Charles Kerans

University of Texas at Austin | UT · Department of Geological Sciences

Oxygen concentration in the ocean is vital for sustaining marine ecosystems. While the potential impacts of deoxygenation on modern oceans are hard to predict, lessons can be learned from better characterizing past geological intervals formed under a greenhouse climate. The greenhouse Cretaceous containing several oceanic anoxic events characterize...

Seismic horizons play a significant role in reservoir model construction and sedimentary facies interpretation, providing crucial low-frequency constraints for seismic inversion. In basin and regional interpretations, the assumption that seismic reflections represent a stratigraphic surface with constant geologic time is significant for guiding sei...

The Bahamian Archipelago has been the subject of extensive studies of stratigraphy, carbonate island morphology and diagenetic overprinting for many decades. A recently‐acquired dataset comprised of high‐resolution light detection and ranging, tightly spaced cored boreholes with image logs, thin sections, porosity and permeability measurements, and...

Lower to Middle Permian strata in the Delaware Basin in southeast New Mexico and West Texas present a unique system to assess spatial and temporal variations in carbonate slopes as well as controls on variation. Detailed subsurface gamma-ray well-log mapping and visualization using approximately 8000 densely spaced well logs in the northern portion...

Carbonate contourite drifts formed by bottom currents are common on modern sea floors but are rarely defined in the rock record. Regional subsurface well-log mapping in the northern Delaware Basin in southeast New Mexico, USA, reveals early Permian carbonate-dominated elongate, mounded accumulations along the slope of the western margin of the basi...

The world-class Middle-Upper Devonian carbonate outcrops of the Lennard Shelf, Canning Basin, Western Australia, allow for examination of long-term reefal carbonate shelf-to-basin systems within a variety of settings and contexts, including hierarchical accommodation trends, global biological crises, greenhouse-to-transitional climatic changes and...

The windward islands of the Lucayan Archipelago (Bahamas) form an Atlantic Ocean– facing transect spanning >950 km in length and 6° of latitude. The islands’ topography is largely constructed from carbonate wind-blown dunes (i.e., aeolianites) deposited during the interglacial phases of the Late Pleistocene and Holocene. New digital elevation data...

Despite the numerous examples of siliciclastic and carbonate sediments interaction in mixed depositional systems, sequence stratigraphic interpretations seem to disassociate the two lithologies. Where a subaerial exposure surface is recognized in the carbonate-domain of a basin, for example, advancement of siliciclastics in the adjacent domain is i...

Banana holes are karst depressions that have primarily been reported from strandplains within the Bahamian archipelago. Banana holes have been hypothesized to form by downward dissolution in the vadose zone and in the phreatic zone by mixing dissolution and/or spatial variability in organic carbon inputs to the water table. While vadose models have...

Carbonate storm beds (tempestites) that are common on carbonate ramps form potential hydrocarbon reservoir facies, as they often display excellent porosity and permeability. Sedimentological characterization of these deposits in the outcrop is a valuable approach for recognizing and modeling them in the subsurface. This study aims to provide detail...

Isolated carbonate platforms have been historically attractive hydrocarbon exploration targets in both frontier and mature basins. Their isolated nature attributes them to high-risk-high-reward targets which is well demonstrated by globally recognized success stories ranging from the Paleozoic (Tengiz and Kashagan fields, Devonian platforms of Cana...

Ocean chemistry and carbonate sedimentation link Earth's climate, carbon cycle, and marine pH. The carbonate system in seawater is complex and there are large uncertainties in key parameters in deep time. Here, we link sedimentary textures formed in arid coastal environments and preserved in the rock record to past seawater carbonate chemistry. Pri...

Plain Language Summary Carbonate minerals precipitate from ions dissolved in water. Thick packages of carbonate rocks often form in shallow, tropical waters, and their accumulation rate depends on the availability of ions as well as biological agents that catalyze carbonate deposition such as animals and microbes. Geologic patterns in carbonate roc...

Flank margin caves are extreme endmembers of vuggy porosity which forms as diagenesis drives the progressive coalescence of smaller solutional pore spaces. Due to their morphological isolation during formation, the prevailing hypothesis has been that fluid flow in and out of flank margin caves occurs via the matrix permeability and that adjacent ch...

