Direct Inversion Method of Fault Slip Analysis to Determine The
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Strike and Dip Refer to the Orientation Or Attitude of a Geologic Feature. The
Name__________________________________ 89.325 – Geology for Engineers Faults, Folds, Outcrop Patterns and Geologic Maps I. Properties of Earth Materials When rocks are subjected to differential stress the resulting build-up in strain can cause deformation. Depending on the material properties the result can either be elastic deformation which can ultimately lead to the breaking of the rock material (faults) or ductile deformation which can lead to the development of folds. In this exercise we will look at the various types of deformation and how geologists use geologic maps to understand this deformation. II. Strike and Dip Strike and dip refer to the orientation or attitude of a geologic feature. The strike line of a bed, fault, or other planar feature, is a line representing the intersection of that feature with a horizontal plane. On a geologic map, this is represented with a short straight line segment oriented parallel to the strike line. Strike (or strike angle) can be given as either a quadrant compass bearing of the strike line (N25°E for example) or in terms of east or west of true north or south, a single three digit number representing the azimuth, where the lower number is usually given (where the example of N25°E would simply be 025), or the azimuth number followed by the degree sign (example of N25°E would be 025°). The dip gives the steepest angle of descent of a tilted bed or feature relative to a horizontal plane, and is given by the number (0°-90°) as well as a letter (N, S, E, W) with rough direction in which the bed is dipping. -
Field Geology
FIELD GEOLOGY GUIDEBOOK AND NOTES ILLINOIS STATE UNIVERSITY 2018 Version 2 Table of Contents Syllabus 5 Schedule 8 Hazard Recognition Mitigation 9 Geologic Field Notes 17 Reconnaissance Notes 17 Measuring Stratigraphic Column Notes 18 Geologic Mapping Notes 19 Geologic Maps and Mapping 22 Variables affecting the appearance of a geologic map 23 Techniques to test the quality and accuracy of your map 23 Common map errors 24 Official USGS map colors 24 Rule of V’s 25 Geologic Cross Sections 26 Basic principles of cross section construction 26 Apparent dips: correct use of strike and dip data in cross sections 27 Common cross section errors 27 Steps in making a topographic profile for a geologic cross section 28 Constructing geologic cross sections using down-plunge projection 29 Phanerozoic Stratigraphy of North America 33 Tectonic History of the U.S. Cordillera 38 Regional Cross-sections through Wyoming 41 Wyoming Stratigraphic Nomenclature Chart 42 Rock Sequence in the Bighorn Basin 43 Rock Sequence in the Powder River Basin 44 Black Hills Precambrian Geology 45 Project Descriptions 47 Regional Stratigraphy 47 Amsden Creek Big Game Winter Range 49 Steerhead Ranch 50 Alkali 53 South Fork 55 Mickelson 57 Moonshine 60 Appendix 1: Essential Analysis Tools and Techniques for Field Geology 62 Field description of rocks 62 Measuring stratigraphic sections 69 Calculating layer thicknesses 76 Alignment diagram for calculating apparent dip 77 Calculating strike and dip of a surface from contacts on a map 78 Calculating outcrop patterns from field -
Faults and Joints
133 JOINTS Joints (also termed extensional fractures) are planes of separation on which no or undetectable shear displacement has taken place. The two walls of the resulting tiny opening typically remain in tight (matching) contact. Joints may result from regional tectonics (i.e. the compressive stresses in front of a mountain belt), folding (due to curvature of bedding), faulting, or internal stress release during uplift or cooling. They often form under high fluid pressure (i.e. low effective stress), perpendicular to the smallest principal stress. The aperture of a joint is the space between its two walls measured perpendicularly to the mean plane. Apertures can be open (resulting in permeability enhancement) or occluded by mineral cement (resulting in permeability reduction). A joint with a large aperture (> few mm) is a fissure. The mechanical layer