P11 GEOLOGI STRUKTUR Analisis Geofisika Struktur Geologi

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Transcript of P11 GEOLOGI STRUKTUR Analisis Geofisika Struktur Geologi

  • Geologi Struktur(Analisis Geofisika Struktur Geologi)

    Oleh :Irvani

    Universitas Bangka Belitung Jurusan Teknik Pertambangan

  • Referensi : Van Der Pluijm, B. A. and Marshak, S. 2004. Earth Structure. 2nd Edition. W. W.

    Norton & Company, Inc., USA. Rowland, S.M., Duebendorfer, E.M. and Schiefelbein, I.M. 2007. Structural Analysis

    and Synthesis : A Laboratory Course in Structural Geology. 3th Edition. Blacwell Publishing Ltd. Voctoria, Australia.

    Bates, R.L. and Jackson, J.A., 1987. Glossary Geology. 3th Edition. American Geological Institute Elexandria, Virginia.

    Davis, G.H. 1984. Structural Geology of Rocks and Regions. John Wiley & Sons, New York.

    Ragan, D.M. 2009. Structural Geology : An Introduction to Geometrical Techniques. 4th Edition. Cambridge University Press, New York.

    Twiss R.J. And Moores, E.M. 2007. Structural Geology. 2nd Edition. W.H. Freeman and Company, USA.

    Ramsey J. and Huber, M. 1983. The Techniques of Modern Structural Geology : Strain Analysis. Vol. 1. Academic Press, Inc., London.

    Ramsey J. and Huber, M. 1987. The Techniques of Modern Structural Geology : Fold and Fractures. Vol. 2. Academic Press, Inc., London.

    Ramsey J. and Huber, M. 2000. The Techniques of Modern Structural Geology : Applications of Continuum Mechanics in Structural Geology. Vol. 3. Elsevier Academic Press, Inc., California.

    Cox, A. and Hart, R.B. 1986. Plate Tectonics : How It Works. Blacwell Scienific Publications, Inc., California.

    Trouw, R.A.J. and Passchier, C.W. 1996. Microtectonics. Springer Verlag Berlin Heidelberg, Germany.

    DLL.

    Universitas Bangka Belitung Jurusan Teknik Pertambangan

  • Pokok Bahasan :I Pendahuluan (P.1)

    II Tektonika & Orogenesa (P.2-3)a. Tektonik lempengb. Orogenesa

    III Gaya, Tegangan, Strain & Deformasi (P.4-5)

    a. Gaya & Teganganb. Strain & Deformasi

    IV Struktur Geologi (P.6-9)a. Unsur strukturb. Lipatan c. Kekar d. Sesar/Patahan

    V Identifikasi Struk. Geologi (P.10-11)a. Pengukuran dan analisis

    struktur geologib. Analisis geofisika struktur

    geologi

    VI Aplikasi Struk. Geologi (P.12-13)a. Mineralisasi b. Migasc. Kebencanaan geologi

    VII Geologi Struk. Indonesia (P.14)a. Umumb. Sumatra&Jawa c. Bangka Belitung

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  • Geophysical Imaging of the Continental LithosphereSismic

    Pluijm & Marshak (2004)

    Universitas Bangka Belitung Jurusan Teknik Pertambangan

  • P-waves have a particle motion parallel with the propagation direction of the wavefront and it is therefore a compressional wave. The S-wave has a motion that is perpendicular to the direction of propagation, it is a transverse waveform. The Love and Raleigh waves have rather complex particle motions. The latter two are surface-related movements that do not show a great penetration depth and a rapid vertical decrease in amplitude away from the interface (modified after Kearey and Brooks 1991).

    Veeken (2007)

    Universitas Bangka Belitung Jurusan Teknik Pertambangan

  • Reflection and refraction

    Snells law,

    Milsom (2003)

    Universitas Bangka Belitung Jurusan Teknik Pertambangan

  • Diagram illustrating different P-wave raypath in seismic acquisition set-up for a horizontal interface. Various rays are shown in the depth model at the top and their recording in the time domain TX-graph at the bottom. The reflected waveform is represented by a hyperbolic curve. Veeken (2007)

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  • Ranges of P-wave velocities and rippabilities in common rocks. The vertical axis, for each rock type, is intended to show approximately the relative numbers of samples that would show a given velocity.

