Jeremy Robin Davies

Aberystwyth University | AU · Institute of Geography and Earth Sciences

As part of an international effort to evaluate potential replacement sections for the current Aeronian GSSP, the stratigraphy of the Rheidol Gorge section (central Wales, UK) is being restudied. A total of 28 samples from the Rhuddanian–Aeronian boundary interval at Rheidol Gorge were studied for chitinozoans. This famous Welsh Basin section, its s...

The Welsh Ice Cap was a dynamic component of the last British–Irish Ice Sheet at the Last Glacial Maximum, but there are few chronological constraints on the pace and timing of deglaciation. This paper presents new geomorphological and geochronological evidence that constrains the timing of the separation of the Welsh Ice Cap from the Irish Sea Ice...

The early Silurian (Llandovery) Gondwanan South Polar ice sheet experienced episodes of ice retreat and re-advance. Marine base level curves constructed for the interval are widely assumed to provide a record of the associated glacioeustasy. In revealing a series of progradational sequences (progrades) bounded by flooding surfaces, recent work on t...

Here we present a chitinozoan biostratigraphical framework for the South Wales upper Katian and Hirnantian (Ashgill) succession. The current study indicates that three of the six Avalonian Ashgill chitinozoan biozones are recognized in the Welsh Basin; the bergstroemi, fossensis and umbilicata Biozones. The Baltoscandian and Laurentian Hercochitina...

The isolated outlier of Visean (Mid Mississippian) limestones and sandstones near Corwen, North Wales, UK, provides a critical constraint on regional tectonic and palaeogeographical models. The late Asbian to Brigantian succession comprises a series of shoaling-upwards cycles (parasequences). These were the product of forced, glacioeustatic regress...

The global standard for the Llandovery Series (early Silurian) in central Wales is re-assessed in the light of detailed geological surveying, biostratigraphical sampling and a rigorous examination of published datasets. A new sedimentary and biostratigraphical architecture is presented. Key graptolite, brachiopod, acritarch and, for the first time,...

Recent detailed work on the Type Llandovery succession in central Wales, UK has allowed the erection of a thoroughly revised sedimentary architecture and new sequence stratigraphical model. Significant new chitinozoan, acritarch and graptolite discoveries have refined the succession's potential for international correlation. The new analysis reveal...

Distal environs of the Ludlow-age Trichrug Formation from south central Wales (UK) detail deposition on the outer fringe of an ephemeral debris flow-dominated alluvial fan. Debrites and subordinate sheetflood deposits are interbedded with sporadic thin sandstone-dominated heterolithic units deposited in shallow, ephemeral ponds in the axial valley....

A new component of the Early Palaeozoic arthropod fauna is described from a monospecific accumulate of carapaces in a Late Ordovician (Katian) hemipelagic mudstone from the Cardigan district of southwest Wales (UK). Its non-biomineralized carapace is preserved as a carbonaceous residue, as is more labile anatomy (soft-parts) including the inner lam...

The discovery of a previously unrecognized unconformity and of new faunas in the type Llandovery area underpins a revised correlation of Hirnantian strata in mid Wales. This has revealed the sedimentary and faunal events which affected the Lower Palaeozoic Welsh Basin during the global rise in sea level that followed the end‐Ordovician glacial maxi...

A lack of stratigraphical, sedimentological and geochemical data for sediment accumulation rates and indicators of productivity and anoxia means that causative models for ancient black shales are largely inferred from modern settings. Coastal upwelling has been suggested as a general hypothesis for Ordovician black shale deposition within the Iapet...

Morphometric analysis of graptolites from the persculptus and acuminatus biozones of central Wales identifies four successive morphospecies of normalograptids. These graptolites can be used for biostratigraphical subdivision of these strata as follows: (i) an early persculptus Biozone interval containing broad forms with geniculate thecae that have...

The newly recognized Nant Brianne turbidite system was a focus of laterally supplied coarse-grade sediment deposition that, along with the Caban–Ystrad Meurig system, punctuated late Hirnantian to early Telychian, mudstone-dominated slope apron deposition along the SE margin of the southern Welsh Basin. Geological mapping coupled with detailed bios...

This article presents the results of a geomorphological and sedimentological investigation of former glacial meltwater drainage in the region of the lower Afon Teifi, one of the major rivers of southwest Wales. Former drainage characteristics in the region are reconstructed concentrating on palaeo-drainage routes associated with successive Pleistoc...

To help calibrate the emerging Upper Ordovician chitinozoan biozonation with the graptolite biozonation in the Anglo-Welsh, historical type basin, the graptolite-bearing Caradoc–Ashgill successions between Fishguard and Cardigan, and at Whitland, SW Wales, have been collected for chitinozoans. In the Cardigan district, finds of Armoricochitina reti...

