Conodont faunas from sequences on or marginal to the Anakie Inlier (Central Queensland, Australia) in relation to Devonian transgressions


Authors: Mawson R, Talent JA

Published in: Bulletin of Geosciences, volume 78, issue 4; pages: 335 - 358; Received 11 August 2003; Accepted in revised form 24 September 2003;

Keywords: Conodonts, Devonian, Emsian, Eifelian, Famennian, transgressions, Queensland, Australia,

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Sedimentary intervals with limestones reflecting transgressive/regressive (T/R) events of various ages on or marginal to the Anakie Inlier in east-central Queensland are displayed in the Ukalunda Beds at Mary Creek, Douglas Creek Limestone at Copperfield, Greybank Volcanics near Fletchers Awl, the Glendarriwell Beds near Anakie, and the Sedgewick Formation south of Alpha. Conodonts from these and other occurrences enable the ages of these events to be specified:
o Conodonts from the Douglas Creek Limestone, resting unconformably on Proterozoic Bathampton Metamorphics, demonstrate that this transgressive event commenced sometime late in the perbonus/gronbergi/nothoperbonus interval, with marine conditions persisting through until at least well into the inversus Zone. The transgression was therefore coeval with a deepening event well displayed in the Buchan-Murrindal area of eastern Victoria.
o Conodonts from the Ukalunda Beds show that at least part of that sequence accumulated during the perbonus/gronbergi/nothoperbonus and inversus zones coeval with accumulation of the Douglas Creek Limestone.
o Conodonts from the allochthonous limestone occurrences in the Dunstable Beds at 'Telemon' document carbonate sedimentation, at least in that area, through much or all of the interval from at least inversus Zone (but possibly perbonus/gronbergi/nothoperbonus interval as well) through to late Eifelian australis and kockelianus zones or even earliest Givetian.
o Conodonts from the exposures of Sedgeford Formation indicate an age within the interval late Eifelian (australis Zone) to earliest Givetian (hemiansatus Zone). These provide an age for what were arguably nearshore regressive environments, broadly coeval with the youngest limestones of a 'now lost carbonate platform' or fringing reefs, the source of the allochthonous limestone clasts in the primarily volcaniclastic Dunstable Beds.
o Conodonts from a marine transgression at the base of the Greybank Volcanics near Fletcher's Awl date the transgression as Late and/or Latest crepida Zone (Late Devonian; mid-early Famennian). This corresponds precisely with a global transgression event within interval IIe of the Johnson et al. (1985) T-R scheme inferred from Euramerican sequences. In an appendix, the previously imprecisely calibrated transgression event in the Coffee Hill Member at the base of the Columbine Sandstone in east-central New South Wales is argued to represent the same event.
o Conodonts from the Glendarriwell Limestone on the southern flank of the Anakie Inlier document a marine incursion at the base of the middle Famennian marginifera Zone. This transgression, identified from many areas around the world and widespread in the Burdekin Basin (Mawson and Talent 1997), is here named the Myrtlevale Transgression.