January 2024
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34 Reads
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Publications (13)
August 2023
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73 Reads
We report an unusual polymict melt rock megabreccia in the form of an allochthonous non-volcanic megablock within the Tertiary volcanic province of the Bohemian Massif. It is considered a relict of a suspected low-altitude airburst impact.
![Fig. 1. A: Section of the geological general map 1 : 500,000 of the Czech Republic. Arrow: the Megabreccia near Luzice. Purple and light purple: volcanic rocks. B: The Megabreccie in a section of the quarry wall. C: An exposed block of polymict breccia composed of dense reddish components and blackish slag-like components D: Cut of a breccia component with large (engassing?) cavities. E, F: Photomicrographs of thin sections show very different microstructures. Light and darker glass components (see below) interpenetrate and mark flow structures. PPL. The geological setting: According to the geological survey map 1 :500 000 [1], the outcrop is located in a smaller area of Miocene gravels and clays overlying the Upper Cretaceous, partially bounded by volcanic rocks. These are generally widespread assemblages of partially weathered basaltic rocks, unspecified melilitic olivine-bearing rocks, and subvolcanic breccias. Other adjacent complexes consist of basaltic volcaniclastics (predominantly redeposited autoclastics, and some epiclastics and pyroclastics from earlier effusions in the Central Bohemian Mountains [1]). Not further specified occurrences of porcelanites are mentioned. The Upper Cretaceous rocks are described as calcareous claystones and marls. The megabreccia: Fig.1 shows the rocks of the megabreccia in increasing scales. A key observation on the origin of the megabreccia is provided by the thin sections of a dozen samples (Fig.1 E, F) of quite different lithofacies composition. Under the polarizing microscope, they prove to be optically isotropic throughout; they are thus completely transformed to glass with the peculiarity that the glass is completely free of mineral grains of any size. Weak, hardly perceptible recrystallization seems to have started in a few places. Discussion: The continuous transformation of the most diverse breccia samples into practically pure glass without any mineral grains means that the rock was more or less homogeneously heated to temperatures above 1,720 °C (melting temperature of quartz) or more, and a relationship to volcanism can be excluded. We therefore formulate our model for the formation of the Luzice mega-melt breccia as follows: # There has been an impact in the region as the heat source, according to presumed Cretaceous components in the megabreccia in the Upper Cretaceous or younger. # The megabreccia belongs in some way to the excavation and ejection of the cratering. # A companion impact to the recently discovered 20 km diameter Kolešovice crater [2] about 60 km south of Luzice is thought possible. # Our extensive scanning of high-resolution digital terrain models does not detect a twin crater. # Hence, subsequent volcanism and densely scattered extrusions (Fig. 1 A) may have completely destroyed an existing impact structure. # Impact rarefaction and transtension tensile features may have initiated and facilitated volcanism. # A low-altitude airburst impact and very shallow impact features (like with the Kolešovice impact) would only allow a relatively short survival due to dense volcanic overprinting. # In connection with an impact event, the widespread occurrences of the redeposited auto-, epi-and pyroclastics and (subvolcanic) breccias, as well as the porcellanites and melilitic rocks, could also be seen. # That the mapping geologists thought of volcanism but not of impact is only too understandable. Conclusions: The melt glass megabreccia excludes volcanism and stands for an impact event in the region. The geological circumstances speak for a low-altitude airburst, without a more exact sequence being recognizable. A mixture of volcanic and impactitic conditions is conceivable, which new geologic mapping would have to reveal. References: [1] Czech Geological Survey. [2] Molnár, M. et al. (2023). 54th LPSC, Abstract #1428.](https://www.researchgate.net/profile/Kord-Ernstson/publication/371970162/figure/fig1/AS:11431281171533600@1688210524680/A-Section-of-the-geological-general-map-1-500-000-of-the-Czech-Republic-Arrow-the_Q320.jpg){kind=icon}
July 2023
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146 Reads
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1 Citation
We report an unusual polymict melt rock megabreccia in the form of an allochthonous non-volcanic megablock within the Tertiary volcanic province of the Bohemian Massif. It is considered to be a relict of a suspected low-altitude airburst impact.
March 2023
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245 Reads
March 2022
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164 Reads
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5 Citations
April 2021
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254 Reads
February 2021
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996 Reads
Introduction: Moldavites are tektites with a beautiful, mostly green discoloration and a very pronounced sculpture (Fig.1), which have been studied many times e.g. [1-3]).According to the most probable theory, they were formed 14.5 million years ago together with the Ries crater meteorite impact in Germany. They belong to the mid-European tektite strewn field and fell mostly in Bohemia. The prominent sculpture is considered the result of acidic waters in the ground having etched away the more alkaline parts of the moldavite and left lechatelierite inclusions as sharp edges and peaks. Originally, the curious pitting and wrinkles on the surfaces were compared to meteorite regmaglypts and the moldavites ascribed to a cosmic, meteorite origin (F.E. Suess 1900). Lechatelierite is amorphous SiO2 silica glass and commonly forms at very high temperatures in lightning strike fulgurites and as a result of shock metamorphism during meteorite impact cratering. Authors [4, 5] state that it is 99% SiO2- based. A comparison reveals (Tab. 1).While refractive index and density are very close to each other, the main difference lies in the temperatures of the softening point, which differs by more than 400 °C. This led to the question what is it that reduces the melting point so rigidly and increases acid resistance. The conclusion from the present comparison is clear. Lechatelierite from moldavite is not a pure SiO2 glass. Here we report on experimental investigations that pursue this question and lead to new findings of the lechatelierite composition.
