Silicified Cone-in-Cone Structures from Erfoud (Morocco): A Comparison with Impact-Generated Shatter Cones

Lugli, Stefano; Reimold, W. U.; Koeberl, Christian

doi:10.1007/3-540-27548-7_3

Cited by 13 publications

(19 citation statements)

References 35 publications

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“…Table 1). Although wind erosion of exposed rocks or silicified cone-in-cone structures can produce analogous features (Lugli et al, 2005), in some places the perceived apices seem to point towards the centers of the structures. However, this should be confirmed by further measurements in the field, and we could not clearly observe the typical striation patterns of shatter cones (Sagy et al, 2004).…”

Section: Shatter-cone-like Features and Brecciasmentioning

confidence: 99%

An extended field of crater-shaped structures in the Gilf Kebir region, Egypt: Observations and hypotheses about their origin

Paillou

Reynard

Malézieux

et al. 2006

Journal of African Earth Sciences

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Section: Shatter-cone-like Features and Brecciasmentioning

confidence: 99%

An extended field of crater-shaped structures in the Gilf Kebir region, Egypt: Observations and hypotheses about their origin

Paillou

Reynard

Malézieux

et al. 2006

Journal of African Earth Sciences

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“…Our group once travelled to Morocco to follow up on a report of shatter cones in the Sahara. In that case, the alleged shatter cones were identified as sedimentary cone-in-cone structures (Lugli et al 2005). However, a number of confirmed (e.g., Roter Kamm, Namibia) and proposed (Arkenu structures, Libya) impact structures have wind abrasion features (ventifacts), that is, striations formed due to sand blasting under persistent wind direction and possibly superposed on mineral lineations in the rocks concerned.…”

mentioning

confidence: 99%

The Impact Crater Bandwagon (Some problems with the terrestrial impact cratering record)

Reimold¹

2007

Meteorit & Planetary Scien

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“…(e.g., more or less curved fracture surfaces that are characterized by generally divergent striations. They are distinctive in appearance and show some important differences to slickensides (see, e.g., French 1998 and references therein; Lugli et al 2005). The striae on shatter cones typically emanate from the apex of a conical fracture and diverge distinctly, so that the base of a shatter cone segment is usually wider than the apex area (Fig.…”

Section: Introductionmentioning

confidence: 99%

“…In cases where striations are subparallel to parallel (see below), they can still be distinguished from those on slickenside surfaces that are characterized by a diagnostic unidirectional, step-like pattern that actually allows investigation of the sense of movement on such fractures (e.g., Passchier and Trouw 1996). Lugli et al (2005) provided extensive discussion of the recognition criteria of shatter cones and the difficulties involved in distinguishing this impact deformation phenomenon from cone-in-cone structures and the products of other geological processes (tectonics, wind ablation, and sedimentary percussion marks). Dietz (1947Dietz ( , 1959Dietz ( , 1964) must be credited with establishing shatter cones as a diagnostic shock deformation feature of meteorite impact structures, with his thorough analytical work, especially in the Kentland and Sudbury structures.…”

Section: Introductionmentioning

confidence: 99%

New observations on shatter cones in the Vredefort impact structure, South Africa, and evaluation of current hypotheses for shatter cone formation

Wieland

Reimold

Gibson

2006

Meteorit & Planetary Scien

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available online at http://meteoritics.org New observations on shatter cones in the Vredefort impact structure, South Africa, and evaluation of current hypotheses for shatter cone formation Abstract-Shatter cones have been described from many meteorite impact structures and are widely regarded as a diagnostic macroscopic recognition feature for impact. However, the origin of this meso-to macroscopic striated fracture phenomenon has not yet been satisfactorily resolved, and the timing of shatter cone formation in the cratering process still remains enigmatic. Here, previous results from studies of shatter cones from the Vredefort impact structure and other impact structures are discussed in the light of new field observations made in the Vredefort Dome. Contrary to earlier claims, Vredefort cone fractures do not show uniform apex orientations at any given outcrop, nor do small cones show a pattern consistent with the previously postulated "master cone" concept. Simple back-rotation of impact-rotated strata to a horizontal pre-impact position also does not lead to a uniform centripetal-upward orientation of the cone apices. Striation patterns on the cone surfaces are variable, ranging from the typically diverging pattern branching off the cone apex to subparallel-toparallel patterns on almost flat surfaces. Striation angles on shatter cones do not increase with distance from the center of the dome, as alleged in the literature. Instead, a range of striation angles is measured on individual shatter cones from a specific outcrop. New observations on small-scale structures in the collar around the Vredefort Dome confirm the relationship of shatter cones with subparallel sets of curviplanar fractures (so-called multipli-striated joint sets, MSJS). Pervasive, meter-scale tensile fractures cross-cut shatter cones and appear to have formed after the closely spaced MSJ-type fractures.The results of this study indicate that none of the existing hypotheses for the formation of shatter cones are currently able to adequately explain all characteristics of this fracturing phenomenon. Therefore, we favor a combination of aspects of different hypotheses that includes the interaction of elastic waves, as supported by numerical modeling results and which reasonably explains the variety of shatter cone shapes, the range of striation geometries and angles, and the relationship of closely spaced fracture systems with the striated surfaces. In the light of the currently available theoretical basis for the formation of shatter cones, the results of this investigation lead to the conclusion that shatter cones are tensile fractures and might have formed during shock unloading, after the passage of the shock wave through the target rocks.

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Silicified Cone-in-Cone Structures from Erfoud (Morocco): A Comparison with Impact-Generated Shatter Cones

Cited by 13 publications

References 35 publications

An extended field of crater-shaped structures in the Gilf Kebir region, Egypt: Observations and hypotheses about their origin

An extended field of crater-shaped structures in the Gilf Kebir region, Egypt: Observations and hypotheses about their origin

The Impact Crater Bandwagon (Some problems with the terrestrial impact cratering record)

New observations on shatter cones in the Vredefort impact structure, South Africa, and evaluation of current hypotheses for shatter cone formation

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