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NEWSIn the news this issuen Chinaman Creek Limestonen National Rock Garden updaten IGCP FundingNational Rock Garden —Chinaman Creek LimestoneGSA Rock of the Month — September 2012This new TAG feature will highlight some of Australia’s most interestingrocks — rocks that are spectacular or scientifically, economically orculturally significant, and potentially likely to be featured in the NationalRock Garden (NRG). Please let us know if you think they should or shouldnot be included. The NRG is a project initiated by GSA to celebrate thegeological heritage of Australia, to build a unique and fascinatinggeoscience education facility for the 165 000+ school students from allover Australia that visit their national capital each year. The NRG aimsto promote the role that geology plays in the lives of all Australians.If you have a passion for or interest in the geosciences, or theeducation of our children, or have drawn a livelihood from industriesderived from our rocks, please help us establish a globally uniquecelebration of the geology of Australia in our nation’s capital.We have selected the Devonian Chinaman Creek Limestone from theBroken River Province of North Queensland as our first ‘Rock of theMonth’ because it is spectacular, acquirable and displays a significantcollection of fossils, many yet to be documented. Are there moreimportant Devonian fossiliferous limestones available that are equallyor more spectacular?The Chinaman Creek Limestone is a major component of the BrokenRiver Group that formed a broad shelfal succession in the northern partof the Graveyard Creek Subprovince, southwest of Greenvale in northQueensland. The formation is up to 790 m thick and consists largely ofclastic limestone intervals up to 250 m thick of very thick to thin-beddedcalcirudite and calcarenite and sporadic, thin interbeds of calcareousmudstone, siltstone and sandstone. More substantial siliciclasticintervals of lithic sandstone, siltstone and mudstone, and rareconglomerate up to 100 m thick are interlayered.Reefal limestone intervals up to 30 m thick and 2 km long are locallyrepresented in the unit, mainly in its lower parts. These are mainlystromatoporoid–heliolitid–rugose coral framestone, with prominentheads of the rugosans Endophyllum and Phillipsastraea in the upper andlower parts of the succession, respectively.Bioclastic components are largely of stromatoporoid or corallinedebris (with Amphipora characteristics), but fragments of crinoids,brachiopods, bivalves, gastropods, ostracods and calcareous algae arealso represented. Corals and stromatoporoids are locally found in growthpositions and large valves of Stringocephalus and megalodont bivalvesare prominent in the upper part (Withnall, 2012).Devonian Chinaman Creek Limestone from north Qld, also featuring LindaMcClure, Marketing Manager, North Queensland Marble Pty Ltd. The limestoneis quarried near the old Pandanus Creek homestead and is being sawnon-site and transported to Townsville for shipment overseas. The companyspecialises in rare and unique ‘top end of the market’ dimension stones forthe international market. Image courtesy Rob Cameron (North QueenslandMarble Pty Ltd), 2012.Megalodont bivalves (superfamily Megalodontoidea) are unusualand very distinctive fossils of the middle Paleozoic to early Mesozoic.Many species are large and thick-shelled, and have great preservationpotential. So, it is surprising that, although these clams had a largelycosmopolitan distribution in the Silurian and Devonian and were locallyvery abundant, their taxonomy and paleoecology are poorly known. Theywere inclined mud resters, oriented with sagittal plane vertical, and grewpartly submerged in, or on top of, generally firm lime mud substrates,in tropical shallow water (de Freitas et al, 1993).Megalodont bivalves are predominant in the spectacular slab oflimestone shown in the photograph accompanying this article.Most of the specimens in the slab represent slices through the ‘beak’part of articulated shells, many still in growth position. Others showdifferent sections of the shell — still the ‘beak’ area but sliced moreobliquely so that a small part of the valves distal to the ‘beak’ are alsoshown (they look like spines). The shells were projecting at an angle fromthe sea-floor (hence the oblique sections) as the slab has been cut atan angle to bedding. Bits of sliced valve away from the thick beak regionshow as much thinner curved white lines (Henderson, 2012).JOHN BAINCurator NRGR E F E R E N C E Sde Freitas, Brunton and Bernecker 1993 Silurian Megalodont Bivalves of theCanadian Arctic and Australia: Paleoecology and Evolutionary Significance. Palaiosvol. 8, p. 450–464.Henderson, Bob (James Cook University) pers. comm. to Rob Cameron May 2012.Withnall, Ian (GSQ), pers. comm. July 2012.TAG September 2012| 23