High‐Resolution Anisian Marine Perturbation by Volcanism in the Eastern Paleo‐Tethys

Following the end‐Permian mass extinction, the Middle Triassic Anisian Stage was still characterized by environmental perturbations that hindered biological flourishing, yet it remains uncertain whether these persistent Tethyan disturbances were coupled with the closure of the Paleo‐Tethys Ocean. This study presents a high‐resolution integrated analysis of the Anisian Pha Kan Formation in the Lampang Basin, Southeast Asia, combining zircon U–Pb geochronology, chemostratigraphy, and magnetic susceptibility. We established a floating astronomical time scale (ATS) tuned to 405‐kyr long eccentricity cycles anchored by a high‐precision U–Pb age of 244.24 ± 0.78 Ma. The results reveal two distinct environmental regimes. The early Anisian period was characterized by intense regional volcanism coupled with sharp negative carbon and oxygen isotope excursions, indicating volcanic activity‐driven climate instability. Subsequently, the Pelsonian substage records the Pelsonian Negative Carbon Isotope Excursion (PENCIE). Our high‐resolution analysis reveals that this carbon cycle perturbation is precisely coupled with a significant sedimentary shift at ∼244 Ma, marked by enhanced sedimentary noise and a synchronous rise in magnetic susceptibility (MS) and frequency‐dependent MS. We interpret this synchronous transition as a tectonically driven forced regression and enhanced terrigenous input from pedogenically mature soils. The timing of this uplift event provides critical constraints on the assembly of Southeast Asia, supporting a Middle Triassic collision between the Sibumasu and Indochina terranes. Collectively, these findings suggest that sustained environmental perturbations driven by the coupling of arc volcanism and orogenic uplift hindered ecosystem recovery throughout the Middle Triassic, challenging the paradigm of Anisian environmental stability.