Limits to timescale dependence in erosion rates: Quantifying glacial and fluvial erosion across timescales.

Earth's topography and climate result from the competition between uplift and erosion, but it has been debated whether rivers or glaciers are more effective erosional agents. We present a global compilation of fluvial and glacial erosion rates alongside simple numerical experiments, which show that the "Sadler effect," wherein geological rates show an inverse relationship with measurement timescale, comprises three distinct effects: a measurement thickness bias, a bias of erosion and redeposition, and a bias introduced by not observing quiescent intervals. Furthermore, we find that, globally, average glacial erosion rates exceed fluvial erosion rates through time by an order of magnitude, and that this difference cannot be explained by Sadlerian biases or by variations in hillslope, precipitation, or latitude.

Thermochronologic constraints on the origin of the Great Unconformity.

The origin of the phenomenon known as the Great Unconformity has been a fundamental yet unresolved problem in the geosciences for over a century. Recent hypotheses advocate either global continental exhumation averaging 3 to 5 km during Cryogenian (717 to 635 Ma) snowball Earth glaciations or, alternatively, diachronous episodic exhumation throughout the Neoproterozoic (1,000 to 540 Ma) due to plate tectonic reorganization from supercontinent assembly and breakup. To test these hypotheses, the temporal patterns of Neoproterozoic thermal histories were evaluated for four North American locations using previously published medium- to low-temperature thermochronology and geologic information.