Barremian-Cenomanian palaeotemperatures for Australian seas based on new oxygen-isotope data from belemnite rostra

Oxygen‐isotope ratio (δ¹⁸O) data are presented for 55 belemnite rostra specimens of late Aptian–Albian age from the Great Artesian Basin of eastern Australia and of late Barremian–early Cenomanian age from the Carnarvon Basin of Western Australia. The belemnites were carefully screened for diagenesis by means of catholuminescence and trace element geochemistry. The δ¹⁸O record for the Carnarvon Basin (palaeolatitude ~40°S) is interpreted to show a long‐term warming trend from ~10 °C in the Aptian to a maximum of ~15 °C in the Cenomanian. Shorter-term fluctuations in the mid-Albian are also apparent. Data from the Great Artesian Basin (palaeolatitude 40°–55°S) show a wider δ¹⁸O range which is attributed to the epeiric sea context of this sample set. The larger range in δ¹⁸O is interpreted to reflect differing water mass characteristics, due possibly to a combination of variable freshwater dilution, seasonal temperature fluctuations and isotopic exchange between seawater and pyroclastic sediment within the epeiric sea. Nevertheless, the Aptian–Albian δ¹⁸O trends are still comparable to those obtained for the Carnarvon Basin. The inferred palaeotemperature trends for the Australian sedimentary basins are consistent with records from other regions and demonstrate that broadly synchronous palaeotemperature variations can be recognised on a global scale during the Cretaceous. Although our data do indeed show cool temperatures within the Aptian (and the Albian) reaching a low of ~10 °C, these estimates are somewhat warmer than those based on glendonite genesis. However, the exact position of the glendonite-bearing and dropstone-rich parts of the Bulldog Shale is poorly constrained with respect to our isotope data, and the warmest temperatures were of late Albian and early Cenomanian age. However, to conform to greenhouse warmth and equability, and to achieve parity with other palaeotemperature records, the δ¹⁸O(seawater) estimate of −1.0‰ that is generally used for Cretaceous oceans in an ice-free world needs to be adjusted to a slightly higher value

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Not AvailableTwelve crossbred pigs (32.10±1.03 kg, 3.8 months) were divided into two groups of six each in a completely randomized block design to study the effect of replacing maize with sugar beet on nutrient utilization. Animals were fed on two different rations containing 0% and 10% sugar beet in T1 and T 2 groups respectively. The protein content (% DM) of the ration ranged from 17.95±0.06 in ration T2 to 18.41±0.05 in ration T1. Nitrogen free extract content (% DM) of the rations ranged from 67.36±0.13 in ration T1 to 67.13±0.18 in ration T 2. The digestibility coefficient of dry matter, organic matter, crude protein, crude fibre, ether extract and nitrogen free extract was similar in T1 and T2 groups. The average daily gain (g/day) was 266.67±33.34 in T1 and 283.33±16.67 in T2 groups. The growth was found similar among the groups. The feed conversion ratio was 3.43±0.43 in T1 and 3.19±0.19 in T2 groups which was similar among the groups. It is concluded that 10% replacement of maize with sugar beet did not alter production performance of crossbred grower pigs.Not Availabl

Ubiquitous karst hydrological control on speleothem oxygen isotope variability in a global study

Speleothem oxygen isotopic (δ¹⁸O) records are used to reconstruct past hydroclimate yet records from the same cave do not always replicate. We use a global database of speleothem δ18O to quantify the replicability of records to show that disagreement is common worldwide, occurs across timescales and is unrelated to climate, depth or lithology. Our global analysis demonstrates that within-cave differences in mean speleothem δ¹⁸O values are consistent with those of dripwater, supporting a ubiquitous influence of flowpaths. We present a case study of four new stalagmite records from Golgotha Cave, southwest Australia, where the isotopic differences between them are informed by cave monitoring. It is demonstrated that karst hydrology is a major driver of within-cave speleothem and dripwater δ¹⁸O variability, primarily due to the influence of fractures on flowpaths. Applying our understanding of water movement through fractures assists in quantitative reconstruction of past climate variability from speleothem δ¹⁸O records.Pauline C. Treble, Andy Baker, Nerilie J. Abram, John C. Hellstrom, Jagoda Crawford, Michael K. Gagan, Andrea Borsato, Alan D. Griffiths, Petra Bajo, Monika Markowska, Stacey C. Priestley, Stuart Hankin, David Paterso