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Heavy minerals as a guide to turbidite provenance in the Lower Palaeozoic Southern Welsh Basin: a pilot study

Published online by Cambridge University Press:  01 May 2009

A. C. Morton ,
J. R. Davies  and
R. A. Waters
A. C. Morton
Affiliation:
British Geological Survey, Keyworth, Nottingham NG12 5GG, U.K.
J. R. Davies
Affiliation:
British Geological Survey, Bryn Eithyn Hall, Llanfarian, Aberystwyth, Dyfed SY23 4BY, U.K.
R. A. Waters
Affiliation:
British Geological Survey, Bryn Eithyn Hall, Llanfarian, Aberystwyth, Dyfed SY23 4BY, U.K.
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Abstract

A pilot study has demonstrated that heavy mineral analysis is a useful guide to the provenance of Silurian turbidites in the Southern Welsh Basin. The results confirm the sedimentological evidence for two distinct source areas of coarse clastic detritus, one lying to the south and the other to the east. They also provide mineralogical criteria by which the two source areas may be distinguished. The southern area provided material with relatively low mineral diversity, and is characteristic in having low rutile/zircon ratios, whereas the eastern source provided more diverse assemblages, generally with high rutile/zircon ratios. The southern source shows variations in terms of apatite/tourmaline ratio, with the older Aberystwyth Grits Group tending to contain relatively low apatite compared with the younger Cwmystwyth Grits Group (Rhuddnant and Pysgotwr Grits formations). There is evidence for polycyclic material and volcanic detritus in both southerly and easterly derived samples; however, easterly-sourced sandstones apparently tapped a more lithologically-diverse terrain.

Type
Articles
Information
Geological Magazine , Volume 129 , Issue 5 , September 1992 , pp. 573 - 580
Copyright
Copyright © Cambridge University Press 1992

