Evaporite karst geohazards in the Delaware Basin, Texas: review of traditional karst studies coupled with geophysical and remote sensing characterization

Evaporite karst throughout the Gypsum Plain of west Texas is complex and extensive, including manifestations ranging from intrastratal brecciation and hypogene caves to epigene features and suffosion caves. Recent advances in hydrocarbon exploration and extraction has resulted in increased infrastructure development and utilization in the area; as a result, delineation and characterization of potential karst geohazards throughout the region have become a greater concern. While traditional karst surveys are essential for delineating the subsurface extent and morphology of individual caves for speleogenetic interpretation, these methods tend to underestimate the total extent of karst development and require surficial manifestation of karst phenomena. Therefore, this study utilizes a composite suite of remote sensing and traditional field studies for improved karst delineation and detection of potential karst geohazards within gypsum karst. Color InfraRed (CIR) imagery were utilized for delineation of lineaments associated with fractures, while Normalized Density Vegetation Index (NDVI) analyses were used to delineate regions of increased moisture flux and probable zones of shallow karst development. Digital Elevation Models (DEM) constructed from high-resolution LiDAR (Light Detection and Ranging) data were used to spatially interpret sinkholes, while analyses of LiDAR intensity data were used in a novel way to categorize local variations in surface geology. Resistivity data, including both direct current (DC) and capacitively coupled (CC) resistivity analyses, were acquired and interpreted throughout the study area to delineate potential shallow karst geohazards specifically associated with roadways of geohazard concern; however, detailed knowledge of the surrounding geology and local karst development proved essential for proper interpretation of resistivity inversions. The composite suite of traditional field investigations and remotely sensed karst delineations used in this study illustrate how complex gypsum karst terrains can be characterized with greater detail through the utilization of rapidly advancing technologies, especially in arid environments with low vegetation densities

Hypogene Calcitization: Evaporite Diagenesis in the Western Delaware Basin

Evaporite calcitization within the Castile Formation of the Delaware Basin is more widespread and diverse than originally recognized. Coupled field and GIS studies have identified more than 1000 individual occurrences of calcitization within the Castile Formation outcrop area, which includes both calcitized masses (limestone buttes) and laterally extensive calcitized horizons (limestone sheets). Both limestone buttes and sheets commonly contain a central brecciated zone that we attribute to hypogene dissolution. Lithologic fabric of calcitized zones ranges from little alteration of original varved laminae to fabrics showing extensive laminae distortion as well as extensive vuggy and open cavernous porosity. Calcitization is most abundant in the western portion of the Castile outcrop region where surface denudation has been greatest. Calcitization often forms linear trends, indicating fluid migration along fractures, but also occurs as dense clusters indicating focused, ascending, hydrocarbon-rich fluids. Native sulfur, secondary tabular gypsum (i.e. selenite) and hypogene caves are commonly associated with clusters of calcitization. This assemblage suggests that calcium sulfate diagenesis within the Castile Formation is dominated by hypogene speleogemesis

Physical and Chemical Controls on Suffosion Development in Gypsic Soil, Culberson County, Texas

In the Gypsum Plain, suffosion processes have encouraged road failure through dissolution and transport of gypsic soils; however, no prior research has been conducted within the Delaware Basin in regard to these processes. These phenomena were evaluated in both field and laboratory settings in order to assess the parameters of suffosion development associated with Ranch to Market (RM) 652 in Culberson County, Texas, where infrastructure extends across Castile and Rustler strata. Field studies simulated surficial ponding in various gypsic soils and correlated suffosion potential with soil composition and thickness. Soluble fractions of gypsic soils were delineated through geochemical analyses, further expanding upon the soil descriptions published in the Culberson County Soil Survey (USDA, 2013). Suffosion modeling replicated processes observed in the field through repeated infiltration of Dellahunt and Elcor soils—soil piping and subsidence were induced within suffosion models. Lineaments inferred as solutional fractures were delineated using color infrared (CIR) images to determine regional suffosion potential. Results obtained from this research were used to form a conceptual model of suffosion development in order to better mitigate damage imposed on infrastructure in evaporite karst terrains. Regions with thick, heterogeneous soils of low to moderate gypsum content (10-70%) and moderate fracture densities (100-800 m/km2) are optimal for suffosion development. This model should be considered for future projects in not only the Gypsum Plain, but for other arid environments with significant evaporite karst and gypsic soils as well

Epigene and Hypogene Karst Manifestations of the Castile Formation: Eddy County, New Mexico and Culberson County, Texas, USA