February 2020
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70 Reads
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1 Citation
April 2019
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86 Reads
March 2019
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37 Reads
Introduction: The Ries crater impact structure in Germany measuring about 25 km in diameter, formed almost 15 million years ago in the Upper Miocene. In the early seventies, when the Ries impact origin began to replace the earlier volcanic explosion theory among most geologists, research results of the reputable Ba-varian geologist Erwin Rutte caused quite a stir, because they described the Ries (and Steinheim) impact event as much more far-reaching than the traditional German impact researchers believed at that time [1, 2 and references therein]. This was followed by a strong recognition in the geological community, replaced by a vehement rejection of the whole hypothesis and a subsequent ignorance and oblivion. Here we report on a resumption of research on a particularly puzzling component of this then completely new impact hypothesis, which is put in a new light with new findings.
Citations (5)
... The following are some proposed examples of low-altitude Type 2 airbursts that caused extensive damage to Earth's surface: (i) Chrudim/Pardubice in the Czech Republic [12,13], (ii) Nalbach/Saarlouis in Germany [14][15][16]. (iii) Chiemgau in Germany [17][18][19][20][21][22][23][24][25][26][27], (iv) Niederrhein in Germany [28], (v) Franconia in Germany [29], (vi) Sachsendorf Bay in Germany [30], (vii) seven possibly related strewn fields across about half of the Czech Republic [13], (viii) a 6400-year-old strewn field in Finland [31], (ix) the Luzice melt rock and megabreccia outcrops, proposed as evidence of a low-altitude airburst [32], (x) the 20-km-diameter Kolesovice airburst crater in the Czech Republic [33], (xi) a 2600-year old strewn field in Kansas [34], (xii) a human settlement whose destruction by a cosmic airburst led possible eyewitnesses to construct an oral history that was written down centuries later [1]. For further discussions of this evidence, see Bunch et al. [1] and references [2][3][4][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82]. ...
- Citing Conference Paper
- Full-text available
July 2023
... Several years ago, research into the Chiemgau impact was given a huge boost by the application and analysis of the extremely high-resolution digital terrain model, which can now be acquired online free of charge in the form of the original data sets for the entire crater strewn field and the closer and wider area around the crater strewn ellipse. With this data and the enormous possibilities of modern graphics programs, impact research has led to a paradigm shift, which is justified in particular by the new findings on the Chiemgau impact and the widespread newly recognized impact fields in Central Europe between the Czech Republic and the Lorraine-French border (Poßekel et al. 2022). While the Canadian database mentions around 200 names worldwide as established, apparently proven impact structures (which has been repeatedly criticized, e.g., Claudin and Ernstson 2023), a paradigm shift becomes clear with the simplest geological considerations together with the results of the digital terrain models that are now increasingly available in many countries. ...
- Citing Poster
- File available
March 2022
... # The basin formation cuts sharply into older stratigraphic units and can be dated with younger deposits to an age between Upper Cretaceous and Tertiary, that is the Kolešovice impact has nothing to do with the recently discovered and described Pleistocene/Holocene meteorite impact strewn fields, distributed all over the Czech Republic [9][10][11][12]. ...
- Citing Conference Paper
- Full-text available
February 2020
... # The basin formation cuts sharply into older stratigraphic units and can be dated with younger deposits to an age between Upper Cretaceous and Tertiary, that is the Kolešovice impact has nothing to do with the recently discovered and described Pleistocene/Holocene meteorite impact strewn fields, distributed all over the Czech Republic [9][10][11][12]. ...
- Citing Poster
- File available
March 2018
... Previous studies conclude that although airbursts mainly vaporize the bolide, fragments commonly reach the ground surface, and the kinetic energy of the airburst vapor jet may be high enough to produce shallow craters [7,9,11], along with shocked quartz, meltglass, microspherules, breccia, and other impact-related proxies. The following are some proposed examples of low-altitude Type 2 airbursts that caused extensive damage to Earth's surface: (i) Chrudim/Pardubice in the Czech Republic [12,13], (ii) Nalbach/Saarlouis in Germany [14][15][16]. (iii) Chiemgau in Germany [17][18][19][20][21][22][23][24][25][26][27], (iv) Niederrhein in Germany [28], (v) Franconia in Germany [29], (vi) Sachsendorf Bay in Germany [30], (vii) seven possibly related strewn fields across about half of the Czech Republic [13], (viii) a 6400-year-old strewn field in Finland [31], (ix) the Luzice melt rock and megabreccia outcrops, proposed as evidence of a low-altitude airburst [32], (x) the 20-km-diameter Kolesovice airburst crater in the Czech Republic [33], (xi) a 2600-year old strewn field in Kansas [34], (xii) a human settlement whose destruction by a cosmic airburst led possible eyewitnesses to construct an oral history that was written down centuries later [1]. ...
- Citing Conference Paper
- Full-text available
April 2017