Low-latitude arc-continent collision as a driver for global cooling

Area of Science:

• Geology
• Paleoclimatology
• Plate Tectonics

Background:

• The Neo-Tethys Ocean's tectonic evolution involved significant emplacement of mafic and ultramafic rocks onto continental crust.
• These emplacement events occurred in low-latitude, tropical humid regions approximately 90-70 million years ago and 50-40 million years ago.
• These periods coincide with major global cooling events, including the end of the Cretaceous Thermal Maximum and the Early Eocene Climatic Optimum.

Purpose of the Study:

• To model the impact of CO2 drawdown and addition on global climate between 100 and 40 million years ago.
• To investigate the role of ophiolite emplacement and chemical weathering in atmospheric CO2 reduction.
• To explore the connection between tectonic events, chemical weathering, and long-term global climate change.

Main Methods:

• Modeling atmospheric CO2 drawdown due to chemical weathering of obducted ophiolites.
• Modeling atmospheric CO2 addition from arc volcanism in the Neo-Tethys.
• Comparing modeled net CO2 drawdown rates with ocean bottom water temperature variations.

Main Results:

• Modeled CO2 drawdown rates closely matched observed ocean bottom water temperature changes from 100 to 40 million years ago.
• Significant CO2 consumption requires both mafic/ultramafic rock lithology and a tropical humid climate with high precipitation.
• Ophiolite emplacement in low-latitude, high-precipitation environments is a key factor in atmospheric CO2 reduction.

Conclusions:

• Ophiolite emplacement in the Neo-Tethys likely played a major role in driving global climate cooling.
• The lithology of emplaced rocks and tropical humid conditions are crucial for efficient CO2 consumption.
• Low-latitude ocean basin closure may have triggered other long-term global cooling events, such as the Middle to Late Ordovician cooling.