Articles | Volume 13, issue 1
Solid Earth, 13, 1–14, 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Method article 04 Jan 2022
Method article | 04 Jan 2022
Virtual field trip to the Esla Nappe (Cantabrian Zone, NW Spain): delivering traditional geological mapping skills remotely using real data
Manuel I. de Paz-Álvarez et al.
Related subject area
Subject area: Tectonic plate interactions, magma genesis, and lithosphere deformation at all scales | Editorial team: Structural geology and tectonics, rock physics, experimental deformation | Discipline: Structural geologyMarine forearc structure of eastern Java and its role in the 1994 Java tsunami earthquakeRoughness of fracture surfaces in numerical models and laboratory experimentsImpact of basement thrust faults on low-angle normal faults and rift basin evolution: a case study in the Enping sag, Pearl River BasinEvidence for and significance of the Late Cretaceous Asteroussia event in the Gondwanan Ios basement terranesInvestigating spatial heterogeneity within fracture networks using hierarchical clustering and graph distance metricsDating folding beyond folding, from layer-parallel shortening to fold tightening, using mesostructures: lessons from the Apennines, Pyrenees, and Rocky MountainsDeformation-enhanced diagenesis and bacterial proliferation in the Nankai accretionary prismRheological stratification in impure rock salt during long-term creep: morphology, microstructure, and numerical models of multilayer folds in the Ocnele Mari salt mine, RomaniaMulti-disciplinary characterizations of the Bedretto Lab – a unique underground geoscience research facilityGeodynamic and seismotectonic model of a long-lived transverse structure: The Schio-Vicenza Fault System (NE Italy)De-risking the energy transition by quantifying the uncertainties in fault stabilityBiotite supports long-range diffusive transport in dissolution-precipitation creep in haliteNeogene kinematics of the Giudicarie Belt and eastern Southern Alpine orogenic front (northern Italy)Fault interpretation uncertainties using seismic data, and the effects on fault seal analysis: a case study from the Horda Platform, with implications for CO2 storageReply to Norini and Groppelli's comment on “Estimating the depth and evolution of intrusions at resurgent calderas: Los Humeros (Mexico)” by Urbani et al. (2020)Emplacement of “exotic” Zechstein slivers along the inverted Sontra Graben (northern Hessen, Germany): clues from balanced cross sections and geometrical forward modelingKinematics of subduction in the Ibero-Armorican arc constrained by 3D microstructural analysis of garnet and pseudomorphed lawsonite porphyroblasts from Île de Groix (Variscan belt)Frictional properties and microstructural evolution of dry and wet calcite–dolomite gougesExperimental evidence that viscous shear zones generate periodic pore sheetsInfluence of inherited structural domains and their particular strain distributions on the Roer Valley graben evolution from inversion to extensionThe Piuquencillo fault system: a long-lived, Andean-transverse fault system and its relationship with magmatic and hydrothermal activityExtensional reactivation of the Penninic frontal thrust 3 Myr ago as evidenced by U–Pb dating on calcite in fault zone cataclasiteDistribution, microphysical properties, and tectonic controls of deformation bands in the Miocene subduction wedge (Whakataki Formation) of the Hikurangi subduction zoneAnalysis of deformation bands associated with the Trachyte Mesa intrusion, Henry Mountains, Utah: implications for reservoir connectivity and fluid flow around sill intrusionsCharacterization of discontinuities in potential reservoir rocks for geothermal applications in the Rhine-Ruhr metropolitan area (Germany)On a new robust workflow for the statistical and spatial analysis of fracture data collected with scanlines (or the importance of stationarity)Micro- and nano-porosity of the active Alpine Fault zone, New ZealandUnraveling the origins and P-T-t evolution of the allochthonous Sobrado unit (Órdenes Complex, NW Spain) using combined U–Pb titanite, monazite and zircon geochronology and rare-earth element (REE) geochemistryFracture attribute scaling and connectivity in the Devonian Orcadian Basin with implications for geologically equivalent sub-surface fractured reservoirsStructural control on fluid flow and shallow diagenesis: insights from calcite cementation along deformation bands in porous sandstonesThe growth of faults and fracture networks in a mechanically evolving, mechanically stratified rock mass: a case study from Spireslack Surface Coal Mine, ScotlandRelationship between