Research on impact geology, geophysics, petrology, and impact cratering
Chiemgau impact: is there a parallel with the Saarland region?
The earlier stated assumption that the Chiemgau impact may have a counterpart in the Saarland region
has been strengthened by new finds and new geologic and petrographic features. A respective update article may be clicked here:
by Ferran Claudin & Kord Ernstson (2012)
Abstract
A nappe-like thrust of Cambrian over Tertiary, the Daroca thrust, in northeast Spain has puzzled geologists since longtime. Because of a lacking root zone and a lacking relief it didn’t match a reasonable geologic pattern. In the younger regional geologic literature the thrust is nevertheless incorporated in Alpine regional tectonics. An obviously first closer investigation of the involved Cambrian and Tertiary units, their facies and structural setting leads to a model that relates the Daroca thrust to the nearby roughly 40 km-diameter Azuara impact structure. The thrust is part of the excavation stage of impact cratering which may have affected both the Cambrian plate and the diamictic Tertiary below. The model is strongly substantiated by comparison with the Ries impact structure where similar thrusts and related features occur. The Daroca thrust is one more example reflecting the work of the regional geologists who pretend the giant Azuara impact event with the formation of the Azuara impact structure and the adjacent about 70 km Rubielos de la Cérida elongated impact basin never happened. Hence, all their regional geologic models still developed which completely ignore the impact and its radical influence on the Tertiary regional geology are without any scientific relevance.
1 Introduction
Fig. 1. Daroca, Province of Zaragoza, Spain.
The very nice town of Daroca in the Spanish Province of Zaragoza (Fig. 1) 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. 2). Older layers over younger ones are not uncommon in geology, and overthrust and thrust faulting are related processes. Continue reading “Azuara impact structure: The Daroca thrust geologic enigma – solved? A Ries impact structure analog”
The investigation of the Azuara and Rubielos large impact structures now lasts about 30 years. Since the early eighties of the last century we have produced abundant and very exciting evidence for this unique geological scenario on the Iberian peninsula – despite much bitter opposition from various sides, persons and for various motives, which can be looked up elsewhere on this website. Much of our geological and petrographical material is being presented here in the web, but it is only part of an accumulation many times greater. Therefore we have decided to add little by little to the complex of the Azuara and Rubielos de la Cérida impact geology, and we don’t give up hope that a few more geologists become motivated to visit this extraordinary meteorite impact ensemble of some 120 km length.
We begin with an outcrop scenario easily accessible roadside at the village of Moyuela in the middle of the Azuara structure (Fig. 1) typically showing the enormous destruction the impact exerted on the well-bedded Jurassic limestones, which is inexplicable by normal Alpidic tectonics.
Continue reading “New images – Azuara impact structure: peculiar megabrecciation near Moyuela”
by Kord Ernstson & Ferran Claudin (2012)
Shocked quartzite cobbles making up widely spread Triassic Buntsandstein conglomerates in Northern Spain have been reported (Ernstson et al. 1999, 2001) to be related to the Mid-Tertiary large Azuara multiple impact event with the formation of the Azuara impact structure and the Rubielos de la Cérida elongated impact basin (Hradil et al. 2001, Ernstson et al. 2001, 2002, Schüssler et al. 2002, Claudin & Ernstson 2003, Ernstson et al. 2003). The quartzite cobbles (and boulders) are peculiarly and intensively pockmarked and cratered (Figs. 1, 2) and show in general a closely spaced subparallel fracturing (Fig. 3). The cobbles’ characteristics become especially evident when they are found scattered in the field as a result of the conglomerate weathering (Fig. 4).
Fig. 1. Typically pockmarked, cratered and polished (the large boulder) quartzite cobbles and boulders from the Triassic Buntsandstein conglomerates.
“Understanding the Impact Cratering Process: a Simple Approach” – Now, we added a submenu to this item comprising records with a high-speed camera of a true hypervelocity impact in the laboratory and some explanations. A video that shows the formation of an impact crater can be downloaded THERE. Results of more experiments will be posted soon.
that addresses also the formation of very small hypervelocity impact craters (Carancas, Peru, type).
Here we remind of an interesting abstract article presented at the 2011 Lunar and Planetary Science Conference (LPSC):
SEM and TEM analyses of minerals xifengite, gupeiite, Fe2Si (hapkeite?), titanium carbide (TiC) and cubic moissanite (SiC) from the subsoil in the Alpine Foreland: Are they cosmochemical?
