The Azuara impact event in the Spanish TV

ATT00014.jpg

On June 9, 2006, TV Aragón presented a film report on the exhibition about the Azuara impact event. Settings of the film were

a geological exposure in the field and the impact exhibition in the town hall of Azuara both together with Ferran Claudin and Kord Ernstson.
a study in the university of Zaragoza with a computer monitor and a geological map presented by A. L. Cortés.
The reporter clearly presented both positions of the controversy underlined especially by the following subtitles in the TV:

Ferran Claudin and Kord Ernstson are working on the impact since two decades.
The impactor could have been a comet that hit the ground at a velocity between 20 and 70 km/s.
The exhibition in the Azuara town hall can also be visited in the Internet
And

The university of Zaragoza denies the existence of the impact of a meteorite.

Comment by F. Claudin & K. Ernstson

Although it would have been possible to film a joint discussion in the field or/and in the Azuara exhibition, A. L. Cortés preferred to avoid that (like with the inauguration of the Azuara impact exhibition, when the Zaragoza geologists had explicitly been invited but nobody came). Thus the Zaragoza geologists are practicing what they have been doing since 20 years: to refuse any joint field campaigns with the visit and discussion of impact outcrops as well as to refuse joint studies of Azuara shock effects (PDFs, shock melt, diaplectic glass etc) under the microscope.

Instead they are judging about the impact event from their studies extracting geological maps from their bookcases and regarding computer monitors. In the course of the 2001 IMPACT workshop in Granada they originally had the brilliant idea to discuss on the Azuara impact by presenting own videos of exposures. When we refused and in the end a field trip came about, they solely aimed to completely confuse the foreign participants and to utilize their very poor knowledge of the regional geology (see http://www.impact-structures.com/spain/workshop.htm).

Thus, presenting A. L. Cortés in his study was a nice documentation by TV Aragón about Zaragoza geologists’ considering the impact phenomena.

We would like to add some further comments on A. L. Cortés’ TV contribution. Neither Cortés nor any other geologists from the Zaragoza university have ever worked on meteorite impacts, and only recently a paleontologist from this university remarked that he cannot understand his geological colleagues who are discussing on impacts without any knowledge of this matter.

In the TV report, Cortés repeats the same old story that the Spanish regional geologists have made proper mapping and many thin-sections and that all impact evidences can be explained by normal geological processes. Cortés mentions once more the impact megabreccia as apparently exposed all over Spain and keeps completely quiet about his permanently confusing the facies of the Cortés de Tajuña Fm. with the impact megabreccia (see http://www.impact-structures.com/spain/controversy/megabrecha.htm ).

The geological mapping of Cortés and his colleagues is not as proper as he claims, and this is especially demonstrated by the large-scale erroneous mappings near Teruel or near Visiedo in the Rubielos de la Cérida impact basin. Near Visiedo, very large areas of outcropping Permotriassic sandstones and quartzites have been confused with Malmian limestones (!) both on the geological maps of 1 : 50 000 and 1 : 200 000 scales. The erroneous mapping near Teruel is especially highlighting, because Teruel has explicitly been mentioned by Cortés in the TV film. Near Teruel, the geological map shows an extremely curious setting. A large Buntsandstein complex of the size of many square kilometers is completely surrounded by and mapped in direct contact to the Rhaetian-Liassic (Cortés de Tajuña Fm.). The complete sequence of Muschelkalk and Keuper layers, several 100 meters thick, is absolutely missing on the geological map although otherwise always existent all over northern Spain. What’s the matter?

Going to the field, the Rhaetian-Liassic, mapped in direct contact to the Buntsandstein Fm. (Permotriassic), actually proves to be Muschelkalk limestones and dolomites and thus exhibiting the quite normal stratigraphic setting of Muschelkalk overlying Buntsandstein.

Why could the Muschelkalk have been completely confused with the Rhaetian-Liassic ? The reason is simple: The Buntsandstein complex and the surrounding Muschelkalk rocks are exposed exactly in the rim zone of the large Rubielos de la Cérida impact basin, where the Muschelkalk in the excavation and modification stage of impact cratering has been transformed to a giant megabreccia exposed over kilometers and kilometers (see http://www.impact-structures.com/Archiv/archiv.html) . And because evidently, for Cortés and his mapping colleagues the equation

extensive breccias = Cortés de Tajuña -Formation = Rhaeto-liassic age

automatically holds, the unbelievable confusion found its way to the geological maps.

So much about A. L. Cortés and his TV contribution about geological mapping and the «non-existing» impact.

An Impact Crater Chain in Northern Spain:

So heißt der Titel eines Artikels, der in METEORITE, The International Quarterly of Meteorites and Meteorite Science, erschienen ist. Für die Leser von METEORITE (aber auch für andere) zeigen wir die SW-Abbildungen des Artikels hier original in Farbe.

 


Fig. 1. Location map for the Azuara – Rubielos de la Cérida impact crater chain (frame in Fig. 2) and suspected impact locations (A, B, C).

