http://earthwise.bgs.ac.uk/index.php?action=history&feed=atom&title=Geology_of_the_Bath_area%3A_TriassicGeology of the Bath area: Triassic - Revision history2026-04-30T22:14:21ZRevision history for this page on the wikiMediaWiki 1.42.3http://earthwise.bgs.ac.uk/index.php?title=Geology_of_the_Bath_area:_Triassic&diff=23762&oldid=prevDbk: /* Rhaetian */2015-12-02T13:20:16Z<p><span dir="auto"><span class="autocomment">Rhaetian</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 14:20, 2 December 2015</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The red mudstone of the undivided Mercia Mudstone Group grades rapidly up into the Blue Anchor Formation (BAn), an up to 5 m-thick succession of grey, greenish grey and green partly dolomitic mudstone, its green colouration indicating a reducing environment and reflecting a change to a wetter climate. At this time the landscape of the district comprised extensive coastal flats, interrupted by denuded outcrops of Palaeozoic rocks which formed low-relief hills.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The red mudstone of the undivided Mercia Mudstone Group grades rapidly up into the Blue Anchor Formation (BAn), an up to 5 m-thick succession of grey, greenish grey and green partly dolomitic mudstone, its green colouration indicating a reducing environment and reflecting a change to a wetter climate. At this time the landscape of the district comprised extensive coastal flats, interrupted by denuded outcrops of Palaeozoic rocks which formed low-relief hills.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The Mercia Mudstone Group is disconformably overlain by the Penarth Group (PnG), formed by a continuation of the marine transgression which began with the deposition of the Blue Anchor Formation, and persisted throughout Rhaetian times and into the Early Jurassic. Consequently the group oversteps the older Triassic rocks to lie unconformably upon the Palaeozoic rocks in the north and east of the district, as seen in the inliers at Wick, Codrington, and in the Chipping Sodbury railway cutting. The group thins north from 10 m to less than 7 m, but its outcrop is too narrow to be subdivided on the map. It may also thicken south-eastwards at depth. The basal division, the Westbury Mudstone Formation, comprises 3 to 5 m of very dark grey to black pyritic mudstone, with thin muddy limestone beds and locally a basal bed containing pebbles and abundant fish teeth and vertebrate debris (‘Rhaetic Bone Bed’). The formation yields a varied fauna including fish, gastropods and bivalves. Overall, the Westbury Mudstone represents deposition in a series of fringing lagoons. A transition from lagoonal to more open marine environments is represented by the overlying Cotham Formation, which comprises about 3 m of grey-green mudstone, calcareous mudstone and limestone, with a thin stromatolitic limestone (the Cotham Marble) at the top. The succeeding White Lias Formation is a 0.6 to 3 m-thick unit of pale, well-bedded limestone with thin mudstone interbeds '''(<del style="font-weight: bold; text-decoration: none;">Plate 2</del>)''' (Donovan and Kellaway, 1984)<ref>Donovan, D T, and Kellaway, G A. 1984. Geology of the Bristol district: the Lower Jurassic rocks. Memoir of the British Geological Survey.</ref>. A shallow marine setting is envisaged for the deposition of this unit, with the sea bed suffering periods of emergence. An erosion surface that caps the highest limestone in the succession is marked by desiccation cracks and numerous Diplocraterion burrows.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The Mercia Mudstone Group is disconformably overlain by the Penarth Group (PnG), formed by a continuation of the marine transgression which began with the deposition of the Blue Anchor Formation, and persisted throughout Rhaetian times and into the Early Jurassic. Consequently the group oversteps the older Triassic rocks to lie unconformably upon the Palaeozoic rocks in the north and east of the district, as seen in the inliers at Wick, Codrington, and in the Chipping Sodbury railway cutting. The group thins north from 10 m to less than 7 m, but its outcrop is too narrow to be subdivided on the map. It may also thicken south-eastwards at depth. The basal division, the Westbury Mudstone Formation, comprises 3 to 5 m of very dark grey to black pyritic mudstone, with thin muddy limestone beds and locally a basal bed containing pebbles and abundant fish teeth and vertebrate debris (‘Rhaetic Bone Bed’). The formation yields a varied fauna including fish, gastropods and bivalves. Overall, the Westbury Mudstone represents deposition in a series of fringing lagoons. A transition from lagoonal to more open marine environments is represented by the overlying Cotham Formation, which comprises about 3 m of grey-green mudstone, calcareous mudstone and limestone, with a thin stromatolitic limestone (the Cotham Marble) at the top. The succeeding White Lias Formation is a 0.6 to 3 m-thick unit of pale, well-bedded limestone with thin mudstone interbeds '''(<ins style="font-weight: bold; text-decoration: none;">P239116</ins>)''' (Donovan and Kellaway, 1984)<ref>Donovan, D T, and Kellaway, G A. 1984. Geology of the Bristol district: the Lower Jurassic rocks. Memoir of the British Geological Survey.