Oxygen isotopic composition of carbonate concretions from the lower Cretaceous of Victoria, Australia: implications for the evolution of meteoric waters on the Australian continent in a paleopolar environment

Depositional Environment of the Lower Cretaceous (Upper Albian) Winton Formation At Isisford, Central-West Queensland, Australia, Inferred From Sandstone Concretions

“…The moderate negative linear relationship between δ 13 C VPDB and δ 18 O VPDB seen in Figure 9 (Shackleton and Kennett 1975;De Lurio and Frakes 1999;Ferguson et al 1999). Cool water temperatures have previously been estimated for the Eromanga Sea during the Early Cretaceous, with seasonal freezing conditions in the southern portion of the sea between latitudes 70° and 50° S proposed (Haig 1979;Gregory et al 1989;Dettmann et al 1992;Frakes et al 1995;Frakes 1997). Although the presence of these seasonal freezing conditions are debated (Douglas and Williams 1982;Jell and Duncan 1986), there still appears to be a consensus on relatively cool water and air temperatures across eastern Australia during the Early Cretaceous between approximately 10 and 18°C for 54° south, the approximate location of Isisford during the late Albian (based on van Hinsbergen et al 2015) (Stevens and Clayton 1971;Frakes 1997;Williamson 2006;Hay 2011;Price et al 2012;Fletcher et al 2014 (1) where T is temperature in degrees Celsius, δ c is the calcite cement δ 18 O VPDB in ‰, and δ w is the surface water δ 18 O VSMOW in ‰.…”

“…FIG. 11.-Plot of δ 13 C VPDB versus δ 18 O VPDB in calcite cements from both sandstone concretions and nonconcretionary sandstones (in purple), plotted against typical isotopic values recorded for various environments by El Albani et al (2001) 1 , Gregory et al (1989) 2 , Hendry et al (1996) 3 , Longstaffe and Ayalon (1987) 4 , McBride and Milliken (2006) 5 , Pirrie and Marshall (1991) 6 , and Sass and Kolodny (1972) 7 , and modified from figures in Carpenter et al (1988) 8 , Coniglio et al (2000) 9 , McBride et al (2003) 10 , Montaggioni (2009) 11 , andNyman et al (2014) 12 . All values come from calcite cement interpreted as precipitated during shallow burial.…”

“…Shallow-burial end members used in comparison with our data were sourced from the following papers dealing with the isotopic composition of calcite cements in Cretaceous aged sandstones and concretions forming in freshwater, deltaic, estuarine, and shallow marine deposits (given the unknown stratigraphic position of the Winton Formation at Isisford in relation to the conformably underlying marine Mackunda Formation): Sass and Kolodny (1972), Longstaffe and Ayalon (1987), Carpenter et al (1988), Gregory et al (1989), Pirrie and Marshall (1991), Hendry et al (1996) The δ 18 O VPDB values for the Isisford calcite indicates a mixture of fresh and marine water in pore fluids, and closely aligns with the deltaic end member shown in Figure 11. We attribute the wide range of δ 13 C VPDB in the Isisford calcite cement (-5.3 to 4.1 ‰) to fluctuations between methanogenesis and sulfate reduction under anaerobic oxidizing conditions, and varying input of organic matter between aerobic and anaerobic zones.…”

Polar dinosaurs on parade: a review of dinosaur migration

“…Rich et al (1988) described a flora dominated by ginkgoes, podocarps, and araucarian conifers. Isotopic (d 18 O) records indicate that mean annual palaeotemperatures were around 58C (Rich et al 1988, Gregory et al 1989, with seasonal freezing as evidenced by cryoturbation structures (Constantine et al 1998), although Morath & White (2004) have suggested that a marine influence may have had an ameliorating affect on the climate. As such, temperatures were markedly warmer at the poles then than they are today, allowing a flourishing dense polar vegetation that was not conducive to freedom of movement (i.e.…”

Morphological variation of stratigraphically important species in the genus Pilosisporites Delcourt & Sprumont, 1955 in the Gippsland Basin, southeastern Australia

“…The palaeogeographic setting of southeastern Australia was significant in that it was near or inside the Antarctic Circle (Rich and Vickers-Rich, 2000; Wagstaff et al, 2013). Therefore, in spite of the high carbon dioxide levels characteristic of the Cretaceous Greenhouse, and warm and equable global climates (Spicer and Corfield, 1992), it is suggested that in the Aptian-Albian this region would still have been cold (Gregory et al, 1989) and in winter would have experienced months of darkness.…”