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The geology of the Llanuwchllyn to Llanymawddwy area, south gwynedd, north wales
Author(s) -
Lockley M. G.
Publication year - 1980
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.3350150105
Subject(s) - geology , facies , outcrop , stratigraphy , paleontology , siltstone , series (stratigraphy) , oil shale , group (periodic table) , tectonics , chemistry , organic chemistry , structural basin
A geological map of the Caradoc rocks of the Llanuwchllyn to Llanymawddwy area is presented and the geology of the area described in detail. Hitherto unrecorded outcrops provide important stratigraphical evidence which is used to redraw the Caradoc‐Ashgill Series boundary and many of the formational boundaries within the Caradoc Series. The stratigraphy of the area is revised to conform with the standard classification of the Caradoc Series in the Bala region. The only modifications are as follows: the Llaethnant Siltstone is proposed as a formational name for a group of beds which are broadly equivalent to the Glyn Gower Formation but which represent a distinct facies. The greater part of the Nod Glas Formation north of Dinas Mawddwy is shown to be laterally equivalent to the upper part of the Gelli‐grin Formation; it is also subdivided into two members, the Dyfi Mudstone and the Corris Shale, differentiated on lithological and faunal grounds. The stratigraphy of the Dinas Mawddwy area is also amended. Faunal elements (genera) new to the Caradoc Series of this area, and to Wales, are noted.