Stratigraphic and Structural Framework of the Soda Lake Geothermal Field, Western Nevada - Implications for Understanding Geothermal Systems in the Great Basin Region
This report provides a detailed stratigraphic analysis, conceptual structural model, and three-dimensional (3D) geological model of the Soda Lake geothermal field, a geothermal system in the Carson Sink basin in northwestern Nevada. We first present an updated stratigraphy of the field area based on re-analysis of drill cuttings, geophysical logs, and radiometric dates from key igneous units. The stratigraphy was validated against bedrock sections in surrounding ranges and basin-fill sections derived from wells in the Carson Sink. In the second section, we present a detailed 3D geological model of the field based on three inputs: 1) well intercepts interpreted in context with the new stratigraphy, 2) block tilt estimates from borehole bedding attitude logs, and 3) a fault framework derived from drill intercepts and a 3D seismic reflection survey.
The stratigraphic framework at the Soda Lake geothermal field is dominated by 1) ~1 km of late Miocene to Quaternary basin-fill sediments and volcanic units, 2) an underlying ~1-km-thick section of middle to late Miocene volcanic and sedimentary rock, and 3) Mesozoic metamorphic and granitic basement. Unconsolidated late Miocene to Quaternary basin fill can be divided into distinctive upper and lower units. The upper unit is highly variable but dominated by pebble to silt-size quartzo-feldspathic detritus. It contains 2–3 marker beds, the most significant of which is a 30- to 60-m-thick mudstone layer at ~245–275 m depth. Basin-fill sediments below this mudstone horizon are moderately coarse grained but become increasingly lithic-rich and epiclastic down section. The lower basin-fill unit includes a lithic lapilli crystal ash tuff and an underlying ~300 to 400-m-thick section of lacustrine silt and mud. The basin fill is interrupted by a small, 5.1 Ma trachyandesite volcanic center near the heart of the Soda Lake well field. The basin-fill sediments are underlain by a ~1-km-thick section of middle to late Miocene volcanic and sedimentary strata. It is dominated by mafic flows that are similar to Miocene lavas in the surrounding highlands. The Tertiary bedrock section also includes minor intervals of intermediate to felsic tuff, clastic sediments, and limestone. Two of the thicker and more continuous non-volcanic intervals serve as stratigraphic marker units. Granitic and metasedimentary Mesozoic basement units intercepted in wells at the Soda Lake geothermal field are correlated with recognized assemblages in the surrounding region.
The structural framework at the Soda Lake geothermal field is dominated by a series of east-dipping, N5˚E-striking normal faults that are ~10 km in length. This set of faults bound a series of west-tilted fault blocks and half-grabens. The most closely spaced of these east-dipping faults are near the center of the Soda Lake well field and define the west side of a deep central graben. They step slightly to the left in tandem a few hundred meters west of one of the current production zones. Maximum throws on the largest of these faults range from 200 to 450 m at the Mesozoic basement contact, and dips range from 65˚to 75˚ east. The maximum fault block tilt in the central graben is ~35˚ west, based on well intercepts and dipmeter data. A subordinate set of north-striking, west-dipping normal faults is also present, and limited data suggest they are similar in strike length to the more dominant east-dipping fault set. A ~2-km-long, nearly vertical, southeast-dipping, east-northeast-striking cross-fault is present in the production area and appears to intersect the most prominent east-dipping faults slightly south of the step-over. Offset on all fault sets appears to be roughly contemporaneous, with extension constrained from ~13 Ma to present. Tilt versus age measurements suggest graben development slowed significantly at ~5 Ma. However, the main faults continued to accommodate minor normal slip into the late Pleistocene. The east- and west-dipping normal faults are inferred to intersect beneath the central graben.
