Abstract

Colorful outcrop exposures of diagenetic iron oxide, clay, and carbonate cements in the Jurassic Navajo Sandstone reflect a multi-phase history of fluid–rock interactions. Characteristic mineralogical and geochemical variability occurs on microscopic and outcrop scales throughout southern Utah. We identify six common diagenetic facies and evaluate formation mechanisms, paragenetic relationships, and relative timing between alteration events. The diagenetic facies have distinctive visual characteristics, variations in mineralogy, major oxides, trace elements, and carbon and oxygen isotopes. They include red and bleached sandstone, diffuse and concretionary iron oxide precipitates, and carbonate concretions. Development of these facies requires changes in the interstitial fluid environment and an open geochemical system with basinwide fluid flow and variations in redox conditions. Spatial and temporal changes in paleohydrologic and diagenetic conditions indicate complex coupling and feedbacks between stratigraphic architecture, fluid flow, and basin evolution.

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