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References

British Geological Survey. In press, a. 1:50000 Sheet 179 (Rhayader).Google Scholar
British Geological Survey. In press, b. 1:50000 Sheet 178 (Llanilar).Google Scholar
Cave, R. 1979. Sedimentary environments of the basinal Llandovery of mid-Wales. In The Caledonides of the British Isles - reviewed (eds Harris, A. L., Holland, C. H., and Leake, B. E.), pp. 517–526. Special Publication, Geological Society of London No. 8.Google Scholar
Cave, R. & Hains, B. A. 1986. Geology of the country between Aberystwyth and Machynlleth. Memoir of the British Geological Survey, Sheet 163 (England and Wales).Google Scholar
Cummins, W. A. 1957. The Denbigh Grits; Wenlock greywackes in Wales. Geological Magazine 94, 433–51.Google Scholar
Cummins, W. A. 1969. Patterns of sedimentation in the Silurian rocks of Wales. In The Pre-Cambrian and Lower Palaeozoic rocks of Wales (ed. Wood, A.), pp. 219–34. Cardiff: University of Wales Press.Google Scholar
Davies, J. R., Fletcher, C. J. N., Waters, R. A., Wilson, D., Woodhall, D. G. & Zalasiewicz, J. A. in press. Geology of the country around Llanilar and Rhayader. Memoir of the British Geological Survey, Sheets 178 and 179 (England and Wales).Google Scholar
Force, E. R. 1980. The provenance of rutile. Journal of Sedimentary Petrology 50, 485–8.Google Scholar
Galehouse, J. S. 1971. Point-counting. In Procedures in Sedimentary Petrology (ed. Carver, R. E.), pp. 385–407. New York: Wiley-Interscience.Google Scholar
Hansley, P. F. 1987. Petrologic and experimental evidence for the etching of garnets by organic acids in the Upper Jurassic Morrison Formation, northwestern New Mexico. Journal of Sedimentary Petrology 57, 666–81.Google Scholar
Henningsen, D. 1967. Crushing of sedimentary rock samples and its effect on shape and number of heavy minerals. Sedimentology 8, 253–5.CrossRefGoogle Scholar
James, D. M. D. & James, J. 1969. The influence of deep fractures on some areas of Ashgillian-Llandoverian sedimentation in Wales. Geological Magazine 106, 562–82.CrossRefGoogle Scholar
Kelling, G. 1962. The petrology and sedimentation of Upper Ordovician rocks in the Rhinns of Galloway, south-west Scotland. Transactions of the Royal Society of Edinburgh 65, 107–37.CrossRefGoogle Scholar
Kelling, G. & Woollands, M. A. 1969. The stratigraphy and sedimentation of the Llandoverian rocks of the Rhayader district. In The Pre-Cambrian and Lower Palaeozoic rocks of Wales (ed. Wood, A.), pp. 255–82. Cardiff: University of Wales Press.Google Scholar
Loydell, D. K. 1991. The biostratigraphical and formational relationships of the upper Aeronian and lower Telychian (Llandovery, Silurian) formations of western mid-Wales. Geological Journal 26, 209–44.CrossRefGoogle Scholar
Mackie, A. & Smallwood, S. 1987. A revised stratigraphy and sedimentology of the Abergwesyn-Pumpsaint area, Mid-Wales. Geological Journal 22, 45–60.Google Scholar
Milliken, K. L. 1988. Loss of provenance information through subsurface diagenesis in Plio-Pleistocene sandstones, northern Gulf of Mexico. Journal of Sedimentary Petrology 58, 992–1002.Google Scholar
Morton, A. C. 1984. Stability of detrital heavy minerals in Tertiary sandstones of the North Sea Basin. Clay Minerals 19, 287–308.Google Scholar
Morton, A. C. 1985. A new approach to provenance studies: electron microprobe analysis of detrital garnets from Middle Jurassic sandstones of the northern North Sea. Sedimentology 32, 553–66.CrossRefGoogle Scholar
Morton, A. C. & Smale, D. 1990. The effects of transport and weathering on heavy minerals from the Cascade River, New Zealand. Sedimentary Geology 68, 117–23.CrossRefGoogle Scholar
Morton, A. C., Stiberg, J. P., Hurst, A. & Qvale, H. 1989. Use of heavy minerals in lithostratigraphic correlation, with examples from the Brent sandstones of the northern North Sea. In Correlation in Hydrocarbon Exploration (ed. Collinson, J.), pp. 217–30. London: Graham & Trotman.CrossRefGoogle Scholar
Smith, A. J. & Long, G. H. 1969. The Upper Llandovery sediments of Wales and the Welsh Borderlands. In The Pre-Cambrian and Lower Palaeozoic rocks of Wales (ed. Wood, A.), pp. 239–54. Cardiff: University of Wales Press.Google Scholar
Smith, R. D. A. 1987 a. The griestoniensis Zone Turbidite System, Welsh Basin. In Marine Clastic Sedimentology: Concepts and Case Studies (eds Leggett, J. K. and Zuffa, G. G.), pp. 89–107. London: Graham & Trotman.CrossRefGoogle Scholar
Smith, R. D. A. 1987 b. Structure and deformation history of the Central Wales Synclinorium, northeast Dyfed: Evidence for a long-lived basement structure. Geological Journal 22, 183–98.CrossRefGoogle Scholar
Smith, R. D. A. 1990. Discussion on palaeocurrent evidence for a northern structural high to the Welsh Basin during the late Llandovery. Journal of the Geological Society 147, 886–7.Google Scholar
Smith, R. D. A., Waters, R. A. & Davies, J. R. 1991. Late Ordovician and early Silurian turbidite systems in the Welsh Basin. 13th International Geological Congress, Nottingham, Field Guide No. 20. British Sedimentological Research Group, Cambridge, 45 pp.Google Scholar
Soper, N. J. & Woodcock, N. H. 1990. Silurian collision and sediment dispersal patterns in southern Britain. Geological Magazine 127, 527–42.CrossRefGoogle Scholar
Styles, M. T., Stone, P. & Floyd, J. D. 1989. Arc detritus in the Southern Uplands: mineralogical characterisation of a ‘missing’ terrane. Journal of the Geological Society 146, 397–400.CrossRefGoogle Scholar
Warren, P. T., Price, D., Nutt, M. J. C. & Smith, E. G. 1984. Geology of the country around Denbigh and Rhyl. Memoir of the British Geological Survey, Sheets 95 and 107 and parts of Sheets 94 and 106 (England and Wales).Google Scholar
Waters, R. A., Davies, J. R., Fletcher, C. J. N., Wilson, D., Zalasiewicz, J. A. & Cave, R. 1992 a. Llandovery basinal and slope sequences of the Rhayader District. In Geological excursions in Powys, Wales (eds Woodcock, N. H. and Bassett, M. G.); in press. Cardiff: University of Wales Press, National Museum of Wales and Geologists' Association (South Wales Group).Google Scholar
Waters, R. A., Davies, J. R., Fletcher, C. J. N. & Wilson, D. 1992 b. Discussion of ‘A late Ordovician/early provenance Silurian non-depositional slope and perched basin along the Twyi Anticline, Mid Wales’ by D. M. D. James (1991). Geological Journal 27 (in press).Google Scholar
Wilson, D., Dames, J. R., Fletcher, C. J. N. & Waters, R. A. 1992 a. The Ordovician rocks of the Rhayader district. In Geological excursions in Powys, Wales (eds. Woodcock, N. H. and Bassett, M. G.); in press. Cardiff: University of Wales Press, National Museum of Wales and Geologists' Association (South Wales Group).Google Scholar
Wilson, D., Davies, J. R., Waters, R. A. & Zalasiewicz, J. A. 1992 b. A fault-controlled depositional model for the Aberystwyth Grits turbidite system. Geological Magazine 129, 595–607.CrossRefGoogle Scholar
Wood, A. & Smith, A. J. 1959. The sedimentation and sedimentary history of the Aberystwyth Grits (Upper Llandoverian). Quarterly Journal of the Geological Society of London 114, 163–95.CrossRefGoogle Scholar
Woodcock, N. H. 1990. Transpressive Acadian deformation across the Central Wales lineament. Journal of Structural Geology 12, 329–37.CrossRefGoogle Scholar