</ref>. A shallow marine setting is envisaged for the deposition of this unit, with the sea bed suffering periods of emergence. An erosion surface that caps the highest limestone in the succession is marked by desiccation cracks and numerous Diplocraterion burrows.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==References==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==References==</div></td></tr>
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</table>Dbkhttp://earthwise.bgs.ac.uk/index.php?title=Geology_of_the_Bath_area:_Triassic&diff=20153&oldid=prevDbk at 15:38, 28 July 20152015-07-28T15:38:33Z<p></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Rhaetian===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Rhaetian===</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:P239116.jpg|thumb|350px|The Penarth Group at Chipping Sodbury railway cutting. Exposed during excavation in 1901, mudstone beds of the Cotham Formation are overlain by the prominent limestone of the White Lias Formation, succeeded by interbedded mudstone and limestone of the basal part of the Blue Lias Formation. Approximate location [7285 8160]. (Photographer S H Reynolds; P239116).]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:P239116.jpg|thumb|350px|The Penarth Group at Chipping Sodbury railway cutting. Exposed during excavation in 1901, mudstone beds of the Cotham Formation are overlain by the prominent limestone of the White Lias Formation, succeeded by interbedded mudstone and limestone of the basal part of the Blue Lias Formation. Approximate location [7285 8160]. (Photographer S H Reynolds; P239116).]]</div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The red mudstone of the undivided Mercia Mudstone Group grades rapidly up into the Blue Anchor Formation (BAn), an up to 5 m-thick succession of grey, greenish grey and green partly dolomitic mudstone, its green colouration indicating a reducing environment and reflecting a change to a wetter climate. At this time the landscape of the district comprised extensive coastal flats, interrupted by denuded outcrops of Palaeozoic rocks which formed low-relief hills.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The red mudstone of the undivided Mercia Mudstone Group grades rapidly up into the Blue Anchor Formation (BAn), an up to 5 m-thick succession of grey, greenish grey and green partly dolomitic mudstone, its green colouration indicating a reducing environment and reflecting a change to a wetter climate. At this time the landscape of the district comprised extensive coastal flats, interrupted by denuded outcrops of Palaeozoic rocks which formed low-relief hills.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div><References/></div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div><References/></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>== Geology of the Bath area <del style="font-weight: bold; text-decoration: none;">- </del>contents ==</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>== Geology of the Bath area <ins style="font-weight: bold; text-decoration: none;">— </ins>contents ==</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{Bathpapges}}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{Bathpapges}}</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[category:Bath - the geology of the area| 005]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[category:Bath - the geology of the area| 005]]</div></td></tr>
