Lithological and structural characteristics of the Lake Bosumtwi impact crater, Ghana: Interpretation of acoustic televiewer images

Hunze, Sabine; Wonik, Thomas

doi:10.1111/j.1945-5100.2007.tb01074.x

Cited by 16 publications

(15 citation statements)

References 14 publications

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“…The parameter SUS is very suitable because it has characteristic variations with high dynamic and high vertical resolution but without any statistical disturbance, such as a gamma ray log has, and is much easier to measure on cores than the gamma ray log is. Hunze and Wonik (2007) note that the physical properties (e.g., resistivity, P-wave velocity, magnetic susceptibility) of the breccia differ significantly from those of the metagraywackes and slate/phyllites. Fractures observed in the televiewer images indicate steep dip angles (50-70°) and the two main dip directions are southeast and southwest.…”

Section: Geophysical Results From Drilling and Loggingmentioning

confidence: 93%

“…The tool set delivers a primary set of 15 parameters comprising total natural gamma ray, contents of potassium, uranium, and thorium, three-component magnetic field, magnetic susceptibility, electrical resistivity for deep and shallow penetration, sonic compressional velocity and full "sonic waveforms," borehole 4-arm caliper, deviation and azimuth, and acoustic borehole wall images. Further processing derives other parameters: sonic shear wave velocity, total magnetic field, structural dipmeter data, and structural data from borehole wall images that are used by other investigators Hunze and Wonik 2007).…”

Section: Downhole Logging Operations and Borehole Geophysical Surveysmentioning

confidence: 99%

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An international and multidisciplinary drilling project into a young complex impact structure: The 2004 ICDP Bosumtwi Crater Drilling Project—An overview

Koeberl

Milkereit

Overpeck

et al. 2007

Meteorit & Planetary Scien

102

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Abstract-The Bosumtwi impact crater in Ghana, arguably the best-preserved complex young impact structure known on Earth, displays a pronounced rim and is almost completely filled by Lake Bosumtwi, a hydrologically closed basin. It is the source crater of the Ivory Coast tektites. The structure was excavated in 2.1-2.2 Gyr old metasediments and metavolcanics of the Birimian Supergroup. A drilling project was conceived that would combine two major scientific interests in this crater: 1) to obtain a complete paleoenvironmental record from the time of crater formation about one million years ago, at a near-equatorial location in Africa for which very few data are available so far, and 2) to obtain a complete record of impactites at the central uplift and in the crater moat, for ground truthing and comparison with other structures.Within the framework of an international and multidisciplinary drilling project led by the International Continental Scientific Drilling Program (ICDP), 16 drill cores were obtained from June to October 2004 at six locations within Lake Bosumtwi, which is 8.5 km in diameter. The 14 sediment cores are currently being investigated for paleoenvironmental indicators. The two impactite cores LB-07A and LB-08A were drilled into the deepest section of the annular moat (540 m) and the flank of the central uplift (450 m), respectively. They are the main subject of this special issue of Meteoritics & Planetary Science, which represents the first detailed presentations of results from the deep drilling into the Bosumtwi impactite sequence. Drilling progressed in both cases through the impact breccia layer into fractured bedrock. LB-07A comprises lithic (in the uppermost part) and suevitic impact breccias with appreciable amounts of impact melt fragments. The lithic clast content is dominated by graywacke, besides various metapelites, quartzite, and a carbonate target component. Shock deformation in the form of quartz grains with planar microdeformations is abundant. First chemical results indicate a number of suevite samples that are strongly enriched in siderophile elements and Mg, but the presence of a definite meteoritic component in these samples cannot be confirmed due to high indigenous values. Core LB-08A comprises suevitic breccia in the uppermost part, followed with depth by a thick sequence of graywacke-dominated metasediment with suevite and a few granitoid dike intercalations. It is assumed that the metasediment package represents bedrock intersected in the 484 C. Koeberl et al.