Fig. 2. The topography of the Azuara/Rubielos de la Cérida crater chain (from the digital map of Spain, 1 : 250,000; provided by Manuel Cabedo).


Fig. 3. Photomicrograph of strongly shocked quartz from the Rubielos de la Cérida basin.


Fig. 4. Part of the central uplift chain emerging from the
Rubielos de la Cérida impact basin.


Fig. 5. The crater rim in the southern part of the impact chain.


Fig. 6. Megabreccia and polished friction plane in the southern part of the central-uplift chain.


Fig. 7. Impact breccia (suevite) exposed in the southern part of the central-uplift chain.


Fig. 8. Probable impact ejecta near Peñacerrada (location B in Fig. 1).

The Sirente craters (Italy): On the possible origin of geomagnetic anomalies (Ormö et al. 2007)

by Werner Mayer1, Ferran Claudin2 & Kord Ernstson3

 

Abstract. – Abundant finds of exploded ordnance in the Sirente crater field suggest that geomagnetic anomalies measured in connection with some of the craters may have a simple explanation. Without a consideration of these iron-metallic fragments and of possible unexploded ordnance, any conclusions with respect to the crater formation based on magnetometer surveys only, are questionable.

 

Introduction

The Sirente crater field in Italy consists of about 30 depressions with a main rimmed 120 m-diameter crater. The origin of the craters is disputed and has been ascribed to meteorite impact (Ormö 2002), to mud volcanic processes (Stoppa 2006) and to anthropogenic activities (Speranza et al. 2004). So far, no impact features like meteoritic material, geochemical signature or shock metamorphism have been identified (Ormö et al. 2006). According to Oril et al. (2007) seismic data from the main crater support the meteorite impact interpretation but do not exclude other hypotheses.

In a recent article printed in the Meteoritics & Planetary Sciencejournal (editorial handling – John Spray), Ormö et al. (2007) are reporting on a magnetometer survey in the Sirente crater field. From a modeling of magnetic anomalies measured over some of the smaller depressions they reason uplifted crater rims and buried meteorites. Here, we report on a field trip to the Sirente crater area revealing that measured magnetic anomalies may at least partly be related with exploded and/or unexploded ordnance.

 

Field evidence

On April 12, 2004, one of the authors (W. M.) together with Christian Siegl visited the Sirente crater field (Fig. 1). The field trip was initiated after the discovery of the Holocene Chiemgau impact strewn field in Southeastern Germany (Rappenglück et al. 2004, Schüssler et al. 2005, CIRT 2006, and others) with the intention of comparing both locations.

 

Fig. 1. The Sirente crater field in Italy. Photo W. Mayer.

In the course of a close field inspection guided among others by the hope of finding meteorites, metallic fragments could actually be sampled in great quantities (Fig. 2), and a concentration was observed in the environs of the smaller depressions in the north and northeast of the main structure. Here, many iron-metallic fragments were found even at the floor of smaller craters. On extrapolation of the finds, several thousands of iron fragments or a mass of estimated one ton at least are expected to exist in the Sirente field.

Fig. 2. Exploded ordnance iron splinters from the Sirente crater field. Photo W. Mayer.

 

Rapidly, it became explicit that the sampled iron splinters, typically shown in Fig. 2, were fragments of exploded ordnance like bombs and grenades.

 

Discussion and conclusions

The find of abundant fragments of exploded ordnance has implications and poses some questions. In the first place and disregarding for the moment the dating of some craters to ~ 500 A.D. (Ormö et al. 2006), we pose the question whether some of the smaller craters (with diameters between 1.5 and 20 m and a maximum depth of about 2 m) could have originated from military operations implying bombing and, therefore, are simple explosion craters. On the other hand, in areas of exploded ordnance there is in general also unexploded ordnance to be encountered. It is well known that, e.g., in World War II roughly 10 – 20% of released bombs survived unexploded in the ground. In Italy, more than 1 million bombs were air-dropped by the Allied Forces, and at least 10 % did not explode (Furlanello & Merler 2001). In most cases they are leaving only small flat depressions to be possibly seen in aerial photographs. In the case of the Sirente ground of carbonate mud, the penetration of an unexploded bomb could perhaps have produced a somewhat larger depression although the hole of entry is in general much smaller (see, e.g., War Department 1943). The depth of penetration of blind shells has frequently been considered. For a 250 kg sized bomb, the depth has been found to be 5 m on average and 12 m maximum, and for a smaller, 50 kg sized bomb the respective numbers are 3.5 m and slightly less than 12 m (War Department 1943). In a soft muddy ground like in the Sirente area, a penetration depth at the upper limit can be expected.

Both exploded and unexploded ordnance are known to be related with magnetic anomalies, and magnetometer surveys by total-field and gradiometer soundings are basic in the detection of unexploded ordnance. A typical bomb magnetic anomaly is shown in Fig. 3., while Fig. 4 exhibits a magnetic map of a field full of exploded ordnance.

