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

Reimold, W. U.

doi:10.1111/j.1945-5100.2007.tb00585.x

Cited by 34 publications

(25 citation statements)

References 26 publications

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“…The ex is tence of such a sys tem has been con firmed through DTM anal y sis car ried out for the present study. How ever, the pres ence of cir cu lar and ra dial mor pholog i cal fea tures with out any other di ag nos tic fea tures is not suffi cient to in ter pret it as an im pact struc ture (Koeberl, 2004;Reimold, 2007;French and Koeberl, 2010;Reimold et al, 2014). The to pog ra phy of the pre-Qua ter nary sur face in the study area is there fore an es sen tial (al though in di rect) ar gument in fa vour of this hy poth e sis.…”

Section: Fig 3 Map Of Morpholineaments Against the Background Of Slmentioning

confidence: 99%

Identification of a circular structure in eastern Pomerania (northern Poland) – a hypothesis of its origin

Uścinowicz

2016

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The pos si ble ex is tence of a cir cu lar struc ture in the Kooecierzyna re gion (north ern Po land) was sug gested in two pa pers in the 1980s. The cur rent stud ies were aimed at ver i fy ing this hy poth e sis. Anal y sis of a dig i tal ter rain model of the pre-Qua ter nary sur face re lief as well as of the pres ent ter rain re vealed the ex is tence of a large struc ture of ca. 50 km in di am e ter. Its ge om etry was es tab lished based on a model of the Neo gene/Plio cene sur face and iden ti fi able lin ea ments. Its char ac ter is tic fea ture is the pres ence of rim-like forms, an in ter nal pla teau, and a "high" in the cen tre. The struc ture is es ti mated to date from be fore the Pleis to cene. The cir cu lar struc ture has been re shaped by gla cial ero sion and ac cu mu la tion, and is now bur ied un der Qua ter nary de pos its. The ex is tence of the Kooecierzyna cir cu lar struc ture was con firmed by con ducted stud ies, but my hypoth e sis of an im pact or i gin is still un cer tain and needs to be con firmed by fu ture re search.

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Section: Fig 3 Map Of Morpholineaments Against the Background Of Slmentioning

confidence: 99%

Identification of a circular structure in eastern Pomerania (northern Poland) – a hypothesis of its origin

Uścinowicz

2016

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“…Of these features, single to multiple sets of thin, closely spaced PMs in feldspar and quartz-interpreted as shock-induced planar deformation features (PDFs)-are considered uniquely diagnostic of shock metamorphism (cf. Reimold 2007).…”

Section: Western Rim Rock Alteration Featuresmentioning

confidence: 99%

Identification of the Bloody Creek structure, a possible impact crater in southwestern Nova Scotia, Canada

Spooner

Stevens

Morrow

et al. 2009

Meteorit & Planetary Scien

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Abstract--An approximately 0.4 km diameter elliptical structure formed in Devonian granite in southwestern Nova Scotia, herein named the Bloody Creek structure (BCS), is identified as a possible impact crater. Evidence for an impact origin is based on integrated geomorphic, geophysical, and petrographic data. A near-continuous geomorphic rim and a 10 m deep crater that is infilled with lacustrine sediments and peat define the BCS. Ground penetrating radar shows that the crater has a depressed inner floor that is sharply ringed by a 1 m high buried scarp. Heterogeneous material under the floor, interpreted as deposits from collapse of the transient cavity walls, is overlain by stratified and faulted lacustrine and wetland sediments. Alteration features found only in rim rocks include common grain comminution, polymict lithic microbreccias, kink-banded feldspar and biotite, single and multiple sets of closely spaced planar microstructures (PMs) in quartz and feldspar, and quartz mosaicism, rare reduced mineral birefringence, and chlorite showing plastic deformation and flow microtextures. Based on their form and crystallographic orientations, the quartz PMs consist of planar deformation features that document shock-metamorphic pressures ≤25 GPa.The age of the BCS is not determined. The low depth to diameter ratio of the crater, coupled with anomalously high shock-metamorphic pressures recorded at its exposed rim, may be a result of significant post-impact erosion. Alternatively, impact onto glacier ice during the waning stages of Wisconsinian deglaciation (about 12 ka BP) may have resulted in dissipation of much impact energy into the ice, resulting in the present morphology of the BCS.

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“…This suggests that there may be further flaws in the already less than sufficient statistics of terrestrial impact ages (Jourdan et al 2007b;Reimold 2007;Kelley 2007) and highlights the need for ongoing high-resolution chronology of impact-melt rocks, including further chronological effort on Roter Kamm impact-melt rocks.…”

Section: Roter Kamm Impact Agementioning

confidence: 99%

New impact‐melt rock from the Roter Kamm impact structure, Namibia: Further constraints on impact age, melt rock chemistry, and projectile composition

Hecht

Reimold

Sherlock

et al. 2008

Meteorit & Planetary Scien

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Abstract-A new locality of in situ massive impact-melt rock was discovered on the southsouthwestern rim of the Roter Kamm impact structure. While the sub-samples from this new locality are relatively homogeneous at the hand specimen scale, and despite being from a nearby location, they do not have the same composition of the only previously analyzed impact-melt rock sample from Roter Kamm. Both Roter Kamm impact-melt rock samples analyzed to date, as well as several suevite samples, exhibit a granitic-granodioritic precursor composition. Micro-chemical analyses of glassy matrix and Al-rich orthopyroxene microphenocrysts demonstrate rapid cooling and chemical disequilibrium at small scales. Platinum-group element abundances and ratios indicate an ordinary chondritic composition for the Roter Kamm impactor. Laser argon dating of two sub-samples did not reproduce the previously obtained age of 3.7 ± 0.3 (1σ) for this impact event, based on 40 Ar/ 39 Ar dating of a single vesicular impact-melt rock. Instead, we obtained ages between 3.9 and 6.3 Ma, with an inverse isochron age of 4.7 ± 0.3 Ma for one analyzed sub-sample and 5.1 ± 0.4 Ma for the other. Clearly a post-5 Ma impact at Roter Kamm remains indicated, but further analytical work is required to better constrain the currently best estimate of 4-5 Ma. Both impactor and age constraints are clearly obstructed by the inherent microscopic heterogeneity and disequilibrium melting and cooling processes demonstrated in the present study.

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

Cited by 34 publications

References 26 publications

Identification of a circular structure in eastern Pomerania (northern Poland) – a hypothesis of its origin

Identification of a circular structure in eastern Pomerania (northern Poland) – a hypothesis of its origin

Identification of the Bloody Creek structure, a possible impact crater in southwestern Nova Scotia, Canada

New impact‐melt rock from the Roter Kamm impact structure, Namibia: Further constraints on impact age, melt rock chemistry, and projectile composition

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