Multiple proxies demonstrate the mechanism of dolomitization variations during global warming periods

Abstract

The genesis of the sedimentary dolomite has been an unexplained mystery for more than two centuries, known as the 'dolomite problem'. There may be some coupling relationship between the Phanerozoic variations in dolomite abundance and major geological events (i.e., mass extinction, oceanic anoxia, global warming, and ocean acidification); but its cause is still not adequately understood, which impedes our understanding of global geochemical cycles and long-term climate change. Understanding the controlling factors of dolomitization variations during global warming periods is the key to resolving this issue. Multiple factors controlling the dolomitization of the Middle Eocene Bohai Bay Basin, Holocene Lake Van, and Permian-Triassic dolomitization event were (re)evaluated in this study using astronomical tuning, correlation coefficient analysis, and multiple regression analysis. We demonstrate that dolomitization is more intense during global warming periods, and that its variation is more affected by temperature and pH cycling resulting from astronomical forcing. These phenomena may be caused by the Cannikin Law or the strengthening of temperature and pH cycling during global warming periods. The elevated atmospheric pCO2 and associated ocean acidification strengthen the temperature and pH cycling, thereby promoting the dolomitization of metastable carbonates by a non-equilibrium cyclic growth and replacement mechanism. This process is an important overlooked reason for the higher dolomite abundance during global warming. This study offers a novel perspective on the ‘dolomite problem’, ocean acidification and their relationship.

Keywords

• Dolomite
• Bohai Bay Basin
• Middle Eocene Climate Optimum
• Astronomical forcing
• Temperature and pH cycling
• Ocean acidification