02333nas a2200205   4500008004100000245014900041210006900190300001400259490000800273520165600281653001301937653001201950653001901962653002601981653001602007100001602023700002002039700002002059856004802079       2013                        eng d00aReconstructing the Avalonia Palaeocontinent in the Cambrian: A 519 Ma Caliche in South Wales and Transcontinental Middle Terreneuvian Sandstones0 aReconstructing the Avalonia Palaeocontinent in the Cambrian A 51  a1022-10460 v1503 a<p>An Early Cambrian caliche on the St Non's Formation (emended) is the base of the Caerfai Bay Formation (unit-term changed) at Caerfai Bay, South Wales. Subaerial exposure and the caliche mean the two formations were not genetically related units. The St Non's is an older sand sheet (likely tidalitic, not delta-related) referred to Avalonian depositional sequence (ADS) 2, and the Caerfai Bay is a shallow mud basin unit referred to ADS 4A. The similar Random Formation (upper ADS 2) in North American Avalonia has a basal age of <em>c</em>. 528 Ma and is unconformably overlain by red mudstones or sandstones in fault-bounded basins on the Avalonian inner platform. Coeval British sandstones (lower Hartshill, Wrekin, St Non's, Brand Hills?) are unconformably overlain by latest Terreneuvian (ADS 3) or Epoch 2 (ADS 4A) units. Dates of 519 Ma on Caerfai Bay ashes give an upper bracket on the late appearance of Avalonian trilobites and suggest an ADS 2–4A hiatus of several million years. Post-St Non's and post-Random basin reorganization led to abundant Caerfai Bay Formation volcanic ashes and sparse Brigus Formation ashes in Newfoundland. The broad extent of erosional sequence boundaries that bracket lithologically similar to identical units emphasize that ‘east’ and ‘west’ Avalonia formed one palaeocontinent. The inner platform in southern Britain was larger than the Midlands craton, a tectonically defined later Palaeozoic area unrelated to terminal Ediacaran – Early Palaeozoic depositional belts. The cool-water successions of Early Palaeozoic Avalonia were distant from coeval West Gondwanan carbonate platforms.</p>
10aAvalonia10acaliche10aEarly Cambrian10asequence stratigraphy10aSouth Wales1 aLanding, E.1 aWestrop, S., R.1 aBowring, S., A.  uhttp://dx.doi.org/10.1017/S0016756813000228