Enigmatic Impact Breccias Probably Linked to the Ries Crater (Germany) Impact Event -Alemonites from Bavaria and sunstones from the Czech Republic
Alemonite (DE) and sunstone (CZ) samples from the field
ERNSTSON CLAUDIN IMPACT STRUCTURES – METEORITE CRATERS
Research on impact geology, geophysics, petrology, and impact cratering
Alemonite (DE) and sunstone (CZ) samples from the field
Diametral radargram across one of the most spectacular craters in the Chiemgau meteorite impact strewn field. Loamy-gravelly target material. Impact melt rocks, strong shock metamorphism. Strong reflectivities down to several meters depth are explained by extreme high-temperature sintering of the underground material. Note the complex excavation with the ring wall wandering outwards (as indicated with “real reflections”). 25 MHz center frequency with modulated 200 MHz.
More about GPR measurements over young meteorite craters: Click HERE
REM image. – Formation in spontaneous shock carbonization of the vegetation in the impact area. Investigations at the Diamond Laboratory, Geological Institute, Russian Academy of Science Syktyvkar, with optical and atomic force microscopy (AFM), X-ray fluorescence spectroscopy (RFA), scanning electron (SEM) and transmission electron (TEM) microscopy, high-resolution Raman spectroscopy, X-ray diffraction (XRD) and differential thermal analysis (DTA) as well as δ13C and 14C radiocarbon isotope data analysis.
Approx. 95% carbon; detection of diamond and carbyne; formation conditions for the latter 2500 – 4000°C and some GPa pressure.
Very “smart” people are still of the opinion that it is coke. Take a look at that too: file: EGU 2019 chiemite poster.pdf – Wikipedia
Using shock effects in quartz as an impact indicator has a long tradition. They are created in the first phase of impact cratering (contact and compression phase) and produce well known PDFs, PFs and diaplectic glasses in various minerals. The fact that thermal shock has so far been virtually ignored in impact research is due to the fact that the effects mentioned above precede thermal shock during pressure release. However, if extreme shock pressures lead to melting and vaporization of the rocks (> roughly 50 GPa), violent thermal shock can occur when slightly or not at all shocked material is immersed in melt and/or vapor. In anticipation of a publication, some photomicrographs of isolated quartz grains from meteorite impact sites are shown here, which have obviously experienced such a short thermal shock and reveal quite unusual micro-fracturing patterns.
Photomicrographs (crossed polarizers): Isolated quartz grains (size about 1 mm) “floating” in a fine grained matrix. In many of the grains this micro-fracturing is more or less sharply limited to a concentric rim zone encasing a largely untouched core with a few sub-planar fractures in some cases. Chrudim impact, Czech Republic.
Quartz grains from the same impact site showing irregular micro-fracturing that merges into sets of planar fractures (PF) after the rhombohedron.
Saarland impact: Quartz grains in impact melt nearly pulverized by extreme micro-fracturing.
Ballen structures in silica form a characteristic texture in quartz that in general is considered a result from various stages of phase transformation and recrystallization of amorphous silica like e.g., diaplectic glass and hence are regarded as shock indicator. A different model has recently been suggested that proposes a formation of ballen in quartz in an extreme thermal shock event.
Ballen structures (photomicrographs, plane light and crossed polarizers; field width 560 µm). – Saarland (Nalbach, Saarlouis) impact.
Ballen structures impact merging into tridymite and cristobalite.(photomicrographs, crossed polarizers and plane light; field width 1.4 mm). – Saarland (Nalbach, Saarlouis) impact.
Ballen structures (plane light and crossed polarizers), Chiemgau impact meteorite crater strewn field; Stöttham archeological excavation, catastrophe layer. Click the LPSC poster!
Ballen structures; Chrudim – Pardubice impact site (Czech Republic); asphaltic polymict impact breccia.
Ballen structures (photomicrograph, plane light); granitic impact melt rock sheet, Bach/Regensburg (Germany) impact site.
Comment on: ” Schmieder, M. and Kring, D. A. (2020) Earth’s Impact Events Through Geologic Time: A List of Recommended Ages for Terrestrial Impact Structures and Deposits. – Astrobiology, 20, 91-141.”
by Kord Ernstson1 & Ferran Claudin2 (Jan. 2021)
Abstract: We use Schmieder and Kring’s article to show how science still works within the so-called “impact community” and how scientific data are manipulated and “rubber-stamped” by reviewers (here, e.g., C. Koeberl and G. Osinski). We accuse the authors of continuing to list the Azuara and Rubielos de la Cérida impact structures and one of the world’s most prominent ejecta occurrences of the Pelarda Fm. in Spain as non-existent in the compilation. The same applies to the spectacular Chiemgau impact in Germany, which has been proven by all impact criteria for several years. For the authors’ dating list, we propose that the multiple impact of Azuara is included together with the crater chain of the Rubielos de la Cérida impact basin as a dated candidate for the third, so far undated impact markers in the Massignano outcrop in Italy.
1 University of Würzburg, 97074 Würzburg (Germany); firstname.lastname@example.org. 2 Associate Geological Museum Barcelona (Spain); email@example.com
A PDF of the complete article may be downloaded here.
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