It is well established that sedimentary margins grow by sediments bypassing through shelf- and slope-incising canyons onto the basin floor and by sediments being deposited incrementally across clinoforming and prograding margins. However, we argue that these two distinctive types of deep-water sediment supply to the basin floor and to the margin ar...

Integrative characterizations of karst systems on low-lying eogenetic carbonate platforms are rare and often limited to areas of direct observation where caves can be entered and explored. Because hydraulic properties of eogenetic limestones have been implicitly assumed to be homogeneous, classical models of carbonate island karst development stres...

Pleistocene carbonates of the Bahamas-Florida archipelago are crucial archives of past sea levels (SL) and paleo-seascapes formed by physical and biological processes. In this study, we use new high-resolution LiDAR data obtained from the National Oceanic and Atmospheric Administration (NOAA) to shed light on the spatial distribution of a fossilize...

Oligocene–Miocene carbonates are prolific hydrocarbon reservoirs in Southeast Asia. Extensive subsurface data for this stratigraphic section has become available through exploration and production activities. A carbonate shelf in the study area showed an evolution in shelf architecture and lithofacies during this period. Despite the economic import...

We address concerns raised by Wanless and Dravis (2020) on our paper documenting the late Quaternary evolution of West Caicos island. We negate the claim that omitting their paper (Dravis and Wanless, 2017) had any consequences for our interpretations. We also provide reasoning and data to demonstrate that our interpretation of the Quaternary strat...

We address concerns raised by Wanless and Dravis (2020) on our paper documenting the late Quaternary evolution of West Caicos island. We negate the claim that omitting their paper (Dravis and Wanless, 2017) had any consequences for our interpretations. We also provide reasoning and data to demonstrate that our interpretation of the Quaternary strat...

Severe global climate change led to the deterioration of environmental conditions in the oceans during the Toarcian Stage of the Jurassic. Carbonate platforms of the Western Tethys Ocean exposed in Alpine Tethyan mountain ranges today offer insight into this period of environmental upheaval. In addition to informing understanding of climate change...

Severe global climate change led to the deterioration of environmental conditions in the oceans during the Toarcian Stage of the Jurassic. Carbonate platforms of the Western Tethys Ocean exposed in Alpine Tethyan mountain ranges today offer insight into this period of environmental upheaval. In addition to informing understanding of climate change...

We address concerns raised by Wanless and Dravis (2020) on our paper documenting the late Quaternary evolution of West Caicos island. We negate the claim that omitting their paper (Dravis and Wanless, 2017) had any consequences for our interpretations. We also provide reasoning and data to demonstrate that our interpretation of the Quaternary strat...

This study documents the detailed facies and sequence stratigraphic architecture of a multi‐cyclic patch‐reef and its associated ramp interior facies that formed during Oceanic Anoxic Event 1b in the Mural Limestone, Arizona, USA. Ramp interior facies are comprised of bedded wackestone/packstone, rudist build‐up and coral–algal patch‐reef facies lo...

One of the remaining questions in carbonate geology and reservoir studies is the origin of steep-walled carbonate platform margins and the role of gravity versus other structural processes in controlling the distribution of fracture networks and failure surfaces. This study is an attempt to document the role of gravity, interacting with stratigraph...

Fossilized reefs can preserve critical information about changes in marine environments over a relatively short period of time. The interpretation of these changes is often hindered by the complexity of reef growth with respect to architecture, biotic zonation, and time. High-resolution mapping and data collection incorporating both sequence strati...

Geochemical data from carbonates often constrain the nature of environmental change during biotic turnover events. Many ancient carbonates, however, formed in geographically-isolated basins subject to local environmental factors, resulting in varying extinction rates between open ocean and restricted settings. It follows that high-resolution data f...

We tested the validity of tracking seismic events as representations of chronostratigraphic surfaces at the subseismic, high-frequency-cycle level. A high-resolution geocellular model was generated from approximately 400 m of mixed clastic-carbonate sequences in the San Andres and Grayburg Formations in the Permian Basin, with 0.3-0.6 m layering an...

The three-dimensionally complex, highly progradational mixed siliciclastic–carbonate strata of the San Andres and Grayburg Formations have long been the backbone of conventional hydrocarbon reservoir production from the Permian Basin, and significant recovery continues via waterflooding and CO2 injection. Besides, nonreservoir equivalents of these...

