The Formation of Ferromanganese Crusts From the Western Mariana Ridge and Implications for Deep-Water Environment Since the Late Pliocene

Abstract

Pacific Deep Water (PDW) plays a crucial role in the dynamics of the global thermohaline circulation. Understanding the evolution of the PDW is significant to reveal the global carbon cycle and its climatic responses. We present a comprehensive study of ferromanganese crusts from the Western Mariana Ridge (WMR), which includes mineralogical and high-resolution geochemical data and Be isotopes. The mineralogical compositions are vernadite, quartz, anorthite, albite. calcite, sanidine and illite. Ferromanganese crusts on the Western Mariana Ridge are hydrogenetic in origin. We constrained the chronological framework using three Be isotope age control points at 3.04, 1.21, and 0.35 Ma. Based on the microstructure and geochemical variations of the ferromanganese crust, the PDW of the WMR can be divided into three stages: Stage I: 3.04 to 1.99 Ma, Stage II: 1.99 to 0.59 Ma, and Stage III: 0.59 Ma to present. These stages are influenced by paleoceanographic events such as Northern Hemisphere Glaciation (NHG), and the Mid-Pleistocene Transition (MPT). Global cooling may have been the main driving force affecting changes in the regional deep-water environment, thereby influencing the extent of the oxygen minimum zone (OMZ).