Sedimentology, structural evolution and tectonic setting of the late Precambrian Longmyndian Supergroup of the Welsh Borderland, UK
| Autor: | J. C. Pauley |
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| Rok vydání: | 1990 |
| Předmět: | |
| Zdroj: | Geological Society, London, Special Publications. 51:341-351 |
| ISSN: | 2041-4927 0305-8719 |
| DOI: | 10.1144/gsl.sp.1990.051.01.22 |
| Popis: | The Longmyndian Supergroup is an approximately 6500 m thick sedimentary sequence of late Precambrian age. Major unconformities within this sequence are lacking. The Longmyndian Supergroup can be divided into four facies associations: (1) turbidite, (2) subaqueous delta, (3) alluvial floodplain, and (4) braided alluvial. These are organized into a single, broadly upwards-coarsening, progradational sequence, with the turbidite association at the base and the braided alluvial association towards the top. The sediments are interpreted to have been deposited in a forearc, or possibly interarc, basin which lay to the north of a contemporaneous magmatic arc, of which the (now adjacent) Uriconian Volcanic Complex is considered to have been a part. The Longmyndian Supergroup has been deformed into a tight NNE-SSW trending syncline. Fault patterns and strain markers within the Longmyndian indicate that it was deformed during sinistral transpression. The adjacent Pontesford-Linley and Church Stretton fault systems are considered to be major strike-slip fault systems which were initiated at about the same time as the deformation of the Longmyndian Supergroup. Strike-slip movements along these fault systems resulted in the juxtaposition of the Uriconian Volcanic Complex with the Longmyndian Supergroup. Late Precambrian/early Cambrian deformation is indicated by some stratigraphic and radiometric age-dating evidence. Since there is evidence that the fault systems have suffered strike-slip displacements during the Palaeozoic it is difficult to be certain of the magnitude and style of the late Precambrian/early Cambrian deformation. However, the recognition of late Precambrian/early Cambrian sinistral transpressional deformation in northwest Wales suggests that the Precambrian of the Welsh Borderland was similarly deformed during the late Precambrian/early Cambrian. |
| Databáze: | OpenAIRE |
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