Geological fissures: linking sub-surface structures to surface processes

2021 ◽  
Author(s):  
Bob Holdsworth ◽  
Kit Hardman ◽  
Rich Walker ◽  
Alodie Bubeck ◽  
Cat Greenfield ◽  
...  
Keyword(s):  
Sedimentary Basins ◽  
Wall Rock ◽  
Surface Processes ◽  
Major Influence ◽  
Normal Faults ◽  
High Porosity ◽  
Block Rotation ◽  
Geothermal Resources ◽  
Diverse Range ◽  
Near Surface

<p>Dilatant fissures are a common feature at the Earth’s surface in active rift systems where faults cut mechanically-strong rocks, such as igneous rocks, metamorphic basement or carbonates. Much attention has focused on modern examples of large-aperture fissures in basaltic rocks, where in most cases, only the near-surface-expression is accessible to depths of ~100 m. Numerous mechanisms have been proposed for the formation of such dilatant fractures, including near-surface tensile fracturing along active normal faults at depth, geometric mismatch along faults, and fault-block rotation. However, fissure system architecture and connectivity in the subsurface, and the depth to which dilatant sections can grow are less well understood, as are the ways in which such structures may interact with surface processes.</p><p>In this presentation, we focus on dilatant faults and fractures from the ancient rock record, including examples hosted in rocks below regional erosional unconformities, commonly on the upfaulted flanks of nearby sedimentary basins. Such fissures are typically sub-vertical Mode I fractures that can be kilometres long, tens of metres wide and can extend to depths of 1 km or more below the palaeosurface. They are filled with a remarkably diverse range of high porosity, high permeability fills which act as natural proppants holding fractures open for tens to hundreds of million years. Fills include: wall rock collapse breccias; clastic or carbonate sediment; fossiliferous materials, and a variety of epithermal mineral deposits with characteristically vuggy forms and cockade-like textures. Alteration related to weathering and/or near-surface epithermal mineralization may extend down fissure systems to depths of many hundreds of metres. The subterranean clastic fills are commonly water-lain and preserve a unique record of the stratigraphic or fossil record that may be missing due to erosion at the overlying unconformity. Fissures can form along active normal faults at depth, as later-stage reactivations of pre-existing exhumed fault zones and along regional joint sets associated with folds. Some fissures form along the margins or interior of pre-existing mafic dykes or may act as sites of subsequent dyke emplacement – or both. Sub-unconformity fissure systems and their associated fills are likely to be a major influence on both the fluid storage capacity and flow behaviour in subsurface reservoirs including those hosting hydrocarbons, geothermal resources, and in aquifers worldwide.</p>

scholarly journals Evolution of rift systems and their fault networks in response to surface processes

2021 ◽  
Author(s):  
Derek Neuharth ◽  
Sascha Brune ◽  
Thilo Wrona ◽  
Anne Glerum ◽  
Jean Braun ◽  
...  
Keyword(s):  
Sedimentary Basins ◽  
Field Studies ◽  
Fault Analysis ◽  
Growth Patterns ◽  
Surface Processes ◽  
Fault System ◽  
Normal Faults ◽  
Continental Margins ◽  
Geodynamic Models ◽  
Fault Growth

Continental rifting is responsible for the generation of major sedimentary basins, both during rift inception and during the formation of rifted continental margins. Geophysical and field studies revealed that rifts feature complex networks of normal faults but the factors controlling fault network properties and their evolution are still matter of debate. Here, we employ high-resolution 2D geodynamic models (ASPECT) including two-way coupling to a surface processes code (FastScape) to conduct 12 models of major rift types that are exposed to various degrees of erosion and sedimentation. We further present a novel quantitative fault analysis toolbox (Fatbox), which allows us to isolate fault growth patterns, the number of faults, and their length and displacement throughout rift history. Our analysis reveals that rift fault networks may evolve through five major phases: 1) distributed deformation and coalescence, 2) fault system growth, 3) fault system decline and basinward localization, 4) rift migration, and 5) breakup. These phases can be correlated to distinct rifted margin domains. Models of asymmetric rifting suggest rift migration is facilitated through both ductile and brittle deformation within a weak exhumation channel that rotates subhorizontally and remains active at low angles. In sedimentation-starved settings, this channel satisfies the conditions for serpentinization. We find that surface processes are not only able to enhance strain localization and to increase fault longevity but that they also reduce the total length of the fault system, prolong rift phases and delay continental breakup.

