Impact-generated carbonate accretionary lapilli in the Late Devonian Alamo Breccia

Warme, John E.; Morgan, Matthew L.; Kuehner, Hans-Christian

doi:10.1130/0-8137-2356-6.489

Cited by 20 publications

(29 citation statements)

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“…8b-d) are very similar to volcanic and impact-generated accretionary lapilli (e.g., Graup, 1981;Gilbert and Lane, 1994;Schumacher and Schmincke, 1995;Warme et al, 2002). We have observed no evidence for a distinct phosphate enrichment that could indicate a biogenic origin (so-called coprolites).…”

Section: Carbonate Clastsmentioning

confidence: 72%

“…The slight variations in grain size of individual particles, as well as the tangential mineral orientation and the rareness of concentric structures point to a rather quick formation of the accretionary lapilli (Schumacher and Schmincke, 1995). Following Warme et al (2002), calcination (T > 900°), and subsequent slaking (hydration) may explain the immediate hardening Blanks were about 0.02 ng for Rb, 0.04 ng for Sr, 125 pg for Nd, and 73 pg for Sm and. Decay constants used in this paper are 1.42 Â 10 À11 a À1 for 87 Rb (Steiger and Jäger, 1977) and 6.54 Â 10 À12 a À1 for 147 Sm (Lugmair and Marti, 1978 of these particles after accretion that prevented them from disintegration either during transport, subsequent settling through the 1500-m-thick water column, or after deposition.…”

Section: Carbonate Clastsmentioning

confidence: 96%

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A dual-layer Chicxulub ejecta sequence with shocked carbonates from the Cretaceous–Paleogene (K–Pg) boundary, Demerara Rise, western Atlantic

Schulte

Deutsch

Salge

et al. 2009

Geochimica et Cosmochimica Acta

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Section: Carbonate Clastsmentioning

confidence: 72%

Section: Carbonate Clastsmentioning

confidence: 96%

A dual-layer Chicxulub ejecta sequence with shocked carbonates from the Cretaceous–Paleogene (K–Pg) boundary, Demerara Rise, western Atlantic

Schulte

Deutsch

Salge

et al. 2009

Geochimica et Cosmochimica Acta

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“…The Devonian Alamo Breccia contains some of the beststudied impact accretionary lapilli (Fig. 9b), yet their impact origin might still be in dispute were it not for the shocked quartz crystals they contain (Warme et al, 2002). The fact that the accretionary lapilli in the Alamo Breccia consist of carbonate rather than silicate is not enough to rule out a volcanic origin since well-preserved carbonate accretionary lapilli occur in carbonatitic tuffs (Deans and Roberts, 1984, their Fig.…”

Section: Fig 5 Photomicrographs In Plane-polarized Light Of Impact mentioning

confidence: 94%

Petrographic Criteria for Recognizing Certain Types of Impact Spherules in Well-Preserved Precambrian Successions

Simonson

2003

Astrobiology

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Impact spherule layers in sedimentary successions can open a new window on large impacts to complement the better-known record of terrestrial craters. At least six spherule layers have been found in well-preserved late Archean to Paleoproterozoic strata, and a growing body of geochemical evidence indicates they are impact ejecta. The most distinctive characteristics of these impact spherules are: (1) a predominance of highly spherical grains; (2) the presence of grains with unusual shapes such as teardrops and dumbbells; (3) fibroradial aggregates of K-feldspar crystals nucleated on the edges of spherules; and (4) clear internal spots representing both cement-filled vesicles and replaced glass cores, which, in contrast to the nuclei of ooids and armored lapilli, are not always located in the centers of the spherules. These characteristics permit the reliable differentiation of these impact spherules from spheroidal particles of other origins, such as sedimentary ooids or volcanic accretionary lapilli, often with just a hand lens. However, petrographic identification becomes progressively more difficult as the spherules become smaller or more altered. Moreover, impact spherules in other layers of other ages sometimes have different textures, so the ones described here are not representative of all types of impact spherules. They are provided as a starting point for researchers interested in identifying impact spherule layers. Given the visible record of impacts on the Moon and the much greater mass of the Earth, there should be many more impact spherule layers on Earth than have been discovered to date.

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“…18.15), similar to volcanic and impact lapilli (Graup, 1981;Schumacher and Schmincke, 1994;Warme et al, 2002;Koeberl et al, 2007). The fine-grained Figure 18.14 A typical large impact-melt clast, 20 cm in length, is shown after excavation from the eastern ejecta blanket (image H.E.…”

Section: Spherules and Lapilli In Lonar Ejectamentioning

confidence: 99%

Comparison of Simple Impact Craters: A Case Study of Meteor and Lonar Craters

et al. 2012

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Impact-generated carbonate accretionary lapilli in the Late Devonian Alamo Breccia

Cited by 20 publications

References 0 publications

A dual-layer Chicxulub ejecta sequence with shocked carbonates from the Cretaceous–Paleogene (K–Pg) boundary, Demerara Rise, western Atlantic

A dual-layer Chicxulub ejecta sequence with shocked carbonates from the Cretaceous–Paleogene (K–Pg) boundary, Demerara Rise, western Atlantic

Petrographic Criteria for Recognizing Certain Types of Impact Spherules in Well-Preserved Precambrian Successions

Comparison of Simple Impact Craters: A Case Study of Meteor and Lonar Craters

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