Azuara impact geology

Diamictic impact ejecta in a new outcrop near Aguilón

by Daniel Gorgas, Ferran Claudin & Kord Ernstson (October 2013)

Aguilón exposure Azuara impact structure

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

76th Annual Meteoritical Society Meeting (2013), Edmonton, Canada

meteoritical society meeting 2013 edmonton

The following contributions to the MetSoc Meeting may be downloaded here:

Michael A. Rappenglück, Frank Bauer, Michael Hiltl, Andreas Neumair, Kord Ernstson:


Poster CAIs mini Click Poster CAIs

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(download problems? Click here: Abstract CAIs)


Andreas Neumair, Kord Ernstson:


Poster distal ejecta png  Click Poster Distal Ejecta

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(download problems? Click here: Abstract distal ejecta )


Kord Ernstson, Werner Müller, Andreas Neumair:

Poster Nalbach Chiemgau mini  Click Poster Nalbach Chiemgau

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(download problems? Click here: Abstract Nalbach – Chiemgau)


Frank Bauer, Michael Hiltl, Michael A. Rappenglück, Andreas Neumair, Kord Ernstson:

Poster hapkeite mini  Click Poster Hapkeite

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(download problems? Click here: Abstract hapkeite)


The Weaubleau impact structure “round rocks” (“Missouri rock balls”, “Weaubleau eggs”): possible analogues in the Spanish Azuara/Rubielos de la Cérida impact structures.

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.

1 Introduction

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.

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Impact deposit at the Moneva reservoir, Azuara impact structure (Spain)

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.

Google Earth Azuara impact structure

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

Suspected Saarland impact and Chiemgau impact – do they form a pair?

Saarland impact and Chiemgau impact locations on the map of Germany

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:

Azuara impact structure: The Daroca thrust geologic enigma – solved? A Ries impact structure analog

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. 

1 Introduction

Daroca Province of Zaragoza Spain

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

Impact-induced surface hardening of polished quartzite cobbles, Triassic Buntsandstein conglomerates, Northern Spain

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).

shocked and polished quartzite cobbles from Molina de Aragón

Fig. 1. Typically pockmarked, cratered and polished (the large boulder) quartzite cobbles and boulders from the Triassic Buntsandstein conglomerates.

Continue reading