The nature of the KT impactor. A 54Cr reappraisal

Trinquier, Anne; Birck, J. L.; Allègre, Claude J.

doi:10.1016/j.epsl.2005.11.006

Cited by 85 publications

(90 citation statements)

References 42 publications

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“…This is consistent with the C-complex nature of the BAF. Trinquier et al (2006) found that the closest match between trace Cr signatures found at different K-T ejecta layer sites and the known meteorites are those found in CM2 carbonaceous chondrites. Thus, BAF members may have CM2-like compositions.…”

Section: Scenario 3 CM Clasts Produced By a Recent Disruption Eventmentioning

confidence: 95%

On the origin of shocked and unshocked CM clasts in H‐chondrite regolith breccias

Rubin

Bottke

2009

Meteorit & Planetary Scien

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Abstract--CM chondrite clasts that have experienced different degrees of aqueous alteration occur in H-chondrite and HED meteorite breccias. Many clasts are fragments of essentially unshocked CM projectiles that accreted at low relative velocities to the regoliths of these parent bodies. A few clasts were heated and dehydrated upon impact; these objects most likely accreted at higher relative velocities. We examined three clasts and explored alternative scenarios for their formation. In the first scenario, we assumed that the H and HED parent bodies had diameters of a few hundred kilometers, so that their high escape velocities would effectively prevent soft landings of small CM projectiles. This would imply that weakly shocked CM clasts formed on asteroidal fragments (family members) associated with the H and HED parent bodies. In the second scenario, we assumed that weakly shocked CM clasts were spall products ejected at low velocities from larger CM projectiles when they slammed into the H and HED parent bodies. In both cases, if most CM clasts turn out to have ancient ages (e.g., ~3.4-4

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Section: Scenario 3 CM Clasts Produced By a Recent Disruption Eventmentioning

confidence: 95%

On the origin of shocked and unshocked CM clasts in H‐chondrite regolith breccias

Rubin

Bottke

2009

Meteorit & Planetary Scien

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“…The vast majority of craters larger than 1.5 km, for which a chondritic projectile has been identified, were produced by ordinary chondrites (see Table 5). So far, the only impact structure with a carbonaceous chondritic projectile is the Cretaceous-Tertiary boundary crater Chicxulub (Kyte 1998;Shukolyukov and Lugmair 1998;Trinquier et al 2006). Additionally, material linked to carbonaceous chondrites were found in the 3.5 to 3.2 Ga old Barberton spherule beds in South Africa (Shukolyukov and Lugmair 2000).…”

Section: Ordinary Chondrites As Impactorsmentioning

confidence: 99%

“…This identification agrees well with the type of projectile suggested by Shukolyukov and Lugmair (2000) and Koeberl et al (2007) based on 53 Cr excesses detected in the Lappajärvi impact-melt rocks. It is noteworthy that a positive ε 53 Cr rules out a carbonaceous chondritic projectile because this type of chondrite has negative ε values (Shukolyukov and Lugmair 1998;Trinquier et al 2006). The Lappajärvi projectile originates from an asteroid parent body with a composition similar to that of actual H-chondrite meteorites and a diameter of approximately 1 km.…”

Section: Lappajärvi and H Chondritesmentioning

confidence: 99%

Traces of an H chondrite in the impact‐melt rocks from the Lappajärvi impact structure, Finland

Tagle

Öhman

Schmitt

et al. 2007

Meteorit & Planetary Scien

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Abstract-Here we present the results of a geochemical study of the projectile component in impactmelt rocks from the Lappajärvi impact structure, Finland. Main-and trace-element analyses, including platinum group elements (PGEs), were carried out on twenty impact-melt rock samples from different locations and on two shocked granite fragments. The results clearly illustrate that all the impact melt rocks are contaminated with an extraterrestrial component. An identification of the projectile type was performed by determining the projectile elemental ratios and comparing the corresponding element ratios in chondrites. The projectile elemental ratios suggest an H chondrite as the most likely projectile type for the Lappajärvi impact structure. The PGE composition of the highly diluted projectile component (~0.05 and 0.7 wt% in the impact-melt rocks) is similar to the recent meteorite population of H chondrites reaching Earth. The relative abundance of ordinary chondrites, including H, L, and LL chondrites, as projectiles at terrestrial impact structures is most likely related to the position of their parent bodies relative to the main resonance positions. This relative abundance of ordinary chondrites suggests a strong bias of the impactor population toward inner Main Belt objects.