Upwelling fluids at the field appear to be controlled by a hybrid setting that includes the minor step-over, fault intersection between the north- and east-northeast-striking faults on the west side of the central graben, and intersecting oppositely dipping normal faults beneath the central graben. Three or more historically or presently active wells intersect the east-dipping, northerly striking normal faults that form the west side of the central graben. Two currently active geothermal wells ≥700–800 m southeast of the step-over intersect the main west-dipping fault that bounds the east side of the central graben. Two notable stratigraphic features may influence the geothermal system. The ~5 Ma trachyandesite volcanic center that underlies the well field may provide subvertical fracture permeability, enhancing shallow production from wells that do not intersect the major normal faults. Production may also be enhanced by the low permeability mudstone horizon in the upper basin fill that may act as a clay cap for the geothermal upwellings along subjacent faults.
Landslide susceptibility mapping requires knowledge of geological criteria, including grain size and lithological boundaries. The north shore of Lake Erie (Ontario) is prone to landslides in areas with steep lake bluffs, such as in the Port Stanley area. Several regional stratigraphic models have been developed for the Lake Erie basin; however, the lithological heterogeneity (facies), sedimentary architecture, and interpreted depositional processes and environments in the Port Stanley area have not been reported in the literature. This paper presents new sedimentological data recorded in logs from lake bluffs in the Port Stanley (Hawk Cliff) area. This study applies a facies analysis approach to 1) understand the localized depositional processes and environments, 2) delineate the sedimentary architecture (geological framework), and 3) develop a facies model to characterize the depositional system. The sedimentary succession records nearly continuous deposition of glaciolacustrine and prodelta muds, sand, and diamicts that transition upward to delta slope sands, which are truncated by a distributary channel fill succession and delta front sediments. A facies model for a prograding sandy delta in an ice-contact glacial lake under normal- and forced-regression during overall ice retreat from the basin is proposed, which may facilitate correlation to process-related units elsewhere and provide insight to the broader geological history of the Lake Erie basin. The superposition of low-permeability muds at the base and overlying higher permeability sands results in water saturation at the mud-sand contact which, together with toe erosion, may contribute to landslide susceptibility along the north shore of Lake Erie.
J. Slomka· Canadian journal of earth sc...· 0 citations
Geological mapping is essential for understanding the relationships among geomorphology, stratigraphy, lithology, and structural geology, which collectively control landscape evolution. This study aims to characterize the geomorphology, stratigraphy, structural geology, and geological evolution of the Rembang area and its surroundings in the North Serayu Zone, Central Java, Indonesia. The research employed an integrated qualitative and quantitative geological mapping approach combining field investigations, geomorphological analysis, stratigraphic interpretation, structural measurements, petrographic observations, Geographic Information System (GIS), and Digital Elevation Model (DEM-SRTM) analysis over a 16 km² study area. The results identified two principal geomorphological units, namely denudational hills (55%) and denudational plains (45%), characterized by dendritic to sub-dendritic drainage patterns controlled by lithological resistance and tectonic structures. Stratigraphically, the area consists of three major lithological units: Andesite Intrusion, Andesite Breccia, and Quaternary Alluvial Deposits, representing successive magmatic, volcanic, and surface depositional processes. Structural analysis revealed a dominant northwest-southeast tectonic trend expressed by joints and a dextral normal fault that significantly controls ridge alignment, valley orientation, and drainage development. Petrographic observations indicate porphyritic to aphanitic andesite composed predominantly of plagioclase, quartz, and biotite, confirming shallow intrusive magmatism. The reconstructed geological evolution suggests that the area experienced Pliocene magmatism, followed by Pleistocene volcanism, subsequent tectonic deformation, and ongoing Holocene denudation and fluvial sedimentation. These findings demonstrate that the present landscape represents the combined effects of lithological resistance, tectonic deformation, and prolonged denudational processes, providing valuable insights for regional geological interpretation, geohazard assessment, land-use planning, and geotourism development.
