Capturing the tempo of landscape response across a range of temporal scales and variable rates of tectonic forcing
In actively growing mountain systems, tectonics and climate interact to grow and denude mountain topography, respectively. However, understanding this time-integrated coupling between tectonic and climatic forcing and the subsequent rate of landscape response remains as one of the greatest challenges in tectonics and geomorphology. A number of field and analytical studies have used actively growing mountain belts such as the Himalayas and Taiwan to demonstrate that tectonics is the first order control on landscape response, and thus the rate that topography is denuded is mostly a function of tectonic uplift rate. Alternately, a number of numerical studies have demonstrated that climate, and particularly prevailing wind direction and precipitation distribution, can exert a first-order control on tectonic evolution and may even influence the localization of crustal-deformation features such as large thrust and normal faults. This enigma persists primarily because interactions between tectonics, climate, and the landscape response is two-way coupled and understanding the nature and rate of such a response across a range of timescales requires that these processes can be documented in landscape features that represent a variety of nested temporal scales. At the temporal wavelength of mountain range growth and decay, low-T thermochronologic techniques such as apatite U-Th/He (AHe) and apatite fission track (AFT) yield long-term ‘averaged’ response times. However, it remains unclear if these time averaged rates are representative of erosional and exhumational processes operating over shorter temporal wavelengths, such as those documented by cosmogenic and radiochemical techniques and those preserved in the detrital record of Quaternary moraines and even more recent range-front lake sediments. Thus, to execute these natural experiments and resolve these signals, it is necessary to identify study areas that both allow for first-order boundary conditions such as tectonic forcing to be constrained independently and preserve erosional signals across a variety of nested temporal scales and mechanisms. This talk will explore how an integrated team of geoscientists are using the Teton system to examine this longstanding dilemma from multiple temporal scales, including long-term incision rates documented from geochronology, short-term incision rates documented in a new lake seismic survey of Jackson Lake, and new glacial moraine and talus volume analysis using the National Park Service LiDAR dataset.