</table>Dbkhttp://earthwise.bgs.ac.uk/index.php?title=Geology_of_the_Bath_area:_Triassic&diff=6814&oldid=prevDbk at 13:02, 30 January 20152015-01-30T13:02:03Z<p></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Rhaetian===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Rhaetian===</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[Image:P239116.jpg|thumb|<del style="font-weight: bold; text-decoration: none;">300px</del>|The Penarth Group at Chipping Sodbury railway cutting. Exposed during excavation in 1901, mudstone beds of the Cotham Formation are overlain by the prominent limestone of the White Lias Formation, succeeded by interbedded mudstone and limestone of the basal part of the Blue Lias Formation. Approximate location [7285 8160]. (Photographer S H Reynolds; P239116).]]</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[Image:P239116.jpg|thumb|<ins style="font-weight: bold; text-decoration: none;">350px</ins>|The Penarth Group at Chipping Sodbury railway cutting. Exposed during excavation in 1901, mudstone beds of the Cotham Formation are overlain by the prominent limestone of the White Lias Formation, succeeded by interbedded mudstone and limestone of the basal part of the Blue Lias Formation. Approximate location [7285 8160]. (Photographer S H Reynolds; P239116).]]</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The red mudstone of the undivided Mercia Mudstone Group grades rapidly up into the Blue Anchor Formation (BAn), an up to 5 m-thick succession of grey, greenish grey and green partly dolomitic mudstone, its green colouration indicating a reducing environment and reflecting a change to a wetter climate. At this time the landscape of the district comprised extensive coastal flats, interrupted by denuded outcrops of Palaeozoic rocks which formed low-relief hills.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The red mudstone of the undivided Mercia Mudstone Group grades rapidly up into the Blue Anchor Formation (BAn), an up to 5 m-thick succession of grey, greenish grey and green partly dolomitic mudstone, its green colouration indicating a reducing environment and reflecting a change to a wetter climate. At this time the landscape of the district comprised extensive coastal flats, interrupted by denuded outcrops of Palaeozoic rocks which formed low-relief hills.</div></td></tr>
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</table>Dbkhttp://earthwise.bgs.ac.uk/index.php?title=Geology_of_the_Bath_area:_Triassic&diff=6813&oldid=prevDbk: /* Rhaetian */2015-01-30T13:01:45Z<p><span dir="auto"><span class="autocomment">Rhaetian</span></span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Rhaetian===</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>===Rhaetian===</div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">[[Image:P239116.jpg|thumb|300px|The Penarth Group at Chipping Sodbury railway cutting. Exposed during excavation in 1901, mudstone beds of the Cotham Formation are overlain by the prominent limestone of the White Lias Formation, succeeded by interbedded mudstone and limestone of the basal part of the Blue Lias Formation. Approximate location [7285 8160]. (Photographer S H Reynolds; P239116).]]</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The red mudstone of the undivided Mercia Mudstone Group grades rapidly up into the Blue Anchor Formation (BAn), an up to 5 m-thick succession of grey, greenish grey and green partly dolomitic mudstone, its green colouration indicating a reducing environment and reflecting a change to a wetter climate. At this time the landscape of the district comprised extensive coastal flats, interrupted by denuded outcrops of Palaeozoic rocks which formed low-relief hills.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The red mudstone of the undivided Mercia Mudstone Group grades rapidly up into the Blue Anchor Formation (BAn), an up to 5 m-thick succession of grey, greenish grey and green partly dolomitic mudstone, its green colouration indicating a reducing environment and reflecting a change to a wetter climate. At this time the landscape of the district comprised extensive coastal flats, interrupted by denuded outcrops of Palaeozoic rocks which formed low-relief hills.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div><del style="font-weight: bold; text-decoration: none;">[[Image:P239116.jpg|thumb|300px|The Penarth Group at Chipping Sodbury railway cutting. Exposed during excavation in 1901, mudstone beds of the Cotham Formation are overlain by the prominent limestone of the White Lias Formation, succeeded by interbedded mudstone and limestone of the basal part of the Blue Lias Formation. Approximate location [7285 8160]. (Photographer S H Reynolds; P239116).]]