thickness of the deforming rock controls joint growth. If present in sufficient number, open joints may provide adequate porosity and permeability such that an otherwise impermeable rock may become a productive fractured reservoir. In quarrying, the largest block size depends on joint frequency; abundant fractures are desirable for quarrying crushed rock and gravel. Joint sets and systems Joints are ubiquitous features of rock exposures and often form families of straight to curviplanar fractures typically perpendicular to the layer boundaries in sedimentary rocks. A set is a group of joints with similar orientation and morphology. Several sets usually occur at the same place with no apparent interaction, giving exposures a blocky or fragmented appearance. Two or more sets of joints present together in an exposure compose a joint system. -
FM 5-410 Chapter 2
FM 5-410 CHAPTER 2 Structural Geology Structural geology describes the form, pat- secondary structural features. These secon- tern, origin, and internal structure of rock dary features include folds, faults, joints, and and soil masses. Tectonics, a closely related schistosity. These features can be identified field, deals with structural features on a and m appeal in the field through site inves- larger regional, continental, or global scale. tigation and from remote imagery. Figure 2-1, page 2-2, shows the major plates of the earth’s crust. These plates continually Section I. Structural Features undergo movement as shown by the arrows. in Sedimentary Rocks Figure 2-2, page 2-3, is a more detailed repre- sentation of plate tectonic theory. Molten material rises to the earth’s surface at BEDDING PLANES midoceanic ridges, forcing the oceanic plates Structural features are most readily recog- to diverge. These plates, in turn, collide with nized in the sedimentary rocks. They are adjacent plates, which may or may not be of normally deposited in more or less regular similar density. If the two colliding plates are horizontal layers that accumulate on top of of approximately equal density, the plates each other in an orderly sequence. Individual will crumple, forming mountain range along deposits within the sequence are separated the convergent zone. If, on the other hand, by planar contact surfaces called bedding one of the plates is more dense than the other, planes (see Figure 1-7, page 1-9). Bedding it will be subducted, or forced below, the planes are of great importance to military en- lighter plate, creating an oceanic trench along gineers. -
Horst Inversion Within a Décollement Zone During Extension Upper Rhine Graben, France Joachim Place, M Diraison, Yves Géraud, Hemin Koyi
Horst Inversion Within a Décollement Zone During Extension Upper Rhine Graben, France Joachim Place, M Diraison, Yves Géraud, Hemin Koyi To cite this version: Joachim Place, M Diraison, Yves Géraud, Hemin Koyi. Horst Inversion Within a Décollement Zone During Extension Upper Rhine Graben, France. Atlas of Structural Geological Interpretation from Seismic Images, 2018. hal-02959693 HAL Id: hal-02959693 https://hal.archives-ouvertes.fr/hal-02959693 Submitted on 7 Oct 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Horst Inversion Within a Décollement Zone During Extension Upper Rhine Graben, France Joachim Place*1, M. Diraison2, Y. Géraud3, and Hemin A. Koyi4 1 Formerly at Department of Earth Sciences, Uppsala University, Sweden 2 Institut de Physique du Globe de Strasbourg (IPGS), Université de Strasbourg/EOST, Strasbourg, France 3 Université de Lorraine, Vandoeuvre-lès-Nancy, France 4 Department of Earth Sciences, Uppsala University, Sweden * [email protected] The Merkwiller–Pechelbronn oil field of the Upper Rhine Graben has been a target for hydrocarbon exploration for over a century. The occurrence of the hydrocarbons is thought to be related to the noticeably high geothermal gradient of the area. -
Structural Geology