microstructures and resistance in mafic assemblages that deform and transformMultiphase, decoupled faulting in the southern German Molasse Basin – evidence from 3-D seismic dataNear-surface Palaeocene fluid flow, mineralisation and faulting at Flamborough Head, UK: new field observations and U–Pb calcite dating constraintsGeologic characterization of nonconformities using outcrop and core analogs: hydrologic implications for injection-induced seismicityMapping the fracture network in the Lilstock pavement, Bristol Channel, UK: manual versus automaticPrecambrian faulting episodes and insights into the tectonothermal history of north Australia: microstructural evidence and K–Ar, 40Ar–39Ar, and Rb–Sr dating of syntectonic illite from the intracratonic Millungera BasinTransverse jointing in foreland fold-and-thrust belts: a remote sensing analysis in the eastern PyreneesPre-inversion normal fault geometry controls inversion style and magnitude, Farsund Basin, offshore southern NorwayUncertainty assessment for 3D geologic modeling of fault zones based on geologic inputs and prior knowledgeControl of pre-existing fabric in fracture formation, reactivation and vein emplacement under variable fluid pressure conditions: an example from Archean greenstone belt, IndiaExtension and inversion of salt-bearing rift systemsStructure and kinematics of an extensional growth fold, Hadahid Fault System, Suez Rift, EgyptThrow variations and strain partitioning associated with fault-bend folding along normal faultsResolved stress analysis, failure mode, and fault-controlled fluid conduitsAn active tectonic field for CO2 storage management: the Hontomín onshore case study (Spain)Evolution of structures and hydrothermal alteration in a Palaeoproterozoic supracrustal belt: Constraining paired deformation–fluid flow events in an Fe and Cu–Au prospective terrain in northern SwedenEstimating the depth and evolution of intrusions at resurgent calderas: Los Humeros (Mexico)Abutting faults: a case study of the evolution of strain at Courthouse branch point, Moab Fault, UtahFluid-mediated, brittle–ductile deformation at seismogenic depth – Part 2: Stress history and fluid pressure variations in a shear zone in a nuclear waste repository (Olkiluoto Island, Finland)
Yueyang Xia, Jacob Geersen, Dirk Klaeschen, Bo Ma, Dietrich Lange, Michael Riedel, Michael Schnabel, and Heidrun Kopp
Solid Earth, 12, 2467–2477,Short summary
The 2 June 1994 Java tsunami earthquake ruptured in a seismically quiet subduction zone and generated a larger-than-expected tsunami. Here, we re-process a seismic line across the rupture area. We show that a subducting seamount is located up-dip of the mainshock in a region that did not rupture during the earthquake. Seamount subduction modulates the topography of the marine forearc and acts as a seismic barrier in the 1994 earthquake rupture.
Steffen Abe and Hagen Deckert
Solid Earth, 12, 2407–2424,Short summary
We use numerical simulations and laboratory experiments on rock samples to investigate how stress conditions influence the geometry and roughness of fracture surfaces. The roughness of the surfaces was analyzed in terms of absolute roughness and scaling properties. The results show that the surfaces are self-affine but with different scaling properties between the numerical models and the real rock samples. Results suggest that stress conditions have little influence on the surface roughness.
Chao Deng, Rixiang Zhu, Jianhui Han, Yu Shu, Yuxiang Wu, Kefeng Hou, and Wei Long
Solid Earth, 12, 2327–2350,Short summary
This study uses seismic reflection data to interpret the geometric relationship and evolution of intra-basement and rift-related structures in the Enping sag in the northern South China Sea. Our observations suggest the primary control of pre-existing thrust faults is the formation of low-angle normal faults, with possible help from low-friction materials, and the significant role of pre-existing basement thrust faults in fault geometry, paleotopography, and syn-rift stratigraphy of rift basins.
Sonia Yeung, Marnie Forster, Emmanuel Skourtsos, and Gordon Lister
Solid Earth, 12, 2255–2275,Short summary
We do not know when the ancient Tethys Ocean lithosphere began to founder, but one clue can be found in subduction accreted tectonic slices, including Gondwanan basement terranes on the island of Ios, Cyclades, Greece. We propose a 250–300 km southwards jump of the subduction megathrust with a period of flat-slab subduction followed by slab break-off. The initiation and its subsequent rollback of a new subduction zone would explain the onset of Oligo–Miocene extension and accompanying magmatism.
