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The Llandeilo (Ordovician) series in the core of the Tywi Anticline, Llanwrtyd, Powys, UK
Author(s) -
Cave R.,
Rushton A. W. A.
Publication year - 1996
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/(sici)1099-1034(199603)31:1<47::aid-gj690>3.0.co;2-a
Subject(s) - geology , biozone , ordovician , anticline , igneous rock , stratigraphic section , paleontology , clastic rock , large igneous province , geochemistry , sedimentary rock , volcanic rock , structural basin , volcano , magmatism , tectonics
The Llandeilo and Caradoc volcanic rocks that form an inlier near Llanwrtyd, south‐west of Builth, Powys, consist of acidic tuffs and basaltic rocks. They are interbedded with marine mudstones deposited in conditions of low oxygenation, and turbidites, slumps and debris flows. The cored Gilfach Farm No. 1 Borehole shows that this igneous activity is of Llandeilo age, extending from the teretiusculus Biozone to the gracilis Biozone. Evidence from exposures suggests that this igneous activity ceased at about the end of gracilis Biozone times (early Caradoc) and was probably extrusive; but evidence from the core, especially the presence of peperites towards its base, also indicates intrusion into wet sediments. Evidence is given for an early Caradoc basin‐wide sedimentary event.