. Bulletin of the British Museum (Natural History), Geology. ENVIRONMENTAL CHANGES 379 1 Oslo P acuminatus G persculptus HIRNANTIAN 50-70m b RAWTHEYAN 3 Clastic shelves 2 Glynceinog 20-70m Regressive shoreface sequence Shallow shell Deep shelf ( ) Low energy shallow marine sequence Coquinoid limestones Mid-shallow shelf 3 Girvan -30m b Shallow marine sands Deep shelf 4 Garth Mid Wales P acuminatus G persculptus b 15-50m HIRNANTIAN RAWTHEYAN3 t -20m Mid -deep shell ( ) Vastergdtland Sweden Deep shell (G ) t Shoreface or channel sands t »1-5m Shallow shell
. Bulletin of the British Museum (Natural History), Geology. ENVIRONMENTAL CHANGES 379 1 Oslo P acuminatus G persculptus HIRNANTIAN 50-70m b RAWTHEYAN 3 Clastic shelves 2 Glynceinog 20-70m Regressive shoreface sequence Shallow shell Deep shelf ( ) Low energy shallow marine sequence Coquinoid limestones Mid-shallow shelf 3 Girvan -30m b Shallow marine sands Deep shelf 4 Garth Mid Wales P acuminatus G persculptus b 15-50m HIRNANTIAN RAWTHEYAN3 t -20m Mid -deep shell ( ) Vastergdtland Sweden Deep shell (G ) t Shoreface or channel sands t »1-5m Shallow shell Deep shelf ( ) 9 t 0-5-3m Mid-deep shelf Shallow oolite sheet Mid-deep shelf Deep shelf ( ) Gorges China »0-3m b Deep shelf (G ) Mid shell ( ) Deep shelf (G ) 7 Plynlimon Central Wales P acuminatus G persculptus HIRNANTIAN 3 -3701 RAWTHEYAN Muddy debris flows Slope base debris flovi Clastic basins Towyn-Corris 9 Moffat b ^Channelised turbidites a* Slumps and debris (lows and pebbly turbidites 0-96m I Anaerobic basin shales Oxidized basin shales Fig. 1 Generalized sections to show the sequence of environmental changes near the Ordovician/ Silurian boundary. Data for the interpretations are to be found in the following references. Section 1: (a) Husbergoya Shale, (b) Langoyene Sandstone; Brenchley & Newall 1980. 2: (a) Dolhir Formation, (b) Glyn Formation; Hiller 1981; Brenchley & Cullen 1984. 3: (a) Drummuck Group, (b) High Mains Formation; Harper 1981. 4: (a) Wenallt Formation, (b) Cwm Clyd Formation; Williams & Wright 1981. 5: (a) Dalmanitina Beds; Stridsberg 1980. 6: (a) Wufeng Formation, (b) Guanyinqiao Formation; Geng Liang-yu 1982. 7: (a) Nant-y-Moch Formation, (b) Drosgol For- mation; James 1971; Cave 1979; James 1983. 8: Garnedd-Wen Formation; James 1972; James 1985. 9: (a) Upper Hartfell Shale Formation, (b) Birkhill Shale Formation; Williams Please note that these images are extracted from scanned p
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