The Influence of lithosphere and basement properties on the stretching factor and the development of extensional faults across the Otway Basin and eastern Bight Basin

2020 ◽  
Author(s):  
nasim kharazizadeh
Keyword(s):  
Sedimentary Basins ◽  
Passive Margin ◽  
Tectonic Activity ◽  
Major Influence ◽  
Normal Faults ◽  
Basement Faults ◽  
Stretching Factor ◽  
Minor Influence ◽  
Basement Structures ◽  
A Minor

<p>The Influence of lithosphere and basement properties on the stretching factor and the development of extensional faults across the Otway Basin and eastern Bight Basin</p><ol><li><strong> KHARAZIZADEH*, W.P. SCHELLART, J.C. DUARTE </strong></li> </ol><p>School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC 3800, Australia</p><p>Department of Earth Sciences, Vrije Universiteit Amsterdam, Amsterdam, Netherlands</p><p>Instituto Dom Luiz (ILD) and Geology Department, Faculty of Sciences of the University of Lisbon, Campo Grande, Lisbon, Portugal  </p><p> </p><p>*[email protected]</p><p>*[email protected]</p><p> </p><p><strong>Abstract</strong></p><p>The large southern continental margin of Australia, with a wide variety of sedimentary basins, formed during Mesozoic rifting. The evolution of sedimentary basins is mainly controlled by plate tectonic activity and the mechanism of continental extension. This work presents a comparative study between two main depocentres of the Bight Basin (Ceduna, Duntroon sub-basins) and the Otway Basin. Here, the total amount of extension (∆L) and stretching factor (β) have been measured across the Otway Basin and eastern Bight Basin. The results show significant variation in extensional stretching along the basins, with the smallest stretching factors in the Ceduna and Duntroon sub-basins (1.2<β<1.4), and the largest amount of extension (~ 177 km) and the largest stretching factor (β=1.85) in the eastern part of the passive margin. The regions with the lowest β factor are underlain mostly by thicker lithosphere, while the regions with the largest β factor and amount of extension are related to younger and thinner lithosphere. The main basement structures have been mapped throughout South Australia and Victoria to examine the possible relationships between the new pattern of extensional faults and old basement fabrics. The distribution pattern of normal faults varies considerably along onshore and offshore components of basins. It is proposed that in some regions fault strike varies due to changes in orientation of pre-existing structures in the basement. For example, the north-south Coorong Shear Zone seems to affect the geometry of normal faults by changing their strike from E-W to NW-SE and also, in the easternmost part of the basin, the Bambra Fault changes the strike of normal faults to the NE-SW. Also, the NE-SW basement structures in the western part of the Gawler Craton have some control on normal faults in the western Ceduna sub-basin. Normal faults in the easternmost and westernmost parts of the Otway Basin have a similar orientation to the basement faults. However, in most regions basement faults are perpendicular to the normal faults and there is a minor influence on the new pattern of faulting. Our results imply that the properties of the continental lithosphere (age, thickness and strength of lithosphere) exert a major influence on the β factor and amount of crustal extension but only a minor influence on the geometry of extensional faults.</p><p><strong>Keywords:</strong> Otway Basin, Ceduna and Duntroon sub-basins, rifting, total amount of extension, β factor, normal faults, lithosphere properties</p><p> </p>

A new sedimentary cover model for the southern area of the East European Platform and the Pre-Caucasus based on decompensation gravity anomalies data

2021 ◽  
Author(s):  
Mikhail Kaban ◽  
Alexei Gvishiani ◽  
Roman Sidorov ◽  
Alexei Oshchenko ◽  
Roman Krasnoperov
Keyword(s):  
East European Platform ◽  
Sedimentary Cover ◽  
Gravity Anomalies ◽  
Sedimentary Basins ◽  
The Caucasus ◽  
Near Surface ◽  
New Model ◽  
Origin And Evolution ◽  
East European ◽  
Bouguer Anomalies

<p><span>A new model has been developed for the density and thickness of the sedimentary cover in a vast region at the junction of the southern part of the East European Platform, the Pre-Caucasus and some structures adjacent to the south, including the Caucasus. Structure and density of sedimentary basins was studied by employing the approach based on decompensation of gravity anomalies. Decompensative correction for gravity anomalies reduces the effect of deep masses providing compensation of near-surface density anomalies, in contrast to the conventional isostatic or Bouguer anomalies. . The new model of sediments, which implies their thickness and density, gives a more detailed description of the sedimentary thickness and density and reveals new features which were not or differently imaged by previous studies. It helps in better understanding of the origin and evolution of the basins and provides a background for further detailed geological and geophysical studies of the region.</span></p>

Two-dimensional elastic pseudo-spectral modeling of wide-aperture seismic array data with application to the Wichita Uplift-Anadarko Basin region of southwestern Oklahoma

