THE EFFECT OF LATE CENOZOIC GLACIATION ON DENUDATION IN THE WHITE MOUNTAINS OF NEW HAMPSHIRE

Understanding the controls on landscape development in glaciated mountains is challenging because of the large range of factors that control rates of denudation and sediment transfer in these dynamic environments. We have studied the Presidential and Carter Ranges of the White Mountains in New Hampshire using DEMs, field observations, and geochronology to quantify controls on landscape development over different spatial and temporal scales. This area is a tectonically quiescent region that experienced both alpine and ice sheet glaciation throughout the late Cenozoic. The expectation of low erosion rates by cold-based continental ice sheets, polythermal erosion by alpine glaciers, and reworking by interglacial fluvial processes in a low rock uplift rate setting make the White Mountains an ideal case study on the complex controls on denudation in a glacial setting.

Previous studies on Mount Washington have determined slow erosion rates (0.02mm/yr) from apatite fission track dating (Roden-Tice et al., 2012, Geomorphology) and variable ¹⁰Be cosmogenic summit ages (22ka and 124ka) (Bierman et al., 2000). In this study we determined basin-wide and summit erosion rates from short, glacially coincident timescales (10^3-5 years) using ¹⁰Be terrestrial cosmogenic nuclide methods and long-term erosion rates (10^5-7 years) using apatite (U-Th)/He thermochronometry. Comparison of the results of denudation on these different timescales will shed light on the thresholds of glacial erosion such as glacier type, ice basal temperature, and ice thickness.