Lithostratigraphy of the impactite and bedrock section of <scp>ICDP</scp> drill core D1c from the El'gygytgyn impact crater, Russia

• Published in: Meteoritics & Planetary Science
• Main Authors: Raschke, Ulli, Reimold, Wolf Uwe, Zaag, Patrice Tristan, Pittarello, Lidia, Koeberl, Christian
• Other Authors: German Science Foundation, Austrian Science Foundation, ICDP, US National Science Foundation, German Ministry of Research and Education, Russian Academy of Sciences, Austrian Ministry for Science and Research
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2013
• Subjects: Space and Planetary Science; Geophysics; Chukotka; Chukotka Peninsula
• Online Access: http://dx.doi.org/10.1111/maps.12072; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fmaps.12072; https://onlinelibrary.wiley.com/doi/pdf/10.1111/maps.12072

Abstract In 2008/2009, the International Continental Scientific Drilling Program ( ICDP ) obtained drill cores from the El'gygytgyn impact structure located on the Chukotka Peninsula (Russia). These cores provide the most complete geological section ever obtained from an impact structure in siliceous volcanic rock. The lithostratigraphy comprises a thick sequence of lacustrine sediments overlying impact breccias and deformed target rock. The interval from 316 m (below lake floor—blf) to the end of the core at 517 m depth can be subdivided into four lithological sequences. At 316 m depth, the first mesoscopic clasts of shocked target rock occur in lacustrine sediments. The growing abundance of target rock clasts with increasing depth and corresponding decrease of lacustrine sediment components indicate the extent of this transition zone to 328 m depth. It constitutes a zone of mixed reworked impact breccia and lacustrine sediments. Volcanic clasts in this reworked suevite section show all stages of shock metamorphism, up to melting. The underlying unit (328–390 m depth) represents a suevite package, a polymict impact breccia, with considerable evidence of shock deformation in a wide variety of volcanic clasts. This includes fragments with quartz that exhibit planar fractures and planar deformation features ( PDF ). In addition, at three depths, several centimeter‐sized clasts with shatter cones were detected. Due to microanalytical identification of relatively rare, microscopic impact melt particles in the matrix of this breccia, this material can be confidently labeled a suevite. Also in this sequence, three unshocked, <1 m thick intersections of volcanic blocks occur at 333.83, 351.52, and 383.00 m depths. The upper bedrock unit begins at 390.74 m depth, has a thickness of 30.15 m, and represents a sequence of different volcanic rocks—an upper part with basaltic composition from 390.74 to 391.79 m depth overlying a lower, rhyodacitic part from 391.79 to 420.27 m depth. This (parautochthonous) basement unit ...