whereas Moseberg retains a clearly developed NCIE despite minor stratigraphic truncation across the boundary interval. Moseberg is further distinguished by higher proportions of hydrogen-rich organic matter and enhanced organic-matter preservation associated with short-lived dysoxic conditions. Enrichment factors of redox-sensitive trace elements (Mo, U, Cu, V) indicate predominantly oxic to weakly suboxic conditions at all sites, ruling out sustained anoxia. Collectively, these results demonstrate that depositional position and sea-level–controlled accommodation exert a strong influence on the apparent magnitude and completeness of TJB carbon-cycle signals in nearshore epicontinental settings, underscoring the importance of paleoenvironmental context when comparing boundary records.