    Milsom (2003)

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  • Diagram showing how echo sounding, seismic reflection, andsidescan sonar are used to study the sea floor. Modified from U.S. Geological Survey Fact Sheet 039-02

    Carlson et al. (2009)

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  • Unconformities

    Veeken (2007)

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  • Stratigraphic subdivision in two wells from the sedimentary Mandawa Basin (Tanzania) based on biostratigraphic, seismic and lithostratigraphic information. The 2D seismic line below illustrates the structural style of the basin fill. The transfer zone penetrated in the Mbuo-1 well contains sands with hydrocarbon shows directly overlying the basement pop-up block.

    Veeken (2007)

    Universitas Bangka Belitung Jurusan Teknik Pertambangan

  • Seismic section illustrating the structuration of the Macuspana Basin (onshore Mexico). The two high areas are prospective areas for hydrocarbon exploration.The structure on the right has been tested and contains HCs in the Miocene-Pliocene sequence. The structure on the left is untested, but has amplitude anomalies associated with it. The kitchen is situated in the deeper graben below, in which Jurassic and Cretaceous source rocks are mature (courtesy Pemex).Veeken (2007)

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  • Complex tectonic history resulted in tectonic inversion of the sediments across the Fahud fault zone in northern Oman.The velocity distribution is anomalous due to the Tertiary uplift on the right hand side, disturbing the natural increase in velocity due to ongoing burial and compaction is no longer valid. This should be taken into account when doing TD conversion. Local velocity trends are calibrated by wells and should be respected by the conversion procedure (Veeken et al. 2005).

    Veeken (2007)

    Universitas Bangka Belitung Jurusan Teknik Pertambangan

  • Veeken (2007)

    Universitas Bangka Belitung Jurusan Teknik Pertambangan

  • Seismic reflection profile across the southern Rocky Mountain Trench near the Canada-U.S. border. Note that the prominent layering, which is drilled on the west and is known to be dominantly Proterozoic sills, is offset along a west-dipping listric normal fault that has about 10 km of dip-slip displacement. Data were recorded by Duncan Energy of Denver, Colorado.

    Pluijm & Marshak (2004)

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  • Seismic profile from the Wind River Mountains in Wyoming (USA). The Wind River fault juxtaposes crystalline rocks of the Wind River Mountains with sedimentary rocks of the Green River Basin along a moderately east-dipping fault, and this provides a simple explanation for the prominent reflection. Below a travel time of about 3.54.0 s,however, the fault zone places crystalline rocks onto crystalline rocks and the reflections must be caused by other mechanisms. Datarecorded by COCORP (Consortium for Continental Reflection Profiling) in 1977. Pluijm & Marshak (2004)

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  • Seismic profile from the Proterozoic Trans-Hudson Orogen in northern Saskatchewan (Canada) illustrating prominent subhorizontalreflections that have been interpreted as intrusive rocks. Note that the reflector appears to cross cut several dipping reflections. Note also the prominent Moho on these data.

    Pluijm & Marshak (2004)

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  • Some reflection characteristics of the crustmantle transition. (a) Profile from south-central portion of the Canadian Cordillera illustrating a relatively simple, single reflection from near the transition. On the right side of the figure, the numbers 6.0 and 7.0 represent the positions of the Moho, as identified from adjacent seismic refraction data, for average velocities of 6.0 and 7.0 km/s, respectively. RM represents the preferred position of the Moho using the crustal velocity structure determined from the refraction profile. Note that the Moho appears to be located at the base of crustal reflectivity, and that the underlying mantle has fewer reflections (e.g., MR). Data were recorded by LITHOPROBE in 1988.

    372

    Pluijm & Marshak (2004)

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  • Reflection characteristics of the crustmantle transition. Portion of a seismic profile that illustrates listric structures into the crustmantle transition. Data were recorded by LITHOPROBE in 1996. This segment is from beneath the Great Bear arc region on the regional profile.

    Pluijm & Marshak (2004)

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  • (upper) Regional seismic profile from ancient (>2.6 Ga) rocks of the SlaveProvince on the east, across the Proterozoic (2.11.85 Ga) Wopmay Orogen in the center, and then the younger Proterozoic ( 1.740.55 Ga) Fort Simpson Basin on the west. The data are plotted to 32.0 s travel time, or about 120 km depth. Note the prominent crustal reflectivity, the crustmantle transition, and sparse, but important reflections from within the upper mantle (M1 and M2). A general interpretation is shown (lower) to illustrate that the accretion of the Proterozoic rocks to the Slave Province probably resulted from subduction, the remnants of which are probably the dipping mantle reflections. Pluijm & Marshak (2004)

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  • Enlargement of a segment of the regional profile from the Slave Province. Here, the Moho appears to have a series of dipping surfaces (arrows) that are cross cut by horizontal reflections (RM). One possible interpretation is that these horizontal reflectionsrepresent intrusives. Pluijm & Marshak (2004)

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  • Portion of a seismic profile that illustrates many lower crustal layers that are parallel to the Moho as well as a possible truncation (T?). Data were recorded by LITHOPROBE in 1996.

