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Sedimentology and petrography of three tuff horizons in the Caradocian sequence of the Bala area (North Wales)
Author(s) -
Schiener E. J.
Publication year - 1970
Publication title -
geological journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.721
H-Index - 54
eISSN - 1099-1034
pISSN - 0072-1050
DOI - 10.1002/gj.3350070103
Subject(s) - geology , pyroclastic rock , lithology , sedimentology , subaerial , petrography , sequence (biology) , geochemistry , sedimentary rock , volcanic ash , geomorphology , volcano , genetics , biology
Three interstratified pyroclastic deposits in the Caradocian marine sequence around Bala (N. Wales) are investigated. Their petrology is used for identification and correlation. The Cefn Gwyn Ash is a vitric tuff, locally indicating subaerial deposition. The Frondderw Ash is the product of subaqueous pyroclastic flows, giying evidence of very short‐lived volcanic activity. The Pont‐y‐Ceunant Ash is a waterlaid vitric crystal tuff. Lateral changes in lithology allow a north‐easterly source‐area to be inferred for the former two members. Sedimentary structures show partial emergence of the area during Soudleyan times. The highest member, the Pont‐y‐Ceunant Ash, is restricted to the south‐west of the area.