Rahul Prabhakaran, Giovanni Bertotti, Janos Urai, and David Smeulders
Solid Earth, 12, 2159–2209,Short summary
Rock fractures are organized as networks with spatially varying arrangements. Due to networks' influence on bulk rock behaviour, it is important to quantify network spatial variation. We utilize an approach where fracture networks are treated as spatial graphs. By combining graph similarity measures with clustering techniques, spatial clusters within large-scale fracture networks are identified and organized hierarchically. The method is validated on a dataset with nearly 300 000 fractures.
Olivier Lacombe, Nicolas E. Beaudoin, Guilhem Hoareau, Aurélie Labeur, Christophe Pecheyran, and Jean-Paul Callot
Solid Earth, 12, 2145–2157,Short summary
This paper aims to illustrate how the timing and duration of contractional deformation associated with folding in orogenic forelands can be constrained by the dating of brittle mesostructures observed in folded strata. The study combines new and already published absolute ages of fractures to provide, for the first time, an educated discussion about the factors controlling the duration of the sequence of deformation encompassing layer-parallel shortening, fold growth, and late fold tightening.
Vincent Famin, Hugues Raimbourg, Muriel Andreani, and Anne-Marie Boullier
Solid Earth, 12, 2067–2085,Short summary
Sediments accumulated in accretionary prisms are deformed by the compression imposed by plate subduction. Here we show that deformation of the sediments transforms some minerals in them. We suggest that these mineral transformations are due to the proliferation of microorganisms boosted by deformation. Deformation-enhanced microbial proliferation may change our view of sedimentary and tectonic processes in subduction zones.
Marta Adamuszek, Dan M. Tămaş, Jessica Barabasch, and Janos L. Urai
Solid Earth, 12, 2041–2065,Short summary
We analyse folded multilayer sequences in the Ocnele Mari salt mine (Romania) to gain insight into the long-term rheological behaviour of rock salt. Our results indicate the large role of even a small number of impurities in the rock salt for its effective mechanical behaviour. We demonstrate how the development of folds that occur at various scales can be used to constrain the viscosity ratio in the deformed multilayer sequence.
Xiaodong Ma, Marian Hertrich, Florian Amann, Kai Bröker, Nima Gholizadeh Doonechaly, Valentin Gischig, Rebecca Hochreutener, Philipp Kästli, Hannes Krietsch, Michèle Marti, Barbara Nägeli, Morteza Nejati, Anne Obermann, Katrin Plenkers, Antonio P. Rinaldi, Alexis Shakas, Linus Villiger, Quinn Wenning, Alba Zappone, Falko Bethmann, Raymi Castilla, Francisco Seberto, Peter Meier, Thomas Driesner, Simon Löw, Hansruedi Maurer, Martin O. Saar, Stefan Wiemer, and Domenico Giardini
Solid Earth Discuss.,
Revised manuscript accepted for SEShort summary
Questions such as anthropogenic earthquakes and deep geothermal energy developments require a better understanding of the fractured rock. Experiments conducted at reduced scales but with closer, controlled observation can shed some light. To this end, the Bedretto Underground Laboratory for Geosciences and Geoenergies was recently established in a tunnel in Ticino, Switzerland, with preliminary efforts to characterize realistic rock mass behavior at the hectometer scale.
Dario Zampieri, Paola Vannoli, and Pierfrancesco Burrato
Solid Earth, 12, 1967–1986,Short summary
The long-lived Schio-Vicenza Fault System is a major shear zone cross-cutting the foreland and the thrust belt of the eastern southern Alps. We review 150 years of scientific works and explain its activity and kinematics, characterized by sinistral and dextral transcurrent motion along its southern and northern sections, respectively, by a geodynamic model that has the Adria indenter as the main actor and coherently reconciles the available geological and geophysical evidence collected so far.
David Healy and Stephen Hicks
Solid Earth Discuss.,
Revised manuscript accepted for SEShort summary
The energy transition involves operations in faulted rocks. To manage the technical challenges and public concern over induced earthquakes, we need to quantify the risks. We calculate the probability of fault slip based on uncertain inputs – stresses and fluid pressures, and the mechanical properties of rocks in fault zones. Our examples highlight the specific gaps in our knowledge. Citizen science projects could produce useful data, and include the public in the discussions about hazard.
