Articles | Volume 6, issue 2
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
the Creative Commons Attribution 3.0 License.
An evaluation of different measures of dynamically recrystallized grain size for paleopiezometry or paleowattometry studies
M. A. Lopez-Sanchez
Departamento de Geología, Universidad de Oviedo, Oviedo, Spain
Departamento de Geología, Universidad de Oviedo, Oviedo, Spain
Related subject area
Structural geologyA contribution to the quantification of crustal shortening and kinematics of deformation across the Western Andes ( ∼ 20–22° S)Rift thermal inheritance in the SW Alps (France): insights from RSCM thermometry and 1D thermal numerical modellingThe Luangwa Rift Active Fault Database and fault reactivation along the southwestern branch of the East African RiftClustering has a meaning: optimization of angular similarity to detect 3D geometric anomalies in geological terrainsTime-dependent Frictional Properties of Granular Materials Used In Analogue Modelling: Implications for mimicking fault healing during reactivation and inversionShear zone evolution and the path of earthquake ruptureAnalogue modelling of the inversion of multiple extensional basins in foreland fold-and-thrust beltsMechanical compaction mechanisms in the input sediments of the Sumatra subduction complex – insights from microstructural analysis of cores from IODP Expedition 362Detecting micro fractures: a comprehensive comparison of conventional and machine-learning-based segmentation methodsMultiscale lineament analysis and permeability heterogeneity of fractured crystalline basement blocksStructural characterization and K–Ar illite dating of reactivated, complex and heterogeneous fault zones: lessons from the Zuccale Fault, Northern ApenninesHow do differences in interpreting seismic images affect estimates of geological slip rates?Progressive veining during peridotite carbonation: insights from listvenites in Hole BT1B, Samail ophiolite (Oman)Tectonic evolution of the Indio Hills segment of the San Andreas fault in southern California, southwestern USAGrain size dependent large rheology contrasts of halite at low deviatoric stress: evidence from microstructural study of naturally deformed gneissic Zechstein-2 rock salt (Kristallbrockensalz) from the Northern NetherlandsStructural diagenesis in ultra-deep tight sandstones in the Kuqa Depression, Tarim Basin, ChinaVariscan structures and their control on latest to post-Variscan basin architecture: insights from the westernmost Bohemian Massif and southeastern GermanyMulti-disciplinary characterizations of the BedrettoLab – a new underground geoscience research facilityBiotite supports long-range diffusive transport in dissolution–precipitation creep in halite through small porosity fluctuationsDe-risking the energy transition by quantifying the uncertainties in fault stabilityVirtual field trip to the Esla Nappe (Cantabrian Zone, NW Spain): delivering traditional geological mapping skills remotely using real dataMarine 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, RomaniaGeodynamic and seismotectonic model of a long-lived transverse structure: The Schio-Vicenza Fault System (NE Italy)Neogene 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 storageApplication of anisotropy of magnetic susceptibility (AMS) fabrics to determine the kinematics of active tectonics: examples from the Betic Cordillera, Spain, and the Northern Apennines, ItalyReply 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)Mapping and evaluating kinematics and the stress and strain field at active faults and fissures: a comparison between field and drone data at the NE rift, Mt Etna (Italy)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 sandstones
Tania Habel, Martine Simoes, Robin Lacassin, Daniel Carrizo, and German Aguilar
Solid Earth, 14, 17–42,Short summary
The Central Andes are one of the most emblematic reliefs on Earth, but their western flank remains understudied. Here we explore two rare key sites in the hostile conditions of the Atacama desert to build cross-sections, quantify crustal shortening, and discuss the timing of this deformation at ∼20–22°S. We propose that the structures of the Western Andes accommodated significant crustal shortening here, but only during the earliest stages of mountain building.
Naïm Célini, Frédéric Mouthereau, Abdeltif Lahfid, Claude Gout, and Jean-Paul Callot
Solid Earth, 14, 1–16,Short summary
We investigate the peak temperature of sedimentary rocks of the SW Alps (France), using Raman spectroscopy on carbonaceous material. This method provides an estimate of the peak temperature achieved by organic-rich rocks. To determine the timing and the tectonic context of the origin of these temperatures we use 1D thermal modelling. We find that the high temperatures up to 300 °C were achieved during precollisional extensional events, not during tectonic burial in the Western Alps.
Luke N. J. Wedmore, Tess Turner, Juliet Biggs, Jack N. Williams, Henry M. Sichingabula, Christine Kabumbu, and Kawawa Banda
Solid Earth, 13, 1731–1753,Short summary
Mapping and compiling the attributes of faults capable of hosting earthquakes are important for the next generation of seismic hazard assessment. We document 18 active faults in the Luangwa Rift, Zambia, in an active fault database. These faults are between 9 and 207 km long offset Quaternary sediments, have scarps up to ~30 m high, and are capable of hosting earthquakes from Mw 5.8 to 8.1. We associate the Molaza Fault with surface ruptures from two unattributed M 6+ 20th century earthquakes.
