Synchronous very low-grade metamorphism, contraction and inversion in the central part of the Welsh Lower Palaeozoic Basin
| Autor: | Steven Hirons, B. Roberts, D. Wilson, C. J. N. Fletcher, Richard J. Merriman |
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| Rok vydání: | 1996 |
| Předmět: | |
| Zdroj: | Journal of the Geological Society. 153:277-285 |
| ISSN: | 2041-479X 0016-7649 |
| DOI: | 10.1144/gsjgs.153.2.0277 |
| Popis: | A metamorphic map (white mica crystallinity) based on 663 data points has been generated for the recently published British Geological Survey 1:50 000 geological sheets 178 (Llanilar) and 179 (Rhayader). Epizone, upper anchizone, lower anchizone and sub-anchizone are delineated. Metamorphic cross-sections are drawn and superimposed on structural cross-sections. Assumptions made in order to draw metamorphic cross-sections are: (1) the anchizone spans 100°C; (2) the metamorphic field gradient was 36°Ckm −1 ; (3) metamorphic surfaces were initially generated parallel to the contemporary ground surface. Restoration of the sections indicates that at the time of metamorphism a contractional phase had begun because reverse movement on earlier extensional faults, development of back-thrusts, footwall short-cuts and limited growth of precursor folds had taken place. Metamorphism continued locally during later stages of the contractional phase as a strain-related phenomenon. Finally, tensional faulting followed the cessation of folding and metamorphism. |
| Databáze: | OpenAIRE |
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