</del></div></td><td colspan="2" class="diff-side-added"></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The Mercia Mudstone Group is disconformably overlain by the Penarth Group (PnG), formed by a continuation of the marine transgression which began with the deposition of the Blue Anchor Formation, and persisted throughout Rhaetian times and into the Early Jurassic. Consequently the group oversteps the older Triassic rocks to lie unconformably upon the Palaeozoic rocks in the north and east of the district, as seen in the inliers at Wick, Codrington, and in the Chipping Sodbury railway cutting. The group thins north from 10 m to less than 7 m, but its outcrop is too narrow to be subdivided on the map. It may also thicken south-eastwards at depth. The basal division, the Westbury Mudstone Formation, comprises 3 to 5 m of very dark grey to black pyritic mudstone, with thin muddy limestone beds and locally a basal bed containing pebbles and abundant fish teeth and vertebrate debris (‘Rhaetic Bone Bed’). The formation yields a varied fauna including fish, gastropods and bivalves. Overall, the Westbury Mudstone represents deposition in a series of fringing lagoons. A transition from lagoonal to more open marine environments is represented by the overlying Cotham Formation, which comprises about 3 m of grey-green mudstone, calcareous mudstone and limestone, with a thin stromatolitic limestone (the Cotham Marble) at the top. The succeeding White Lias Formation is a 0.6 to 3 m-thick unit of pale, well-bedded limestone with thin mudstone interbeds '''(Plate 2)''' (Donovan and Kellaway, 1984)<ref>Donovan, D T, and Kellaway, G A. 1984. Geology of the Bristol district: the Lower Jurassic rocks. Memoir of the British Geological Survey.</ref>. A shallow marine setting is envisaged for the deposition of this unit, with the sea bed suffering periods of emergence. An erosion surface that caps the highest limestone in the succession is marked by desiccation cracks and numerous Diplocraterion burrows.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The Mercia Mudstone Group is disconformably overlain by the Penarth Group (PnG), formed by a continuation of the marine transgression which began with the deposition of the Blue Anchor Formation, and persisted throughout Rhaetian times and into the Early Jurassic. Consequently the group oversteps the older Triassic rocks to lie unconformably upon the Palaeozoic rocks in the north and east of the district, as seen in the inliers at Wick, Codrington, and in the Chipping Sodbury railway cutting. The group thins north from 10 m to less than 7 m, but its outcrop is too narrow to be subdivided on the map. It may also thicken south-eastwards at depth. The basal division, the Westbury Mudstone Formation, comprises 3 to 5 m of very dark grey to black pyritic mudstone, with thin muddy limestone beds and locally a basal bed containing pebbles and abundant fish teeth and vertebrate debris (‘Rhaetic Bone Bed’). The formation yields a varied fauna including fish, gastropods and bivalves. Overall, the Westbury Mudstone represents deposition in a series of fringing lagoons. A transition from lagoonal to more open marine environments is represented by the overlying Cotham Formation, which comprises about 3 m of grey-green mudstone, calcareous mudstone and limestone, with a thin stromatolitic limestone (the Cotham Marble) at the top. The succeeding White Lias Formation is a 0.6 to 3 m-thick unit of pale, well-bedded limestone with thin mudstone interbeds '''(Plate 2)''' (Donovan and Kellaway, 1984)<ref>Donovan, D T, and Kellaway, G A. 1984. Geology of the Bristol district: the Lower Jurassic rocks. Memoir of the British Geological Survey.</ref>. A shallow marine setting is envisaged for the deposition of this unit, with the sea bed suffering periods of emergence. An erosion surface that caps the highest limestone in the succession is marked by desiccation cracks and numerous Diplocraterion burrows.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
</table>Dbkhttp://earthwise.bgs.ac.uk/index.php?title=Geology_of_the_Bath_area:_Triassic&diff=6812&oldid=prevDbk at 13:01, 30 January 20152015-01-30T13:01:29Z<p></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 14:01, 30 January 2015</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l9">Line 9:</td>
<td colspan="2" class="diff-lineno">Line 9:</td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The red mudstone of the undivided Mercia Mudstone Group grades rapidly up into the Blue Anchor Formation (BAn), an up to 5 m-thick succession of grey, greenish grey and green partly dolomitic mudstone, its green colouration indicating a reducing environment and reflecting a change to a wetter climate. At this time the landscape of the district comprised extensive coastal flats, interrupted by denuded outcrops of Palaeozoic rocks which formed low-relief hills.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The red mudstone of the undivided Mercia Mudstone Group grades rapidly up into the Blue Anchor Formation (BAn), an up to 5 m-thick succession of grey, greenish grey and green partly dolomitic mudstone, its green colouration indicating a reducing environment and reflecting a change to a wetter climate. At this time the landscape of the district comprised extensive coastal flats, interrupted by denuded outcrops of Palaeozoic rocks which formed low-relief hills.