| 词条 | Solva Group |
| 释义 |
| name = Solva Group | image =File:Cliffs at Porth Clais - geograph.org.uk - 479405.jpg | caption =Steeply-dipping sandstones of the Solva Group, just west of Porth Clais | type = Group | age = St David’s Epoch Cambrian | prilithology = sandstones | otherlithology = mudstones | namedfor = Solva | namedby = | region = west Wales | country = Wales | coordinates = | unitof = | subunits = Lower, Middle & Upper Solva (informal) | underlies = Menevian Group | overlies = Caerfai Group | thickness = about 500m | extent = | area = | map = | map_caption = }} The Solva Group is a Cambrian lithostratigraphic group (a sequence of rock strata) in west Wales. The name is derived from Solva on the west coast of Pembrokeshire where the strata are well exposed in coastal cliffs. This rock succession was formerly known as the Solva Series and ascribed to the British regional stratigraphic unit ‘’St David’s Epoch’’, though these terms are now obsolete.[1] OutcropsThese rocks are exposed, along the north coast of St Brides Bay south of St Davids and in particular at Caer Bwdy Bay just southeast of the city where they are seen to overlie the Caerbwdy Sandstone Formation. They are exposed again in the sides of the ria at Solva and occur more widely inland of the village though exposures are less frequent. There are less extensive outcrops further west at St Justinian and on Ramsey Island. To the east they occur again north of Newgale and at Tancredston and to the west of Wolf's Castle.[2] Lithology and stratigraphyThe Group comprises around five hundred metres thickness of occasionally pebbly, green and purple sandstones together with mudstones and siltstones. Trilobite, brachiopod and acritarch fossils are present. Trace fossils suggest that the sediments were laid down in shallow marine conditions though the thick middle sequence is characterized by turbidites and is much less fossiliferous.[3][4] References1. ^{{cite web |url=http://www.bgs.ac.uk/Lexicon/lexicon.cfm?pub=SOS |title=Solva Group |work=The BGS Lexicon of Named Rock Units |publisher=British Geological Survey |accessdate=Oct 8, 2013}} 2. ^British Geological Survey 1:50,000 scale geological map (England & Wales) sheets 209 St David's, 210 Fishguard 3. ^{{cite book|last=Howells|first=M.F.|title=British regional geology : Wales|year=2007|publisher=British Geological Survey|location=Nottingham|isbn=978-085272584-9|page=30|edition=1st }} 4. ^{{cite book|editor-last=Brenchley|editor-first=P.J.|title=The geology of England and Wales.|year=2006|publisher=Geological Society Publishing|location=London|isbn=9781862392007|pages=37, 38|edition=2.|author=London, P.F. Rawson. The Geological Society}} 4 : Cambrian System of Europe|Geology of Wales|Geological groups|Geologic formations of the United Kingdom |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。