WEEK 4 Old Lost Sea: the Iapetus Ocean the Cambrian and Ordovician of Britain

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30/10/2012 A Geological History of Britain WEEK 4 Old Lost Sea: The Iapetus Ocean The Cambrian and Ordovician of Britain Last week 1 30/10/2012 This week V Followed by 2 30/10/2012 Not to mention What is a Wilson Cycle? The cyclical plate tectonic system by which oceans are opened and closed 3 30/10/2012 Start of a Wilson Cycle Hot spot → rifting beneath continent Middle of a Wilson Cycle ACTIVE margin PASSIVE margin 4 30/10/2012 End of a Wilson Cycle Subduction of ocean → continental collision Late Precambrian opening of Iapetus Ocean 5 30/10/2012 Walcott's Cambrian critters Walcott's Cambrian critters 6 30/10/2012 Wilson's wonderings Did the Atlantic close then re-open? Cocks & Fortey (1982) Fossils = more precise timings Cambrian: very different Laurentia & Avalonia far apart Ordovician = getting similar L & A converging Silurian = very similar L & A converged 7 30/10/2012 Cambrian Cambria 8 30/10/2012 Cambrian outcrops Harvey et al. (2011) Llanberis Slate Formation Trilobites @ top = Early Cambrian Penrhyn Quarry, Bethesda 9 30/10/2012 Harlech Dome The Rhinogydd Harlech Dome Yellow: Harlech Grits Group Early-Middle Cambrian sandstones 10 30/10/2012 Harlech Dome Blue: Mawddach Group Middle-Late Cambrian mudstones Northern Pembrokeshire 11 30/10/2012 Early-Mid Cambrian Cambro-Ordovician 12 30/10/2012 Middle of a Wilson Cycle PASSIVE margin PASSIVE margin Avalonia Early Cambrian Laurentia ACTIVE margin Late Cambrian PASSIVE margin Avalonia Laurentia Hebridean Terrane Cambrian-Ordovician rocks of NW Scotland 13 30/10/2012 Passive margin Cambro- Ordovician sediments of NW Scotland Cambrian-Ordovician rocks of NW Scotland - deposition controlled by sea-level changes 14 30/10/2012 Ordovician volcanism ACTIVE margin North Wales Avalonia West Wales Lake District Ordovician volcanism 15 30/10/2012 Early Ordovician Mid-Ordovician 16 30/10/2012 Fishguard Volcanic Group jncc.defra.gov.uk/pdf/gcrdb/GCRsiteaccount282.pdf Late Ordovician 17 30/10/2012 Borrowdale Volcanic Group © BGS Fiamme textures in ignimbrite, Great Paddy Crag, Buckbarrow Ophiolites in Scotland Keen of Hamar, Shetland Also Ballantrae Complex & Highland Border Complex 18 30/10/2012 Old Lost Sea in Newfoundland Gros Morne – UNESCO World Heritage site Next week Building Britain: The Closure of the Iapetus Ocean Q. What was Cooksonia? 19 30/10/2012 Links Palaeogeographical maps of Europe: http://cpgeosystems.com/euromaps.html The Wilson Cycle: http://csmres.jmu.edu/geollab/fichter/Wilson/Wilson.html Simplified geology of Pembrokeshire: http://www.pembrokeshire-online.co.uk/geology2.htm Newfoundland's Old Lost Sea: http://theindependent.ca/2011/06/14/gros-mornes-old-lost-sea/ Geo-nealogy WHERE WERE 20.

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Route Master
magazine autumn 2012 magazine autumn 2012 Wales Wales Aberhosan, Powys Trawsfynydd, Gwynedd 09/08/2012 17:20 Route 05 Route 06 master G Distance 10½km/6½ miles G Time 3½hrs G Type Hill master G Distance 18km/11 miles G Time 7hrs G Type Mountain NAVIGATION LEVEL FITNESS LEVEL NAVIGATION LEVEL FITNESS LEVEL Plan your walk Plan your walk G Snowdonia Chester G GWYNEDD POWYS TRAWSFYNYDD ABERHOSAN G Shrewsbury G G Newtown Rhayader G Aberystwyth G Lampeter G G Llandrindod Wells Brecon WHERE: Circular walk WHERE: Circular walk from Aberhosan via the from Trawsfynydd, in Vaughan-Thomas memorial central Snowdonia’s PHOTOGRAPHY: NEIL COATES PHOTOGRAPHY: viewpoint and Glaslyn. FIONA BARLTROP PHOTOGRAPHY: Rhinogydd mountains. START/END: Aberhosan The village of Aberhosan is The spot was a favourite START/END: Trawsfynydd This is Snowdonia at its most handgate and up a walled track village bus stop (SN810974). situated a few miles south-east viewpoint of his. village car park (SH707356). remote, with few people and past a stone barn to a stile. Drift TERRAIN: Stony and grassy of Machynlleth, off the scenic TERRAIN: Lanes, rough even fewer paths. But the rewards R, roughly parallel to the wall, upland tracks, mountain paths and pathless mountain mountain road that goes via 1. START From the bus stop for your perseverance are an to a higher stile. Climb over and road and country lanes with terrain, which can be the old mining settlement at at the top of Aberhosan incredible Bronze Age monument, aim ahead-L to walk up beside some pathless stretches.
