Palaeoenvironmental Evolution During the Darriwilian Age in the Lower Yangtze Region (South China) and its Controls on Enrichment of Organic Matter

Abstract

The Darriwilian Age, marked by the Great Ordovician Biodiversification Event (GOBE), represents a key interval of global environmental change and widespread organic-rich sedimentation. However, the nature of contemporaneous climatic–oceanographic conditions and the mechanisms governing organic matter (OM) enrichment in South China remain poorly constrained. Here, we present an integrated petrological and geochemical investigation of organic-rich successions from the Ningkuo–Hulo formations in the AY1 core, Lower Yangtze region. Our results identify two distinct phases of OM accumulation. Phase I is characterized by relatively low total organic carbon (TOC) contents and developed under warm, humid climatic conditions, intensified chemical weathering, enhanced terrigenous input, weak upwelling and predominantly suboxic to oxic bottom waters, collectively limiting OM preservation. In contrast, Phase II records markedly higher TOC contents and corresponds to a transition toward cooler and drier climatic conditions, strengthened upwelling and the establishment of anoxic–euxinic bottom waters. These changes promoted nutrient recycling, enhanced primary productivity, reduced sediment dilution and more efficient OM preservation. This study systematically reveals two successive stages of climatic–oceanic evolution during the Darriwilian Age, providing new insights into the coupled evolution of palaeoclimate and palaeomarine processes in regulating organic carbon burial in South China.

Keywords

climatic–oceanographic evolution / Ningkuo–Hulo formations / organic matter enrichment / redox conditions / Darriwilian Age

RIGHTS & PERMISSIONS

2026 Geological Society of China.