 

Fig. 3. Typical WW II blind shell geomagnetic anomaly. Vertical gradient of the geomagnetic vertical field intensity.

Fig. 4. Geomagnetic map of exploded-ordnance anomalies. Vertical gradient of the geomagnetic vertical field intensity.

 

Summarizing, the find of exploded ordnance in the Sirente area points to military activities in the past, and a historical inquiry could possibly provide some insight. As exploded ordnance is frequently accompanied by unexploded ordnance, it cannot be excluded that some magnetic anomalies measured and modeled by Ormö et al. (2007) originate from deeply penetrated bombs. In this case and confusing bomb anomalies with supposed anomalies from meteorites, attempts to recover them (especially when a drilling into an object is to be executed [Ormö et al. 2007]) could be a dangerous endeavor.

This is one side of the coin. The other side concerns the subject of the article (Ormö et al. 2007) that is the discussion of the impact origin for the Sirente crater field and the alleged substantiation by the results of the geomagnetic survey.

To avoid any misunderstanding we explicitly state that we don’t intend to knock the impact hypothesis on the head. To the contrary, an impact origin for at least the largest crater seems to be much plausible. We are also aware of the radiocarbon and TL dating (Ormö et al. 2006) probably excluding an origin from military operations for at least those structures. However, as long as the magnetic survey completely ignores the abundant exploded ordnance and the possibility of anthropogenic magnetic causative bodies in the ground, the article by Ormö et al. (2007) and the conclusions therein are without any value. This yet again demonstrates that a peer review doesn’t prove a recipe for good science.

 

Acknowledgements. – We thank Dr. Hans-Georg Carls, Luftbilddatenbank, Estenfeld, and Frank Dietsch, Ebinger Prüf- und Ortungstechnik GmbH, Köln, for data and valuable information.


References

CIRT – Chiemgau Impact Research Team (2006): The Holocene Tüttensee meteorite impact crater in southeast Germany. –http://www.chiemgau-impact.com/artikel2.pdf.

Furlanello, C. & Merler, S. (2001): Finding unexploded bombs from WWII. Automatic mapping of unexploded air-dropped ordnances: risk map for the Adige valley. In International Conference on Machine Learning. Workshop Session on Spatio-Temporal Methods. Williamstown MA. 28 June/July 2001.

OriI, G.G., Rossi,A.P., Komatsu, G., Ormö, J., M. Rainone, M., Signanini, P., Torrese, P., Sammartino, P., Madonna, R., Baliva, A. & Di Achille, G. (2007): Seismic data from the main crater of the proposed Sirente meteorite crater field (Central Italy). – Lunar and Planetary Science XXXVIII, 1092.pdf

Ormö, J., Rossi, A.P. & Komatsu, G. (2002): The Sirente crater field, Italy. – Meteoritics and Planetary Science, 37, 1507-1523.

Ormö, J., Koeberl, C., Rossi, A.P. & Komatsu, G. (2006): Geological and geochemical data from the proposed Sirente crater field: New age dating and evidence for heating of target. – Meteoritics and Planetary Science, 41, 1331-1345.

Ormö, J., Gomez-Ortiz, D., McGuire, P.C., Henkel, H., Komatsu, G. & Rossi, A.P. (2007): Magnetometer survey of the proposed Sirente meteorite crater field, central Italy: Evidence for uplifted crater rims and buried meteorites. – Meteoritics and Planetary Science, 42, 211-222.

Rappenglück M.A., Ernstson, K. Mayer, Beer, R., Benske G., Siegl, C., Sporn, R.,  Bliemetsrieder, T. & Schüssler, U. (2004): The Chiemgau impact event in the Celtic Period: evidence of a crater strewnfield and a cometary impactor containing presolar matter.http://www.chiemgau-impact.com/.

Schüssler, U., Rappenglück, M.A., Ernstson, K., Mayer, W. & Rappenglück, B. (2005): Das Impakt-Kraterstreufeld im Chiemgau. – Eur. J. Mineral. 17, Beih. 1: 124.

Speranza, F., Sagnotti, L. & Rochette, P. (2004): An anthropogenic origin of the «Sirente crater» , Abruzzi, Italy. – Meteoritics and Planetary Science, 39, 635-649.

Stoppa, F. (2006): The Sirente crater, Italy: Impact versus mud volcano origins. – Meteoritics and Planetary Science, 41, 467-477.

War Department (1943): Ordnance – Unexploded Bombs, Organization and Operation for Disposal. – War Department Field Manual FM 9 – 40, United States Government Printing Office.

 

Kirchweg 14, 83346 Bergen, Germany

2 IES Giola, Llinars del Vallès. Barcelona-08450, Spain

3 Fakultät für Geowissenschaften der Universität Würzburg, Pleicherwall 1, D-97070 Würzburg, Germany

 


here you find the pdf-file