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NLCA06 Snowdonia - Page 1 of 12
National Landscape Character 31/03/2014 NLCA06 Snowdonia Eryri – Disgrifiad cryno Dyma fro eang, wledig, uchel, sy’n cyd-ffinio’n fras â Pharc Cenedlaethol Eryri. Ei nodwedd bennaf yw ei mynyddoedd, o ba rai yr Wyddfa yw mynydd uchaf Cymru a Lloegr, yn 3560’ (1085m) o uchder. Mae’r mynyddoedd eraill yn cynnwys y Carneddau a’r Glyderau yn y gogledd, a’r Rhinogydd a Chadair Idris yn y de. Yma ceir llawer o fryndir mwyaf trawiadol y wlad, gan gynnwys pob un o gopaon Cymru sy’n uwch na 3,000 o droedfeddi. Mae llawer o nodweddion rhewlifol, gan gynnwys cribau llymion, cymoedd, clogwyni, llynnoedd (gan gynnwys Llyn Tegid, llyn mwyaf Cymru), corsydd, afonydd a rhaeadrau. Mae natur serth y tir yn gwneud teithio’n anodd, a chyfyngir mwyafrif y prif ffyrdd i waelodion dyffrynnoedd a thros fylchau uchel. Yn ddaearegol, mae’n ardal amrywiol, a fu â rhan bwysig yn natblygiad cynnar gwyddor daeareg. Denodd sylw rhai o sylfaenwyr yr wyddor, gan gynnwys Charles Darwin, a archwiliodd yr ardal ym 1831. Y mae ymhell, fodd bynnag, o fod yn ddim ond anialdir uchel. Am ganrifoedd, bu’r ardal yn arwydd ysbryd a rhyddid y wlad a’i phobl. Sefydlwyd bwrdeistrefi Dolgellau a’r Bala yng nghyfnod annibyniaeth Cymru cyn y goresgyniad Eingl-normanaidd. Felly, hefyd, llawer o aneddiadau llai ond hynafol fel Dinas Mawddwy. O’i ganolfan yn y Bala, dechreuodd y diwygiad Methodistaidd ar waith trawsffurfio Cymru a’r ffordd Gymreig o fyw yn y 18fed ganrif a’r 19eg. Y Gymraeg yw iaith mwyafrif y trigolion heddiw.
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NLCA05 Tremadoc Bay - Page 1 of 10
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Comparison of the Meguma Supergroup of Nova Scotia with The
atlantic geology . volume 45 . 2009 47 ously below wavebase, suggesting significant subsidence. At the top of the group the stratigraphy is more diverse; alter- nating finer and coarser units show enrichment in manganese and spectacular bioturbation. Rare trilobite fragments indicate Middle Cambrian age. A unit of carbonaceous laminated slate marks the base of the overlying Mawddach Group. The overly- ing Maentwrog Formation comprises rusty-weathering black pyrite-rich slate, siltstone, and sandstone with turbidite struc- tures. Trilobites indicate Late Cambrian age. Higher parts of the group show a clear transition to shallower water conditions above wavebase, with linguloid brachiopods and trilobites indi- cating Tremadocian age. The group is unconformably overlain by the Early Ordovician Rhobell and Aran volcanic groups. Lithological and chronological analogies between the two A Welsh Meguma? Comparison of the successions are striking. However, significant differences in- Meguma Supergroup of Nova Scotia with the clude: (1) the greater thickness of the Meguma succession; (2) Harlech Dome succession of North Wales the presence of shallow marine to non-marine strata at the base and top of the Harlech succession; (3) the possible presence of John W.F. Waldron1 and David I. Schofield2 an unconformity between the two groups in Harlech; and (4) 1. Department of Earth and Atmospheric Sciences, the presence of volcanics near the base and top of the Welsh University of Alberta, Edmonton, AB, Canada T6G 2E3 succession. Nonetheless, the similarities indicate closely simi- <[email protected]> ¶ 2. British Geological Survey, lar evolution for the two basins, and would be consistent with Kingsley Dunham Centre, Nottingham, United Kingdom deposition in connected parts of a peri-Gondwanan rift system.
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