Authors: M. Hiltl 1, F. Bauer 2, K. Ernstson 3, W. Mayer 4, A. Neumair 4, and M.A. Rappenglück 4 – 1 Carl Zeiss Nano Technology Systems GmbH, Oberkochen, Germany (mhiltl@online.de), 2 Oxford Instruments GmbH NanoScience, Wiesbaden, Germany (frank.bauer@oxinst.com), 3 University of Würzburg,Germany (kernstson@ernstson.de), 4 Institute for Interdisciplinary Studies, Gilching, Germany (info@mayer-chiemgau.de, agneumair@arcor.de, mr@infis.org).
The abstract may be downloaded HERE.
In addition to the images shown in the abstract paper we display here a photograph of one of the most highlighting iron silicide particles so far found in the area of the Chiemgau impact meteorite crater strewn field:
Fig. 1. Iron silicide particle (maximum size 18 mm) with cubic moissanite crystals (details see Fig. 2) sticking out from the matrix that is mostly composed of xifengite, Fe5Si3, and gupeiite, Fe3Si. An iron silicide, stoichiometrically Fe2Si, has also been analyzed, which may represent the rare mineral hapkeite. Hapkeite has so far been found on Earth only in the Dhofar 280 meteorite assumed to originate from the Moon.
Fig. 2. SEM image of moissanite crystals from the iron silicide specimen shown in Fig. 1. Source Carl Zeiss Nano Technology Systems GmbH.
An EBSD image of moissanite crystals together with titanium carbide TiC crystals in iron silicide matrix is shown in Fig. 3:
Fig. 3. Titanium carbide (TiC, dark gray), and silicon carbide (moissanite, SiC, black) crystals in a matrix of intergrowth of various iron silicides. Iron silicide particle from the Chiemgau impact meteorite crater strewn field. EBSD image; the field is c. 500 µm wide.
It is interesting to note that the silicon carbide moissanite (SiC) has been reported to occur together with the lonsdaleite diamond variety in impact melt rock from the Ries impact crater (Nördlinger Ries):
R. M. HOUGH, I. GILMOUR, C. T. PILLINGER, J. W. ARDEN, K. W. R. GILKESS, J. YUAN & H. J. MILLEDGE (1995): Diamond and silicon carbide in impact melt rock from the Ries impact crater. – Nature, 378, 41-44.
The authors suggest that the minerals formed by chemical vapour deposition from the ejecta plume in the impact event and hence may be used as a reliable diagnostic tool for hypervelocity impact on Earth.
In the case of the Chiemgau impact, the extreme purity of the moissanite and TiC crystals and their association with the xifengite and gupeiite iron silicides are rather speaking in favor of a primary cosmic origin however.
In the 1 July 2012 issue of the Earth and Planetary Science Letters journal an article has been published on a suspected 100 km sized impact structure that on verification would document the oldest cosmic collision on Earth so far known.
YDB abbreviates Younger Dryas Boundary. The Younger Dryas stadial signifies a sharp onset of a period of cold climatic conditions in Earth’s history lasting roughly 1,000 years between about 11,000 and 10,000 B.C. at the end of the Pleistocene (the “Ice Age”) and the beginning Holocene.
The causes of this event are controversially disputed, and they are conventionally ascribed to perturbations of North Atlantic circulation. In 2007, a new hypothesis on a giant meteorite impact Continue reading “YDB impact: a new chapter”
Kord Ernstson (2012)
Since a few years there is evidence of a doublet meteorite crater at the bottom of Lake Chiemsee (Fig. 3) in the Chiemgau meteorite crater strewn field. The search for a suspected impact into the lake was originally based on reports of fishermen about unusual sharp-edged large stones at the lake bottom that had damaged their fishnets. Such stones are in fact foreign matter in the lake. A general echo sounder campaign, followed by a detailed survey veritably revealed a peculiar structure, likewise a foreign element in the lake (Fig.1), with all evidence of a rimmed doublet crater. The similarity to meteoritic dual craters on Mars that formed synchronously by twin projectiles is striking (Fig. 2).
Fig. 1. The proposed meteorite doublet crater at the bottom of Lake Chiemsee from detailed SONAR echo sounder measurements. Meter scale indicates water depth.
Fig. 2. Meteoritic dual craters on Mars (image source NASA) and a counterpart at the bottom of Lake Chiemsee: A remarkable similarity. The more diffuse contours of the Lake Chiemsee craters is not surprising because of the impact into water and a loosely bound and water-saturated sedimentary target below.
More evidence of a meteorite impact into the lake came up with the frequent finds of pumice at the shore of Lake Chiemsee (more can be read HERE) and the observation of very young tsunami deposits uncovered in the environs of the lake (see HERE and HERE).
Fig. 3. Location map for the Lake Chiemsee in southeast Bavaria hiding the probable meteorite doublet crater.
Unfortunately, because of the deep water the crater is not accessible directly.
