Early Devonian graptolites from Limekilns, New South Wales

WA Museum Records and Supplements | Updated 1 decade ago

Abstract - Graptoloids from the Limekilns district of New South Wales, Australia, previously recorded as the Pragian Monograptus yukonensis by Packham (in Strusz et al. 1972), are reidentified and described as Monograptus uniformis uniformis, based upon original and new collections. This subspecies is a clear indicator of the earliest Devonian, Lochkov Monograptus uniformis Biozone and the occurrence is the first unequivocal record of the Biozone in Australia.

As other palaeontological data from the Limekilns area have indicated a Pragian age for the lower shaley part of the Limekilns Formation and its presumed correlative, the lower part of the Cunningham Formation, this new graptolite identification and the inferred correlation create alignment problems which are discussed but not resolved. The most obvious possible explanations of this situation are: (1) the Limekilns graptolite horizon does have a correlative level in the lower part of the Cunningham Formation which has not yet yielded diagnostic fossils; or (2) there are no equivalent strata in the Cunningham Formation, presumably due to non-deposition or erosion in the Hill End Trough sequence.

Dendrograptus sp. is noted from the Limekilns locality. A graptolite specimen previously record questionably as M. uniformis, from the Pridoli of Cheeseman's Creek, NSW, is reidentified and described as M. prognatus.

A review of all known records and claims of Devonian graptolites in Australia indicates that the valid Lochkov records are M. u. uniformis from Limekilns and M. aequabilis from Victoria. Valid Pragian records are M. thomasi from Victoria and Tasmania, and M. aequabilis notoaequabilis and M. aequabilis cf. notoaequabilis from Victoria.