The late Chadian Foel Formation, previously thought to be confined to the Dyserth area of North Wales, forms a poorly exposed but persistent basal unit to much of the Dinantian crop east of the Clwydian Range, necessitating a revision of the local lithostratigraphy. The formation comprises a peritidal heterolith which, together with the lowest few...

During the late Devensian (late Weichselian) glaciation, a number of large proglacial lakes developed in dammed river valleys along the southwest coast of Wales, U.K. This paper presents sedimentological data, together with a Digital Terrain Model, to establish the sedimentation history, dynamics and evolution of the largest lake, glacial Llyn (Lak...

Graptolites from more than 60 horizons in the basinal Caradoc succession of southwest Wales, between Fishguard and Cardigan, allow recognition of the multidens, clingani and linearis biozones. The biostratigraphy permits recognition of major differences in the sedimentary rock-sequence north and south of structures associated with the Fishguard–Car...

The depositional processes associated with late Devensian ice in areas bordering the Irish Sea basin have been the subject of considerable debate. Among the key areas around the Irish Sea, southwest Wales occupies a particularly crucial position because it is here that ice flowing from the north impinged upon the coast orthogonally and encroached i...

The depositional processes associated with late Devensian ice in areas bordering the Irish Sea basin have been the subject of considerable debate. Among the key areas around the Irish Sea, southwest Wales occupies a particularly crucial position because it is here that ice flowing from the north impinged upon the coast orthogonally and encroached i...

Sequence stratigraphical concepts are applied to a 55 km long transect through the uppermost Ordovician and lower Silurian rocks of the Welsh Basin and the adjoining Midland Platform. The study focuses on sedimentary rocks deposited during the Llandovery epoch (about 439–430 Ma). An early Llandovery slope apron of hemipelagite and laterally supplie...

Throughout much of the Lower Palaeozoic, the Welsh Basin was a small intracratonic basin in which deep-water sediments accumulated (Woodcock 1984a; Soper and Woodcock 1990). It lay on the former microcontinent of Eastern Avalonia, on the south side of the contemporary Iapetus Ocean. To the south and east it was bordered by the Midland Platform, a s...

The Aberystwyth Grits Group was the first in a series of southerly-supplied sandstone-rich turbidite systems that invaded the Welsh Basin during the Telychian Stage (late Llandovery; Silurian). Structural and stratigraphical evidence indicates that deposition of the sand-dominated parts of the system was largely restricted to the east by a zone of...

A pilot study has demonstrated that heavy mineral analysis is a useful guide to the provenance of Silurian turbidites in the Southern Welsh Basin. The results confirm the sedimentological evidence for two distinct source areas of coarse clastic detritus, one lying to the south and the other to the east. They also provide mineralogical criteria by w...

A preliminary geochemical investigation of Silurian (Llandovery) basinal mudstones (turbidites and hemipelagites) from the Southern Welsh Basin is described. Turbidite mudstones show higher concentrations of Fe2O3, MgO, TiO2, MnO, LOI, Zn and Zr than laminated hemipelagites. This is consistent with the observed higher concentrations of chlorite and...

In Volume 26, 7-26 of the Journal, Dr D. M. D. James described the stratigraphy, sedimentology and structure of the late Ordovician to earliest Silurian succession in the core of the Tywi Anticline between the Sugar Loaf and the Wye Valley. He has used these new data to consolidate his previous model of a non-depositional slope, established by Ashg...

Two boreholes in the Vale of Glamorgan have provided new data on the nature of the early Dinantian (Courceyan) transgression in South Wales. This transgression is manifested by the transition from the largely fluviatile, late Devonian, Upper Old Red Sandstone (Quartz Conglomerate Group) to the predominantly marine, early Dinantian, Lower Limestone...

Describes over 20 transgressive/regressive shoaling upwards cycles. Cycle tops are marked by distinctive hummocky surfaces, interpreted as palaeokarstic, commonly overlain by green bentonitic clay palaeosols with fossil rootlets, and locally by red terra-rossa clays. Brecciation re-exposed lower parts of some profiles to secondary phases of calcret...

Marked thickness changes in early Dinantian (Courceyan-Chadian) sediments occur across the Cardiff-Cowbridge Anticline, a major east-west Variscan fold in the Vale of Glamorgan. They resulted from differential subsidence over an active concealed basement fault zone, the Vale of Glamorgan Axis, which is coincident with the hinge of the Anticline; th...

The Lower Carboniferous of Anglesey consists of bioclastic carbonates and subsidiary terrigenous siliciclastics built as a cyclic succession against the northern flank of the contemporary Welsh landmass. Cycle boundaries are marked by subaerial erosive features that are unlike the normal Late Dinantian palaeokarst association, and one such surface,...