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Ejecta of the Azuara impact structure

Pelarda Fm. ejecta between Fonfría and Olalla villages.

General aspect of the continuous deposits, which are up to several 100 m thick.

Conglomeratic component of the Pelarda Fm. ejecta. Note the bad sorting and the matrix-supported clasts. Many of the clasts are strongly striated and heavily crushed (see, e.g., the cobble with the coin displaying radial open fractures).(also see Ernstson & Claudín 1990).

The matrix-supported components, the strong plastic deformations, the size of the components up to 2 m, and the deposition on top of the highest mountains in the region are not compatible with a fluvial sedimentation as suggested by other authors. A Quaternary debris deposit as established in the geological map, can also be excluded.

Azuara impact structure: Pelarda Fm. ejecta. Large-sized Bámbola quartzite components showing prominent striations. Hammer length 42 cm. - The large matrix-supported boulders up to 2 m in diameter on top of the highest mountains in the region and the striated quartzite are not compatible with a fluvial deposition as is yet suggested by geologists and even by a sedimentologist. There are geologists (e.g., Prof. Marcos Aurell from the Zaragoza university) who also pretend that the roundness of many components of the Pelarda layers does not speak in favor of impact ejecta. They believe that the components should be more angular. This is a curious argumentation. The impact target in the Azuara region consisted to a high degree of Tertiary molasse conglomerates, and, therefore, rounded components within the ejecta from excavation and ballistic emplacement are anything but unexpected.

Azuara impact structure: A 9 m-length Buntsandstein megablock embedded within the Pelarda-Fm. ejecta. Exposure between Fonfría and Olalla, and close-up. Hammer length 36 cm; photo-cap diameter 51 mm. - The megablock is composed of typical Buntsandstein sandstone outcropping, e.g., at Monforte de Moyuela. A fluvial deposition can absolutely be excluded. This holds true also for a deposition as Quaternary debris as settled in the geological map and postulated also by Prof. Marcos Aurell from the Zaragoza University.

More images of the Pelarda Fm. ejecta
(photographs taken und described by Ferran Claudin)

Details of the Pelarda Fm. impact ejecta. The heterometric deposit is composed of subangular clasts (quartzites, phyllites, schists; a granitoid clast above the hammer helve) embedded in a sandy-gravelly matrix. Clear stratification is absent. The texture is matrix supported. - Middle zone of the ejecta deposit. 

Pelarda Fm. road cut; lower part of the ejecta deposit. Heterometric, angular to sub-angular clasts of quartzites, phyllites, and schists embedded in a sandy-argillaceous matrix. Stratification is absent.

Pelarda Fm. ejecta outcropping in the large forested area of the Pelarda Fm. deposit; middle to upper part. Note the large blocks of Bámbola quartzite in a sandy matrix. The size of the blocks, which are frequently striated, occasionally exceeds 1 m. The heterometric, polygenetic clasts (quartzites, schists, phyllites) are matrix-supported and are frequently oriented sub-horizontally with the more convex side downwards. Occasionally, the Pelarda Fm. facies reminds of deposits of volcanic surges. There is no evidence of turbulent flow upon formation of the deposit

Detail of the Pelarda Fm. in its upper part. The deposit clearly is heterometric, polygenetic (quartzites, phyllites, schists), composed of sub-rounded (quartzites) to sub-angular (phyllites, schists) clasts which are matrix-supported (sandy-argillaceous matrix). No indication of stratification. The layering reminds of a debris flow. Note the distinctly fractured clast, which would not have survived any transport except for confinement in a non-turbulent regimen. Also note that the smaller clasts are set up to adapt to the morphology of the large central clast (suggesting a kind of plastic flow). 

Pelarda Fm. ejecta, middle zone near the upper one. Heterometric, polymict, and matrix-supported clasts (quartzites up to 1-m size, phyllites, schists). The texture reminds of the facies of debris flows. Note the clast apophyses (to the left) embedded between the sandy matrix (light color) and the argillaceous matrix (reddish color, by admixture of Buntsandstein material). Not any bedding can be observed. This holds true also for fluviatile bars or similar structures.