Shock metamorphism in the Rubielos de la Cérida impact basin (Eocene-Oligocene Azuara multiple impact event, Spain) – reappraisal and photomicrograph image gallery
by Kord Ernstson1 and Ferran Claudin2 (April 2021)
Abstract. – We present a new compilation of previously abundantly studied and published shock effects in minerals and rocks of the Middle Tertiary Rubielos de la Cérida Impact Basin in northeastern Spain. Typologically, we organize by: shock melt – accretionary lapilli – diaplectic glass – planar deformation features (PDF) – deformation lamellae in quartz – isotropic twins in feldspar – kink banding in mica and quartz – micro-twinning in calcite – shock spallation. Included are the newly associated Jiloca-Singra impact in the so-called Jiloca graben and the Torrecilla ring structure, which immediately adjoins the Rubielos de la Cérida basin to the northeast. The compilation and presentation also opposes once more the still existing fundamental rejection of an impact genesis of the Azuara impact event by leading impact researchers of the so-called impact community and by regional geologists from the University of Zaragoza.
Lechatelierite in Moldavite Tektites: New Analyses of Composition. – Martin Molnár, Stanislav Šlang, Karel Ventura. Kord Ernstson.
The Enigmatic Holmajärvi (Northern Sweden) Diamictite: Evidence of a Meteorite Impact Deposit. – Peder Minde and Kord Ernstson
Zhamanshinite-Like Black-Glass Melt Rocks from the Saarland (Germany) Meteorite Impact Site. – Kord Ernstson – Dominic Portz – Werner Müller – Michael Hiltl
The Steinheim Basin, the Ries crater “double disaster” and the mistaken Steinheim crater diameter
by Kord Ernstson1 & Ferran Claudin2 (Febr. 2021)
Abstract. – The article, which we comment here, interprets sedimentological findings (seismite horizons) at a distance of 80 – 180 km from the two impact structures, the Ries crater and the Steinheim basin, to the effect that, contrary to the impacts at a distance of only 40 km from each other, which have always been assumed to be synchronous, the Steinheim basin is supposed to be several 10 000 years younger than the Ries impact. This is against all probability, but because of the purely statistical impact events, it cannot be completely ruled out. This article therefore does not criticize the statement itself, but refers to equally probable alternatives that have not been considered, as well as to a lack of literature citations. The article loses its fundamental significance to the point of the simple alternative: it may be, but it also may not be, a finding without recognizable importance. A major point of criticism of the article is the common practice in the impact literature of suppressing the diameter of the Steinheim impact structure, which at around 7-8 km is actually twice as large, as it was proven almost 40 years ago by detailed morphological analyses and gravimetric measurements and published in a renowned journal. Since the size of the Steinheim Basin is included in the estimates for the formation of the seismites, it must be stated that the authors started from partly false premises. Here, the findings on the much larger Steinheim impact structure, which cannot be explained away, are presented again, combined with the wish to deal with scientific findings more honestly.
1 University of Würzburg, 97074 Würzburg (Germany); email@example.com; 2 Associate Geological Museum Barcelona (Spain); firstname.lastname@example.orgContinue reading “The Steinheim Basin, the Ries crater “double disaster” and the mistaken Steinheim crater diameter”
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); email@example.com. 2 Associate Geological Museum Barcelona (Spain); firstname.lastname@example.org
Taklamakan Desert (China): a mega-impact structure?
University of Würzburg, 97074 Würzburg (Germany), email@example.com
Abstract.- A Google Earth-based morphological analysis of the Taklamakan Desert in the north of the Himalayas shows characteristics of a 1000 km mega-sized impact structure with an elliptical basin and a pronounced elliptical morphological rim. The elliptical structure may possibly have originated from the thrust of the Indian plate and the Himalayas. A gravity anomaly corresponds with the structure. More impact evidence is not known so far.
Key words: Taklamakan Desert, China, impact structure, gravity anomaly, Indian plate
__________________________________________Continue reading “To play with Google Earth …”
When modeling ignores observations: The Jiloca graben (NE Spain) and the Rubielos de la Cérida impact basin
by Kord Ernstson1 and Ferran Claudin2
Abstract. – The Iberian System in NE Spain is characterized by a distinctive graben/basin system (Calatayud, Jiloca, Alfambra/Teruel), among others, which has received much attention and discussion in earlier and very recent geological literature. A completely different approach to the formation of this graben/basin system is provided by the impact crater chain of the Rubielos de la Cérida impact basin as part of the important Middle Tertiary Azuara impact event, which has been published for about 20 years. Although the Rubielos de la Cérida impact basin is characterized by all the geological, mineralogical and petrographical impact findings recognized in international impact research, it has completely been hushed up in the Spanish geological literature to this day. The article presented here uses the example of the Jiloca graben to show the absolute incompatibility of the previous geological concepts with the impact structures that can be observed in the Jiloca graben without much effort. Digital terrain modeling and aerial photography together with structural and stratigraphic alien geology define a new lateral Singra-Jiloca complex impact structure with central uplift and an inner ring, which is positioned exactly in the middle of the Jiloca graben. Unusual topographic structures at the rim and in the area of the inner ring are interpreted as strike-slip transpression and transtension. Geological literature that still sticks to the old ideas and develops new models and concepts for the graben/basin structures, but ignores the huge meteorite impact and does not even enter into a discussion, must at best cause incomprehension.
