Glacial isostatic adjustment deflects the path of the ancestral Hudson River

T Pico,K.L Ferrier,J.X Mitrovica,J Braun

doi:10.1130/g40221.1

Abstract

Quantifying the pace of ice-sheet growth is critical to understanding ice-age climate and dynamics. Here, we show that the diversion of the Hudson River (northeastern North America) late in the last glaciation phase (ca. 30 ka), which some previous studies have speculated was due to glacial isostatic adjustment (GIA), can be used to infer the timing of the Laurentide Ice Sheet’s growth to its maximum extent. Landscapes in the vicinity of glaciated regions have likely responded to crustal deformation produced by ice-sheet growth and decay through river drainage reorganization, given that rates of uplift and subsidence are on the order of tens of meters per thousand years. We perform global, gravitationally self-consistent simulations of GIA and input the predicted crustal deformation field into a landscape evolution model. Our calculations indicate that the eastward diversion of the Hudson River at 30 ka is consistent with exceptionally rapid growth of the Laurentide Ice Sheet late in the glaciation phase, beginning at 50–35 ka.

Highlights

Siddall et al 2008) is an example of landscape phase (Corbett et al, 2017)
Glacial-Isostatic Adjustment Predictions To begin, we predicted the change in topography over the last glacial cycle using the “modified ICE-5G” model
The average rate of change in topography predicted by this simulation from 32 to 26 ka is characterized by west-to-east tilting of the crust, which is pronounced in the region bounding the predicted shorelines at 26 and 32 ka

Summary

Introduction

The Laurentide Ice Sheet reached its maxi- evolution that has been connected—albeit rations of the Laurentide Ice Sheet have been mum extent over the last glacial cycle at the Last speculatively—to crustal deformation related to constructed by Clark et al (1993) on the basis of Glacial Maximum (LGM, 26 ka). Evidence of the growth of the Laurentide Ice Sheet and, in extensive stratigraphic records, and by Kleman et ice-sheet extent during the glaciation phase pre- particular, the dynamics of its peripheral bulge al. Geochronologi- been dated to 40–30 ka using radiocarbon (14C) has not been possible to identify a spatially and cal constraints on ice-sheet history are difficult and amino acid racemization dating

Results

Discussion

Conclusion