Cool Cretaceous climates: new data from the Albian of Western Australia

Abstract

Although previous geological, palaeobotanical and geochemical data from the Albian of Australia have suggested the possibility of cool palaeoclimates, there are few well-constrained stable isotope palaeotemperatures studies from this region. In this paper we present the results of stable isotope analyses of dimitobelid belemnites from the Albian Gearle Siltstone, Carnarvon Basin, Western Australia. Oxygen isotope values for diagenetically least-altered samples give values ranging between δ 18 O −0.02 and 0.85% PDB, which equate to a mean palaeotemperature of 10.08°C (assuming δ w of −1.2% SMOW). This value is broadly consistent with recently published isotope data from the Albian Antarctic and with estimates for mid-Cretaceous latitudinal temperature gradients, implying that cool palaeoclimates occurred during a period of 'Greenhouse' Earth.

CO2-forced climate thresholds during the Phanerozoic

“…Similarly, low CO 2 conditions (<1000 ppm) were present during the earliest Jurassic (Hettangian; Ma) and during brief periods of the mid-Cretaceous (Barremian, Aptian, and Albian; 130.0-99.6 Ma). An increase in the frequency of erratics and diamictites is reported for the Hettangian (Price, 1999), and some evidence exists for cool mid-Cretaceous climates (Frakes et al, 1992;Sellwood et al, 1994;Pirrie et al, 1995;Price, 1999; see also Section 3.5.4), but further work is warranted.…”

Regional to global correlation of lower Cretaceous (Hauterivian–Barremian) shallow-water carbonates of the southern Apennines (Italy) and Dinarides (Montenegro), southern Tethyan Margin

“…Also, high-frequency tectonic movements (''yo-yo tectonics'') as proposed by Cisne (1986) can be excluded since the passive margin of the southern Tethys during the Early Cretaceous was largely evolving in the thermal subsidence phase (Channell et al, 1979;D'Argenio and Alvarez, 1980). Additionally, distinct variations and trends in warming and cooling through the Late JurassicLate Cretaceous climate have been reported (Eyles, 1993;Francis and Frakes, 1993;Sellwood et al, 1994;Abreu et al, 1998;Strasser et al, 2000Strasser et al, , 2001Francis and Poole, 2002) as well as polar glaciations during a greenhouse period (Pirrie et al, 1995), which could produce high-frequency, low amplitude sea-level fluctuations. Still, ''the Mesozoic -Early Cenozoic eustatic history was replete with major sealevel falls of 100 m or more that are comparable in magnitude, if not in frequency, to glacially induced eustatic changes'' (Haq, 1993, p. 104; see also James, 1997;Kroon et al, 2002).…”

Fossil leaves of Banksia, Banksieae and pretenders: resolving the fossil genus Banksieaephyllum

“…Frakes (1999) proposes that the Cretaceous Period also included more temperate intervals, which were accentuated by the effective northward movement of the continent. For example, by the end of the Albian [112-97 Ma], Western Australia was located at palaeolatitudes of between 50-60 0 S and oxygen isotope data indicate SSTs in the Carnarvon Basin had risen to between 7-11 0 C (Stevens and Clayton 1971): Average SSTs in the Eromanga-Surat Seaway were ~12 0 C, reaching up to 16 0 C where marine circulation was more restricted (Pirrie et al 1995). Conversely, water temperatures averaged 0°C (range from -5 0 to +5 0 C) in the Otway Basin at a palaeolatitude of ~85 0 S within the developing Australo-Antarctic Rift System (Gregory et al 1989).…”