• journal_title：Geosphere
• Contributor：A. Nereson ; J. Stroud ; K. Karlstrom ; M. Heizler ; W. McIntosh
• Publisher：Geological Society of America
• Date：2013-06-01
• Format：text/html
• Language：en
• Identifier：10.1130/GES00837.1
• journal_abbrev：Geosphere
• issn：1553-040X
• volume：9
• issue：3
• firstpage：521
• section：INVESTIGATIONS OF NORTH AMERICA AS EARTHSCOPE REACHES ITS MATURITY THEMED ISSUE

The causal mechanisms for the onset and patterns of post-Miocene erosion of the western Great Plains remain the subject of an enthusiastic debate concerning 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. The ⁴⁰Ar/³⁹Ar ages of basalt-capped paleosurfaces define an episodic eruption history in the Raton-Clayton and Ocate volcanic fields and help to quantify patterns, amounts, and rates of differential erosion. Several data sets indicate patterns of NE-trending geologic features that require explanation, including: (1) crude volcanic “belts” of similar age, (2) parallel NE-oriented erosional escarpments retreating toward the NW, (3) differential denudation rates increasing systematically NW from a NE-trending hinge line of “low to no” erosion on the Great Plains, (4) a NE-trending zone of broad (50–100 km) convexities in stream profiles identified by an analysis of strath terraces and channel steepness (k_sn), (5) reorganization of stream networks that took advantage of an apparent relative base-level fall in the SE, and (6) an ∼150-km-long, ⁴⁰Ar/³⁹Ar-dated composite paleosurface that has been tilted 64 millidegrees/Ma since 3.4 Ma. Our synthesis of new ⁴⁰Ar/³⁹Ar geochronology with new calculations of regional surface denudation, channel steepness, and tilt rates shows that post-Miocene patterns of landscape evolution are best interpreted as related to dynamic uplift along the NE-trending Jemez lineament, with second-order impacts from climate-driven geomorphic variables. We interpret this dynamic uplift to be ultimately due to changing mantle structure and buoyancy with associated crustal melt flux.