2 STRUCTURAL GEOLOGY Conventional Map A map is a proportionate representation of an area/structure. The study of maps is known as cartography and the experts are known as cartographers. The maps were first prepared by people of Sumerian civilization by using clay lens. The characteristic elements of a map are scale (ratio of map distance to field distance and can be represented in three ways—statement method, e.g., 1 cm = 0.5 km, representative fraction method, e.g., 1:50,000 and graphical method in the form of a figure), direction, symbol and colour. On the basis of scale, maps are of two types: large-scale map (map gives more information pertaining to a smaller area, e.g., village map: 1:3956) and small: scale map (map gives less information pertaining to a larger area, e.g., world atlas: 1:100 km). Topographic Maps / Toposheet A toposheet is a map representing topography of an area. It is prepared by the Survey of India, Dehradun. Here, a three-dimensional feature is represented on a two-dimensional map and the information is mainly represented by contours. The contours/isohypses are lines connecting points of same elevation with respect to mean sea level (msl). The index contours are the contours representing 100’s/multiples of 100’s drawn with thick lines. The contour interval is usually 20 m. The contours never intersect each other and are not parallel. The characteristic elements of a toposheet are scale, colour, symbol and direction. The various layers which can be prepared from a toposheet are structural elements like fault and lineaments, cropping pattern, land use/land cover, groundwater abstruction structures, drainage density, drainage divide, elongation ratio, circularity ratio, drainage frequency, natural vegetation, rock types, landform units, infrastructural facilities, drainage and waterbodies, drainage number, drainage pattern, drainage length, relief/slope, stream order, sinuosity index and infiltration number. -
Basin Inversion and Structural Architecture As Constraints on Fluid Flow and Pb-Zn Mineralisation in the Paleo-Mesoproterozoic S
https://doi.org/10.5194/se-2020-31 Preprint. Discussion started: 6 April 2020 c Author(s) 2020. CC BY 4.0 License. 1 Basin inversion and structural architecture as constraints on fluid 2 flow and Pb-Zn mineralisation in the Paleo-Mesoproterozoic 3 sedimentary sequences of northern Australia 4 5 George M. Gibson, Research School of Earth Sciences, Australian National University, Canberra ACT 6 2601, Australia 7 Sally Edwards, Geological Survey of Queensland, Department of Natural Resources, Mines and Energy, 8 Brisbane, Queensland 4000, Australia 9 Abstract 10 As host to several world-class sediment-hosted Pb-Zn deposits and unknown quantities of conventional and 11 unconventional gas, the variably inverted 1730-1640 Ma Calvert and 1640-1580 Ma Isa superbasins of 12 northern Australia have been the subject of numerous seismic reflection studies with a view to better 13 understanding basin architecture and fluid migration pathways. Strikingly similar structural architecture 14 has been reported from much younger inverted sedimentary basins considered prospective for oil and gas 15 elsewhere in the world. Such similarities suggest that the mineral and petroleum systems in Paleo- 16 Mesoproterozoic northern Australia may have spatially and temporally overlapped consistent with the 17 observation that basinal sequences hosting Pb-Zn mineralisation in northern Australia are bituminous or 18 abnormally enriched in hydrocarbons. This points to the possibility of a common tectonic driver and shared 19 fluid pathways. Sediment-hosted Pb-Zn mineralisation coeval with basin inversion first occurred during the 20 1650-1640 Ma Riversleigh Tectonic Event towards the close of the Calvert Superbasin with further pulses 21 accompanying the 1620-1580 Ma Isa Orogeny which brought about closure of the Isa Superbasin. -
Tectonic Inversion and Petroleum System Implications in the Rifts Of