1990 ◽  
Vol 80 (6A) ◽  
pp. 1677-1695 ◽  
Author(s):  
Ik Bum Kang ◽  
George A. McMechan
Keyword(s):  
Large Scale ◽  
Deep Structure ◽  
Sedimentary Basins ◽  
P Wave ◽  
Two Dimensional ◽  
Anadarko Basin ◽  
Near Surface ◽  
University Of Texas ◽  
Wide Aperture ◽  
The University

Abstract Full wave field modeling of wide-aperture data is performed with a pseudospectral implementation of the elastic wave equation. This approach naturally produces three-component stress and two-component particle displacement, velocity, and acceleration seismograms for compressional, shear, and Rayleigh waves. It also has distinct advantages in terms of computational requirements over finite-differencing when data from large-scale structures are to be modeled at high frequencies. The algorithm is applied to iterative two-dimensional modeling of seismograms from a survey performed in 1985 by The University of Texas at El Paso and The University of Texas at Dallas across the Anadarko basin and the Wichita Mountains in southwestern Oklahoma. The results provide an independent look at details of near-surface structure and reflector configurations. Near-surface (<3 km deep) structure and scattering effects account for a large percentage (>70 per cent) of the energy in the observed seismograms. The interpretation of the data is consistent with the results of previous studies of these data, but provides considerably more detail. Overall, the P-wave velocities in the Wichita Uplift are more typical of the middle crust than the upper crust (5.3 to 7.1 km/sec). At the surface, the uplift is either exposed as weathered outcrop (5.0 to 5.3 km/sec) or is overlain with sediments of up to 0.4 km in thickness, ranging in velocity from 2.7 to 3.4 km/sec, generally increasing with depth. The core of the uplift is relatively seismically transparent. A very clear, coherent reflection is observed from the Mountain View fault, which dips at ≈40° to the southwest, to at least 12 km depth. Velocities in the Anadarko Basin are typical of sedimentary basins; there is a general increase from ≈2.7 km/sec at the surface to ≈5.9 km/sec at ≈16 km depth, with discontinuous reflections at depths of ≈8, 10, 12, and 16 km.

Surface and Near-Surface Atom Dynamics During Low Energy Xe Ion Bombardment of Si and Fcc Surfaces

1990 ◽  
Vol 193 ◽  
Author(s):  
M. V. R. Murty ◽  
H. S. Lee ◽  
Harry A. Atwater
Keyword(s):  
Molecular Dynamics ◽  
Surface Layer ◽  
Ion Bombardment ◽  
Low Energy ◽  
Surface Processes ◽  
Defect Production ◽  
Near Surface ◽  
Qualitative Nature ◽  
Dynamics Simulations ◽  
Atom Dynamics

ABSTRACTSurface and near-surface processes have been studied during low energy Xe ion bombardment of Si (001) and fcc surfaces using molecular dynamics simulations. Defect production is enhanced near the surface of smooth Si (001) surfaces with respect to the bulk in the energy range 20–150 eV, but is not confined exclusively to the surface layer. The extent and qualitative nature of bombardment-induced dissociation of small fcc islands on an otherwise smooth fcc (001) surface is found to depend strongly on island cohesive energy.

scholarly journals Estimating the Geothermal Electricity Generation Potential of Sedimentary Basins Using genGEO (The Generalizable GEOthermal Techno-Economic Simulator)

2021 ◽  
Author(s):  
Benjamin Adams ◽  
Jonathan Ogland-Hand ◽  
Jeffrey M. Bielicki ◽  
Philipp Schädle ◽  
Martin Saar
Keyword(s):  
Electricity Generation ◽  
Power Plants ◽  
Sedimentary Basin ◽  
Sedimentary Basins ◽  
Heat Extraction ◽  
Subsurface Water ◽  
Geothermal Heat ◽  
Geothermal Resources ◽  
Geothermal Power ◽  
Economic Tools

<p><b>Abstract</b></p><p>Sedimentary basins are ubiquitous, naturally porous and permeable, and the geothermal heat in these basins can be extracted with geologic water or CO<sub>2</sub> and used to generate electricity. Despite this, the broad potential that these formations may have for electricity generation is unknown. Here we investigate this potential, which required the creation of the <u>gen</u>eralizable <u>GEO</u>thermal techno-economic simulator (genGEO). genGEO is built with only publicly available data and uses five standalone, but integrated, models that directly simulate all components of geothermal power plants to estimate electricity generation and cost. As a result of this structure, genGEO, or a portion of it, can be applied or extended to study any geothermal power technology. In contrast, the current techno-economic tools for geothermal power plants rely on characterizations of unpublished ASPEN results and are thus not generalizable enough to be applied to sedimentary basin geothermal power plants which use subsurface CO<sub>2</sub>.</p> <p>In this study, we present genGEO as open-source software, validate it with industry data, and compare its estimates to other geothermal techno-economic tools. We then apply genGEO to sedimentary basin geothermal resources and find that using CO<sub>2</sub> as a subsurface heat extraction fluid compared to water decreases the cost of geothermal electricity across most geologic conditions that are representative of sedimentary basins. Using genGEO results and p50 geologic data, we produce supply curves for sedimentary basin geothermal power plants in the U.S., which suggests that there is present-day potential to profitably increase the capacity of geothermal power by ~10% using water as the subsurface heat extraction fluid. More capacity is available at lower cost when CO<sub>2</sub> is used as the subsurface fluid, but realizing this capacity requires geologically storing between ~2 and ~7 MtCO<sub>2</sub>/MW<sub>e</sub>. But developing sedimentary basin resources in the short-term using subsurface water may not eliminate options for CO₂-based power plants in the long-term because the least-cost order of sedimentary basins is not the same for both CO<sub>2</sub> and water. With sufficient geologic CO<sub>2</sub> storage, developing sedimentary basins using CO<sub>2</sub>- and water-based power plants may be able to proceed in parallel.</p>