Berit Ina Schwichtenberg, Florian Fusseis, Ian B. Butler, and Edward Andò
Solid Earth Discuss.,
Revised manuscript accepted for SEShort summary
Hydraulic rock properties such as porosity and permeability are relevant factors that have an impact on groundwater resources, geological repositories and fossil fuel reservoirs. We investigate the influence of chemical compaction upon the porosity evolution in salt-biotite mixtures and related transport length scales by conducting laboratory experiments in combination with 4D analysis. Our observations invite a renewed discussion of the effect of sheet silicates on chemical compaction.
Vincent F. Verwater, Eline Le Breton, Mark R. Handy, Vincenzo Picotti, Azam Jozi Najafabadi, and Christian Haberland
Solid Earth, 12, 1309–1334,Short summary
Balancing along geological cross sections reveals that the Giudicarie Belt comprises two kinematic domains. The SW domain accommodated at least ~ 18 km Late Oligocene to Early Miocene shortening. Since the Middle Miocene, the SW domain experienced at least ~ 12–22 km shortening, whereas the NE domain underwent at least ~ 25–35 km. Together, these domains contributed to ~ 40–47 km of sinistral offset of the Periadriatic Fault along the Northern Giudicarie Fault since the Late Oligocene.
Emma A. H. Michie, Mark J. Mulrooney, and Alvar Braathen
Solid Earth, 12, 1259–1286,Short summary
Generating an accurate model of the subsurface is crucial when assessing a site for CO2 storage, particularly for a fault-bound storage site that may act as a seal or could reactivate upon CO2 injection. However, we have shown how picking strategy, i.e. line spacing, chosen to create the model significantly influences any subsequent fault analyses but is surprisingly rarely discussed. This analysis has been performed on the Vette Fault bounding the Smeaheia potential CO2 storage site.
Stefano Urbani, Guido Giordano, Federico Lucci, Federico Rossetti, and Gerardo Carrasco-Núñez
Solid Earth, 12, 1111–1124,Short summary
Structural studies in active calderas have a key role in the exploration of geothermal systems. We reply in detail to the points raised by the comment of Norini and Groppelli (2020), strengthening the relevance of our structural fieldwork for geothermal exploration and exploitation in active caldera geothermal systems including the Los Humeros caldera.
Jakob Bolz and Jonas Kley
Solid Earth, 12, 1005–1024,Short summary
To assess the role smaller graben structures near the southern edge of the Central European Basin System play in the basin’s overall deformational history, we take advantage of a feature found on some of these structures, where slivers from older rock units appear along the graben's main fault, surrounded on both sides by younger strata. The implications for the geometry of the fault provide a substantially improved estimate for the magnitude of normal and thrust motion along the fault system.
Domingo G. A. M. Aerden, Alejandro Ruiz-Fuentes, Mohammad Sayab, and Aidan Forde
Solid Earth, 12, 971–992,Short summary
We studied the geometry of foliations and microfolds preserved within metamorphic garnet crystals using X-ray tomography. The studied rocks are blueschists from Ile de Groix formed during Late Devonian subduction of Gondwana under Armorica. Several sets of differently oriented microfabrics were found recording variations in the direction of subduction. Comparison with similar data for Iberia supports that Iberia rotated only 10–20° during the Cretaceous opening of the North Atlantic.
Matteo Demurtas, Steven A.F. Smith, Elena Spagnuolo, and Giulio Di Toro
Solid Earth, 12, 595–612,Short summary
We performed shear experiments on calcite–dolomite gouge mixtures to better understand the behaviour of carbonates during sub-seismic to seismic deformation in the shallow crust. The development of a foliation in the gouge was only restricted to coseismic sliding, whereas fluidisation occurred over a wide range of slip velocities (sub-seismic to coseismic) in the presence of water. These observations will contribute to a better interpretation of the rock record.
James Gilgannon, Marius Waldvogel, Thomas Poulet, Florian Fusseis, Alfons Berger, Auke Barnhoorn, and Marco Herwegh
Solid Earth, 12, 405–420,Short summary
Using experiments that simulate deep tectonic interfaces, known as viscous shear zones, we found that these zones spontaneously develop periodic sheets of small pores. The presence of porous layers in deep rocks undergoing tectonic deformation is significant because it requires a change to the current model of how the Earth deforms. Emergent porous layers in viscous rocks will focus mineralising fluids and could lead to the seismic failure of rocks that are never supposed to have this occur.
