International Journal of Applied Earth Observation and Geoinformation 44 (2016) 70–87 Contents lists available at ScienceDirect International Journal of Applied Earth Observation and Geoinformation journal homepage: www.elsevier.com/locate/jag Remote detection of fluid-related diagenetic mineralogical variations in the Wingate Sandstone at different spatial and spectral resolutions Unal Okyay ∗ , Shuhab D. Khan Department of Earth and Atmospheric Sciences, University of Houston, TX 77204, USA a r t i c l e i n f o Article history: Received 24 March 2015 Received in revised form 31 July 2015 Accepted 3 August 2015 Keywords: Rock alteration Diagenetic minerals Fluid-flow Ground-based hyperspectral imaging Wingate Sandstone a b s t r a c t Well-exposed eolian units of the Jurassic system on the Colorado Plateau including the Wingate Sand- stone, show prominent color variations throughout southeastern Utah due to diagenetic changes that include precipitation and/or removal of iron oxide, clay, and carbonate cement. Spatially variable char- acteristic diagenetic changes suggest fluid-rock interactions through the sandstone. Distinctive spectral signatures of diagenetic minerals can be used to map diagenetic mineral variability and possibly fluid-flow pathways. The main objective of this work was to identify characteristic diagenetic minerals, and map their spatial variability from regional to outcrop scale in Wingate Sandstone exposures of Lisbon Valley, Utah. Laboratory reflectance spectroscopy analysis of the samples facilitated identification of diagnos- tic spectral characteristics of the common diagenetic minerals and their relative abundances between altered and unaltered Wingate Sandstone. Comparison of reflectance spectroscopy with satellite, air- borne, and ground-based imaging spectroscopy data provided a method for mapping and evaluating spatial variations of diagenetic minerals. The Feature-oriented Principal Component Selection method was used on Advanced Spaceborne Thermal Emission and Reflection Radiometer data so as to map com- mon mineral groups throughout the broader Wingate Sandstone exposure in the area. The Minimum Noise Fraction and Spectral Angle Mapper methods were applied on airborne HyMap and ground-based hyperspectral imaging data to identify and map mineralogical changes. The satellite and airborne data showed that out of 25.55 km 2 total exposure of Wingate Sandstone in Lisbon Valley, unaltered sand- stone cover 12.55 km 2 , and altered sandstone cover 8.90 km 2 in the northwest flank and 5.09 km 2 in the southern flank of the anticline. The ground-based hyperspectral data demonstrated the ability to identify and map mineral assemblages with two-dimensional lateral continuity on near-vertical rock faces. The results showed that 39.71% of the scanned outcrop is bleached and 20.60% is unbleached while 6.33% remain unclassified, and 33.36% is masked-out as vegetation. The bleached and unbleached areas are alternating throughout the vertical face of the outcrop. The relative hematite abundance observed in the unbleached areas are somewhat symmetrical. This indicates fairly similar reaction intensities along the upper and lower reaction fronts observed in the vertical section. The distribution geometry and relative abundances of diagenetic minerals not only suggest multiple paths of fluid-flow in Wingate Sandstone but also provides some insight about relative direction of past fluid-flow. © 2015 Elsevier B.V. All rights reserved. 1. Introduction The chemical reactions between rocks and the subsurface flu- ids result in diagenetic changes in the host rock. The flow of these fluids through sedimentary reservoirs controls the subse- quent distribution and evolution of mineral composition, porosity and permeability; therefore, better understanding of fluid-flow through sedimentary units is critical to predict the distribution of ∗ Corresponding author. E-mail address: unalokyay@gmail.com (U. Okyay). alteration minerals, and natural resources such as ground water and hydrocarbons in the subsurface (Bell et al., 2010; Bowen et al., 2007). Several studies have been done to understand the history of fluid-flow in sedimentary units. These studies employed vari- ous methods including numerical modeling (Bethke, 1989; Garven, 1995; Person et al., 1996), fluid inclusion analysis (Goldstein, 2001; Mark et al., 2005), and geochemical analysis of diagenetic miner- als (Boles et al., 2004; Eichhubl et al., 2004; Kyser and Hiatt, 2003; Morad et al., 2000). Although these methods reveal valuable infor- mation about past fluid-rock interactions, the information provided on spatial variability of diagenetic mineralogical changes is limited. The use of reflectance spectroscopic methods, on the other hand, http://dx.doi.org/10.1016/j.jag.2015.08.001 0303-2434/© 2015 Elsevier B.V. All rights reserved.