scholarly journals The GRETA project: the contribution of near-surface geothermal energy for the energetic self-sufficiency of Alpine regions

2017 ◽  
Vol 6 (1) ◽  
Author(s):  
Alessandro Casasso ◽  
Bruno Piga ◽  
Rajandrea Sethi ◽  
Joerg Prestor ◽  
Simona Pestotnik ◽  
...  
Keyword(s):  
Geothermal Energy ◽  
Primary Energy ◽  
Economic Activities ◽  
Geothermal Heat ◽  
Geothermal Resources ◽  
Near Surface ◽  
Alpine Regions ◽  
Heating And Cooling ◽  
Geothermal Heat Pump ◽  
Alpine Space

The Alpine regions are deeply involved in the challenge set by climate change, which is a threat for their environment and for important economic activities such as tourism. The heating and cooling of buildings account for a major share of the total primary energy consumption in Europe, and hence the energy policies should focus on this sector to achieve the greenhouse gas reduction targets set by international agreements. Geothermal heat pump is one of the least carbon-intensive technologies for the heating and cooling of buildings. It exploits the heat stored within the ground, a local renewable energy source which is widely available across the Alpine territory. Nevertheless, it has been little considered by European policies and cooperation projects. GRETA (near-surface Geothermal REsources in the Territory of the Alpine space) is a cooperation project funded by the EU INTERREG-Alpine Space program, aiming at demonstrating the potential of shallow geothermal energy and to foster its integration into energy planning instruments. It started in December 2015 and will last three years, involving 12 partners from Italy, France, Switzerland, Germany, Austria, and Slovenia. In this paper, the project is presented, along with the results of the first year of work.

scholarly journals Seismic reflection data reveal the 3D structure of the newly discovered Exmouth Dyke Swarm, offshore NW Australia

2020 ◽  
Author(s):  
Craig Magee ◽  
Christopher A.-L. Jackson
Keyword(s):  
Seismic Reflection ◽  
Surface Deformation ◽  
3D Structure ◽  
Sedimentary Basins ◽  
Dyke Swarm ◽  
Normal Faults ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Dyke Swarms ◽  
Nw Australia

Abstract. Dyke swarms are common on Earth and other planetary bodies, comprising arrays of dykes that can extend for 10's to 1000's of kilometres. The vast extent of such dyke swarms, and their rapid emplacement, means they can significantly influence a variety of planetary processes, including continental break-up, crustal extension, resource accumulation, and volcanism. Determining the mechanisms driving dyke swarm emplacement is thus critical to a range of Earth Science disciplines. However, unravelling dyke swarm emplacement mechanics relies on constraining their 3D structure, which is extremely difficult given we typically cannot access their subsurface geometry at a sufficiently high enough resolution. Here we use high-quality seismic reflection data to identify and examine the 3D geometry of the newly discovered Exmouth Dyke Swarm, and associated structures (i.e. dyke-induced normal faults and pit craters), in unprecedented detail. The latest Jurassic dyke swarm is located on the Gascoyne Margin offshore NW Australia and contains numerous dykes that are > 170 km long, potentially > 500 km long. The mapped dykes are distributed radially across a 39° arc centred on the Cuvier Margin; we infer this focal area marks the source of the dyke swarm, which was likely a mantle plume. We demonstrate seismic reflection data provides unique opportunities to map and quantify dyke swarms in 3D in sedimentary basins, which can allow us to: (i) recognise dyke swarms across continental margins worldwide and incorporate them into models of basin evolution and fluid flow; (ii) test previous models and hypotheses concerning the 3D structure of dyke swarms; (iii) reveal how dyke-induced normal faults and pit craters relate to dyking; and (iv) unravel how dyking translates into surface deformation.

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