Jef Deckers, Bernd Rombaut, Koen Van Noten, and Kris Vanneste
Solid Earth, 12, 345–361,Short summary
This study shows the presence of two structural domains in the western border fault system of the Roer Valley graben. These domains, dominated by NW–SE-striking faults, displayed distinctly different strain distributions during both Late Cretaceous compression and Cenozoic extension. The southern domain is characterized by narrow, localized faulting, while the northern domain is characterized by wide, distributed faulting. The non-colinear WNW–ESE Grote Brogel fault links both domains.
José Piquer, Orlando Rivera, Gonzalo Yáñez, and Nicolás Oyarzún
Solid Earth, 12, 253–273,Short summary
A proper recognition of deep, long-lived fault systems is very important for society. They can produce potentially dangerous earthquakes. They can also act as pathways for magmas and hydrothermal fluids, leading to the formation of volcanoes, geothermal systems and mineral deposits. However, the manifestations of these very old faults in the present-day surface can be very subtle. Here, we present a detailed, multi-disciplinary study of a fault system of this type in the Andes of central Chile.
Antonin Bilau, Yann Rolland, Stéphane Schwartz, Nicolas Godeau, Abel Guihou, Pierre Deschamps, Benjamin Brigaud, Aurélie Noret, Thierry Dumont, and Cécile Gautheron
Solid Earth, 12, 237–251,Short summary
As a result of the collision between the European and Apulian plates, the Alps have experienced several evolutionary stages. The Penninic frontal thrust (PFT) (major thrust) was associated with compression, and now seismic studies show ongoing extensional activity. Calcite mineralization associated with shortening and extensional structures was sampled. The last deformation stages are dated by U–Pb on calcite at ~ 3.5 and ~ 2.5 Ma. Isotope analysis evidences deep crustal fluid mobilization.
Kathryn E. Elphick, Craig R. Sloss, Klaus Regenauer-Lieb, and Christoph E. Schrank
Solid Earth, 12, 141–170,Short summary
We analysed a sedimentary rock package located in Castlepoint, New Zealand, to test the control of the tectonic setting on the observed deformation structures. In extension and contraction, we observed faults and small fault-like structures characterised by complex spatial patterns and a reduction in porosity and grain size compared with the host rock. With these properties, the structures are likely to act as barriers to fluid flow and cause compartmentalisation of the sedimentary sequence.
Penelope I. R. Wilson, Robert W. Wilson, David J. Sanderson, Ian Jarvis, and Kenneth J. W. McCaffrey
Solid Earth, 12, 95–117,Short summary
Magma accommodation in the shallow crust leads to deformation of the surrounding host rock through the creation of faults, fractures and folds. This deformation will impact fluid flow around intrusive magma bodies (including sills and laccoliths) by changing the porosity and permeability network of the host rock. The results may have important implications for industries where fluid flow within the subsurface adds value (e.g. oil and gas, hydrology, geothermal and carbon sequestration).
Martin Balcewicz, Benedikt Ahrens, Kevin Lippert, and Erik H. Saenger
Solid Earth, 12, 35–58,Short summary
The geothermal potential of a carbonate reservoir in the Rhine-Ruhr area, Germany, was investigated by field and laboratory investigations. The carbonate layer of interest is approx. 150 m thick; located at 4 to 6 km depth; and might extend below Essen, Bochum, and Dortmund. We proposed focusing on discontinuities striking NNW–SSE for geothermal applications, as these are the most common, strike in the direction of the main horizontal stress, and dominate reservoir fluid flow.
Andrea Bistacchi, Silvia Mittempergher, Mattia Martinelli, and Fabrizio Storti
Solid Earth, 11, 2535–2547,Short summary
We present an innovative workflow for the statistical analysis of fracture data collected along scanlines. Our methodology is based on performing non-parametric statistical tests, which allow detection of important features of the spatial distribution of fractures, and on the analysis of the cumulative spacing function (CSF) and cumulative spacing derivative (CSD), which allows the boundaries of stationary domains to be defined in an objective way.
Martina Kirilova, Virginia Toy, Katrina Sauer, François Renard, Klaus Gessner, Richard Wirth, Xianghui Xiao, and Risa Matsumura
Solid Earth, 11, 2425–2438,Short summary
Processes associated with open pores can change the physical properties of rocks and cause earthquakes. In borehole samples from the Alpine Fault zone, we show that many pores in these rocks were filled by weak materials that can slide easily. The amount of open spaces was thus reduced, and fluids circulating within them built up high pressures. Both weak materials and high pressures within pores reduce the rock strength; thus the state of pores here can trigger the next Alpine Fault earthquake.