    Pluijm & Marshak (2004)

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  • Portion of a seismic profile from northern Saskatchewan (Canada) that illustrates a local deepening of the crustmantle transition (Mohokeel). Note that although there is not a prominent reflection near the transition, the reflectivity does diminish near it. In this figure, two locations for estimates of travel time to the reflection Moho are indicated from adjacent refraction profiles. Pluijm & Marshak (2004)

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  • The regional seismic profile across the Proterozoic basin illustrating the huge thickness of strata on the west and the associated shallowing of the Moho.

    Pluijm & Marshak (2004)

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  • Enlargement of the regional profile in the upper part of the Proterozoic Fort Simpson Basin on the west. Note the sedimentary features such as the unconformity at the base of the Paleozoicsediments, unconformities in the eastward-thinning Proterozoiclayers, and the prominent cross-cutting reflection that may be an igneous dike. Pluijm & Marshak (2004)

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  • Enlargement of the regional profile across a feature that has been interpreted as the remnants of an accretionary complex. Note that the mantle reflections, M1, can be followed westward where they correlate with the Moho and that dipping layers above M1 tend to steepen eastward (upper arrows) as is common in accretionarywedges. Pluijm & Marshak (2004)

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  • The Accretionary Prism

    Schematic detail of an accretionary prism, showing different regimes of deformation referred to in the text. (b) Interpreted seismic-reflection profile of the toe edge of anaccretionary prism forming in the Nankai trough off Japan. Several faults can be imaged.

    Pluijm & Marshak (2004)

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  • Abyssal Plains

    Seismic profiler record of an abyssal plain, showing sediment layers that have buried an irregular rock surface in the Atlantic Ocean. From Vogt et al. in Hart, The Earths Crust and Upper Mantle, p. 574, American Geophysical Union

    Carlson et al. (2009)

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  • Fold-Thrust Belts

    the two continents collide. A fold-thrust belt forms in the foreland of the orogen on both sides of the orogen. Slivers of obducted ocean crust may separate lower-plate rocks from the metamorphic hinterland of the orogen and define the suture between the two plates.

    Cross-section sketch of a fold-thrust belt forming at the seaward toe of a passive-margin basin.Pluijm & Marshak (2004)

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  • Vertically exaggerated two-dimensional seismic-reflection profile illustrating an imbricate fan of thrust faults that has developed offshore of Nigeria (passive-margin).

    Pluijm & Marshak (2004)

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  • Strike-slip fault

    Pluijm & Marshak (2004)

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  • Simplified geological map of Sumatra showing the distribution of the main stratigaphic units and the active volcanoes.

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  • Interpreted single-channel seismic reflection sections across the Mentawai Fault in the southern part of the Sumatra forearc basin (after Diament et al. 1992). Line locations as shown. Milsom (2005) in Barber et al. (ed.)

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  • Multi-channel seismic reflection section across the Mentawai Fault south of Enggano, after Schltiter et al. (2002).

    Milsom (2005) in Barber et al. (ed.)

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  • SIO Line 42-43, showing the Mentawai Fault immediately south of Nias. Section provided by Scripps Institution of Oceanography.

    Milsom (2005) in Barber et al. (ed.)

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  • Geometric distortion on seismic sections. The image is of a small graben structure beneath an unconformity. The position of the true fault plane BB (indicated by the dashed line) can be estimated from the positions of the terminations of the sub-horizontal reflectors representing the sediment fill within the graben (although care must be exercised because many of the deeper sub-horizontal events are multiples). The event AA is the seismic image of BB. It is displaced because the techniques used to display the data assume that reflections are generated from points vertically beneath the surface points, whereas they are actually generated by normal-incidence rays that are inclined to the vertical if reflected from dipping interfaces (Section 10.3.2). The reflections from the fault and the opposite side of the graben cross over near the lower symbol A, forming a bow-tie. Convex-upward reflections near point C are diffraction patterns generated by faulting. Milsom (2003)