Key words: Meteorite impact, Azuara impact event, Alfambra-Teruel graben, Calatayud basin, strike-slip transgression, transtension, Singra-Jiloca impact
1 University of Würzburg, 97074 Würzburg (Germany), firstname.lastname@example.org
2 Associate Geological Museum Barcelona (Spain); email@example.com
Sanchez, M.A. ; Gil, A. y Simón, J.L. (2017): Las rocas de falla del cabalgamiento de Daroca (sector central de la Cordillera Ibérica): Interpretación reológica y cinemática. Geogaceta, 61: 75-78. (http://www.sociedadgeologica.es/archivos/geogacetas/geo61/geo61_19p75_78.pdf)
Casas-Sainz, A.M., Gil-Imaz, A., Simón, J.L., Izquierdo Llavall, Aldega, E.L., Román-Berdiel, T., Osácar, M.C., Pueyo-Anchuela, O., Ansón, M., García-Lasanta, C., Corrado, S., Invernizzi, C., Caricchi, C. (2018): Strain indicators and magnetic fabric in intraplate fault zones: Case study of Daroca thrust, Iberian Chain, Spain. Tectonophysics, 730: 29-47 (10.1016/j.tecto.2018.02.013) (https://zaguan.unizar.es/record/78325/files/texto_completo.pdf
Gutierrez, F, Carbonela, D., Sevil, J., Moreno, D., Linares, R, Comas, X., Zarroca, M., Roqué,C., McCalpin, J.P. (2020): Neotectonics and late Holocene paleoseismic evidence in the Plio-Quaternary Daroca Half-graben, Iberian Chain, NE Spain. Implications for fault sorce characterization. Journal of Structural Geology, 131: 1-17 (https://doi.org/10.1016/j.jsg.2019.103933)
by Ferran Claudin & Kord Ernstson (March 2020)
The town of Daroca in the Spanish Province of Zaragoza hides a peculiar geologic scenario – an enigma for geologists from time out of mind. Being enthroned above the town the geologic stratigraphy shows with a very sharp cut Cambrian dolomite (Ribota dolomite) over Tertiary young sediments (Fig. A). Older layers over younger ones are not uncommon in geology, and overthrust and thrust faulting are related processes. But Daroca is different. The Cambrian plate is kilometer-sized and fragmented into larger blocks, and a Tertiary 180° overtrust can reasonably be excluded. Early geologists confronted with the situation in sheer desperation thought of a preexisting Cambrian autochthonous plate and a vast undercutting by the Tertiary. Today this explanation is left out of consideration and simple thrust faulting is being favored. But the case is all but simple. There is no root zone and not any relief from where the giant plate could have started to override the Tertiary around Daroca. Nevertheless, the thrust kinematics are developed further by geologists (e.g., Capote et al. 2002), and tens of kilometers long faults are drawn within models of syn-tectonic sedimentation (Casas et al. 2000; Fig. 3).
Fig. A. The prominent Daroca exposure.
In 2012 we published an extended article (Claudin and Ernstson 2012) under the title “Azuara impact structure: The Daroca thrust geologic enigma – solved? A Ries impact structure analog“.. which proposes a new and in our opinion reasonable model of formation and a physically plausible solution of the enigma. To cut the story short, the Daroca thrust originated in the meanwhile generally established Azuara impact event, when according to the spall plate model of Melosh (1989) the Daroca Ribota dolomite plate started from the developing excavation crater and the near-surface interference zone with extreme velocity (Fig. B), supported by enormous volumes of rock melt, water and gases (water vapor and carbon dioxide from the shocked target) as a kind of hovercraft. This is no speculation but has much earlier been discussed for the so-called role-and-glide mode in the excavation process of the Ries impact crater (Germany). In our paper on the Daroca thrust we write about the affinity of both events and point to Ries giant megablocks having been excavated and transported over enormous distances.
