Late Ordovician to Early Devonian graptolite sequences in Australia

• Autorzy: Sherwin L.
• Języki publikacji: EN

Abstrakty

EN

Late Ordovician graptolites are commonest in the Australian states of Victoria and New South Wales, occurring in sediments which are either folded into complex structures or else interrupted by massive thickness of volcanics and associated with frequent facies changes. Thus it has not been possible to construct a series of zones which have either continuity or an established order of appearance. Present knowledge also suggests that differences occur between coeval faunas from volcanic and no-volcanic strata. Silurian graptolites are most common and best preserved in New South Wales. The full sequence of graptolite zones devised in Britain cannot be recognized in Australia. This can be explained partly on failure of outcrop, and partly upon regional hiatuses. The most continuous Llandovery sequences are in areas with a widespread cover of Cainozoic volcanics and gravels. Nonetheless, the Llandovery zones so far recognized, principally cyphus-gregarius and turriculatus- crisplts, are very wide-spread and occur in differing environments, so that non-representation of zones cannot be attributed wholly to collecting failure. These zones are among those most readily recognized throughout the world, which probably results from their being based upon distinct, easily identified species, and their comparatively long duration. The Wenlock zones are those most poorly represented, this being the part of the Silurian in New South Wales and eastern Victoria most affected by orogenic activity. In areas of central Victoria where sedimentation is believed to have been continuous throughout the Wenlock, the sediments have suffered extensive bioturbation and graptolites are absent. In addition, the extreme rarily of Cyrtograptus means that it is often very difficult to tie an assemblage with an overall Wenlock aspect to any particular zone. The Late Silurian graptolites are those which are most widely distributed, and it has been possible to recognize most of the zones described from the Ludlow and Pridoli of Europe. Sedimentary sequences which cross the Siluro-Devonian boundary are common, but graptolites in Early Devonian strata are frequently in isolated beds separated by great thickness of non-graptolitic strata.

• Wydawca: -
• Czasopismo: Acta Palaeontologica Polonica
• Rocznik: 1979
• Tom: 24
• Numer: 1
• Opis fizyczny: p.155-163,fig.,ref.

Twórcy

autor

Sherwin L.

• Geological Mining Museum, 36 George Street, Sydney N.S.W. 2000 Australia

Bibliografia

• BAILLIE, P. W., BANKS, M. R, and RICKARDS, R. B. - Early Silurian Graptolites from Tasmania and their significance. - Search, (in press).
• BEAVIS, F. C., 1976. Ordovician graptolite faunas in Australia. - J. geol. Soc. Aust., 22 (4), 447-456.
• BROWN, I. A., and SHERRARD, K. 1952. Graptolite zones in the Silurian of the Yass - Bowning District, N. S. W. - J. Proc. Roy. Soc. N. S. W., 85, 127-133.
• CUERDA, A. J. 1974. Monograpten aus dem Ludlow Boliviens. - N. Jb. Geol. Paläont. Mh., 6, 321-335.
• DOUGLAS, J. G., and FERGUSON, J. A., (eds.). 1976. Geology of Victoria. - Spec. Publ. Geol. Soc. Aust., 5, xi +528.
• JAEGER, H. 1967. Preliminary stratigraphical results from graptolite studies in the Upper Silurian and Lower Devonian of southeastern Australia. - J. geol. Soc. Aust., 14 (2), 281-286.
• PACKHAM, G. H. 1968. Monograptus cf. ultimus Perner and Monograptus formosus Bouček from the Hume Series of the Yass district, New South Wales. - Proc. Linn. Soc. N. S. W., 92 (3), 217-221.
• - 1969. The geology of New South Wales. - J. geol. Soc. Aust., 16 (1), xx+654.
• PICKETT, J. W. 1980. The Silurian System in New South Wales. - Mem. geol. Surv. N. S. W. (in press).
• SHERWIN, L. 1971. Stratigraphy of the Cheesemans Creek district, New South Wales. - Rec. geal. Surv. N. S. W., 13 (4), 199-237.
• - 1973. Stratigraphy af the Forbes-Bogan Gate District. - Rec. geol. Surv. N. S. W., 15 (1), 47-101.
• - 1974. Llandovery graptolites from the Forbes District, N. S. W., 149-75. In: Rickards, R B., Jackson, D. E. and Hughes, C. P. Graptolite studies in honour of O. M. B. Bulman. - Spec. Pap. Palaeant., 13, 261 pp.
• - 1975. Silurian graptolites from the Forbes Group, New South Wales. - Rec. geol. Surv. N. S. W., 16 (3), 227-237.
• - 1976. The "Secrets" section through the Cotton Beds. - Q. Notes geol. Surv. B. S. W., 24, 6-10.
• STRUSZ, D. L. 1972. Correlation of the Lower Devonian Rocks of Australasia. - J. geol. Soc. Aust., 18 (4), 427-455.
• TALENT, J. A., et al. 1975. Correlation of the Silurian rocks of Australia, New Zealand, and New Guinea. - Geol. Soc. Amer., Spec. Pap. 150, 108 pp.
• THOMAS, D. E. 1960. The zonal distribution of Australian Graptolites; with a revised bibliography of Australian Graptolites. - Proc. R. Soc. N. S. W., 94 (1), 1-58.
• - and KEBLE, R. A. 1933. The Ordovician and Silurian Rocks of the Bulla-Sunbury Area and discussion of the sequence in the Melbourne Area. - Proc. Roy. Soc. Vic., 45, 33-84.
• WEBBY, B. D. 1976. The Ordovician System in south-eastern Australia, 417-446. In: Basset, M. G. (ed.). The Ordovician System: proceedings of a Palaeontological Association Symposium; Birmingham, September, 1974, 696 pp., University of Wales Press and National Museum of Wales, Cardiff.