Agus Rochmat· International journal of res...· 0 citations
The Po Plain Basin represents the shared foreland system of the Southern Alps and Northern Apennines belts, holding significant importance for geological research and energy resource management. We present a new basin‐scale 3D geomodel of the Pliocene‐Pleistocene succession, interpreted from an extensive dataset of seismic lines and well logs spanning the entire basin. This high‐resolution model enables a detailed, quantitative analysis of tectonic deformation timing and sediment flux over the last 5 My. Analysis of the isobath and isochore maps documents that the Northern Apennines collision with the Southern Alps began in the early Pliocene, subsequently leading to the sequential fragmentation of the central foredeep into three distinct depocenters. Quantitative decompaction analysis revealed a very significant increase in sediment flux in the basin during the mid‐Pleistocene despite a widespread decrease in tectonic activity. We propose that this increase was climate‐driven, due to the combined effect of high‐frequency, high‐amplitude climate cyclicity predating the onset of major glaciations in the Alps and amplifying sediment supply. This work opens new questions about the age of transition from fluvial to glacial‐dominated erosion in the Alps, and provides a new, quantitative tectono‐sedimentary framework for the Po Plain, useful for better understanding the basin dynamics and consequent architecture.
Curious about Yucca Mountain? This report provides a summary of the geologic setting and previous studies of the area, including discussion of existing data gaps that limit understanding of seismic hazards in the region.
Yucca Mountain is a potential geological repository for high-level radioactive waste. The site is situated on federal land adjacent to the Nevada National Security Site (formerly Nevada Test Site) in Nye County, Nevada, about 130 km (80 miles) northwest of Las Vegas Valley. The site lies in an active tectonic setting within a segment of the Pacific–North American plate boundary. As such, active faults and recent volcanic activity characterize the area. Seismic activity could affect the suitability and safety of storage of nuclear waste. Thus, a thorough and accurate assessment of previous and potential future seismic activity in the region surrounding the proposed repository is critical.
From the late 1970s to mid-1990s, deformation related to active faulting in the Yucca Mountain region was extensively studied by the U.S. Department of Energy, U.S. Geological Survey, both the Nevada Bureau of Mines and Geology and Nevada Seismological Laboratory at the University of Nevada, Reno, and other institutions to assist in the evaluation and site characterization of the area for the proposed high-level radioactive waste repository. These studies documented multiple faults with recent activity, significant current seismicity, and ongoing crustal motion related to the Pacific–North American plate boundary and San Andreas fault system. Although these studies applied the most advanced techniques existing at the time, the ages of faulted deposits, essential for precise earthquake hazard estimates, were limited by the available experimental techniques. Significant advances in analysis and dating of faulted materials (i.e., paleoseismology), fault identification by remotely sensed methods, GPS geodetic data, and the scientific community’s general understanding of the regional tectonic setting over the last two decades suggest that the previous studies may not completely describe the seismic hazards in the region.
In this report, the preexisting studies are evaluated in an effort to better understand the state of knowledge of the seismic hazards, as well as the adequacy of the approaches applied to characterize the hazard. Potential information and data gaps that may not have been included in the original evaluation are also addressed. The regional tectonic setting and paleoseismic, seismic, and geodetic studies are all reviewed. The paleoseismic studies record deformation over the past tens to hundreds of thousands of years; the seismic investigations reflect deformation over the past ~150 years; and the geodetic studies account for ongoing crustal deformation in the region (i.e., past couple decades). These datasets permit an overview of recent and geologically relevant deformation important for estimating future seismic hazards in the vicinity of Yucca Mountain.
