A Silurian asymmetric compound delta system in south central Wales, UK

Hillier, Robert ORCID: https://orcid.org/0009-0001-5395-1964; Waters, Richard A.; Davies, Jeremy R.. 2025 A Silurian asymmetric compound delta system in south central Wales, UK. Geological Magazine, 162, e42. 10.1017/S0016756825100289

Before downloading, please read NORA policies.

Preview

Text (Open Access Paper) a-silurian-asymmetric-compound-delta-system-in-south-central-wales-uk.pdf - Published Version Available under License Creative Commons Attribution 4.0. Download (3MB) | Preview

Abstract/Summary

Gorstian sediments in south-central Wales preserve an asymmetric, compound mixed-process delta system north of the Carreg Cennen Disturbance and east of the Golden Grove Axis. The 30 km SW-NE outcrop, extending from the Cennen Valley to Y Pigwn, is oblique to the NNE delta progradation direction. The Hafod Fawr Formation comprises subaqueous delta slope deposits. Sandstone bed amalgamation indicates shoaling and wave/storm influence within the overlying subaqueous delta platform deposits of the Cwar Glas Member. The succeeding Mynydd Myddfai Sandstone Formation contains shoreline delta lithofacies within three geographical tracts. An embryonic Golden Grove Axis shed shoal water shoreline fan-delta and alluvial fan lithofacies (of the Trichrug Formation) in the Cennen Valley Tract. The SW Tract (Cilmaenllwyd to Banc Celynog) was deposited on the updrift flank of the asymmetric delta, with longshore drift to the NE. Amalgamated sandstone bedsets dominate in the mouth bar and terminal distributary channel lithofacies. Pen y Bicws preserves the axial gravel bed distributary channel lithofacies, which created a headland and palaeogeographic divide between the SW and NE tracts. The latter (Sawdde Gorge to Y Pigwn) records deposition in a low-energy bay that hosted cycles of heterolithic lithofacies. Collectively, these tracts occupied part of a sediment supply route to deeper facies of the subsidence-prone Clun Forest Sub-Basin. Emergent delta plain deposits become dominant within the overlying Trichrug Formation. Thin, locally preserved deposits of the Cribyn Du Member record delta abandonment and transgression during the Ludfordian associated with basin reconfiguration and expansion of the Caer’r mynach Seaway.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1017/S0016756825100289
ISSN:	0016-7568
Date made live:	27 Nov 2025 15:11 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/540656

Actions (login required)

View Item

Document Downloads

More statistics for this item...