Silicified faunas, dominated by brachiopods (55 species: an increase of 64% over previous reports), from low in the Early Devonian (mid-Lochkovian) Garra Limestone at Manildra, east-central New South Wales, are documented, complemented by documentation of associated tabulate and rugose corals (12 and 4 species respectively), and conodonts (14 species and subspecies from 57 samples), pivotal in assessing the age of these faunas. Other, surprisingly rare, elements (principally molluscs) are reported but not documented. Also documented are the tabulate and rugose corals from the immediately underlying uppermost Maradana Shale - 4 and 2 spp. respectively, all occurring as well, though less well-preserved, among the silicified faunas of the Garra Limestone - and conodonts from carbonate intervals in the overlying Mandagery Park Formation. The conodont faunas indicate maximum ages of delta Zone for the Garra Limestone at Manildra and pesavis Zone to early Pragian for carbonates in the overlying Mandagery Park Formation. The silicified brachiopod assemblage from the lower beds of the Garra Limestone has Old World Realm biogeographic affinities with noteworthy connections with various brachiopod assemblages from western North America and Arctic Canada. Closest affinities are with the early Quadrithyris Zone or transitional Gypidula pelagica-Quadrithyris Zone of Nevada. Contrary to recent assumptions that the provincial sensitivity of brachiopods makes them of very limited value in making long-range stratigraphic alignments, the consistent ages resulting from conodont data and comparison of the brachiopod faunas with Early Devonian faunas from western and Arctic North America is evidence that compelling stratigraphic alignments may be obtained intercontinentally using brachiopods - providing, as in the present case, the faunas are diverse and are from the same biogeographic realm. New data are provided for as sessing the sedimentary context, palaeoecology and biogeographic affinities of the brachiopod, coral and conodont faunas from Manildra. The deeper-water Maradana Shale shallows upwards into the shallow marine, brachiopod-dominated Garra Limestone. The latter is characterised by angular, poorly sorted allochemical constituents, high mud contents, and encrusting algal mats of Girvanella, all implying low-energy conditions with limited post-mortem transport. This is supported by the relatively low degree of valve disarticulation of the silicified brachiopod assemblages. The sedimentological data accord with a shallow (photic zone), open marine environment, with moderate to low-energy conditions of a protected zone within a carbonate platform or shelf-margin. The Garra Limestone is terminated by an influx of clastics and volcaniclastics, the Mandagery Park Formation (redefined). The 55 species of brachiopods from the Garr a Limestone at Manildra are referred to 36 genera including two new rhynchonellid genera, Protodorsisinus and Discamella, with type species P. similis sp nov. and D. troparvis sp. nov. respectively. A new species of the cemented strophomenid, Colletostracia, is described but not named. None of the coral and conodont taxa documented appear to be new.
|Number of pages||54|
|Journal||Palaeontographica, Abteilung A: Palaozoologie - Stratigraphie|
|Publication status||Published - Oct 2005|