High-resolution carbon-isotope stratigraphy across the Campanian–Maastrichtian boundary at Shatsky Rise (tropical Pacific)

Abstract

The Campanian–Maastrichtian transition is characterized by a negative carbon-isotope excursion, the so-called Campanian–Maastrichtian Boundary Event (CMBE), thought to have been triggered by climatic cooling and sea-level fall. This event is known from stable isotope datasets around the world, but little is known about the causal mechanisms of the proposed cooling or the exact timing of this event. A tool both to enhance our knowledge about this event and to highlight the relative timing between the cooling and the proposed sea-level fall, is high-resolution carbon-isotope stratigraphy. In this study, an upper Campanian–Maastrichtian high-resolution carbon-isotope record from bulk carbonates of Ocean Drilling Program Hole 1210B at Shatsky Rise is presented. The new carbon-isotope record shows a number of distinct variations on short and longer time scales, which can be calibrated with age-diagnostic planktonic foraminifera and calcareous nannoplankton datum levels. This detailed biostratigraphically calibrated carbon-isotope stratigraphy can be correlated with the carbon-isotope record of Deep Sea Drilling Project Site 305 (∼500m deeper in palaeodepth than Hole 1210B). One result of this correlation is the detection of two major hiatuses at Site 305 associated with the lower and upper part of the CMBE. As possible mechanisms for these hiatuses, we discuss the effects of erosion as a result of mass wasting and/or of changes in the strength of bottom currents. By reducing stratigraphic uncertainties our new correlation proves the usefulness of biostratigraphically calibrated carbon-isotope stratigraphy, even for time intervals of small changes in the global carbon cycle as in the late Campanian–Maastrichtian. The new carbon-isotope record of Hole 1210B may serve in future as a reference for detailed calibration and correlation with other well-established δ13C records from shelf seas and open-ocean settings. This will help to enhance our understanding of ocean-climate processes associated with the CMBE.