207 Geoscience Information and Communication: Park Your Public Lands by the Library (Posters)
COLORATION AND DIAGENETIC HISTORY OF JURASSIC NAVAJO SANDSTONE AT COYOTE BUTTES, VERMILION CLIFFS NATIONAL MONUMENT, ARIZONA
Paper number: 207-5
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM
Authors
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Marjorie A. ChanUniversity of Utah, Salt Lake City, UT
Abstract
Sandstone coloration is categorized into four main, large-scale (10's m thick) diagenetic facies: 1) a primary, basal red facies; 2) a red and white banded transition facies; 3) a bleached upper facies; and 4) a secondary red facies associated with the re-introduction of iron-rich fluids along a fault trace. Both the red and white banded and bleached facies are commonly overprinted with two cross-cutting, Liesegang-related zones (m's thick): one of numerous, narrow, cm-scale, multi-colored Liesegang bands, and the second containing multiple orange chemical reaction fronts including iron oxide micro-concretions.
Stratigraphic relationships of reaction fronts show that large-scale diagenetic facies are due primarily to advective fluid flow and iron mobilization within the host rock. Small (cm-scale) and large (10's-m scale) bleaching patterns in the outcrop clearly indicate the upward migration and accumulation of a chemically reducing and bleaching fluid. Smaller-scale, Liesegang-type reaction fronts are due to diffusive mass transfer causing the chemical precipitation of iron oxide mineralogies.
The location draws thousands of wilderness enthusiasts and photographers each year, primarily to a unique geomorphic feature – “The Wave” – where impressive colors accent cross-strata resembling a cresting ocean wave. This study contributes to a better understanding of the intense diagenetic coloration and fluid flow history that distinguishes the Coyote Buttes as an exceptional geologic resource.