Also known as Pentre-bach Quarry North and South, Foel Formation
Where: Wales, United Kingdom (53.6° N, 2.7° W: paleocoordinates 9.1° S, 0.1° W)
• coordinate stated in text
• outcrop-level geographic resolution
When: Foel Formation, Chadian (345.3 - 345.0 Ma)
• The formations in this area in stratigraphic order are: Foel Formation, Dyserth Quarry Limestone Formation, Moel Hiraddug Limestone Formation, and Gop Hill Limestone Formation
• group of beds-level stratigraphic resolution
Environment/lithology: transition zone or lower shoreface; lithified, dolomitic, peloidal, brown, silty limestone and lithified, gray, green, silty mudstone
•The inner shelf environment was very shallow and turbulent as suggested by the presence of intraclastic oncoids, micritized and rounded bioclasts, concentrations of shells in dscrete layers, and frequent cross bedding. Together these imply that the packstones and especially the grainstones were wave- and probably storm-influenced. The stenohaline biota implies sea-water of normal salinities above the shelf.
•Periodically, however, the sedimentation on the shelf changed, with the deposition of porcellanous limestones which have a restricted fauna of ostracods and calcishperes. This suggests quiet-water, probably hypersaline and brackish, subtidal lagoonal or intertidal mudflat environments. These fine-grained lime muds would have formed in a protected area behind a barrier which could have been provided by grainstone shoals. The presence of domal stromatolites in this lithofacies would support a peritidal or restricted quiet-water subtidal lagoonal environment.
•Rare lithotypes include a thin 15-cm thick laminated and cross-stratified sandy dolomite below the top of the formation, and a 10cm thick dark grey porcellanous limestone (micrite) containing thin valved ostracods and calcispheres. The latter lithology occurs 7m above the base of the measured section. A similar porcellanous limestone 15cm thick is found south of Foel Farm (SJ 0652 77??).
Size class: macrofossils
Primary reference: I. D. Somerville, A. R. E. Strank, and A. Welsh. 1989. Chadian faunas and flora from Dyserth; depositional environments and palaeogeographic setting of Visean strata in Northeast Wales. Geological Journal 24(1):49-66 [J. Alroy/C. Simpson/C. Simpson]more details
Purpose of describing collection: biostratigraphic analysis
PaleoDB collection 41451: authorized by John Alroy, entered by Carl Simpson on 14.07.2004
Creative Commons license: CC BY (attribution)