The mid-Cretaceous (Albian-Cenomanian) El Doctor platform of central Mexico is one of a series of isolated platforms that record the final phase of shoal-water carbonate deposition in the Western Gulf of Mexico. Vertical exposures of >400m provide insight into the complex facies relationships between shallow water shelfal carbonates and their margi...

Late Palaeozoic‐age strata from the Capitan Reef in west Texas show facies‐dependent heterogeneity in the sulphur isotopic composition of carbonate‐associated sulphate, which is trace sulphate incorporated into carbonate minerals that is often used to reconstruct the sulphur isotopic composition of ancient seawater. However, diagenetic pore fluid p...

Widespread carbonate platform growth in the Cretaceous Tethys is associated with expansive reef margin and interior patch reef development. These reefs and their associated facies have the potential to be significant hydrocarbon reservoirs, but characterization is challenging because of complex facies distributions, inadequate understanding of biot...

The data set of the island of West Caicos consists of a combination of high-resolution lidar and digital imagery, radiometric data, and amino acid racemization (AAR) D/L values as well as extraordinary preservation of sedimentary and bio-constructed deposits on the island. Together with a well-established regional stratigraphic framework from the n...

The Bone Spring play and associated Avalon subplay represent a succession of calcareous, siliceous, and carbonaceous sediment gravity-flow deposits associated with significant production of oil, condensate, and dry gas in the Delaware Basin, Texas. Correlation of the upper Bone Spring and upper Avalon systems to the outcropping Cutoff Formation slo...

The Global Stratotype Section and Point (GSSP) for the base of the Roadian Stage is identified within the Cutoff Formation in Guadalupe Mountains National Park (GMNP). Previous mapping of the Cutoff Formation near the shelf margin of the buried late Kungurian (late Leonardian using North American terminology) Victorio Peak and equivalent Bone Sprin...

The Middle Jurassic Todilto Member of the Wanakah Formation is a carbonate and gypsum unit inset into the underlying aeolian Entrada Sandstone in the San Juan Basin. Field and thin section study of the uppermost Entrada and Todilto at Ghost Ranch, New Mexico, identified Todilto facies and their relationship to remnant Entrada dune topography. Resul...

We use finite element numerical modeling to show that carbonate platform morphology is a control on syndepositional deformation in steep-walled carbonate platforms. We simulate gravity application on three end-member carbonate platform margin morphologies: (1) a mixed planar-concave up shaped shelf margin from Tobacco Cay, Belize, (2) a concave up...

Stratal geometries and platform trajectories in shelf-Top carbonates contain a record of past eustatic, tectonic, and oceanographic changes throughout earth history. However, intrinsic structural processes such as faulting, fracturing, and differential compaction complicate the interpretation of stratal architecture in these settings. Large-scale s...

The late Paleozoic has long been recognized a time of significant continental glaciation associated with high-frequency, high-amplitude glacioeustasy. Although, precise assessment of glacioeustatic amplitudes are difficult to extract from the stratigraphic record, best approximations may be possible by analyzing spatial and temporal distributions o...

Quaternary evolution of West Caicos Island, Turks and Caicos

Steep, debris-rich, progradational carbonate slope systems have been well-documented around the world in a variety of settings and time periods. While the association of such slopes with deep microbial boundstone upper slope factories, the planar nature of their clinoform profiles, and their toe-of-slope trajectory patterns have been discussed thor...

A sequence stratigraphic framework of the Late Jurassic (Oxfordian) Hanifa Formation at its exposure in Central Arabia is presented for the first time. This study offers the first high-resolution stratigraphic framework of the Hanifa along the Tuwaiq Escarpment by measuring 15 sections (~ 770 m total thickness) over an oblique-to-dip distance of 26...

The carbonate and siliciclastic outcrops of the Guadalupe Mountains in the Permian Basin of West Texas and New Mexico have provided a rich set of basic and advanced conceptual models for geologists across the entire spectrum of experience for carbonate-ramp and steep-rimmed–platform settings as well as the adjacent deep-water siliciclastics not dea...

The world-class Middle–Upper Devonian carbonate outcrops of the Lennard Shelf, Canning Basin, Western Australia, offer a unique opportunity to examine reefal carbonate shelf-to-basin evolution in response to multiple coeval extrinsic and intrinsic drivers. Variable styles of carbonate stratigraphic architecture and heterogeneity developed as a func...