Permian evaporites of the Castile Formation crop out over ~1,800 km2 in the western Delaware Basin (Eddy County, New Mexico and Culberson County, Texas, USA) with abundant and diverse karst manifestations. Epigene karst occurs as well-developed karren on exposed bedrock, while sinkholes dominate the erosional landscape, including both solutional and collapse forms. Sinkhole analyses suggest that more than half of all sinks are the result of upward stoping of subsurface voids, while many solutional sinks are commonly the result of overprinting of collapsed forms. Epigene caves are laterally limited with rapid aperture decreases away from insurgence, with passages developed along fractures and anticline fold axes. Hypogene karst occurs as diverse manifestations, forming the deepest and longest caves within the region as well as abundant zones of brecciation. Hypogene caves exhibit a wide range of morphologies from complex maze and anastomotic patterns to simple, steeply dipping patterns, but all hypogene caves exhibit morphologic features (i.e. risers, outlet cupolas and half-tubes) that provide a definitive suite of evidence of dissolution within a mixed convection (forced and free convection) hydrologic system. Extensive blanket breccias, abundant breccia pipes and numerous occurrences of calcitized evaporites indicate widespread hypogene speleogenesis throughout the entire Castile Formation. Although most cave and karst development within the Castile outcrop region appears to have hypogene origins, epigene processes are actively overprinting features, creating a complex speleogenetic evolution within the Castile Formation

Castile Evaporite Karst Potential Map of the Gypsum Plain, Eddy County, New Mexico and Culberson County, Texas: A GIS Methodological Comparison

Castile Formation gypsum crops out over ,1,800 km2 in the western Delaware Basin where it forms the majority of the Gypsum Plain. Karst development is well recognized in the Gypsum Plain (i.e., filled and open sinkholes with associated caves); however, the spatial occurrence has been poorly known. In order to evaluate the extent and distribution of karst development within the Castile portion of the Gypsum Plain, combined field and Geographic Information System (GIS) studies were conducted, which enable a first approximation of regional speleogenesis and delineate karst-related natural resources for management. Field studies included physical mapping of 50, 1-km2 sites, including identification of karst features (sinkholes, caves, and springs) and geomorphic mapping. GIS-based studies involved analyses of karst features based on public data, including Digital Elevation Model (DEM), Digital Raster Graphic, (DRG) and Digital Orthophoto Quad (DOQ) formats. GIS analyses consistently underestimate the actual extent and density of karst development, based on karst features identified during field studies. However, DOQ analyses coupled with field studies appears to produce accurate models of karst development. As a result, a karst potential map of the Castile outcrop region was developed which reveals that karst development within the Castile Formation is highly clustered. Approximately 40% of the region effectively exhibits no karst development (,1 feature/km2). Two small regions (,3 km2 each) display intense karst development (.40 features/km2) located within the northern extent of the Gypsum Plain, while many regions of significant karst development (.15 features/km2) are distributed more widely. The clustered distribution of karst development suggests that speleogenesis within the Castile Formation is dominated by hypogenic, transverse processes

High-frequency cyclicity in the Mediterranean Messinian evaporites: evidence for solar-lunar climate forcing

The deposition of varved sedimentary sequences is usually controlled by climate conditions. The study of two Late Miocene evaporite successions (one halite and the other gypsum) consisting of annual varves has been carried out to reconstruct the paleoclimatic and paleoenvironmental conditions existing during the acme of the Messinian salinity crisis, ~ 6 Ma, when thick evaporite deposits accumulated on the floor of the Mediterranean basin. Spectral analyses of these varved evaporitic successions reveal significant periodicity peaks at around 3-5, 9, 11-13, 20-27 and 50-100 yr. A comparison with modern precipitation data in the western Mediterranean shows that during the acme of the Messinian salinity crisis the climate was not in a permanent evaporitic stage, but in a dynamic situation where evaporite deposition was controlled by quasi-periodic climate oscillations with similarity to modern analogs including Quasi-Biennial Oscillation, El Ni\~no Southern Oscillation, and decadal to secular lunar- and solar-induced cycles. Particularly we found a significant quasi-decadal oscillation with a prominent 9-year peak that is commonly found also in modern temperature records and is present in the contemporary Atlantic Multidecadal Oscillation (AMO) index and Pacific Decadal Oscillation (PDO) index. These cyclicities are common to both ancient and modern climate records because they can be associated with solar and solar-lunar tidal cycles.Comment: 13 pages, 10 figures, 1 Tabl

GEOPHYSICAL DELINEATION OF MEGAPOROSITY AND FLUID MIGRATION PATHWAYS FOR GEOHAZARD CHARACTERIZATION WITHIN THE DELAWARE BASIN, CULBERSON COUNTY, TEXAS

