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Sanna Alwmark

Sanna Alwmark

Associate senior lecturer

Sanna Alwmark

A possible 5 km wide impact structure with associated 22 km wide exterior collapse terrain in the Alhabia–Tabernas Basin, southeastern Spain

Author

  • Sebastián Tomás Sánchez Gómez
  • Jens Ormö
  • Carl Alwmark
  • Sanna Holm-Alwmark
  • Gabriel Zachén
  • Robert Lilljequist
  • Juan Antonio Sánchez Garrido

Summary, in English

The Tabernas–Alhabia Basin is a structural depression situated in the province of Almería, southeastern Spain. The basin is filled with Neogene, Pliocene, and Pleistocene sediments resting discordantly on a Paleozoic metamorphic basement. During the marine Tortonian sedimentation, a bed of breccia (Gordo megabed) was formed. It consists of rotated sedimentary megablocks commonly capped and/or surrounded by a polymict breccia composed mainly of up to dm-sized clasts of the crystalline (schist) basement. Previous work has suggested the bed to be a seismite corresponding to events induced by earthquakes. Here, we link the formation of the Gordo megabed with an ∼5 km wide, rimmed depression with exposed breccias on the northern flank of the Sierra de Gádor mountain. This semicircular structure, developed in mainly schists and dolostone of the basement, is delimited to the W, S, and E by an up to 350 m high escarpment with overturned stratigraphy. Toward the north, this crater-like structure opens toward the Gordo megabed of the Tabernas Basin. In the southern sector, the overturned strata transform outward for into a blocky allochthonous breccia with decreasing thickness and clast size. In the interior of the structure, there are occurrences of graded breccia and arenite superposed on a blocky, autochthonous breccia. Based on the presence of mineralogical shock metamorphic evidence, potential shatter cones, and a high Ir anomaly (∼500 ppb) as well as the position of the structure near the town of Alhama de Almería, we propose to call it the Alhama de Almería impact structure.

Department/s

  • Lithosphere and Biosphere Science

Publishing year

2023

Language

English

Pages

1512-1539

Publication/Series

Meteoritics and Planetary Science

Volume

58

Issue

10

Document type

Journal article

Publisher

Wiley-Blackwell

Topic

  • Geology

Status

Published

ISBN/ISSN/Other

  • ISSN: 1086-9379