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Section: Geophysical Results From Drilling and Loggingmentioning

confidence: 93%

Section: Downhole Logging Operations and Borehole Geophysical Surveysmentioning

confidence: 99%

An international and multidisciplinary drilling project into a young complex impact structure: The 2004 ICDP Bosumtwi Crater Drilling Project—An overview

Koeberl

Milkereit

Overpeck

et al. 2007

Meteorit & Planetary Scien

102

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“…Cross-plotting or statistical techniques enable evaluation of lithology and pore fluid variations on both regional and detailed reservoir scale [6,7]. Anderson and Gray [8] as well as Gray and Andersen [9] had demonstrated that many different lithologies like coal, shale, sandstone, gas saturated sands and carbonates can be identified by cross-plots of λρ versus µρ (where λ is elastic parameter, µ is rigidity modulus and ρ is density).…”

Section: Introductionmentioning

confidence: 99%

Application of Cross-Plotting Techniques for Delineation of Coal and Non-Coal Litho-Units from Well Logs

Chatterjee¹,

Paul²

2012

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Well log responses can be used to delineate coal and carbonaceous shale from other non-potential litho-units by cross-plotting technique. The cross-plotting between gamma ray and density had been carried out for 15 wells of Jharia coalfield, India. Through these different cross-plots across the study area, different litho-units like; coal, shaly coal, carbonaceous shale, shale, sand/sandstone, shaly sand, jhama and igneous intrusion (mica peridotite) have been identified. Clustering of points for different lithologies in the above cross-plots indicate that the different trends with marginal overlap between carbonaceous shale/shaly coal and shale as well as shaly sand and shale. The coal horizons are mostly overlain and underlain by shale or sandstone. Cross-plot analysis indicates the various coal lithologies which will play important role in CBM exploration and exploitation strategy.

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“…However, the reference line does not appear at the same point on every image; therefore, to bring all the core segments into a common absolute reference frame requires additional information. Since the borehole televiewer imagery is referenced to geomagnetic north it is possible to bring the optical photographic images into an absolute reference frame by comparing the images (Hunze and Wonik 2007). Karatson et al (2002) provide an excellent review of the application of photo-imaging to clast fabric orientation estimation.…”

Section: Introductionmentioning

confidence: 99%

Clast fabric examination of impact‐generated breccias, borehole LB‐07A, Bosumtwi, Ghana

Morris

Ugalde

Clark

et al. 2007

Meteorit & Planetary Scien

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Abstract-An impact event always creates a cloud of ejecta generated through excavation of the target. Subsequent in-filling of the void by crater-fill deposits provides a record of post-impact processes. Full-core digital photographic scans of core segments from borehole LB-07 in the Bosumtwi impact crater provide a complete record of the in-fill process. The shape, orientation, and size of clasts within the impact breccia were measured using a best-fit ellipsoid approach. Clast size and variance, together with clast orientation data, suggest the impact breccias at Bosumtwi can be divided into a simple two-fold subdivision that loosely agrees with the lithological zonation of a lower monomict breccia overlain by a polymict breccia. The lower unit is characterized by a uniform and finer-grained clast size together with a uniform flat-lying clast orientation. The boundary between the two zones is defined by a sharp increase in clast size. The upper zone shows an average increase in clast size with decreasing depth, but full grain size spectrum together with increased grain size deviation suggest that this is a result of mixing between two populations with different grain size distribution. The main population of clasts shows an incremental decrease of clast size with decreasing depth. The upper zone also contains weakly defined shallowly dipping clast fabrics, which may be suggestive of horizontal transport or deposition onto an inclined surface.

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Lithological and structural characteristics of the Lake Bosumtwi impact crater, Ghana: Interpretation of acoustic televiewer images

Cited by 16 publications

References 14 publications

An international and multidisciplinary drilling project into a young complex impact structure: The 2004 ICDP Bosumtwi Crater Drilling Project—An overview

An international and multidisciplinary drilling project into a young complex impact structure: The 2004 ICDP Bosumtwi Crater Drilling Project—An overview

Application of Cross-Plotting Techniques for Delineation of Coal and Non-Coal Litho-Units from Well Logs

Clast fabric examination of impact‐generated breccias, borehole LB‐07A, Bosumtwi, Ghana

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