Michał P. Michalak, Lesław Teper, Florian Wellmann, Jerzy Żaba, Krzysztof Gaidzik, Marcin Kostur, Yuriy P. Maystrenko, and Paulina Leonowicz
Solid Earth, 13, 1697–1720,Short summary
When characterizing geological/geophysical surfaces, various geometric attributes are calculated, such as dip angle (1D) or dip direction (2D). However, the boundaries between specific values may be subjective and without optimization significance, resulting from using default color palletes. This study proposes minimizing cosine distance among within-cluster observations to detect 3D anomalies. Our results suggest that the method holds promise for identification of megacylinders or megacones.
Michael Rudolf, Matthias Rosenau, and Onno Oncken
Analogue models of tectonic processes rely on the reproduction of their geometry, kinematics and dynamics. An important property is fault behaviour which is linked to the frictional characteristics of the fault gouge. This is represented by granular materials, such as quartz sand. In our study we investigate the time-dependent frictional properties of various analogue materials and highlight their impact on the suitability of these materials for analogue models focusing on fault reactivation.
Erik M. Young, Christie D. Rowe, and James D. Kirkpatrick
Solid Earth, 13, 1607–1629,Short summary
Studying how earthquakes spread deep within the faults they originate from is crucial to improving our understanding of the earthquake process. We mapped preserved ancient earthquake surfaces that are now exposed in South Africa and studied their relationship with the shape and type of rocks surrounding them. We determined that these surfaces are not random and are instead associated with specific kinds of rocks and that their shape is linked to the evolution of the faults in which they occur.
Nicolás Molnar and Susanne Buiter
Progression of orogenic wedges over pre-existing extensional structures is common in nature, but deciphering the spatio-temporal evolution of deformation from the geological record remains challenging. Our laboratory experiments provide insights on how horizontal stresses are transferred across a heterogeneous crust, constrain which pre-shortening conditions can either favour or hinder the reactivatation of extensional structures, and explain what implications they have on critical taper theory.
Sivaji Lahiri, Kitty L. Milliken, Peter Vrolijk, Guillaume Desbois, and Janos L. Urai
Solid Earth, 13, 1513–1539,Short summary
Understanding the mechanism of mechanical compaction is important. Previous studies on mechanical compaction were mostly done by performing experiments. Studies on natural rocks are rare due to compositional heterogeneity of the sedimentary succession with depth. Due to remarkable similarity in composition and grain size, the Sumatra subduction complex provides a unique opportunity to study the micromechanism of mechanical compaction on natural samples.
Dongwon Lee, Nikolaos Karadimitriou, Matthias Ruf, and Holger Steeb
Solid Earth, 13, 1475–1494,Short summary
This research article focuses on filtering and segmentation methods employed in high-resolution µXRCT studies for crystalline rocks, bearing fractures, or fracture networks, of very small aperture. Specifically, we focus on the identification of artificially induced (via quenching) fractures in Carrara marble samples. Results from the same dataset from all five different methods adopted were produced and compared with each other in terms of their output quality and time efficiency.
Alberto Ceccato, Giulia Tartaglia, Marco Antonellini, and Giulio Viola
Solid Earth, 13, 1431–1453,Short summary
The Earth's surface is commonly characterized by the occurrence of fractures, which can be mapped, and their can be geometry quantified on digital representations of the surface at different scales of observation. Here we present a series of analytical and statistical tools, which can aid the quantification of fracture spatial distribution at different scales. In doing so, we can improve our understanding of how fracture geometry and geology affect fluid flow within the fractured Earth crust.
Giulio Viola, Giovanni Musumeci, Francesco Mazzarini, Lorenzo Tavazzani, Manuel Curzi, Espen Torgersen, Roelant van der Lelij, and Luca Aldega
Solid Earth, 13, 1327–1351,Short summary
A structural-geochronological approach helps to unravel the Zuccale Fault's architecture. By mapping its internal structure and dating some of its fault rocks, we constrained a deformation history lasting 20 Myr starting at ca. 22 Ma. Such long activity is recorded by now tightly juxtaposed brittle structural facies, i.e. different types of fault rocks. Our results also have implications on the regional evolution of the northern Apennines, of which the Zuccale Fault is an important structure.
Solid Earth, 13, 1281–1290,Short summary
Having a seismic image is generally expected to enable us to better determine fault geometry and thus estimate geological slip rates accurately. However, the process of interpreting seismic images may introduce unintended uncertainties, which have not yet been widely discussed. Here, a case of a shear fault-bend fold in the frontal Himalaya is used to demonstrate how differences in interpretations can affect the following estimates of slip rates and dependent conclusions.
Manuel D. Menzel, Janos L. Urai, Estibalitz Ukar, Thierry Decrausaz, and Marguerite Godard
Solid Earth, 13, 1191–1218,Short summary
Mantle rocks can bind large quantities of carbon by reaction with CO2, but this capacity requires fluid pathways not to be clogged by carbonate. We studied mantle rocks from Oman to understand the mechanisms allowing their transformation into carbonate and quartz. Using advanced imaging techniques, we show that abundant veins were essential fluid pathways driving the reaction. Our results show that tectonic stress was important for fracture opening and a key ingredient for carbon fixation.