ABSTRACT Differential dissolution of gypsum karst within the Delaware Basin poses a significant threat to infrastructure that society depends on. The study area is located in Culberson County, Texas and traverses a distance of approximately 54 kilometers along RM 652 within the Gypsum Plain which is situated on the northern margin of the Chihuahua Desert and includes outcrops of Castile and Rustler strata that host karst geohazards. Regions of karst geohazard potential have been physically surveyed proximal to the study area in evaporites throughout the Castile Formation outcrop; minimal hazards, in comparison to the Castile Formation, have been documented in the Rustler Formation. A TR-5 OhmMapper capacitively-coupled resistivity meter was used to acquire resistivity data for geohazard characterization. This study utilized a traditional dipole-dipole array, with an electrode spacing of 2.5 meters between receivers, and a transmitter offset of 2.5 meters. This geometric configuration combined with the medium analyzed, allowed for resistivity readings to be recorded up to approximately 5 meters deep. Data acquisition was recorded with the OhmMapper attached to a vehicle moving at approximately 3 kilometers per hour and transmitting and receiving once per second (approximately three feet per sample). Resistivity data was processed using AGI’s EarthImager 2D inversion software. Capacitively-coupled resistivity has shown to be effective in locating karst geohazards in the shallow subsurface

CHARACTERIZATION AND DELINEATION OF POTENTIAL EVAPORITE GEOHAZARDS USING ELECTRICAL RESISTIVITY METHODS ALONG FM 2185, CULBERSON COUNTY, TEXAS

Extensive karst development within the Delaware Basin of West Texas and southeastern New Mexico poses a significant geohazard threat to infrastructure. Dissolution of regional evaporite strata have led to manifestations of karst geohazard phenomena including sinkholes, subsidence features, and caves. The study area is located within the Gypsum Plain in Culberson County, Texas, and includes outcrops of Castile and Rustler strata that host gypsum karst geohazards. Land reconnaissance surveys conducted during the summer of 2019 documented numerous surficial manifestations of karst features proximal to Farm to Market Road 2185 (FM 2185). In combination with traditional survey techniques, electrical resistivity methods were used to delineate karst features along a 48-kilometer segment of FM 2185. Capacitively-Coupled Resistivity (CCR) and Direct-Current Resistivity (DCR) methods were used to characterize evaporite karst features that do not manifest surficially but pose potential geohazard concerns. CCR data was acquired using the Geometrics OhmMapper G-858 resistivity system, which uses a dipole-dipole configuration composed of five receivers connected by 2.5-meter coaxial cables and a transmitter offset of 2.5 meters. In combination with the medium analyzed, this geometric configuration enabled resistivity soundings up to 5 meters deep. DCR data was collected with a SuperSting (R8/IP) multi-electrode earth resistivity meter using 112 electrodes with 2-meter spacing and a dipole-dipole array configuration. This enabled a depth of investigation of up to 73 meters. Data was processed using AGI’s (Advanced Geometrics Inc.) EarthImager 2D software and used to delineate and characterize karst-related geohazards in the shallow subsurface within the study area

Soil Gypsum Content Analysis of the Proposed Road Route Extension of FM 2185 in the Gypsum Plain, Culberson County, Texas

Soils serve as the underlying substrate on which foundations for most structures are built. The properties of a soil type are therefore an important consideration in building engineered structures. Gypsic soils are problematic for construction of such structures. One of the main problems with gypsic soils is dissolution. Gypsum (CaSO4·2H2O) in soils dissolves easily creating voids which can be detrimental to the integrity of engineering structures. To mitigate this, it is important to determine the amount of gypsum present in soils, before construction is initiated. In this study, three methods were employed in the determination of gypsum content in soils along a proposed road route in the Gypsum Plain, Culberson County, Texas: the wet chemical method, the X-ray fluorescence method and the thermogravimetric method. Results showed no significant difference in gypsum concentrations using the varying methods on samples obtained at the same point in a location but showed a significant difference in the concentration of samples obtained at different depths in a location. Gypsum contents along the approximately ninety-kilometer road route was predominantly relatively low, with about 65% of sample locations having gypsum content of less than 10%. About 11% of sampling locations, together totaling about three miles of the route, had high gypsum contents of over 70%

Characterization and Delineation of Karst Geohazards Along RM652 Using Electrical Resistivity Tomography, Culberson County, Texas

The Delaware Basin of West Texas and southeastern New Mexico is the major western subdivision of the Permian Basin and a northern extension of the Chihuahuan Desert. The major evaporite unit within the Delaware Basin is the Castile Formation, which consists of gypsum/anhydrite and is highly susceptible to dissolution and karsting. Manifestations of karst within the Castile outcrop are abundant and include sinkholes, subsidence features and caves, both epigene and hypogene in origin. Land reconnaissance surveys conducted during the summer of 2015 documented abundant karst landforms in close proximity to a major thoroughfare, RM 652, in Culberson County, Texas. 2D electrical resistivity surveys were conducted at sixteen sites to characterize and delineate karst related hazards, both laterally and vertically, associated with the road. Data was collected with a SuperSting (R8/IP) multi-electrode earth resistivity meter with a dipole-dipole array type. Resistivity data collected was processed using EarthImager 2D to produce inverted profile sections of each site. Two dimensional electrical resistivity tomography was shown to be effective in detecting karst features in the shallow subsurface within the study area