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[Image:P239116.jpg|thumb|300px| ]]</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[Image:P239116.jpg|thumb|300px|<ins style="font-weight: bold; text-decoration: none;">The Penarth Group at Chipping Sodbury railway cutting. Exposed during excavation in 1901, mudstone beds of the Cotham Formation are overlain by the prominent limestone of the White Lias Formation, succeeded by interbedded mudstone and limestone of the basal part of the Blue Lias Formation. Approximate location [7285 8160]. (Photographer S H Reynolds; P239116).</ins>]]</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The Mercia Mudstone Group is disconformably overlain by the Penarth Group (PnG), formed by a continuation of the marine transgression which began with the deposition of the Blue Anchor Formation, and persisted throughout Rhaetian times and into the Early Jurassic. Consequently the group oversteps the older Triassic rocks to lie unconformably upon the Palaeozoic rocks in the north and east of the district, as seen in the inliers at Wick, Codrington, and in the Chipping Sodbury railway cutting. The group thins north from 10 m to less than 7 m, but its outcrop is too narrow to be subdivided on the map. It may also thicken south-eastwards at depth. The basal division, the Westbury Mudstone Formation, comprises 3 to 5 m of very dark grey to black pyritic mudstone, with thin muddy limestone beds and locally a basal bed containing pebbles and abundant fish teeth and vertebrate debris (‘Rhaetic Bone Bed’). The formation yields a varied fauna including fish, gastropods and bivalves. Overall, the Westbury Mudstone represents deposition in a series of fringing lagoons. A transition from lagoonal to more open marine environments is represented by the overlying Cotham Formation, which comprises about 3 m of grey-green mudstone, calcareous mudstone and limestone, with a thin stromatolitic limestone (the Cotham Marble) at the top. The succeeding White Lias Formation is a 0.6 to 3 m-thick unit of pale, well-bedded limestone with thin mudstone interbeds '''(Plate 2)''' (Donovan and Kellaway, 1984)<ref>Donovan, D T, and Kellaway, G A. 1984. Geology of the Bristol district: the Lower Jurassic rocks. Memoir of the British Geological Survey.</ref>. A shallow marine setting is envisaged for the deposition of this unit, with the sea bed suffering periods of emergence. An erosion surface that caps the highest limestone in the succession is marked by desiccation cracks and numerous Diplocraterion burrows.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The Mercia Mudstone Group is disconformably overlain by the Penarth Group (PnG), formed by a continuation of the marine transgression which began with the deposition of the Blue Anchor Formation, and persisted throughout Rhaetian times and into the Early Jurassic. Consequently the group oversteps the older Triassic rocks to lie unconformably upon the Palaeozoic rocks in the north and east of the district, as seen in the inliers at Wick, Codrington, and in the Chipping Sodbury railway cutting. The group thins north from 10 m to less than 7 m, but its outcrop is too narrow to be subdivided on the map. It may also thicken south-eastwards at depth. The basal division, the Westbury Mudstone Formation, comprises 3 to 5 m of very dark grey to black pyritic mudstone, with thin muddy limestone beds and locally a basal bed containing pebbles and abundant fish teeth and vertebrate debris (‘Rhaetic Bone Bed’). The formation yields a varied fauna including fish, gastropods and bivalves. Overall, the Westbury Mudstone represents deposition in a series of fringing lagoons. A transition from lagoonal to more open marine environments is represented by the overlying Cotham Formation, which comprises about 3 m of grey-green mudstone, calcareous mudstone and limestone, with a thin stromatolitic limestone (the Cotham Marble) at the top. The succeeding White Lias Formation is a 0.6 to 3 m-thick unit of pale, well-bedded limestone with thin mudstone interbeds '''(Plate 2)''' (Donovan and Kellaway, 1984)<ref>Donovan, D T, and Kellaway, G A. 1984. Geology of the Bristol district: the Lower Jurassic rocks. Memoir of the British Geological Survey.</ref>. A shallow marine setting is envisaged for the deposition of this unit, with the sea bed suffering periods of emergence. An erosion surface that caps the highest limestone in the succession is marked by desiccation cracks and numerous Diplocraterion burrows.</div></td></tr>
