Pelarda Fm. – Azuara Impact Structure (Spain) – comprehensive article on one of the biggest, most attractive and scientifically most instructive impact ejecta deposits worldwide

 

PDF article, 81 p., 92 Figs. – The full article can be clicked HERE.

Abstract. – The Pelarda Formation (Fm.), located in the Iberian System in northeast Spain, is a sedimentary deposit with an extension of roughly 12 km x 2.5 km and an estimated thickness of no more than 400 m. The formation was first recognized as a peculiar unit in the early seventies and underwent interpretations like a fluvial or an alluvial fan deposit having a postulated age between Paleogene and Quaternary. Since the early nineties the Pelarda Formation has been considered an impact ejecta deposit originating from the large ca. 40 km-diameter Azuara impact structure and meanwhile being among the largest and most prominent terrestrial impact ejecta occurrences, which however is questioned by regional geologists still defending the fluvial and alluvial fan models. Roughly speaking, the Pelarda Fm. is a grossly unsorted, matrix-supported diamictite with grain sizes between silt fraction and meter-sized clasts and a big intercalated megablock. Strong clast deformations and abundant shock metamorphic effects like planar deformation features (PDF) are observed throughout the Pelarda F. deposit compatible with its impact ejecta origin. Aligned bigger clasts and smaller intercalated bands of sandstones, siltstones and clayey material indicate some local stratification obviously adjusted to flow processes within the impact ejecta curtain. This suggests that gravitational flows predominated in a transport by water in both liquid and gas states. Transport and deposition as a kind of pyroclastic surge are discussed. A sketch sequence describes the emplacement process of the Pelarda Fm. as part of the Azuara crater formation and the integration in the general frame of pre-impact geology and some post-impact layering.

Key words: Pelarda Formation, Iberian System, Upper Eocene/Oligocene, Azuara impact structure, proximal impact ejecta, pyroclastic flow

New article: Michael J. Simms and Kord Ernstson (2019): A reassessment of the proposed ‘Lairg Impact Structure’ and its potential implications for the deep structure of northern Scotland. – Journal of the Geological Society

Bouguer gravity residual anomaly of the Lairg proposed impact structure. A buried complex structure with an inner peak ring of 50 km diameter und derived 100 km full diameter.

Probably the source for the Stac Fada Precambrian impact ejecta deposit.

Gravity residual profiles across the Lairg impact structure revealing an inner peak ring and peripheral depressions.

 

New every week: Impact pictures to click and download – CLICK

MICHAEL RAPPENGLÜCK, BARBARA RAPPENGLÜCK, KORD ERNSTSON (2017):

Collision in prehistory. – The Chiemgau Impact: research in a Bavarian meteorite crater strewn field. – Zeitschrift für Anomalistik, vol. 17 (2017), p. 235-260. 

State of research on the Chiemgau Impact 2017 – English translation of the full article – click here.

 

 

La formación Pelarda: eyecta de la estructura de impacto de Azuara (España): características deposicionales, edad y génesis. Click the article!

[Pelarda Formation – ejecta deposit of the Azuara impact structure (Spain): Deposition characteristics, age and genesis].

New article about one of the most important impact ejecta deposits in the world: 75 pages, more than 90 illustrations – most current version. Spanish with English abstract. 

Ferran Claudin & Kord Ernstson

Abstract. – The Pelarda Formation (Fm.), located in the Iberian System in northeast Spain is a sedimentary deposit with an extension of roughly 12 km x 2.5 km and an estimated thickness of no more than 400 m. The formation was first recognized as a peculiar unit in the early seventies and underwent interpretations like a fluvial or an alluvial fan deposit having a postulated age between Paleogene and Quaternary. Since the early nineties the Pelarda Formation has been considered an impact ejecta deposit originating from the large c. 40 km-diameter Azuara impact structure and meanwhile being among the largest and most prominent terrestrial impact ejecta occurrences, which however is questioned by regional geologists still defending the fluvial and alluvial fan models. Roughly speaking, the Pelarda Fm. is a grossly unsorted, matrix-supported diamictite with grain sizes between silt fraction and meter-sized clasts. Strong clast deformations and abundant shock metamorphic effects like planar deformation features (PDF) are observed throughout the Pelarda F. deposit compatible with its impact ejecta origin. Aligned bigger clasts and smaller intercalated bands of sandstones, siltstones and clayey material indicate some local stratification obviously adjusted to flow processes within the impact ejecta curtain. This suggests that gravitational flows predominated in a transport by water in both liquid and gas states. Transport and deposition as a kind of 2 pyroclastic surge are discussed. A sketch sequence describes the emplacement process of the Pelarda Fm. as part of the Azuara crater formation and the integration in the general frame of pre-impact geology and some post-impact layering.

   Quartzite megaclast from the Pelarda Fm ejecta deposit. PDF in shocked quartz grain; quartzite clast from the ejecta deposit..

