Atsushi Ando and Takeshi Kakegawa
Carbon isotope records of terrestrial organic matter and occurrence of planktonic Foraminifera from the Albian stage of Hokkaido, Japan; ocean-atmosphere delta ¹³ c trends and chronostratigraphic implications
Palaios (July 2007), 22(4):417-432

Abstract:
Carbon isotope compositions of sedimentary organic matter (average -24.1 per mil) from an Albian marine siliciclastic succession in Hokkaido, Japan, exhibit a distinct anomaly by approximately +1.2 per mil with a trifurcate shape across the Albian-Cenomanian boundary and two relatively small shifts (<+1 per mil) in the middle and upper Albian, respectively. The organic matter consist predominantly of woody materials with an insignificant degree of thermal alteration, judged from the visual and elemental characteristics of kerogen; the stratigraphic delta ¹³ C _org fluctuations are independent of lithological or total organic carbon variations. Thus, the Hokkaido delta ¹³ C _org profile is interpreted as representing the temporal delta ¹³ C changes in whole C3 plant vegetation in the provenance of East Asia during Albian time. The patterns and amplitudes in delta ¹³ C _wood values and their relationship with planktonic foraminiferal zones are conformable with coeval Tethyan delta ¹³ C records of pelagic carbonates. This observation reinforces the view that delta ¹³ C compositions of marine and terrestrial carbon reservoirs fluctuated simultaneously by the same amplitude within the ocean-atmosphere-biosphere system regardless of changes in such paleoenvironmental parameters as pCO ₂ . From a chemostratigraphic viewpoint, time-equivalent levels of Oceanic Anoxic Events and stage boundaries are constrained for the Hokkaido sections, allowing for the proposal of a detailed chronostratigraphic framework for future advanced paleoceanographic research in the mid-Cretaceous northwestern Pacific region.