Tectonic Inversion and Petroleum System Implications in the Rifts of Central Africa Marian Jenner Warren Jenner GeoConsulting, Suite 208, 1235 17th Ave SW, Calgary, Alberta, Canada, T2T 0C2 [email protected] Summary The rift system of western and central Africa (Fig. 1) provides an opportunity to explore a spectrum of relationships between initial tectonic extension and later compressional inversion. Several seismic interpretation examples provide excellent illustrations of the use of basic geometric principles to distinguish even slight inversion from original extensional “rollover” anticlines. Other examples illustrate how geometries traditionally interpreted as positive “flower” structures in areas of known transpression/ strike slip are revealed as inversion structures when examined critically. The examples also highlight the degree of compressional inversion as a function in part of the orientation of compressional stress with respect to original rift structures. Finally, much of the rift system contains recent or current hydrocarbon exploration and production, providing insights into the implications of inversion for hydrocarbon risk and prospectivity. Figure 1: Mesozoic-Tertiary rift systems of central and western Africa. Individual basins referred to in text: T-LC = Termit/ Lake Chad; LB = Logone Birni; BN = Benue Trough; BG = Bongor; DB = Doba; DS = Doseo; SL = Salamat; MG = Muglad; ML = Melut. CASZ = Central African Shear Zone (bold solid line). Bold dashed lines = inferred subsidiary shear zones. Red stars = Approximate locations of example sections shown in Figs. 2-5. Modified after Genik 1993 and Manga et al. 2001. Inversion setting and examples The Mesozoic-Tertiary rift system in Africa was developed primarily in the Early Cretaceous, during south Atlantic opening and regional NE-SW extension. -
Chromium Chemistry in Natural Waters, Iceland Deformation Mechanisms in Martian Shergottites
1414 Goldschmidt2013 Conference Abstracts Chromium chemistry in natural Deformation mechanisms in Martian waters, Iceland Shergottites HANNA KAASALAINEN1*, ANDRI STEFÁNSSON1, KACZMAREK M.-A.*12, GRANGE M.1, REDDY S.M.1, INGVI GUNNARSSON2 AND STEFÁN ARNÓRSSON1 AND NEMCHIN A.1 1Institute of Earth Sciences, University of Iceland, Sturlugata 1Department of Applied Geology, The Institute for Geoscience 7, 101 Reykjavik, Iceland, Research, Curtin University of Technology, GPO Box (*correspondence: [email protected]) U1987, Perth, WA 6845, Australia 2Present address: Reykjavik Energy, Bæjarhalsi 1, 110 2Now at University of Lausanne, Institute of Earth Sciences, Reykajvik, Iceland UNIL Mouline, Géopolis, CH-1016 Lausanne, Switzerland Chemistry of Cr and Fe was studied in non-thermal and (*correspondence: [email protected]) geothermal waters in Iceland. Chromium (Cr) is typically present at low concentrations (<1 µg/l) in natural waters, but Nakhla and Zagami are both clinopyroxene-rich basaltic elevated concentrations have been observed in waters with shergottite, with some Fe-rich olivine. The microstructure, the low pH values, e.g. acid mine drainage, and in association preferred orientation of pyroxene using Electron Backscatter with industrial activities. Chromium occurs in two oxidation Diffraction (EBSD) method and the gochemistry are combined states, Cr(III) and (VI), these being characterized by different to study subsamples of both Zagami and Nakhla to decipher (bio)chemical behaviour and solubility. As Cr(VI) is known to deformation processes that have occurred on Mars. be toxic but Cr(III) an essential micronutrient, it is important Nakhla displays a granular texture, essentially composed to determine the two oxidations states. Iron (Fe) is known to of augite, fayalite, plagioclase and magnetite. -
Raplee Ridge Monocline and Thrust Fault Imaged Using Inverse Boundary Element Modeling and ALSM Data
Journal of Structural Geology 32 (2010) 45–58 Contents lists available at ScienceDirect Journal of Structural Geology journal homepage: www.elsevier.com/locate/jsg Structural geometry of Raplee Ridge monocline and thrust fault imaged using inverse Boundary Element Modeling and ALSM data G.E. Hilley*, I. Mynatt, D.D. Pollard Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305-2115, USA article info abstract Article history: We model the Raplee Ridge monocline in southwest Utah, where Airborne Laser Swath Mapping (ALSM) Received 16 September 2008 topographic data define the geometry of exposed marker layers within this fold. The spatial extent of five Received in revised form surfaces were mapped using the ALSM data, elevations were extracted from the topography, and points 30 April 2009 on these surfaces were used to infer the underlying fault geometry and remote strain conditions. First, Accepted 