Diamictic impact ejecta in a new outcrop near Aguilón
by Daniel Gorgas, Ferran Claudin & Kord Ernstson (October 2013)
On the occasion of foundation work for a windmill near Aguilón (Fig. 1) one of the authors (D.G.) once again came across an exposure of highlighting impact geology (Figs. 2, 3) that practically is self-explaining. A big roundish block of (probably) Malmian oncolitic limestone (Fig. 4) is embedded in a diamictite and in the broadest sense is part of this polymictic diamictic deposit within the northern ring anticline of the Azuara impact structure. Since other formation possibilities fail to explain this extraordinary setting (a big landslide, e.g., can be excluded because of lacking relief) the deposit is clear evidence of impact ejecta excavated from the growing Azuara impact cavity. The roundness of this big “ball” can be explained by rotation and transport under high confining pressure exerted by the now embedding diamictic material. Continue reading “Azuara impact geology”
The following contributions to the MetSoc Meeting may be downloaded here:
Michael A. Rappenglück, Frank Bauer, Michael Hiltl, Andreas Neumair, Kord Ernstson:
CALCIUM-ALUMINUM-RICH INCLUSIONS (CAIs) IN IRON SILICIDE (XIFENGITE, GUPEIITE, HAPKEITE) MATTER: EVIDENCE OF A COSMIC ORIGIN
Click Poster CAIs
(download problems? Click here: Abstract CAIs)
Andreas Neumair, Kord Ernstson:
PECULIAR HOLOCENE SOIL LAYERS: EVIDENCE OF POSSIBLE DISTAL EJECTA DEPOSITS IN THE CHIEMGAU REGION, SOUTHEAST GERMANY
Click Poster Distal Ejecta
Kord Ernstson, Werner Müller, Andreas Neumair:
THE PROPOSED NALBACH (SAARLAND, GERMANY) IMPACT SITE: IS IT A COMPANION TO THE CHIEMGAU (SOUTHEAST BAVARIA, GERMANY) IMPACT STREWN FIELD?
Click Poster Nalbach Chiemgau
Frank Bauer, Michael Hiltl, Michael A. Rappenglück, Andreas Neumair, Kord Ernstson:
Fe2Si (HAPKEITE) FROM THE SUBSOIL IN THE ALPINE FORLAND (SOUTHEAST GERMANY): IS IT ASSOCIATED WITH AN IMPACT?
Click Poster Hapkeite
by Kord Ernstson & Ferran Claudin (July 2013)
Abstract. – The “round rocks” of the Weaubleau-Osceola impact structure have phenomenological counterparts in the Spanish Azuara/Rubielos de la Cérida impact structures where they occur within voluminous heavily brecciated rock units. Related nodular bodies within large monomictic movement breccias are observed also in the Ries impact structure. A process similar to the formation of monomictic impact breccias with rounded clasts as part of a mortar texture is suggested. A relation to the Weaubleau-Osceola “round rocks” may exist but not necessarily.
The Weaubleau (or now Weaubleau-Osceola) circular feature in southwestern Missouri is a 19 km-diameter impact structure that formed in the Mid-Carboniferous about 330 million years ago (Evans et al. 2003).
A peculiar feature clearly restricted to and common throughout the Weaubleau structure are the “round rocks” called also “Missouri rock balls” or “Weaubleau eggs” (Figs. 1, 2). Originally considered to be of glacial origin they are in general attributed now to the impact event. The idea of a formation as mega-accrecionary lapilli has been discarded and a diagenetic formation from blasted siltstone clasts intermixed in the fallback breccia and subsequent silification is mostly discussed. Nonetheless, the process of formation is still poorly understood. Here, we present evidence of roughly similar nodules occurring in the Spanish large Azuara and Rubielos de la Cérida impact structures where different from the Weaubleau “round rocks” they can be observed how they developed in situ.
Fig. 1. Weaubleau “round rock”. The typical and most common size runs from golf-balls to grapefruit. Photo: Harmil, WIKIMEDIA COMMONS.
Continue reading “The Weaubleau impact structure “round rocks” (“Missouri rock balls”, “Weaubleau eggs”): possible analogues in the Spanish Azuara/Rubielos de la Cérida impact structures.”
Impact deposit at the Moneva reservoir, Azuara impact structure (Spain)
by Ferran Claudin, Daniel Gorgas & Kord Ernstson (March 2013)
In 2012 in the course of a field trip around the Moneva reservoir (Fig. 1, 2) one of the authors, Daniel Gorgas from Azuara who already in the past had frequently contributed important geologic observations to the Azuara impact research, came across a geologic setting that appeared to drastically deviate from the “normal” deposits well known to him as the extended young Tertiary sediments within the Azuara structure. Following his report we began to study the geological maps of the area around the reservoir (Fig. 2, 3) and then to investigate the outcrops in more detail.
Fig. 1. Location map for the investigated outcrops at the Moneva reservoir within the Azuara impact structure (roughly outlined by a dashed circle). Continue reading “Impact deposit at the Moneva reservoir, Azuara impact structure (Spain)”
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)
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.
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”
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.
Continue reading “Impact-induced surface hardening of polished quartzite cobbles, Triassic Buntsandstein conglomerates, Northern Spain”
Experimental hypervelocity crater generation
“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.
Click a respective article
that addresses also the formation of very small hypervelocity impact craters (Carancas, Peru, type).