Belemnite geochemistry from Albstadt-Pfeffingen (Middle Jurassic, Baden-Württemberg, Germany)

Abstract

Belemnite calcite is an important source of stable isotope (18O, 13C) and element (Fe, Mg, Mn, S, Sr) proxies with potential for high-resolution quantitative reconstructions of palaeoenvironments and seasonality since Urey et al (1951). Belemnites are also a very important archive for environmental reconstructions of the early Toarcian; it is important, however, to study their calcite over intervals of comparative environmental stability to assess the meaning of proxy data extracted from their calcite. Here, we report on recent developments on geochemical proxies derived from belemnite rostra from Albstadt-Pfeffingen, a potential GSSP for the base of the Callovian, in Baden-Württemberg.

Mg/Ca and Sr/Ca as Palaeothermometers: New data from Middle Jurassic Belemnites from Germany and Portugal.

“…The belemnites from Cabo Mondego and the Roschbachtal section presented in this study do not show any correlation between δ 18 O values with Mg/Ca and Sr/Ca ratios (Figure 1). Data tables for this study can be viewed in Wilkin (2021). The absence of a correlation between Mg/Ca and δ 18 O in belemnite samples from both Cabo Mondego and the Roschbachtal section questions the assumption that Mg/Ca in belemnite calcite reflects mainly calcification temperature (e.g., Berlin et al, 1967;Bailey et al, 2003;McArthur et al, 2007a) and suggests that Mg/Ca is an unreliable palaeotemperature indicator for upper Bajocian -lower Callovian belemnites.…”