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“…The mineralogical and geochemical characterization of the peak-ring rocks will provide key information on target rock composition (Koeberl et al, 2012). We will also search for an extraterrestrial signature using platinum group element (PGE) analyses and Os and Cr isotopes (Gelinas et al, 2004;Tagle and Hecht, 2006;Trinquier et al, 2006;Goderis et al, 2012;Sato et al, 2013 to determine whether a measurable fraction of the projectile remains at the impact site or whether most projectile material ends up within the global K-Pg layer (Artemieva and Morgan, 2009). High-resolution 40 Ar/ 39 Ar analyses and electron microscopy on shocked and melted impactites, as well as U/Pb dating of zircon and other geo-and thermochronometers, will be used to study their pressure-temperature-time and deformational history and for highprecision dating of the Chicxulub impact.…”

Section: Eocene and Paleocene Hyperthermals And The Petm Transitionmentioning

confidence: 99%

Volume 364: Chicxulub: Drilling the K-Pg Impact Crater

Morgan¹,

Gulick²,

Mellett³

et al. 2017

Proceedings of the International Ocean Discovery Program

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The Chicxulub impact crater, on the Yucatán Peninsula of Méx-ico, is unique. It is the only known terrestrial impact structure that has been directly linked to a mass extinction event and the only terrestrial impact with a global ejecta layer. Of the three largest impact structures on Earth, Chicxulub is the best preserved. Chicxulub is also the only known terrestrial impact structure with an intact, unequivocal topographic peak ring. Chicxulub's role in the Cretaceous/Paleogene (K-Pg) mass extinction and its exceptional state of preservation make it an important natural laboratory for the study of both large impact crater formation on Earth and other planets and the effects of large impacts on the Earth's environment and ecology. Our understanding of the impact process is far from complete, and despite more than 30 years of intense debate, we are still striving to answer the question as to why this impact was so catastrophic.During International Ocean Discovery Program (IODP) and International Continental Scientific Drilling Program (ICDP) Expedition 364, Paleogene sedimentary rocks and lithologies that make up the Chicxulub peak ring were cored to investigate (1) the nature and formational mechanism of peak rings, (2) how rocks are weakened during large impacts, (3) the nature and extent of post-impact hydrothermal circulation, (4) the deep biosphere and habitability of the peak ring, and (5) the recovery of life in a sterile zone. Other key targets included sampling the transition through a rare midlatitude Paleogene sedimentary succession that might include Eocene and Paleocene hyperthermals and/or the Paleocene/Eocene Thermal Maximum (PETM); the composition and character of suevite, impact melt rock, and basement rocks in the peak ring; the sedimentology and stratigraphy of the Paleocene-Eocene Chicxulub impact basin infill; the geo-and thermochronology of the rocks forming the peak ring; and any observations from the core that may help constrain the volume of dust and climatically active gases released into the stratosphere by this impact. Petrophysical properties measurements on the core and wireline logs acquired during Expedition 364 will be used to calibrate geophysical models, including seismic reflection and potential field data, and the integration of all the data will calibrate models for impact crater formation and environmental effects. The drilling directly contributes to IODP Science Plan goals:Climate and Ocean Change: How does Earth's climate system respond to elevated levels of atmospheric CO 2 ? How resilient is the ocean to chemical perturbations? The Chicxulub impact represents an external forcing event that caused a 75% species level mass extinction. The impact basin may also record key hyperthermals within the Paleogene.Biosphere Frontiers: What are the origin, composition, and global significance of subseafloor communities? What are the limits of life in the subseafloor? How sensitive are ecosystems and biodiversity to environmental change? Impact craters can create habitats fo...

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The nature of the KT impactor. A 54Cr reappraisal

Cited by 85 publications

References 42 publications

On the origin of shocked and unshocked CM clasts in H‐chondrite regolith breccias

On the origin of shocked and unshocked CM clasts in H‐chondrite regolith breccias

Traces of an H chondrite in the impact‐melt rocks from the Lappajärvi impact structure, Finland

Volume 364: Chicxulub: Drilling the K-Pg Impact Crater

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