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
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).
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
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.
The impact of cosmic bodies to produce large impact craters is related with the propagation of seismic waves which may release energies comparable to strongest earthquakes, and even beyond that. It is obvious that similar processes and well-known drastic deformations may result in the ground and at the earth’s surface.
In this context, W. Alvarez and coauthors (Alvarez W., Staley E., O’Connor D., Chan M.A., Synsedimentary deformation in the Jurassic of south-eastern Utah, a case of impact shaking? Geology, 1998, 26, 579-582) went into an interesting question when they related characteristic deformations in exposed older geological layers with a possible meteorite impact in a past geologic epoch thus pointing to the Upheaval Dome impact structure (Utah, USA) and distant rock liquefaction phenomena. Rock liquefaction is an established process during strong earthquakes which can lead to enormous modifications of the earth’s surface and catastrophic damage when the seismic shock affects water-saturated uncemented rocks. For the study of earlier earthquakes in the geologic past (paleoseismicity), observations in older layers may be important, and Alvarez had now pointed to the possibility that fossil sedimentary liquefaction features need not necessarily have originated from earthquakes but may be related with former large impact events. A critical debate, however, submitted that in the special case such a context of the relatively small 6 km-diameter Upheaval Dome impact structure and the geological outcrop some 260 km apart must be questioned.
Now for the first time, a compelling direct evidence for the relation of a large meteorite impact with distinct rock liquefaction features has been established. The recently printed article
describes the first geologic and geophysical investigations of the so-called “Thunderhole” (in German: Donnerloch) phenomenon in the region of the town of Kienberg north of Lake Chiemsee in Southeast Bavaria (Germany).
Fig. 1. A freshly caved-in and a somewhat older thunderhole near the town of Kienberg north of Lake Chiemsee. Strikingly different from customary and well known sink holes e.g. in karst areas, the thunderholes exhibit a highly energetic rock mass transport from the bottom up before collapse, which is typical for liquefaction processes.
The authors conclude that the innumerable enigmatic sudden sinkhole cave-ins having happened in living memory originate from late and even today acting processes of an earlier shock-induced underground rock liquefaction known from strong earthquake shocks. The geologically prominent underground structures that have now been uncovered are considered the result of impact shocks in the course of the formation of the Chiemgau meteorite crater strewn field (Chiemgau impact), and a comparison is made with the famous widespread and strong rock liquefaction features in the large region affected by the catastrophic 1811/1812 New Madrid (Missouri) earthquake series.
More detailed information about the geophysical measurements (resistivity and induced polarization (IP) soundings) of the thunderhole structures was given in a presentation at the 2011 Fall Meeting of the American Geophysical Union (AGU) in San Francisco:
The poster may be clicked here.
Fig. 2. From the geophysical investigation of the impact-induced thunderholes in the Chiemgau impact event. The geoelectrical measurements of induced polarization on a profile across an active depression as a precursor of a future thunderhole reveal perfectly clear the intrusion paths bottom up as a document of impact liquefaction.
ESA’s Mars Express has returned new images of an elongated impact crater in the southern hemisphere of Mars. Probably, the crater was caused by a train of projctiles and thus may be considered a model for the formation of the Rubielos de la Cérida elongated impact basin in Spain.
Rubielos de la Cérida impact basin. For comprehensive information click here.
