LATE CRETACEOUS-EARLY EOCENE CLIMATE CHANGE LINKED TO TECTONIC EEVOLUTION OF NEO-TETHYAN SUBDUCTION SYSTEMS

Over geologic time, atmospheric pCO₂ is regulated by a balance between sources of atmospheric CO₂, such as produced by volcanic activity, and sinks, such as the draw down of atmospheric CO₂ that occurs during silicate weathering. Fundamentally, volcanism, metamorphism and weathering are geologic processes that are the products of plate tectonics and paleogeography. Thus, long-term climate change should be modulated by tectonics, but as of yet, attempts to relate particular episodes of climate change to tectonic events from the Cretaceous to Recent have remained controversial The importance of lithology, exhumation and latitude on silicate weathering is revealed by examining modern SE Asia; the portion of SE Asia that lies within the Inter-Tropical Convergence zone (ITCZ) constitutes only ~ 1.3% of continental area yet accounts for >10% of the global CO₂drawdown due to silicate weathering. This elevated efficiency is due to the combination of significant topography and exhumation, high precipitation and the exposure of large volumes of basaltic and ultramafic rocks. Inspired by this observation, we propose that tectonic process related to closure of the Neo-Tethyan Ocean played a significant role in controlling Late Cretaceous to Early Eocene variations in global climate.

We demonstrate that the two distinct cooling events that followed the Cretaceous Thermal Maximum are temporally correlated with the low-latitude emplacement of ophiolites belts during two episodes of arc-continent collision along the Trans-Tethyan Subduction System. In order to explore the effect of the Trans Tethyan Subduction System on atmospheric CO₂, we model the potential contribution of subduction zone volcanism (source) and ophiolite obduction (sink) to the global atmospheric CO₂ budget.