The causal mechanisms for the onset and patterns of post-Miocene erosion of the western Great Plains remain the subject of an enthusiastic debate between the roles of climatically-modulated geomorphic parameters and tectonic rock uplift as drivers of long-term erosion. This study distinguishes between these drivers on the plains of New Mexico and Colorado where post-Miocene erosion and late Cenozoic volcanism of the Jemez lineament have produced distinctive modern landscapes characterized by deep bedrock canyons and inverted, basalt-capped mesas. 40Ar/39Ar ages are used to define an episodic eruption history in the Raton-Clayton volcanic field and to quantify denudation rates from flow-capped paleosurfaces. Several datasets indicate patterns of surface topography that are consistent with dynamic rock uplift along a NE-trending flexural bulge above the Jemez low-velocity mantle anomaly, but are not well-explained by climate. They include: (1) crude volcanic "belts" of similar age, (2) retreating erosional escarpments, (3) differential landscape denudation measured from a NE-trending hinge-line of "low-to-no" erosion, (4) a NE-trending zone of broad (50-100km) convexities in stream profiles identified by an analysis of channel steepness (5) reorganization of stream networks from ESE-flowing streams, to a SSE flowing Canadian River that takes advantage of a relative base level fall in the SE, and (6) a ~150-km-long, 40Ar/39Ar-dated composite paleosurface which indicates total tilting of 64 millidegrees/Ma (and ~34 millidegrees/Ma of tectonic tilting) since 3.4 Ma. Proposed mantle-driven rock uplift along the NE-trending Jemez zone is overprinted on N-S trending mid-Tertiary uplift of the Rocky Mountain orogenic plateau relative to the Great Plains.
Earth and Planetary Sciences
Level of Degree
Department of Earth and Planetary Sciences
First Committee Member (Chair)
Second Committee Member
dynamic topography, landscape evolution, argon geochronology, Jemez lineament
Nereson, Alexander. "Dynamic topography of the western Great Plains : geomorphic and 40Ar/39Ar evidence for mantle-driven uplift associated with the Jemez lineament, New Mexico and SE Colorado." (2012). https://digitalrepository.unm.edu/eps_etds/58