29 June 2009 we compare elevations extracted from the ALSM data to the publicly available National Elevation Dataset Available online 8 July 2009 10-m DEM (Digital Elevation Model; NED-10) and 30-m DEM (NED-30). While the spatial resolution of the NED datasets was too coarse to locate the surfaces accurately, the elevations extracted at points Keywords: w Monocline spaced 50 m apart from each mapped surface yield similar values to the ALSM data. Next, we used Boundary element model a Boundary Element Model (BEM) to infer the geometry of the underlying fault and the remote strain Airborne laser swath mapping tensor that is most consistent with the deformation recorded by strata exposed within the fold. -
Evidence for Controlled Deformation During Laramide Orogeny
Geologic structure of the northern margin of the Chihuahua trough 43 BOLETÍN DE LA SOCIEDAD GEOLÓGICA MEXICANA D GEOL DA Ó VOLUMEN 60, NÚM. 1, 2008, P. 43-69 E G I I C C O A S 1904 M 2004 . C EX . ICANA A C i e n A ñ o s Geologic structure of the northern margin of the Chihuahua trough: Evidence for controlled deformation during Laramide Orogeny Dana Carciumaru1,*, Roberto Ortega2 1 Orbis Consultores en Geología y Geofísica, Mexico, D.F, Mexico. 2 Centro de Investigación Científi ca y de Educación Superior de Ensenada (CICESE) Unidad La Paz, Mirafl ores 334, Fracc.Bella Vista, La Paz, BCS, 23050, Mexico. *[email protected] Abstract In this article we studied the northern part of the Laramide foreland of the Chihuahua Trough. The purpose of this work is twofold; fi rst we studied whether the deformation involves or not the basement along crustal faults (thin- or thick- skinned deformation), and second, we studied the nature of the principal shortening directions in the Chihuahua Trough. In this region, style of deformation changes from motion on moderate to low angle thrust and reverse faults within the interior of the basin to basement involved reverse faulting on the adjacent platform. Shortening directions estimated from the geometry of folds and faults and inversion of fault slip data indicate that both basement involved structures and faults within the basin record a similar Laramide deformation style. Map scale relationships indicate that motion on high angle basement involved thrusts post dates low angle thrusting. This is consistent with the two sets of faults forming during a single progressive deformation with in - sequence - thrusting migrating out of the basin onto the platform. -
MESOZOIC TECTONIC INVERSION in the NEUQUÉN BASIN of WEST-CENTRAL ARGENTINA a Dissertation by GABRIEL ORLANDO GRIMALDI CASTRO Su
MESOZOIC TECTONIC INVERSION IN THE NEUQUÉN BASIN OF WEST-CENTRAL ARGENTINA A Dissertation by GABRIEL ORLANDO GRIMALDI CASTRO Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY December 2005 Major Subject: Geology MESOZOIC TECTONIC INVERSION IN THE NEUQUÉN BASIN OF WEST-CENTRAL ARGENTINA A Dissertation by GABRIEL ORLANDO GRIMALDI CASTRO Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved by: Chair of Committee, Steven L. Dorobek Committee Members, Philip D. Rabinowitz Niall C. Slowey Brian J. Willis David V. Wiltschko Head of Department, Richard L. Carlson December 2005 Major Subject: Geology iii ABSTRACT Mesozoic Tectonic Inversion in the Neuquén Basin of West-Central Argentina. (December 2005) Gabriel Orlando Grimaldi Castro, B.S., Universidad Nacional de Córdoba, Argentina; M.S., Texas A&M University Chair of Advisory Committee: Dr. Steven L. Dorobek Mesozoic tectonic inversion in the Neuquén Basin of west-central Argentina produced two main fault systems: (1) deep faults that affected basement and syn-rift strata where preexisting faults were selectively reactivated during inversion based on their length and (2) shallow faults that affected post-rift and syn-inversion strata. Normal faults formed at high angle to the reactivated half-graben bounding fault as a result of hangingwall expansion and internal deformation as it accommodated to the shape of the curved footwall during oblique inversion. Contraction during inversion was initially accommodated by folding and internal deformation of syn-rift sedimentary wedges, followed by displacement along half-graben bounding faults.