Chen, W., et al., Geophysical Research Letters, 2026

Title: Barium Isotopes Indicate Spatiotemporal Heterogeneity of Marine Primary Productivity during the Toarcian Oceanic Anoxic Event

Author: Chen, W., Kemp, D.B*., Jenkyns, H.C., Robinson, S.A., Lin, Y., Hu, J., Han, Z., He, T., Zhang, F., Sun, X., Shi, G., Li, C*

Journal: Geophysical Research Letters 

Date of Publication: May 20, 2026

DOI: 10.1029/2026GL121983

Abstract：The Toarcian Oceanic Anoxic Event (T-OAE, similar to 183 Ma) was characterized by globally enhanced organic-carbon burial and a negative carbon-isotope excursion (N-CIE). However, the role of marine productivity at this time, and its spatiotemporal variability, is unclear. We present the first carbonate barium-isotope (delta ¹³⁸Ba_carb) records across the T-OAE from a shallow-water platform (Nianduo, SE Tethys) and a pelagic basin (Dogna, Alpine-Mediterranean Tethys) to reconstruct productivity dynamics. Both sites show positive delta ¹³⁸Ba_carb shifts at the N-CIE onset, indicating supra-regional productivity enhancement. At Nianduo, delta ¹³⁸Ba_carb rises through the onset, consistent with increased export production driven by weathering-derived nutrient inputs. At Dogna, delta ¹³⁸Ba_carb declines within the N-CIE onset due to reduction-driven barite dissolution, followed by a rise during the N-CIE recovery. The Dogna data suggest protracted elevation of pelagic productivity supported by nutrient upwelling and aeolian fertilization. As such, pelagic basins may have acted as an important carbon sink regulating the T-OAE carbon cycle.

Keywords: Toarcian Oceanic Anoxic Event; barium isotopes; primary productivity; pelagic environments