Van Tuyl Lecture: Oliver Jagoutz, MIT
February 7 @ 4:00 pm - 5:00 pm
Oliver Jagoutz, Massachusetts Institute of Technology
241 Berthoud, 4-5PM
Topic: Low-latitude Arc-continent Collision as a Driver for Global Cooling
Abstract: Throughout most of Earth’s history, and certainly over at least the last 500 MA, the global the global climate was much warmer than the climate we experiencing today and the poles were most of the time ice free. However, at least in the last 500 Ma the Earth has experienced a few so-call ice-ages were poles were covered in ice like today. These ice-ages are relatively brief periods and irregularly spaced in time. The global climate is dominantly controlled by pCO2 concentration in the atmosphere/ocean system. Over geologic time, atmospheric pCO2 is regulated by a balance between sources and sinks, including the products of volcanism, metamorphism, and silicate weathering, which are fundamentally the results of plate tectonic processes. However, attempts to relate particular episodes of Cretaceous to recent climate change to specific tectonic events remain controversial.
In this talk I present new constraints on the tectonic evolution of the Neo-Tethys Ocean that indicate that at ∼90–70 Ma and at ∼50–40 Ma, vast quantities of mafic and ultramafic rocks were emplaced at low latitude onto continental crust within the tropical humid belt. These emplacement events correspond temporally with, and are potential agents for, the global climatic cooling events that terminated the Cretaceous Thermal Maximum and the Early Eocene Climatic Optimum. I demonstrate that both the lithology of the obducted rocks (mafic/ultramafic) and a tropical humid climate with high precipitation rate are needed to produce significant consumption of CO2 and initiate ice-ages. Based on these results, I suggest that the low-latitude closure of ocean basins along east–west trending plate boundaries may also have initiated other long-term global cooling events, such as Middle to Late Ordovician cooling and glaciation associated with the closure of the Iapetus Ocean.