Suevite (basal breccia) near Cucalón, Azuara structure. Maximum size is 16 cm.

Glass in the Cucalón suevite (basal breccia). Within a carbonate matrix, the glass fragment with fluidal texture is located in a small void lined by calcite crystals. Photomicrograph: xx nicols to the right; the field is 240 µm wide.

Suevite (basal breccia) near Cucalón. Note the flow texture and the whitish matrix material which may be crystallized carbonate melt. 12 cm maximum horizontal size.

Suevite (basal breccia) near Cucalón. Brownish variety with rare larger clasts. 10.5 cm maximum horizontal size.

Suevite (basal breccia) near Cucalón, fine-grained variety; close-up see below. 14 cm maximum size.

Suevite, fine-grained variety, detail; the field is 2.5 cm wide. Note the many well-rounded clasts, flow texture and the obscure greyish/whitish matrix material. The matrix is assumed to result from decarbonation/melting and recombination/crystallization of carbonate target rocks and, in the strict sense, this variety could be an impact melt rock.

Another variety of the fine-grained Cucalón suevite with a reddish matrix and only very small-sized clasts grading into the matrix. 10.5 cm maximum size of the sample.

Massive outcrop of the Cucalón fine-grained suevite (basal breccia). Note the steeply dipping platy jointing which has possibly originated from cooling of the suevite body.

Suevite, Azuara impact structure (Spain); Portillo variety, S Fuendetodos. Note the ghost fragments and the rudimentary black limestone clast suggesting outflow of melted material. A microscopic investigation of this whitish material by Tanja Katschorek revealed a composition of carbonate microlites in the form of needle-shaped crystallites grown in tufts, and dendritic crystallites, typical of crystallized carbonate melt.

Suevite, Azuara impact structure (Spain); Portillo variety, S Fuendetodos. Note the porphyritic texture of the clastic matrix. Photomicrograph, the field is 2 mm wide.

For more images of the Azuara basal breccia, klick here