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  • Time-migrated seismic profile from southern Appalachian fold-thrust belt (Maher 2002), displayed with approximately no vertical exaggeration. The vertical scale is two-way travel time in seconds. a Uninterpreted. b Interpreted Groshong (2006)

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  • Seismic model of a faulted fold. a Geometry of the model, no vertical exaggeration. b Model time section based on normal velocity variations with lithology and depth. Vertical scale is two-way travel time in milliseconds. (After Morse et al. 1991)

    Groshong (2006)

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  • Time migrated seismic profile from central Wyoming. TWT: Two-way travel time; Ti: interval thickness. a Original profile having a vertical scale of 7.5 in per second and a horizontal scale of 12 traces per in. Vertical exaggeration (ve) is 1.87 :1. b The vertical scale is the same as in a, the horizontal scale is reduced by two-thirds. Vertical exaggeration is 5.6: 1. c Unexaggerated version produced by expanding the horizontal scale. Thickness T1 is now constant across the profile. (After Stone 1991) Groshong (2006)

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  • Normal faults on a vertical profile from a time-migrated 3-D seismic reflection volume. V.E. about 1: 1. The profile is from the Gilbertown graben system, southern Alabama (modified from Groshong et al. 2003a). a Uninterpreted. A: fault trace between arrows; B: reflectors hang over fault trace; C: disturbed zone along fault trace. b Interpreted. The faults indicated with heavier lines have been identified in nearby wells. Numbers next to the faults are heave (regular type) and throw (bold). Throws are determined from the heaves using Throw=Heave times tan (fault dip). Only the most obvious faults are interpreted below the top of the Eutaw Groshong (2006)

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  • Corsair fault, a thin skinned growth fault on the Texas continentalshelf. 48-fold, depthconverted seismic line. F: fault reflectors. (After Christensen 1983)

    Groshong (2006)

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  • Groshong (2006)

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  • Velocity discontinuities create features that look like faults on seismic profiles. a Segment of a seismic line across Wyoming thrust belt (dynamite source, eight-fold common-depth-point stack, migrated time section, approximate vertical exaggeration 1.3 at 2.7 s; Williams and Dixon 1985). b Discontinuities in seismic reflectors that might be normal faults. c Interpretation by Williams and Dixon (1985). d Geologicalcross section using well control and the seismic line; no vertical exaggeration (Williams and Dixon 1985). The box outlines the area of the seismic line. No normal faults are present. TWY: two-way traveltime (s); C: Cambrian; MD: Mississippian-Devonian; IPPM: Pennsylvanian, Permian, Mississippian undifferentiated; P: Permian; Tr, TR: Triassic; J: Jurassic undifferentiated; Jn: Jurassic Nugget sandstone; T: Tertiary

    Groshong (2006)

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  • Faults are visible on seismic sections, but with a certain resolution.

    Veeken (2007)

    Universitas Bangka Belitung Jurusan Teknik Pertambangan

  • Faults are visible on seismic sections, but with a certain resolution.

    Veeken (2007)

    Universitas Bangka Belitung Jurusan Teknik Pertambangan

  • Seismic section across the Troll Field, offshore Norway. A flat spot is seen around 1.7 seconds TWT. The gas containing reservoir sands are Jurassic in age and have an average porosity of 28 percent (modified after Brown 1999, data courtesy Norske Hydro). Veeken (2007)

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  • Gravity anomalies result from variations in rock mass, in principle we should be able to determine the relative positions of different masses at depth.

    Gravity

    There are some limits (spatially), of course, because theanomalies are located according to map position, but it is difficult to determine much more detail without some additional information from other techniques.

    Pluijm & Marshak (2004)

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  • Isostatic gravity map of northwestern Canada plotted with shaded relief (artificial illumination from the west, view toward the northeast). The position of the regional seismic profile is shown by the thick white line. TT represents the Tintina Fault, a late strike-slip fault within the Cordillera, and FS represents the Fort Simpson Trend associated with the Fort Simpson Basin. The gridded digital gravity data were provided by the Canadian Geophysical Data Centre, and the original version of this figure was made by Kevin Hall.Pluijm & Marshak (2004)

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  • Enlargement of the map in the vicinity of the seismic profile to emphasize the relationship of the profile to the FS anomaly. The smaller white line near the bottom right is the location of a secondprofile across the southern portion of the FS trend, and the white circles represent locations of drill holes that penetrated crystalline rocks below the (b) Western Canada Sedimentary Basin strata.Pluijm & Marshak (2004)

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  • Terima Kasih

    Universitas Bangka Belitung Jurusan Teknik Pertambangan