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Wyświetlanie 1-3 z 3
Tytuł:
Meteors and meteorite falls in Morocco
Autorzy:
Ibhi, A.
Powiązania:
https://bibliotekanauki.pl/articles/411969.pdf
Data publikacji:
2013
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Meteor
meteorite
fall
bright bolide
Morocco
Opis:
During the last eighty years, thirteen meteorite falls were recorded in Morocco, which ten are well documented and named Douar Mghila, Oued el Hadjar, Itqiy, Zag, Bensour, Oum Dreyga, Benguerir, Tamdakht, Tissint and Aoussred. It represent only 0.011 % of the Moroccan declared meteorites.The authenticated observed falls represent three types of different meteorites, eight ordinary chondrites (Four of type LL, three of type H and one of type EH), one carbonaceous chondrite and one Shergottite basaltic achondrites. The Morocco meteorite fall recovery rate, during the past eighty years, is low 0.11 falls per year on average per 2.11 km2 (or approximately one fall recovery per 10 year time interval).
Źródło:
International Letters of Chemistry, Physics and Astronomy; 2013, 12; 28-35
2299-3843
Pojawia się w:
International Letters of Chemistry, Physics and Astronomy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Short-term survival of ammonites in New Jersey after the end-Cretaceous bolide impact
Autorzy:
Landman, N.H.
Garb, M.P.
Rovelli, R.
Ebel, D.S.
Edwards, L.E.
Powiązania:
https://bibliotekanauki.pl/articles/22198.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
short-term survival
ammonite
New Jersey
Cretaceous
bolide impact
Ammonoidea
biostratigraphy
extinction
Paleogene
boundary
Opis:
A section containing the Cretaceous/Paleogene (= Cretaceous/Tertiary) boundary in Monmouth County, New Jersey, preserves a record of ammonites extending from the end of the Cretaceous into possibly the beginning of the Danian. The section includes the upper part of the Tinton Formation and lower part of the Hornerstown Formation. The top of the Tinton Formation is represented by a richly fossiliferous unit (the Pinna Layer) that contains many bivalves in life position as well as ammonite jaws preserved inside body chambers. Ammonites include Pachydiscus (Neodesmoceras) mokotibensis, Sphenodiscus lobatus, Eubaculites carinatus, E. latecarinatus, Discoscaphites iris, D. sphaeroidalis, D. minardi, and D. jerseyensis. The Pinna Layer probably represents a relatively short interval of time lasting tens to hundreds of years; it is conformably overlain by the Burrowed Unit, which contains a single fragment of Discoscaphites sp. and several fragments of E. latecarinatus, as well as several isolated specimens of ammonite jaws including two of Eubaculites. Examination of the mode of preservation of the ammonites and jaws suggests that they were fossilized during deposition of the Burrowed Unit and were not reworked from older deposits. Based on the ammonites and dinoflagellates in the Pinna Layer and the Burrowed Unit, these strata traditionally would be assigned to the uppermost Maastrichtian, corresponding to calcareous nannofossil Subzone CC26b. However, a weak iridium anomaly (500–600 pg/g) is present at the base of the Pinna Layer, which presumably represents the record of the bolide impact. Correlation with the iridium layer at the Global Stratotype Section and Point at El Kef, Tunisia, would, therefore, imply that these assemblages are actually Danian, provided that the iridium anomaly is in place and the ammonites and dinoflagellates are not reworked. If the iridium anomaly is in place, or even if it has migrated downward from the top of the Pinna Layer, the ammonites would have survived the impact at this site for a brief interval of time lasting from a few days to hundreds of years.
Źródło:
Acta Palaeontologica Polonica; 2012, 57, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Alvarez impact theory of mass extinction; limits to its applicability and the "great expectations syndrome"
Autorzy:
Racki, G.
Powiązania:
https://bibliotekanauki.pl/articles/20155.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Alvarez impact theory
mass extinction
great expectation syndrome
bolide impact
extraterrestrial marker
impact crater
Cretaceous
Paleogene
Triassic
Jurassic
Frasnian
Famennian
boundary
Opis:
For the past three decades, the Alvarez impact theory of mass extinction, causally related to catastrophic meteorite impacts, has been recurrently applied to multiple extinction boundaries. However, these multidisciplinary research efforts across the globe have been largely unsuccessful to date, with one outstanding exception: the Cretaceous–Paleogene boundary. The unicausal impact scenario as a leading explanation, when applied to the complex fossil record, has resulted in force−fitting of data and interpretations (“great expectations syndrome”). The misunderstandings can be grouped at three successive levels of the testing process, and involve the unreflective application of the impact paradigm: (i) factual misidentification, i.e., an erroneous or indefinite recognition of the extraterrestrial record in sedimentological, physical and geochemical contexts, (ii) correlative misinterpretation of the adequately documented impact signals due to their incorrect dating, and (iii) causal overestimation when the proved impact characteristics are doubtful as a sufficient trigger of a contemporaneous global cosmic catastrophe. Examples of uncritical belief in the simple cause−effect scenario for the Frasnian–Famennian, Permian–Triassic, and Triassic–Jurassic (and the Eifelian–Givetian and Paleocene–Eocene as well) global events include mostly item−1 pitfalls (factual misidentification), with Ir enrichments and shocked minerals frequently misidentified. Therefore, these mass extinctions are still at the first test level, and only the F–F extinction is potentially seen in the context of item−2, the interpretative step, because of the possible causative link with the Siljan Ring crater (53 km in diameter). The erratically recognized cratering signature is often marked by large timing and size uncertainties, and item−3, the advanced causal inference, is in fact limited to clustered impacts that clearly predate major mass extinctions. The multi−impact lag−time pattern is particularly clear in the Late Triassic, when the largest (100 km diameter) Manicouagan crater was possibly concurrent with the end−Carnian extinction (or with the late Norian tetrapod turnover on an alternative time scale). The relatively small crater sizes and cratonic (crystalline rock basement) setting of these two craters further suggest the strongly insufficient extraterrestrial trigger of worldwide environmental traumas. However, to discuss the kill potential of impact events in a more robust fashion, their location and timing, vulnerability factors, especially target geology and palaeogeography in the context of associated climate−active volatile fluxes, should to be rigorously assessed. The current lack of conclusive impact evidence synchronous with most mass extinctions may still be somewhat misleading due to the predicted large set of undiscovered craters, particularly in light of the obscured record of oceanic impact events.
Źródło:
Acta Palaeontologica Polonica; 2012, 57, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-3 z 3

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