Cambrian stratigraphy of St Tudwal's Peninsula, Gwynedd, northwest Wales

Young, T.; Martin, F.; Dean, W.T.; Rushton, A.W.A.

doi:10.1017/S0016756800011109

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Cambrian stratigraphy of St Tudwal's Peninsula, Gwynedd, northwest Wales

Young, T.; Martin, F.; Dean, W.T.; Rushton, A.W.A. (1994). Cambrian stratigraphy of St Tudwal's Peninsula, Gwynedd, northwest Wales. Geol. Mag. 131(3): 335-360. http://dx.doi.org/10.1017/S0016756800011109

In: Geological Magazine. Cambridge University Press: London. ISSN 0016-7568; e-ISSN 1469-5081

Available in	Authors
VLIZ: Open Marine Archive 255644 [ download pdf ]

Keywords

British Isles, Wales
Geological time > Phanerozoic > Paleozoic > Palaeozoic > Cambrian
Acritarcha [WoRMS]
Wales [Marine Regions]
Marine/Coastal

Authors		Top
Young, T. Martin, F. Dean, W.T. Rushton, A.W.A.

Abstract

Lithostratigraphic units of early to late Cambrian age established by T. C. Nicholas in 1915 in the St Tudwal's Peninsula are revised. They comprise, in ascending order: Hell's Mouth Formation (> 190 m); Trwyn y Fulfran Formation (37 m); Cilan Formation (400 m); Ceiriad Formation (40 m seen); Nant-y-big Formation (> 110 m seen); Maentwrog Formation (in part, 50 m seen, an estimated 250 m concealed); Ffestiniog Flags Formation (in part. c. 120 m seen). The 'calcareous grit' at the top of Nicholas's Nant-pig Mudstones spans the unconformable boundary between the Nant-y-big and Maentwrog formations. Previously described limestone clasts in the 'grit' are probably erosional remnants of an in situ bioclastic limestone bed; their contained trilobites include genera and species found in the Andrarum Limestone (late Middle Cambrian) of Scania, Sweden. Acritarchs are documented and compared particularly with those from eastern Newfoundland. Those from the highest part of the 'calcareous grit' include Cymatiogalea sp. and are of late Cambrian age. One new species, Heliosphaeridium ? llynense Martin, comes from the lower part of the Nant-y-big Formation (middle Middle Cambrian), where it appears a little earlier than the Adara alea Biozone.

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