James Faulds, Rich Koehler, Kenneth D. Smith et al.· 0 citations
The Midyan Basin in the NEOM region of northwestern Saudi Arabia is a promising yet underexplored geothermal province situated within the tectonically active Red Sea Rift and Gulf of Aqaba transform system. Despite evidence of elevated regional heat flow and shallow Curie depths, the structural controls governing geothermal fluid circulation remain poorly constrained. This study identifies structurally controlled geothermal targets by integrating remote sensing, airborne geophysics, and field observations within a unified exploration framework. Multi-temporal Landsat-8 imagery acquired during six months of the year 2024 was used to derive land surface temperature (LST) through radiance-to-brightness temperature conversion and NDVI-based emissivity correction. Surface structural lineaments were interpreted from multidirectional hillshade models derived from a 30-m digital elevation model (DEM), while subsurface fault systems were delineated from airborne magnetic data using tilt-derivative analysis. Fault fracture density (FFD) mapping identified structurally enhanced permeability zones, which were integrated with persistent LST anomalies to delineate geothermal prospectivity. The analysis identified 5,809 surface lineaments and 1,262 basement-rooted magnetic lineaments, both dominated by NW–SE and NE–SW structural trends associated with the Red Sea Rift and Gulf of Aqaba transform system. Geothermal prospectivity is concentrated within discrete basement-rooted fault corridors rather than being uniformly distributed across the basin. The highest-confidence targets occur along the western and northwestern coastal escarpments, where high surface and subsurface fracture densities spatially coincide with persistent multi-season thermal anomalies, indicating enhanced permeability and structurally controlled heat transfer. Three priority geothermal target zones (Surface Zones A, B, and C and corresponding Subsurface Zones A′, B′, and C′) were identified, with Zone B/B′ representing the most prospective area owing to its strong structural continuity across surface and subsurface datasets. Field observations of dense fracture networks, fault-controlled granite–carbonate contacts, and subvertical dike swarms further corroborate the interpreted permeability pathways. Although direct geothermal manifestations and drilling data are not yet available, the integrated structural, thermal, and field evidence demonstrates that the Midyan Basin possesses favorable geological conditions for both hydrothermal resources and Enhanced Geothermal Systems (EGS). The proposed workflow provides a robust, cost-effective screening approach for reducing exploration uncertainty and prioritizing geothermal targets. It also guides future geothermal exploration and development within NEOM.
J. Rafiq, I. Abu-Mahfouz, K. Chavanidis et al.· Environmental Earth Sciences· 0 citations
Subaqueous gravity-driven mass movements and their resulting mass transport deposits (MTDs) are primary agents in shaping continental margins and volcanic edifices. This study provides a high-resolution geomorphological and geophysical characterization of MTDs in the Graham Bank, a complex setting in the Sicily Channel (Central Mediterranean) where active rifting, anorogenic volcanism, and vigorous oceanographic circulation converge. High-resolution multibeam bathymetry (5 m grid) integrated with sub-bottom CHIRP seismic profiles documents a complex seafloor shaped by the interaction of tectonics, volcanism, and oceanographic processes at water depths between ~ 10 and 350 m. We mapped and classified a diverse spectrum of deposits into three thematic categories: (i) large-scale volcaniclastic debris avalanches (up to 2.2 km
2
and thicknesses exceeding 20–30 m) characterized by blocky topography and amphitheater scars; (ii) tectonically-controlled rockfalls at the foot of steep escarpments; and (iii) soft-sediment deformation structures (slumps and channelized-fills) showing mounded hummocky facies and basal erosional unconformities. These features are variably distributed across three main physiographic domains: the volcanic sector, a fault-bounded erosive channel, and an adjacent flat outer-shelf area. Our findings suggest a conceptual "cascading" morphogenetic framework where tectonic rifting with NW–SE-oriented normal faulting and high regional heat flow (75–100 mW/m
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) pre-condition the slopes, while regional seismicity (M
L
≥ 5) and bottom-current erosion (Atlantic Ionian Stream) act as possible transient destabilizing mechanisms. Volcanic-driven instabilities may be related to volcanic activity; the 1831 eruption illustrates the system’s capacity for rapid morphodynamic change, though direct temporal links to individual MTDs cannot be established without sediment dating. The Graham Bank thus represents a high-instability environment where MTDs record the combined effects of internal geodynamic forcing and external oceanographic modulation, providing a key natural laboratory for assessing gravity-driven processes. The proximity of these features to submarine cables and pipelines, coupled with the recent volcanic history of the area (e.g., the 1831 eruption), underscores a preliminary geohazard concern warranting further investigation in this sector of the Mediterranean.
L.uca Basilone, Daniele Spatola, A. Sulli et al.· Landslides· 1 citation