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</table>Dbkhttp://earthwise.bgs.ac.uk/index.php?title=Geology_of_the_Bath_area:_Triassic&diff=6656&oldid=prevDbk at 16:46, 28 January 20152015-01-28T16:46:56Z<p></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==References==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==References==</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>{{<del style="font-weight: bold; text-decoration: none;">reflist</del>}}</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"><References/></ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">== Geology of the Bath area - contents ==</ins></div></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>{{<ins style="font-weight: bold; text-decoration: none;">Bathpapges</ins>}}</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[category:Bath - the geology of the area| 005]]</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[category:Bath - the geology of the area| 005]]</div></td></tr>
</table>Dbkhttp://earthwise.bgs.ac.uk/index.php?title=Geology_of_the_Bath_area:_Triassic&diff=5782&oldid=prevDbk at 12:42, 7 July 20142014-07-07T12:42:08Z<p></p>
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<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">__NOTOC__</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{BathSE}}</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{{BathSE}}</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>By the Early Triassic, the northern part of Pangaea, which included the British Isles, lay a little north of the equator. The wider region was still largely high ground, and although alluvial sediments (Sherwood Sandstone Group) were probably being deposited to the east, it was not until Late Triassic (Carnian to Norian) times that deposition recommenced in the Bath district.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>By the Early Triassic, the northern part of Pangaea, which included the British Isles, lay a little north of the equator. The wider region was still largely high ground, and although alluvial sediments (Sherwood Sandstone Group) were probably being deposited to the east, it was not until Late Triassic (Carnian to Norian) times that deposition recommenced in the Bath district.</div></td></tr>
</table>Dbkhttp://earthwise.bgs.ac.uk/index.php?title=Geology_of_the_Bath_area:_Triassic&diff=5756&oldid=prevDbk at 11:08, 7 July 20142014-07-07T11:08:33Z<p></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>[[category:Bath - the geology of the area| <del style="font-weight: bold; text-decoration: none;">004</del>]]</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>[[category:Bath - the geology of the area| <ins style="font-weight: bold; text-decoration: none;">005</ins>]]</div></td></tr>
</table>Dbkhttp://earthwise.bgs.ac.uk/index.php?title=Geology_of_the_Bath_area:_Triassic&diff=5750&oldid=prevDbk at 10:54, 7 July 20142014-07-07T10:54:40Z<p></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 11:54, 7 July 2014</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l8">Line 8:</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The red mudstone of the undivided Mercia Mudstone Group grades rapidly up into the Blue Anchor Formation (BAn), an up to 5 m-thick succession of grey, greenish grey and green partly dolomitic mudstone, its green colouration indicating a reducing environment and reflecting a change to a wetter climate. At this time the landscape of the district comprised extensive coastal flats, interrupted by denuded outcrops of Palaeozoic rocks which formed low-relief hills.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The red mudstone of the undivided Mercia Mudstone Group grades rapidly up into the Blue Anchor Formation (BAn), an up to 5 m-thick succession of grey, greenish grey and green partly dolomitic mudstone, its green colouration indicating a reducing environment and reflecting a change to a wetter climate. At this time the landscape of the district comprised extensive coastal flats, interrupted by denuded outcrops of Palaeozoic rocks which formed low-relief hills.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">[[Image:P239116.jpg|thumb|300px| ]]</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The Mercia Mudstone Group is disconformably overlain by the Penarth Group (PnG), formed by a continuation of the marine transgression which began with the deposition of the Blue Anchor Formation, and persisted throughout Rhaetian times and into the Early Jurassic. Consequently the group oversteps the older Triassic rocks to lie unconformably upon the Palaeozoic rocks in the north and east of the district, as seen in the inliers at Wick, Codrington, and in the Chipping Sodbury railway cutting. The group thins north from 10 m to less than 7 m, but its outcrop is too narrow to be subdivided on the map. It may also thicken south-eastwards