José Manuel Benítez-Pérez, Pedro Castiñeiras, Juan Gómez-Barreiro, José R. Martínez Catalán, Andrew Kylander-Clark, and Robert Holdsworth
Solid Earth, 11, 2303–2325,Short summary
The Sobrado unit represents an allochthonous tectonic slice of exhumed high-grade metamorphic rocks formed during a complex sequence of orogenic processes in the middle to lower crust. We have combined U–Pb geochronology and REE analyses (LASS-ICP-MS) of accessory minerals in migmatitic paragneiss (monazite, zircon) and mylonitic amphibolites (titanite) to constrain the evolution. A Middle Devonian minimum age for HP metamorphism has been obtained.
Anna M. Dichiarante, Ken J. W. McCaffrey, Robert E. Holdsworth, Tore I. Bjørnarå, and Edward D. Dempsey
Solid Earth, 11, 2221–2244,Short summary
We studied the characteristics of fracture systems in the Devonian rocks of the Orcadian Basin in Caithness. These mineral-filled fractures have properties that may be used to predict the size and spatial arrangement of similar structures in offshore basins. This includes the Clair field in the Faroe–Shetland Basin.
Leonardo Del Sole, Marco Antonellini, Roger Soliva, Gregory Ballas, Fabrizio Balsamo, and Giulio Viola
Solid Earth, 11, 2169–2195,Short summary
This study focuses on the impact of deformation bands on fluid flow and diagenesis in porous sandstones in two different case studies (northern Apennines, Italy; Provence, France) by combining a variety of multiscalar mapping techniques, detailed field and microstructural observations, and stable isotope analysis. We show that deformation bands buffer and compartmentalize fluid flow and foster and localize diagenesis, recorded by carbonate cement nodules spatially associated with the bands.
Billy James Andrews, Zoe Kai Shipton, Richard Lord, and Lucy McKay
Solid Earth, 11, 2119–2140,Short summary
Through geological mapping we find that fault zone internal structure depends on whether or not the fault cuts multiple lithologies, the presence of shale layers, and the orientation of joints and coal cleats at the time of faulting. During faulting, cementation of fractures (i.e. vein formation) is highest where the fractures are most connected. This leads to the counter-intuitive result that the highest-fracture-density part of the network often has the lowest open-fracture connectivity.
Nicolas Mansard, Holger Stünitz, Hugues Raimbourg, Jacques Précigout, Alexis Plunder, and Lucille Nègre
Solid Earth, 11, 2141–2167,Short summary
Our rock deformation experiments (solid-medium Griggs-type apparatus) on wet assemblages of mafic compositions show that the ability of minerals to react controls the portions of rocks that deform and that minor chemical and mineralogical variations can considerably modify the strength of deformed assemblages. Our study suggests that the rheology of mafic rocks, which constitute a large part of the oceanic crust, cannot be summarized as being rheologically controlled by monophase materials.
Vladimir Shipilin, David C. Tanner, Hartwig von Hartmann, and Inga Moeck
Solid Earth, 11, 2097–2117,Short summary
In our work, we carry out an in-depth structural analysis of a geometrically decoupled fault system in the southern German Molasse Basin using a high-resolution 3-D seismic dataset. Based on this analysis, we reconstruct the tectonic history and changes in the stress regimes to explain the structure and evolution of faults. The results contribute in understanding the driving mechanisms behind formation, propagation, and reactivation of faults during foreland basin formation.
Nick M. W. Roberts, Jack K. Lee, Robert E. Holdsworth, Christopher Jeans, Andrew R. Farrant, and Richard Haslam
Solid Earth, 11, 1931–1945,Short summary
We characterise a well-known fractured and faulted exposure of Cretaceous chalk in NE England, combining field observations with novel U–Pb calcite dating. We show that the faulting and associated fluid flow occurred during the interval of ca. 64–56 Ma, predating earlier estimates of Alpine-related tectonic inversion. We demonstrate that the main extensional fault zone acted as a conduit linking voluminous fluid flow and linking deeper sedimentary layers with the shallow subsurface.
