A sub-millennial-resolution lacustrine record of Large Igneous Province volcanism during Early Cretaceous OAE1a

Large Igneous Province (LIP) volcanism is widely invoked as a primary driver of major carbon-cycle perturbations and climate extremes in Earth history, yet its short-term eruptive tempo and terrestrial environmental impacts remain poorly constrained. Most existing models assume temporally smoothed volcanic carbon release, largely due to the limited temporal resolution of marine sedimentary archives. Here we present a sub-millennial-resolution lacustrine sedimentary record spanning Oceanic Anoxic Event 1a (OAE1a) from the Aptian Jiufotang Formation in the Kazuo Basin, northeastern China, providing a rare terrestrial perspective on high-frequency LIP activity. A total of 199 samples were collected from a ~130 kyr interval (covering the transition from high to low ¹⁸⁷Os/¹⁸⁸Os) of organic-rich lacustrine black shales, achieving a temporal resolution of ~0.3–1.0 kyr per sample—comparable to Quaternary paleoclimate studies but applied to a deep-time volcanic event. High-resolution stratigraphic profiles of carbon isotopes reveal repeated, abrupt excursions, indicating episodic volatile release associated with super-eruptive volcanism. These geochemical signals are stratigraphically coupled with sedimentological features, including volcanic ash layers, sulfide laminae, and storm-induced deposits, demonstrating that individual eruptive pulses are not only geochemically resolvable but also sedimentologically expressed. Additional Pb isotope constraints further support an Ontong Java Plateau mantle source. Importantly, the magnitude and frequency of lacustrine carbon isotope excursions exceed those typically observed in coeval marine records, implying strong terrestrial amplification through enhanced organic carbon burial, primary productivity blooms, and potentially intensified methanogenesis. These results challenge conventional time-averaged carbon-cycle models and highlight that the climatic and ecological impacts of LIP volcanism are governed by short-lived, threshold-crossing forcing events. Lacustrine systems thus provide a uniquely sensitive archive for resolving the true temporal structure of deep-time volcanic perturbations and their consequences for Earth’s surface environments.