51:
278:
Note that the names of many of the sandstone units are derived from the marine bands (themselves named for diagnostic fossils within them) beneath which they typically occur. Not all of the sandstones occur within any one place, the
Subcrenatum thins out to the east whilst the typically
254:
The sequence as developed along the north crop of the South Wales
Coalfield varies along its length but within the mudstone which forms the greater thickness of the Bishopston Mudstone Formation, the following are observed:
247:, above. The mudstone itself contains a few bands of sandstone such as the ‘Twelve Foot Sandstone’ and locally the ‘Cumbriense Sandstone’. Likewise the Twrch Sandstone contains bands of mudstone, often correlating with
279:
double-layered
Cumbriense Sandstone thins out to the west. Further west in Pembrokeshire the sequence above and including the Sub-Carbonicola is absent and is replaced by the Telpyn Point Sandstone Formation.
239:
of these latter two formations was formerly known as the ‘Middle Shales’, a name reflecting the position of this sequence sandwiched between the Basal Grit below and the
401:
British
Geological Survey Research Report RR/07/01: Lithostratigraphical framework for Carboniferous successions of Great Britain (Onshore) Waters, C.N. et al 2007
417:
315:
blocks of the Twrch
Sandstone and Bishopston Mudstone formations are responsible for much of the dramatic scenery within the national park's
50:
350:
where these rocks are well exposed in spectacular coastal cliffs. The Twrch
Sandstone derives its name from the vicinity of the
300:
422:
316:
95:
323:
248:
160:
296:
77:
Aberkenfig
Formation, Bishopston Formation, Twrch Sandstone Formation, Telpyn Point Sandstone Formation
67:
355:
331:
85:
55:
Sandstones and interbedded mudstones of the Telpyn Point
Sandstone Formation, Haroldston Chins,
308:
56:
195:
but are now distinguished from the similar but geographically separate rock sequences of the
304:
184:
359:
347:
330:. In contrast, the contact with the overlying Farewell Rock which lies at the base of the
312:
292:
287:
The Twrch
Sandstone Formation gives rise to numerous positive landscape features such as
192:
411:
354:
where these beds reach their maximum thickness. The mudstones derive their name from
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240:
200:
196:
181:
164:
38:
367:
343:
327:
288:
17:
351:
220:
216:
135:
121:
236:
177:
118:
42:
363:
204:
188:
150:
131:
391:(Second ed.). Geoserv Publishing. pp. 141–144.
227:(formerly the ‘Basal Grit’) which is overlain by the
156:
146:
141:
127:
114:
109:
101:
91:
81:
73:
63:
32:
342:The Marros Group is named from the locality (
243:, the lowermost sandstone of the South Wales
8:
49:
29:
389:The Geology of South Wales; a field guide
191:. These rocks were formerly known as the
176:is the name given to a suite of rocks of
366:and the Telpyn Point Sandstone from the
379:
27:Geological term for rock in south Wales
207:and northeast Wales by this new name.
322:The Marros Group is underlain by the
7:
25:
418:Carboniferous System of Europe
1:
368:coastal locality of that name
303:and the plateau surfaces of
301:Brecon Beacons National Park
215:The Group comprises a thick
439:
387:George, Gareth T. (2015).
332:South Wales Coal Measures
271:Sub-Cancellatum Sandstone
268:Sub-Carbonicola Sandstone
180:age laid down during the
48:
37:
265:Sub-Cumbriense Sandstone
96:Pembroke Limestone Group
324:Carboniferous Limestone
233:Telpyn Point Sandstone
326:, the boundary being
274:Twelve-foot Sandstone
259:Subcrenatum Sandstone
193:Millstone Grit Series
161:South Wales Coalfield
262:Cumbriense Quartzite
299:in the west of the
229:Bishopston Mudstone
86:Coal Measures Group
39:Stratigraphic range
317:Waterfall Country
309:Mynydd Llangynidr
297:Gwaun Cefnygarreg
170:
169:
16:(Redirected from
430:
423:Geology of Wales
402:
399:
393:
392:
384:
334:is conformable.
305:Mynydd Llangatwg
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30:
21:
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431:
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428:
427:
408:
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400:
396:
386:
385:
381:
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362:, southwest of
360:Gower Peninsula
348:Carmarthenshire
346:) in southwest
340:
338:Origin of names
293:Tair Carn Uchaf
285:
225:Twrch Sandstone
213:
59:
28:
23:
22:
18:Twrch Sandstone
15:
12:
11:
5:
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394:
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57:St Bride's Bay
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26:
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14:
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10:
9:
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3:
2:
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370:near Marros.
369:
365:
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357:
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349:
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335:
333:
329:
328:unconformable
325:
320:
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311:in the east.
310:
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298:
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290:
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273:
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257:
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245:Coal Measures
242:
241:Farewell Rock
238:
234:
230:
226:
223:known as the
222:
218:
210:
208:
206:
202:
201:Peak District
198:
194:
190:
186:
183:
182:Carboniferous
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175:
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165:Pembrokeshire
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105:20 m to 750 m
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31:
19:
397:
388:
382:
341:
321:
286:
277:
253:
249:marine bands
232:
228:
224:
214:
211:Stratigraphy
203:of northern
174:Marros Group
173:
171:
33:Marros Group
289:Carreg Dwfn
412:Categories
374:References
356:Bishopston
352:Afon Twrch
283:Landscapes
219:of coarse
237:mudstones
221:sandstone
187:in South
136:limestone
122:sandstone
110:Lithology
102:Thickness
82:Underlies
74:Sub-units
231:and the
197:Pennines
178:Namurian
142:Location
119:mudstone
92:Overlies
43:Namurian
364:Swansea
358:on the
313:Faulted
205:England
147:Country
115:Primary
344:Marros
235:. The
185:Period
157:Extent
189:Wales
151:Wales
132:chert
128:Other
68:Group
307:and
217:unit
199:and
172:The
64:Type
414::
319:.
295:,
291:,
251:.
163:,
134:,
41::
20:)
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