Elizabeth S. Petrie, Kelly K. Bradbury, Laura Cuccio, Kayla Smith, James P. Evans, John P. Ortiz, Kellie Kerner, Mark Person, and Peter Mozley
Solid Earth, 11, 1803–1821,Short summary
A summary of observed rock properties across the contact between crystalline basement rock and the overlying younger sedimentary rocks from outcrop and core samples is presented. The data span a range of tectonic settings and describe the rock types immediately adjacent to the contact. The range of features observed at these contacts can influence the migration of fluids. The observations presented here are critical for the safe implementation of fluid injection and geothermal production.
Christopher Weismüller, Rahul Prabhakaran, Martijn Passchier, Janos L. Urai, Giovanni Bertotti, and Klaus Reicherter
Solid Earth, 11, 1773–1802,Short summary
We photographed a fractured limestone pavement with a drone to compare manual and automatic fracture tracing and analyze the evolution and spatial variation of the fracture network in high resolution. We show that automated tools can produce results comparable to manual tracing in shorter time but do not yet allow the interpretation of fracture generations. This work pioneers the automatic fracture mapping of a complete outcrop in detail, and the results can be used as fracture benchmark.
I. Tonguç Uysal, Claudio Delle Piane, Andrew James Todd, and Horst Zwingmann
Solid Earth, 11, 1653–1679,Short summary
This study represents an integrated approach to radiometric age dating using potassium-bearing clay minerals formed during faulting and provides insights into the enigmatic time–space distribution of Precambrian tectonic zones in north-central Australia. Specifically, our work firmly indicates a late Mesoproterzoic minimum age for the Millungera Basin in north Australia and a previously unrecorded concealed late Mesoproterozoic–early Neoproterozoic tectonic event in north-central Australia.
Stefano Tavani, Pablo Granado, Amerigo Corradetti, Thomas Seers, Josep Maria Casas, and Josep Anton Muñoz
Solid Earth, 11, 1643–1651,Short summary
Using orthophotos, we manually digitized 30 000 joints in the eastern Ebro Basin of the Pyrenees. Joints are perpendicular to the belt in the frontal portion of the belt and in the inner and central portion of the foredeep basin. Joint orientations in the external portion of the foredeep become less clustered. Joints in the studied area formed in the foredeep in response to foredeep-parallel stretching, which becomes progressively less intense within the external portion of the foredeep basin.
Thomas B. Phillips, Christopher A.-L. Jackson, and James R. Norcliffe
Solid Earth, 11, 1489–1510,Short summary
Normal faults often reactivate under compression, in a process called inversion. The 3D geometry of these structures (and the effect on resultant inversion structural style) is often not considered. Using seismic reflection data, we examine how stresses form different inversion styles that are controlled by the geometry of the pre-existing structure. Geometrically simple faults are preferentially reactivated; more complex areas are typically not reactivated and instead experience bulk uplift.
Ashton Krajnovich, Wendy Zhou, and Marte Gutierrez
Solid Earth, 11, 1457–1474,Short summary
In this paper, a novel methodology of 3D geologic model uncertainty assessment that considers both input data and prior knowledge is developed and applied to characterize fault zones – areas of damaged rock surrounding a fault surface that are important to subsurface engineering projects. The results of the study demonstrate how existing frameworks can be expanded to incorporate new types of information to arrive at a realistic and straightforward model of fault zone geometry in the subsurface.
Sreyashi Bhowmick and Tridib Kumar Mondal
Solid Earth, 11, 1227–1246,Short summary
We explore pre-existing fabric in metabasalts replete with a wide range of crisscross fractures/faults, hosting quartz veins of variable orientations and thicknesses in the Chitradurga region, India. The fractures are identified as components of a riedel shear system. We evaluate reactivation potential of fractures and conclude that episodic changes in fluid pressure conditions triggered fault-valve action, thereby reactivating fabric and fractures, leading to vein emplacement in the region.
Tim P. Dooley and Michael R. Hudec
Solid Earth, 11, 1187–1204,Short summary
Sandbox models investigated extension and inversion of salt-bearing rifts such as those found in the Moroccan High Atlas, North Africa. Sand packs were stretched and the structural lows were filled with a salt analog. Models were then subjected to additional extension and loading that remobilized the salt into diapirs. During shortening the distribution of the salt in the overburden governed the structural styles and trends in the supra-salt strata, strongly decoupled from subsalt deformation.