Jean-Baptiste P. Koehl, Steffen G. Bergh, and Arthur G. Sylvester
Solid Earth, 13, 1169–1190,Short summary
The San Andreas fault is a major active fault associated with ongoing earthquake sequences in southern California. The present study investigates the development of the Indio Hills area in the Coachella Valley along the main San Andreas fault and the Indio Hills fault. The Indio Hills area is located near an area with high ongoing earthquake activity (Brawley seismic zone), and, therefore, its recent tectonic evolution has implications for earthquake prediction.
Jessica Barabasch, Joyce Schmatz, Jop Klaver, Alexander Schwedt, and Janos L. Urai
We analysed Zechstein salt under the microscope and observed specific microstructures that indicate a softer and much faster deformation in fine halite grains when compared to the large grains. This is important because people build large caveties in the subsurface salt for energy storage or want to put radioactive waste inside it. When engineers and scientists use equations that include this mechanisms that we observed, it will help to make better predictions in geological models.
Jin Lai, Dong Li, Yong Ai, Hongkun Liu, Deyang Cai, Kangjun Chen, Yuqiang Xie, and Guiwen Wang
Solid Earth, 13, 975–1002,Short summary
(1) Structural diagenesis analysis is performed on the ultra-deep tight sandstone. (2) Fracture and intergranular pores are related to the low in situ stress magnitudes. (3) Dissolution is associated with the presence of fracture.
Hamed Fazlikhani, Wolfgang Bauer, and Harald Stollhofen
Solid Earth, 13, 393–416,Short summary
Interpretation of newly acquired FRANKEN 2D seismic survey data in southeeastern Germany shows that upper Paleozoic low-grade metasedimentary rocks and possible nappe units are transported by Variscan shear zones to ca. 65 km west of the Franconian Fault System (FFS). We show that the locations of post-Variscan upper Carboniferous–Permian normal faults and associated graben and half-graben basins are controlled by the geometry of underlying Variscan shear zones.
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 Loew, Hansruedi Maurer, Martin O. Saar, Stefan Wiemer, and Domenico Giardini
Solid Earth, 13, 301–322,Short summary
Questions on issues such as anthropogenic earthquakes and deep geothermal energy developments require a better understanding of the fractured rock. Experiments conducted at reduced scales but with higher-resolution observations can shed some light. To this end, the BedrettoLab was recently established in an existing tunnel in Ticino, Switzerland, with preliminary efforts to characterize realistic rock mass behavior at the hectometer scale.
Berit Schwichtenberg, Florian Fusseis, Ian B. Butler, and Edward Andò
Solid Earth, 13, 41–64,Short 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 4-D analysis. Our observations invite a renewed discussion of the effect of sheet silicates on chemical compaction.
David Healy and Stephen Paul Hicks
Solid Earth, 13, 15–39,Short summary
The energy transition requires operations in faulted rocks. To manage the technical challenges and public concern over possible induced earthquakes, we need to quantify the risks. We calculate the probability of fault slip based on uncertain inputs, stresses, 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 hazards.
Manuel I. de Paz-Álvarez, Thomas G. Blenkinsop, David M. Buchs, George E. Gibbons, and Lesley Cherns
Solid Earth, 13, 1–14,Short summary
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.
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.
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.
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.
David J. Anastasio, Frank J. Pazzaglia, Josep M. Parés, Kenneth P. Kodama, Claudio Berti, James A. Fisher, Alessandro Montanari, and Lorraine K. Carnes
Solid Earth, 12, 1125–1142,Short summary
The anisotropy of magnetic susceptibility (AMS) technique provides an effective way to interpret deforming mountain belts. In both the Betics, Spain, and Apennines, Italy, weak but well-organized AMS fabrics were recovered from young unconsolidated and unburied rocks that could not be analyzed with more traditional methods. Collectively, these studies demonstrate the novel ways that AMS can be combined with other data to resolve earthquake hazards in space and time.
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.
Alessandro Tibaldi, Noemi Corti, Emanuela De Beni, Fabio Luca Bonali, Susanna Falsaperla, Horst Langer, Marco Neri, Massimo Cantarero, Danilo Reitano, and Luca Fallati
Solid Earth, 12, 801–816,Short summary
The Northeast Rift of Mt Etna is affected by ground deformation linked to gravity sliding of the volcano flank and dike injection. Drone surveys show that the rift is affected by NE-striking extensional fractures and normal faults. Given an age of 1614 CE for the offset lavas, we obtained an extension rate of 1.9 cm yr−1 for the last 406 years. The stress field is characterised by a NW–SE σHmin. Drone surveys allow us to quickly collect data with a resolution of 2–3 cm.
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.
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This contribution tests the various measures of grain size used in the paleopiezometry and proposes the frequency peak of the apparent 2D grain size distribution as the most robust estimator. The novelty of the approach resides in the use of the Gaussian kernel density estimator as an alternative to the classical histograms, which improves reproducibility. A free and easy-to-handle script (http://bit.ly/grainSizeTools) was developed with the aim of facilitating the adoption of this measure.
This contribution tests the various measures of grain size used in the paleopiezometry and...