Obscure-bedded Ejecta Facies from the Popigai Impact Structure, Siberia: Lithological Features and Mode of Origin

Abstract

The lithology and distribution of proximal ejecta facies that formedduring the late stages of formation of the Popigai impact crater,Siberia, are described. These deposits are distinct from other rockfacies of the crater fill due to obscure bedding (or unclear layering),poor or moderate sorting, and some other specific lithological features(character of debris, presence of accretionary lapilli etc). Three typesof such ejecta facies occur in the upper parts of the crater fill; theseare are composed of lithic microbreccias and suevites (A type), sueviteswith minor tagamites (B type), and suevites (C type). Similar rockfacies, according to previously published data, may be distinguished insome other impact craters (e.g., Ries, Sudbury, and Logoisk). Thepreliminary interpretation of the mode of origin of these ejecta faciesare air fall (A), pyroclastic-like flow (B), and base surge (C)deposits, which resemble some features of volcanic pyroclasticformations. It is possible that similar rock facies may be found in thecrater fill of some other well-preserved impact craters.