 

Part 1: Observations and first hypothesis of formation

Kord Ernstson* (2018)

Abstract. – Pink quartz, not to be confused with rose quartz, is an extremely rare color variety, which is completely transparent and is only known from a few occurrences worldwide. It is believed that the pink color is due to small amounts of aluminum and phosphorus that substitute silicon, and exposure of the quartz to natural gamma radiation. Sands with a dominating proportion of pink quartz excavated from the soil and extracted from a breccia layer in the crater strewn field of the Chiemgau meteorite impact suggest that normally colorless quartz sand was irradiated during the impact event and may possibly be found at other impact sites.

Key words: Pink and rose quartz, Chiemgau meteorite impact, neutron-gamma radiation

**********************************************************

*Faculty of Philosophy I, University of Würzburg, Germany, email: kernstsoneternstson.de

The full article can be downloaded here.

 

Lunar & Planetary Science Conference (LPSC) March 19 – 23, 2018, The Woodlands, Texas, USA – Poster Presentations on newly suggested meteorite impact sites

At the LPSC 2018 abstracts and posters (click the titles) on new impact sites have been presented:

M. Molnár, P. Švanda, L. Beneš, K. Ventura, K. Ernstson: Asphaltic (Bituminous) Breccias with Carbolite (Carbon Allotrope) and Ballen Structures in Silica as Indicative of Thermal Shock: More Evidence of a Holocene Meteorite Impact Event in the Czech Republic, Poster     Abstract

A. Ure, R. Westaway, D. R. Bridgland, T. Demir, K. Ernstson: Impact Hypothesis for the Kaş Bay Structure (Turkey/Greece) Strengthened,  Poster       Abstract

R. Fox, K. Ernstson: In Honor of Doctor Robert E. Cohenour, the Great Salt Lake Astrobleme (GSLA), Revisited, Poster      Abstract

K. Ernstson, W. Müller, A. Gawlik-Wagner: The Saarlouis Semi Crater Structure: Notable Insight into the Saarland (Germany) Meteorite Impact Event Achieved, Poster    Abstract

G. Waldmann, F. Herten, M. Hiltl, K. Ernstson: The Enigmatic Niederrhein (Germany) Deposit: Evidence of a Middle-Pleistocene Meteorite Impact Strewn Field, Poster  Abstract

“The convincing identification of terrestrial meteorite impact structures: What works, what doesn’t, and why”

by Kord Ernstson & Ferran Claudin (Dec. 2013)

Abstract. – We use and variegate the title of this article published in Earth-Science Reviews to show how science may (mal)function, how scientific results are manipulated, and how a few exposed impact researchers (the authors of the Earth-Science Reviews article included) are counteracting exactly the ideas presented in that article.

1 Introduction 

“The convincing identification of terrestrial meteorite impact structures: What works, what doesn’t, and why” is the title of a comprehensive and in principle not too bad article written by Bevan M. French and Christian Koeberl and published in Earth-Science Reviews (French & Koeberl 2010). We however would like to take up this title to once more point to the large Azuara and Rubielos de la Cérida impact structures in Spain and the related controversy shedding light on how science is manipulated, in this case with regard to some impact researchers from the so-called “impact community” (whatever that may be).

2 What doesn’t work

With a slight modification we begin with “what doesn’t work”. As for the identification of meteorite impact structures it obviously doesn’t work to publish clear and generally accepted impact shock features (like they are addressed in that article) to get an impact structure being established. This holds true for both the Azuara and Rubielos de la Cérida impact sites that are still opposed vehemently by a few leading impact researchers. Apart from the manifold geologic and geophysical evidence like ubiquitous monomictic and polymictic breccias, large systems of monomictic and polymictic breccia dikes, enormous and extended megabreccias, shatter cones, extended impact ejecta, gravity and geomagnetic anomalies, the unambiguously established shock metamorphism like shock melt, planar deformation features (PDFs) and diaplectic glass in various minerals appears not to convince (title!) Christian Koeberl, Falko Langenhorst, John Spray and others. Therefore, we once more present a collection of impact shock features from the Azuara and Rubielos de la Cérida impact structures in Spain that have all been published earlier in various journals:

Azuara impact structure: Planar deformation features (PDFs)

 

Fig. 1 A-D: PDFs in quartz from the Azuara impact structure. A, B: in quartzite rocks from the impact ejecta deposit (Pelarda Fm.). C: from a polymictic strongly shocked breccia. D: Frequency diagram of Azuara PDFs based on data elaborated by Dr. A. Therriault. All figures have been published earlier.

An independent investigation of PDFs in samples from the Azuara impact structure (a polymictic dike breccia and Pelarda Fm. ejecta) was made at the Geological Survey of Canada by Dr. Ann Therriault (Therriault 2000). She analyzed the crystallographical orientation of PDFs in quartz (Fig. 1 D) and other parameters such as density, sharpness, spacing, and spreading over the grain (Fig. 1 C). And we cite from her report: Up to five sets of PDFs per grain were observed. The spacing is 1 µm or less, the PDF density high. Practically all sets are decorated. All shocked grains have reduced birefringence of 0.004 – 0.008.  Continue reading “Reminder: Manipulation in science”

A new book has recently been published: Hannu Ahokas: Previously unidentified meteorite impacts in South Finland. In Finnish with English abstract – Click HERE for more information.