Pronounced central uplift identified in the Bosumtwi impact structure, Ghana, using multichannel seismic reflection data

Scholz, Christopher A.; Karp, Tobias; Brooks, Keely M.; Milkereit, B.; Amoako, P. Y.; Arko, Justice A.

doi:10.1130/0091-7613(2002)030<0939:pcuiit>2.0.co;2

Cited by 61 publications

(61 citation statements)

References 16 publications

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“…P-wave velocities in hand specimens of bedrock outcrops around the lake are generally much higher (ϳ4950 m/s, Niessen et al, 2006). This suggests that the bedrock is brecciated at least in its upper part, as is the case in other craters (e.g., Bosumtwi crater, Ghana, Africa; Karp et al, 2002;Scholz et al, 2002). The central ring structure is overlain by a layer interpreted as allochthonous fallback breccia characterized by seismic velocities of ϳ3000 m/s.…”

Section: Results and Interpretationmentioning

confidence: 87%

Central ring structure identified in one of the world's best-preserved impact craters

Gebhardt

Niessen

Kopsch

2006

Geol

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Seismic refraction and reflection data were acquired in 2000 and 2003 to study the morphology and sedimentary fill of the remote El'gygytgyn crater (Chukotka, northeastern Siberia; diameter 18 km). These data allow a first insight into the deeper structure of this unique impact crater. Wide-angle data from sonobuoys reveal a five-layer model: a water layer, two lacustrine sedimentary units that fill a bowl-shaped apparent crater morphology consisting of an upper layer of fallback breccia with P-wave velocities of ϳ3000 m/s, and a lower layer of brecciated bedrock (velocities Ͼ3600 m/s). The lowermost layer shows a distinct anticline structure that, by analogy with other terrestrial and lunar craters of similar size, can be interpreted as a central ring structure. The El'gygytgyn crater exhibits a well-expressed morphology that is typical of craters formed in crystalline target rocks.

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Section: Results and Interpretationmentioning

confidence: 87%

Central ring structure identified in one of the world's best-preserved impact craters

Gebhardt

Niessen

Kopsch

2006

Geol

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“…3e) Scholz et al 2002), and the recent ICDP coring resolved the post-impact stratigraphy ). The present-day central uplift/high, with a diameter of 1.9 km and a maximum height of 130 m, was a positive feature immediately after impact as progressive onlap and distinct thickness variations are present within the post-impact sediments (Fig.…”

Section: Post-impact Infillingmentioning

confidence: 99%

Post‐impact structural crater modification due to sediment loading: An overlooked process

Tsikalas

Faleide

2007

Meteorit & Planetary Scien

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Abstract-Post-impact crater morphology and structure modifications due to sediment loading are analyzed in detail and exemplified in five well-preserved impact craters: Mjølnir, Chesapeake Bay, Chicxulub, Montagnais, and Bosumtwi. The analysis demonstrates that the geometry and the structural and stratigraphic relations of post-impact strata provide information about the amplitude, the spatial distribution, and the mode of post-impact deformation. Reconstruction of the original morphology and structure for the Mjølnir, Chicxulub, and Bosumtwi craters demonstrates the long-term subsidence and differential compaction that takes place between the crater and the outside platform region, and laterally within the crater structure. At Mjølnir, the central high developed as a prominent feature during post-impact burial, the height of the peak ring was enhanced, and the cumulative throw on the rim faults was increased. The original Chicxulub crater exhibited considerably less prominent peakring and inner-ring/crater-rim features than the present crater. The original relief of the peak ring was on the order of 420-570 m (currently 535-575 m); the relief on the inner ring/crater rim was 300-450 m (currently ∼700 m). The original Bosumtwi crater exhibited a central uplift/high whose structural relief increased during burial (current height 101-110 m, in contrast to the original height of 85-110 m), whereas the surrounding western part of the annular trough was subdued more that the eastern part, exhibiting original depths of 43-68 m (currently 46 m) and 49-55 m (currently 50 m), respectively. Furthermore, a quantitative model for the porosity change caused by the Chesapeake Bay impact was developed utilizing the modeled density distribution. The model shows that, compared with the surrounding platform, the porosity increased immediately after impact up to 8.5% in the collapsed and brecciated crater center (currently +6% due to post-impact compaction). In contrast, porosity decreased by 2-3% (currently −3 to −4.5% due to post-impact compaction) in the peak-ring region. The lateral variations in porosity at Chesapeake Bay crater are compatible with similar porosity variations at Mjølnir crater, and are considered to be responsible for the moderate Chesapeake Bay gravity signature (annular low of −8 mGal instead of −15 mGal). The analysis shows that the reconstructions and the long-term alterations due to post-impact burial are closely related to the impact-disturbed target-rock volume and a brecciated region of laterally varying thickness and depthvarying physical properties. The study further shows that several crater morphological and structural parameters are prone to post-impact burial modification and are either exaggerated or subdued during post-impact burial. Preliminary correction factors are established based on the integrated reconstruction and post-impact deformation analysis. The crater morphological and structural parameters, corrected from post-impact loading and modification effects, can be used to better const...

