Integrated ocean drilling program expedition 341 Preliminary report: Southern Alaska margin- Interactions of tectonics, climate, and sedimentation

Abstract

Global climate during the Neogene is distinguished by the transition into a colder, more variable world dominated by the onset and intensification of major Northern Hemisphere glaciations. This transition to the icehouse world corresponds with a global increase in erosion rates and sediment delivery to basins. The effects of this increased erosion may be profound, as worldwide analyses of orogenic belts have shown that Earth systems cannot be considered to be the product of a series of distinct, decoupled tectonic and climatic processes. Rather, there is complex interplay between deformation, exhumation, and climate systems. Exhumation plays a key role in controlling the regional distribution of metamorphic rocks, local climate change, and development of structures throughout an orogen. As tectonic processes influence regional climate by raising mountains that enhance orographic precipitation patterns and intensity, the Neogene climate transition, in turn, likely affected tectonic processes through changes in erosion rates, which redistributed mass and subsequently altered stresses in orogenic wedges. Analytical models examining the coupling between glacial erosion and orogenic processes reveal that glacial erosion can significantly modify the patterns and rates of erosion in an orogenic wedge. A critical question is at what stage of the deteriorating Neogene climate is an orogen ultimately driven into subcriticality? Does this state lead to increased exhumation in the glaciated core of a mountain belt, enhanced topographic relief, and migration of the locus of sediment accumulation to the toes of an orogen that impacts deformation patterns?