Support of high elevation in the southern Basin and Range based on the composition and architecture of the crust in the Basin and Range and Colorado Plateau

Andy Frassetto, Hersh Gilbert, George Zandt, Susan Beck, Matthew J. Fouch

Research output: Contribution to journalArticle

14 Scopus citations

Abstract

To explore the nature of how the structure and physical properties of the crust vary from extended to relatively unextended domains we present teleseismic receiver functions which measure crustal thickness, shear wavespeed structure and the Vp/Vs ratio at 12 seismic stations in eastern Arizona. The crustal thickness is ∼ 28 km, increases slightly eastward, and remains nearly uniform beneath the varying elevations in the southern Basin and Range. The observed Vp/Vs ratio in the Basin and Range (∼ 1.78) exceeds the global average. The southern Colorado Plateau exhibits thicker crust (∼ 40 km) and a slightly greater observed Vp/Vs (∼ 1.81). A discrete region in the Colorado Plateau generates an unusually high Vp/Vs ratio (1.90) and contains low wavespeed zones which serve as evidence of partial melt related to Quaternary volcanism. The metamorphic core complexes in the southern Basin and Range likewise exhibit anomalously high Vp/Vs values (1.79-1.87) and lack locally compensating crustal roots. Density models show that ∼ 85 kg/m3 lighter crust or ∼ 35 kg/m3 lighter mantle than that of the surrounding Basin and Range helps these metamorphic core complexes maintain their high elevation. Compositional modeling of intrusive bodies exposed throughout the Catalina-Rincon metamorphic core complex indicates that the observed high Vp/Vs ratio and modeled low density could result from substantial amounts of a plagioclase-rich, quartz-poor rock. These Vp/Vs data are evidence that significant compositional heterogeneity of the crust can occur over a short distance and provide a clue as to how these areas that underwent significant Tertiary extension may have been preconditioned for orogenic collapse.

Original languageEnglish (US)
Pages (from-to)62-73
Number of pages12
JournalEarth and Planetary Science Letters
Volume249
Issue number1-2
DOIs
StatePublished - Sep 15 2006

Keywords

  • Basin and Range
  • Colorado Plateau
  • Vp/Vs ratio
  • isostasy
  • metamorphic core complex
  • receiver function

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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