183:
which outcrop across the region. The rocks of the
Rhayader Mudstone Formation have variously been known as the Rhayader Pale Shales, Rhayader Pale Shales Formation and Cwmsymlog Formation.
347:
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where the turbiditic mudstones of the
Derwenlas Formation are exposed in the hillside beneath the dam. They are seen again in the vicinity of
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British
Geological Survey 1:50,000 scale geological map (England & Wales) sheets 149, 163, 164, 179, 194-6, 212
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These rocks are exposed, though often poorly, in a belt of country which runs east from the
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age whilst the
Rhayader Mudstones are assigned to the
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and in the core and margins of the Cothi and
Doethie
271:of the Silurian period. The Derwenlas rocks are of
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199:. A narrow outcrop also stretches northeast from
51:Rhayader Mudstones Formation, Derwenlas Formation
203:. A more extensive outcrop reaches south from
215:areas and indeed through the eastern part of
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348:Geological groups of the United Kingdom
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175:are exposed. The Group comprises the
7:
301:The BGS Lexicon of Named Rock Units
14:
297:"Rhayader Mudstones Formation"
1:
16:Geological group in mid Wales
239:The Group represents anoxic
177:Rhayader Mudstones Formation
303:. British Geological Survey
163:. The name is derived from
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235:Lithology and stratigraphy
338:Silurian System of Europe
243:of 125-500m thickness of
26:
263:laid down in the marine
195:coast northeast of
181:Derwenlas Formation
179:and the underlying
28:Stratigraphic range
217:Claerwen Reservoir
150:lithostratigraphic
60:various formations
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343:Geology of Wales
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269:Llandovery epoch
70:Cwmere Formation
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155:(a sequence of
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229:Mynydd Mallaen
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143:Claerwen Group
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22:Claerwen Group
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253:hemipelagites
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305:. Retrieved
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221:Llyn Brianne
193:Cardigan Bay
190:
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176:
142:
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125:Type section
307:28 February
267:during the
265:Welsh Basin
205:Machynlleth
157:rock strata
332:Categories
283:References
261:sandstones
257:siltstones
249:turbidites
225:anticlines
209:Llanidloes
197:Llangranog
171:where the
95:turbidites
277:Telychian
259:and thin
245:mudstones
159:) in mid
130:Named for
85:mudstones
76:Lithology
56:Underlies
48:Sub-units
273:Aeronian
213:Rhayader
201:Aberdyfi
187:Outcrops
165:Claerwen
147:Silurian
134:Claerwen
101:Location
66:Overlies
32:Silurian
30:: early
227:around
207:to the
117:Country
81:Primary
241:facies
173:strata
106:Region
255:with
247:with
169:Powys
161:Wales
153:group
145:is a
120:Wales
111:Wales
91:Other
42:Group
309:2014
251:and
211:and
141:The
109:mid
38:Type
167:in
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299:.
279:.
231:.
311:.
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