at depth. The basal division, the Westbury Mudstone Formation, comprises 3 to 5 m of very dark grey to black pyritic mudstone, with thin muddy limestone beds and locally a basal bed containing pebbles and abundant fish teeth and vertebrate debris (‘Rhaetic Bone Bed’). The formation yields a varied fauna including fish, gastropods and bivalves. Overall, the Westbury Mudstone represents deposition in a series of fringing lagoons. A transition from lagoonal to more open marine environments is represented by the overlying Cotham Formation, which comprises about 3 m of grey-green mudstone, calcareous mudstone and limestone, with a thin stromatolitic limestone (the Cotham Marble) at the top. The succeeding White Lias Formation is a 0.6 to 3 m-thick unit of pale, well-bedded limestone with thin mudstone interbeds '''(Plate 2)''' (Donovan and Kellaway, 1984)<ref>Donovan, D T, and Kellaway, G A. 1984. Geology of the Bristol district: the Lower Jurassic rocks. Memoir of the British Geological Survey.</ref>. A shallow marine setting is envisaged for the deposition of this unit, with the sea bed suffering periods of emergence. An erosion surface that caps the highest limestone in the succession is marked by desiccation cracks and numerous Diplocraterion burrows.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The Mercia Mudstone Group is disconformably overlain by the Penarth Group (PnG), formed by a continuation of the marine transgression which began with the deposition of the Blue Anchor Formation, and persisted throughout Rhaetian times and into the Early Jurassic. Consequently the group oversteps the older Triassic rocks to lie unconformably upon the Palaeozoic rocks in the north and east of the district, as seen in the inliers at Wick, Codrington, and in the Chipping Sodbury railway cutting. The group thins north from 10 m to less than 7 m, but its outcrop is too narrow to be subdivided on the map. It may also thicken south-eastwards at depth. The basal division, the Westbury Mudstone Formation, comprises 3 to 5 m of very dark grey to black pyritic mudstone, with thin muddy limestone beds and locally a basal bed containing pebbles and abundant fish teeth and vertebrate debris (‘Rhaetic Bone Bed’). The formation yields a varied fauna including fish, gastropods and bivalves. Overall, the Westbury Mudstone represents deposition in a series of fringing lagoons. A transition from lagoonal to more open marine environments is represented by the overlying Cotham Formation, which comprises about 3 m of grey-green mudstone, calcareous mudstone and limestone, with a thin stromatolitic limestone (the Cotham Marble) at the top. The succeeding White Lias Formation is a 0.6 to 3 m-thick unit of pale, well-bedded limestone with thin mudstone interbeds '''(Plate 2)''' (Donovan and Kellaway, 1984)<ref>Donovan, D T, and Kellaway, G A. 1984. Geology of the Bristol district: the Lower Jurassic rocks. Memoir of the British Geological Survey.</ref>. A shallow marine setting is envisaged for the deposition of this unit, with the sea bed suffering periods of emergence. An erosion surface that caps the highest limestone in the succession is marked by desiccation cracks and numerous Diplocraterion burrows.</div></td></tr>
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</table>Dbkhttp://earthwise.bgs.ac.uk/index.php?title=Geology_of_the_Bath_area:_Triassic&diff=5614&oldid=prevJeth1 at 14:29, 3 July 20142014-07-03T14:29:57Z<p></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 15:29, 3 July 2014</td>
</tr><tr><td colspan="2" class="diff-lineno" id="mw-diff-left-l1">Line 1:</td>
<td colspan="2" class="diff-lineno">Line 1:</td></tr>
<tr><td colspan="2" class="diff-side-deleted"></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">{{BathSE}}</ins></div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>By the Early Triassic, the northern part of Pangaea, which included the British Isles, lay a little north of the equator. The wider region was still largely high ground, and although alluvial sediments (Sherwood Sandstone Group) were probably being deposited to the east, it was not until Late Triassic (Carnian to Norian) times that deposition recommenced in the Bath district.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>By the Early Triassic, the northern part of Pangaea, which included the British Isles, lay a little north of the equator. The wider region was still largely high ground, and although alluvial sediments (Sherwood Sandstone Group) were probably being deposited to the east, it was not until Late Triassic (Carnian to Norian) times that deposition recommenced in the Bath district.</div></td></tr>
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</table>Jeth1