Christopher A.-L. Jackson, Paul S. Whipp, Robert L. Gawthorpe, and Matthew M. Lewis
Solid Earth, 11, 1027–1051,Short summary
Plate tectonics describes the creation, motion, and ultimate destruction of the Earth's continents and oceans. A key plate tectonic process is continental extension; this occurs when the Earth's plates are pulled apart to ultimately form a new ocean. Giant fractures (faults) accommodate plate stretching, although buckling (folding) is thought to be locally important. We use field data to understand how fracturing and buckling relate to each other, demonstrating they are spatially complex.
Efstratios Delogkos, Muhammad Mudasar Saqab, John J. Walsh, Vincent Roche, and Conrad Childs
Solid Earth, 11, 935–945,Short summary
Normal faults have irregular geometries on a range of scales. A quantitative model has been presented which illustrates the range of deformation arising from movement on fault surface irregularities, with fault-bend folding generating geometries reminiscent of normal drag and reverse drag. We show that fault throw can be subject to errors of up to ca. 50 % for realistic fault bend geometries (up to ca. 40°), even on otherwise sub-planar faults with constant displacement.
David A. Ferrill, Kevin J. Smart, and Alan P. Morris
Solid Earth, 11, 899–908,Short summary
This paper explores failure modes and deformation behavior of faults in the mechanically layered Eagle Ford Formation, an ultra-low permeability self-sourced oil and gas reservoir and aquitard in southwest Texas, USA. The role of dilation versus slip relates in predictable ways to mechanical stratigraphy, stress field, and dilation and slip tendency. We conclude that dilation tendency vs. slip tendency can be used to infer fault and fracture deformation modes and conduit versus seal behaviour.
Raúl Pérez-López, José F. Mediato, Miguel A. Rodríguez-Pascua, Jorge L. Giner-Robles, Adrià Ramos, Silvia Martín-Velázquez, Roberto Martínez-Orío, and Paula Fernández-Canteli
Solid Earth, 11, 719–739,Short summary
Long-term monitoring of CO2 of onshore storage has to consider thousands of years as a medium lifetime of the storage. In this wide time interval, the stress and strain properties of the reservoir change and earthquakes could occur. Therefore, we have to identify those fault sets which can be reactivated by changing the stress conditions. We need to know the role of active fault sets and model the changing conditions to prevent induced seismicity.
Joel B. H. Andersson, Tobias E. Bauer, and Edward P. Lynch
Solid Earth, 11, 547–578,Short summary
In this field-based study, geological structures and hydrothermal alterations in one of the least known geological terrains in Sweden are investigated. The area is located above the polar circle in northwestern Sweden that produces a significant portion of the iron and copper in the EU. A new tectonic model based on field evidence and microstructures is presented and it is shown that minerals typical for iron and copper–gold deposits can be linked to different phases of the structural evolution.
Stefano Urbani, Guido Giordano, Federico Lucci, Federico Rossetti, Valerio Acocella, and Gerardo Carrasco-Núñez
Solid Earth, 11, 527–545,Short summary
In Los Humeros, through field structural–geological mapping and analogue experiments, we show a discontinuous and small-scale (areal size ~ 1 km2) uplift of the caldera floor due to the emplacement of multiple shallow (< 1 km) magmatic bodies. These results allow for a better assessment of the subsurface structure of Los Humeros, with crucial implications for planning future geothermal exploration, which should account for the local geothermal gradient affected by such a shallow heat source.
Heijn van Gent and Janos L. Urai
Solid Earth, 11, 513–526,Short summary
Faults form due to stresses caused by crustal processes. As faults influence the stress field locally, fault interaction leads to local variations in the stress field, but this is difficult to observe directly. We describe an outcrop of one fault abuting into another one. By careful measurement of structures in the overlapping deformation zones and separating them using published relative age data, we show a rotation in the local stress field resulting from the faults growing to each other
Francesca Prando, Luca Menegon, Mark Anderson, Barbara Marchesini, Jussi Mattila, and Giulio Viola
Solid Earth, 11, 489–511,
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We describe a virtual geological mapping course implemented in response to travelling and social restrictions derived from the ongoing COVID-19 pandemic. The course was designed to replicate a physical mapping exercise as closely as possible with the aid of real field data and photographs collected by the authors during previous years in the Cantabrian Zone (NW Spain). The course is delivered through Google Earth via a KMZ file with outcrop descriptions and links to GitHub-hosted photographs.
We describe a virtual geological mapping course implemented in response to travelling and social...