In the case of the Daroca thrust this impressive way of transport can so nicely and conclusively be observed on the geological general map 1 : 200 000, sheet Daroca, which we show in simplified manner below (Fig. B) and in a copy of the geological map in Fig. 11 of the Spanish complete version).
Fig. B. The impact cratering model for the Daroca thrust – no intraplate fault zone (see text).
We do not know with certainty whether the authors of the three papers have read our paper and whether they have understood the herein presented simple explanation, but strangely enough since the publication of our paper on the Daroca thrust with the close relation to the Azuara impact structure, practically “overnight” a series of publications has appeared to demonstrate that the Daroca thrust has a normal tectonic fault origin, after not any geologist from Spain or elsewhere had paid attention to the enigma for decades (apart from the Casas et al. (2000) and Capote et al. (2002) papers, only seeing a tectonic fault despite all non-tectonic field evidence).
Of course, science thrives on controversy on certain topics and especially on new discoveries and models, but one principle is that the different views should be on a scientific level and that both views should be carefully discussed and balanced.
In all three papers we miss the observance of this basic scientific constitution. Not a single word is used to mention the Daroca article and the Azuara impact structure in general, and not a single one of the abundant publications on one of the most spectacular geological scenarios in Spain is found in their works. Today the Internet is a common medium and broadly used to get information about serious scientific publications (ResearchGate e.g.), and on preparing their papers a few clicks by the authors of the three papers had of course opened a host of literature about the Azuara impact event and the Daroca thrust.
In principle our Comment article could therefore end here. But we do not want to make the same omission ignoring the papers under discussion here. In the main part of our Comment paper following below, F. Claudin has compiled an exhaustive analysis of the three Daroca “tectonic” papers confronting their in many respects rather questionable claims with standard geologic literature and with the impressive meteorite impact-related features, once more described here point by point with a host of figures that do not exist for the authors.
Exemplarily, one point of importance is addressed already here, the Casas-Sainz et. al. paper about magnetic fabric from AMS (anisotropy of magnetic susceptibility) and strain indicators. From the text we learn that magnetic AMS analyses were performed at 6 sites, but only a single one (no.16) is located in Daroca at the thrust exposure (their Fig. 2A). Since the site is navigated at fractures of a second, we have to proceed from a spot analysis (their Table. 1), and the rock for 12 specimen measurements is described as a fault microbreccia (their Table 3). The rest of the 5 AMS sites is located roughly 1 km southeast of Daroca (their Fig. 2A).
We imagine: For the Daroca thrust as described in very detail in our paper (Claudin & Ernstson 2012), a spot few meters sized at best served for an AMS analysis of a microbreccia (we assume of Ribota dolomite) for which it is obviously not known when it acquired the brecciation and a resulting AMS texture.
Considering now the Daroca thrust impact model of an enormously dislocated spall plate, which Casas-Sainz et al. completely ignore, what will a point AMS tell us about old in situ tectonics and intraplate fault zones? Nothing. The Daroca plate may have transported magnetic textures from its original place more than 10 km to the east, intense brecciation and other deformation (which can be seen in Daroca outcrops) in the excavation, ejection, transport and emplacement processes should have produced a completely new texture, not to forget possible strong temperature overprint in the impact cratering process.
The same holds true for the five other sites of AMS analyses. Since the aim and outcome of the paper is basically the AMS of the thrust zone, more than a little methodological insight into the authors’ working cannot be recognized. The paper of Gutierrez et al. (2020) does not differ in any way in this respect. Their ground penetrating radar (GPR) and resistivity measurements at Daroca are good to look at, but for the topic under discussion they are absolutely meaningless. The idea arises that the visual impression of scientific evidence for the so-called Daroca Half-graben is to be created by the pure application of a few geophysical measurements on a very small area.
Chiemite and Muschelkalk cobble are breccia-like interleaved. Saarland impact, cut face, centimeter scale.
The most recent find of chiemite in the Saarland impact region (Nalbach, Saarlouis craters) concerns a cobble in which a larger piece of chiemite is breccia-like interleaved with a cobble (probably Muschelkalk in predominantly sandy facies) (photos). This supports the idea that during the impact the chiemite was mainly formed from a carbon melt (vaporized and condensed carbon from the heavily shocked vegetation) and that when it hit the rock it created a vesicular texture in it (partially carbonate melt, decarbonization).
This find should at least make the self-appointed great impact experts on the Internet think about how the Muschelkalk limestone got into the coal cellar and intimately aggregated with the coke.
From the Saarland impact region: chiemite interleaved with Muschelkalk limestone/Muschelkalk sandstone (cut face in the entrance photo). Picture width 10 cm.
Chiemite remains on the blistered cobble surface.