Oxygen isotope studies on Jurassic and Cretaceous belemnites from New Zealand and their biogeographic significance

Abstract

<' I (0 18 ) and <' I (C13) results and isotopic temperatures are presented for transverse sections of New Zealand belemnites (Belemnopsis, Hibolithes, Dimitobelus) obtained from Jurassic strata correlated with Bajocian-Bathovian, Callovian, Kimmeridgian and Lower Tithonian, and Cretaceous strata correlated with Albian-Maastrichtian. Growth layer analyses also were carried out on 15 Jurassic and Cretaceous belemnites.Many of the belemnite specimens were found to be chemically altered to varying degrees, but growth analyses showed that the high isotopic temperatures which alter· ation is expected to produce were confined to two areas: surrounding the apical line and adjacent to the periphery of the specimen. Between these two areas there are generally plausible isotopic temperatures, and there is no reason to suspect that the temperature record has not been preserved there in its original form. Three or four major growth stages may be recognised in New Zealand belemnite guards and growth layer analyses suggest that these are annual; if this is so then in this respect the belemnites match the modern squids in having a three· or four.year life cycle. Variations in isotopic temperature of the be1mnites are comparable with those experienced seasonally by modern squids. Isotopic temperatures for the Jurassic and Cretaceous of New Zealand can be compared with sea water surface temperatures around the present day New Zealand coasts (36 0 _46 0 S. Lat.)' and inferred temperatures, based on these comparisons, are as follows: Upper Jurassic -temperatures slightly cooler than those of the present day; Albian and Cenomanian -temperatures slightly warmer; Turonian-?Coniacian -temperatures markedly warmer; Santonian-Maastrichtian -tem· peratures slightly warmer in the Santonian, but more so in the Campanian and Upper Maastrichtian. The New Zealand oxygen isotope results indicate a probable mid· latitude position, in the warm·temperate climatic zone, for New Zealand in the Jurassic and Cretaceous. New Zealand oxygen isotope results are compared with those obtained from overseas.

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

“…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 ‰. From this, we determined that given a temperature range of 10-18°C, the δ 18 O VSMOW range for Isisford deltaic or estuarine surface waters had an approximate minimum of -9.13‰ and an approximate maximum of -7.39‰.…”

Oxygen- and Carbon-Isotope Variations and Planktonic Foraminifer Depth Habitats, Late Cretaceous to Paleocene, Central Pacific, Deep Sea Drilling Project Sites 463 and 465

“…Semi-continuous records of Cretaceous oxygen isotopes have been produced for Pacific nannofossils and foraminifers (Douglas and Savin, 1971, 1973, New Zealand belemnites (Stevens and Clayton, 1971), and Pacific Antarctic nannofossils and foraminifers (Margolis et al, 1977). In the Atlantic, records based on foraminifers have been produced by Saito and Van Donk (1974) and Boersma and Shackleton (1979, in press), and on European belemnites by Spaeth et al (1971).…”

High-Resolution Stable Isotope Profiles of a Dimitobelid Belemnite: Implications for Paleodepth Habitat and Late Maastrichtian Climate Seasonality

“…Rare soft-tissue molds of belemnites display a body form similar to that of modern squids. Consequently, inferences regarding belemnite ecology and life history are frequently drawn from modern squid (Stevens and Clayton, 1971;Doyle and MacDonald, 1993). Unfortunately, squids demonstrate a variety of behaviors, making it difficult to generalize belemnite paleoecology.…”