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“…Lake-level changes as large as 170 m (Bartov et al, 2002) have on the one hand been attributed to paleoclimate change, but on the other hand, basin morphology and barriers between subbasins are able to modify and restrict lake-level changes in this area (Bartov et al, 2002, and references therein). The impact crater of Lake Bosumtwi (Ghana, West Africa) is rather small with a diameter of ∼ 8 km (Scholz et al, 2002). This lake is hydrologically closed (Shanahan et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

“…Changes in lake level can be in the order of some meters, but can also be much larger than those recorded in the marine environment. Large-scale lakelevel changes of up to several hundreds of meters were observed in a series of large lakes, such as Lake Tanganyika (Lezzar et al, 1996), Lake Malawi (Scholz, 2007;Lyons et al, 2015), Lake Van (Cukur et al, 2014), Lake Lisan (Machlus et al, 2000), Lake Petén Itzá (Anselmetti et al, 2006), Laguna Potrok Aike (Anselmetti et al, 2009;Gebhardt et al, 2012), Lake Bosumtwi (Scholz et al, 2002), and Lake Chala (Moernaut et al, 2010). Lake Van (eastern Anatolia) is a large lake basin (Degens et al, 1984;Litt et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

High-amplitude lake-level changes in tectonically active Lake Issyk-Kul (Kyrgyzstan) revealed by high-resolution seismic reflection data

et al. 2017

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Abstract.A total of 84 seismic profiles, mainly from the western and eastern deltas of Lake Issyk-Kul, were used to identify lake-level changes. Seven stratigraphic sequences were reconstructed, each containing a series of delta lobes that were formed during former lake-level stillstands or during slow lake-level increase or decrease. The lake level has experienced at least four cycles of stepwise rise and fall of 400 m or more. These fluctuations were mainly caused by past changes in the atmospheric circulation pattern. During periods of low lake levels, the Siberian High was likely to be strong, bringing dry air masses from the Mongolian steppe blocking the midlatitude Westerlies. During periods of high lake levels, the Siberian High must have been weaker or displaced, and the midlatitude Westerlies could bring moister air masses from the Mediterranean and North Atlantic regions.

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Pronounced central uplift identified in the Bosumtwi impact structure, Ghana, using multichannel seismic reflection data

Cited by 61 publications

References 16 publications

Central ring structure identified in one of the world's best-preserved impact craters

Central ring structure identified in one of the world's best-preserved impact craters

Post‐impact structural crater modification due to sediment loading: An overlooked process

High-amplitude lake-level changes in tectonically active Lake Issyk-Kul (Kyrgyzstan) revealed by high-resolution seismic reflection data

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