The Lower Cretaceous stratigraphic section in the northern Gulf of Mexico (GOM) comprises several well-documented carbonate systems that have prominent shelf-margin buildups, including the Berriasian Knowles Limestone ramp and shelf system, Barremian Sligo Formation shelf system, Aptian Pearsall Formation ramp system, and Albian Glen Rose, Edwards,...

Micropore-dominated carbonate reservoirs remain challenging for accurate hydrocarbon evaluation and production because conventional reservoir models using depositional textures and petrophysical properties to distribute porosity and permeability cannot be applied. Nevertheless, understanding the distribution of pore systems and predicting the fluid...

We present 3D outcrop-constrained synthetic seismic models to investigate the chronostratigraphic significance of seismic reflections of a highly-progradational mixed carbonate-siliciclastic shelf margin. Ground-based LIDAR (Light-Detection and Ranging) was paired with field mapping to construct a 3D stratigraphic framework with a known chronostrat...

Discussion points raised by Rose (2016) concentrate on late Albian stratigraphic relationships between formations of the East Texas Basin and the San Marcos Arch of the Comanche Platform in the northern Gulf of Mexico. Criticisms of Phelps et al. (2014) regarding stratigraphic nomenclature, palaeogeography and regional lithostratigraphic correlatio...

We investigate the Pleistocene (<400 Ka) outcrop exposures on West Caicos Island, British West Indies to assess the factors that affect the mechanical behavior of young, recently deposited carbonate grainstone facies. West Caicos provides an ideal location to evaluate the factors that affect the porosity and unconfined compressive strength (UCS) of...

Active carbonate platforms provide modern analogs to study microbial-mat development and taphonomy in the sedimentary record. Microbial-mat descriptions and classifications for tropical tidal-flat environments have focused predominantly on morphological observations. This is exemplified by flat and biscuit-shaped mats, where the mat morphotypes are...

A large-scale inflection (LSI) in the slope profile may develop as a carbonate platform is drowned and abandoned basinward of the active shelf break. The impact of LSIs on the sediment dispersal patterns and stratigraphic architecture of carbonate slopes remains understudied. Outcrops of the Lower–middle Permian Cutoff Formation in the GuadalupeMou...

Pre-existing structural elements can have profound effects on fracture and fault development in younger strata, especially in areas that undergo significant changes in tectonic setting due to reactivation along older structures. Increased fracture development around the faults may be difficult to detect in subsurface data, but highlights the volume...

The use of unmanned aerial vehicles (UAVs) has increased in popularity among field geologists as a method of collecting quantified field data. Digital photographs were collected using a UAV and a 12 megapixel camera. The methods and workflow utilized to acquire, process and construct a high-resolution 3D point cloud (i.e., latitude, longitude, and...

The Devonian stratigraphic record contains a wealth of information that highlights the response of carbonate platforms to both global scale and local phenomena that drive carbonate architecture and productivity. Data sets around the world exhibit repeatable signals embedded in the Middle–Upper Devonian carbonate record that are related to biotic cr...

Many studies document the occurrence of carbonate progradational successions that are driven by overall accommodation-limited conditions and represent periods when substantial volumes of sediment are stored in slope settings. However, few have reported on the detailed internal anatomy and components of prograding clinothems, and furthermore, little...

Carbonate reefal margin and foreslope settings are characteristically heterogeneous and difficult to predict due to a spectrum of sediment source factories, resedimentation processes, resultant deposit types, and controlling parameters. In particular, the effects of changes in long-term accommodation on the composition, architecture, and sediment d...

Facies-averaged acoustic impedance is the most common in forward stratigraphic and seismic modeling workflow. He et al. (2015) highlights challenges to accurately interpreting geologic time lines from seismic models characterized by impedance models with high lateral heterogeneity. Herein, we extend this study to a strongly prograding mixed silicic...

Rudist buildups are important reservoirs in many Cretaceous fields in the Middle East, but they are generally near or below seismic resolution. The dimension, shape, and architecture of rudist buildups can be assessed using outcrop, although only partly so because of pseudo-2D observations of geobodies intersecting with the outcrop. We used ground-...