11:00 〜 13:00
[MIS02-P04] Possibility of the stable carbon isotope stratigraphy of planktonic foraminifera: case study of a sediment core at the Manihiki Plateau in the central Pacific
キーワード：浮遊性有孔虫、熱帯太平洋、マニヒキ海台
Deep-sea sediment cores are dated using magnetostratigraphy, biostratigraphy, and oxygen isotope (δ18O) stratigraphy. Although the δ18O stratigraphy does not give the absolute age, it provides orbital-scale age constraints by correlating the glacial-interglacial (G-IG) changes to a standard curve, which allows for much higher resolution compared to magnetostratigraphy and biostratigraphy. However, the δ18O stratigraphy may not work when sedimentation rate is low. Sediments with low sedimentation rate are strongly affected by bioturbation, which smooths the δ18O variations, making it difficult to identify the Marine oxygen Isotope Stages (MIS). In particular, the identification of MIS before 800 ka will be very difficult due to the smaller amplitude and higher-frequency (41 kyr) of the G-IG cycles compared to the later 100 kyr cycles with larger amplitude.
We constructed an integrated stratigraphy of a low sedimentation rate core at the central tropical Pacific Manihiki Plateau, KR99-12 PC05, for the last 2.2 Ma using magnetostratigraphy, planktonic foraminiferal biostratigraphy and planktonic foraminiferal δ18O stratigraphy. Because benthic foraminifera are very rare in PC05, we use Globigerinoides ruber (sensu stricto) for the δ18O analysis. The δ18O shows clear G-IG variations for the past 800 kyr, but the amplitude of δ18O was too small to capture MIS in earlier intervals. Therefore, there are few δ18O age constraints in the 0.8-2.2 Ma inverval. On the other hand, the stable carbon isotope ratios (δ13C) show a clear G-IG variation, the pattern of which is very similar to that in the western tropical Pacific IODP Site U1488, but with smaller amplitude. In this presentation, we will discuss the possibility of stratigraphic correlation between PC05 and U1488 based on δ13C of planktonic foraminifera.
We constructed an integrated stratigraphy of a low sedimentation rate core at the central tropical Pacific Manihiki Plateau, KR99-12 PC05, for the last 2.2 Ma using magnetostratigraphy, planktonic foraminiferal biostratigraphy and planktonic foraminiferal δ18O stratigraphy. Because benthic foraminifera are very rare in PC05, we use Globigerinoides ruber (sensu stricto) for the δ18O analysis. The δ18O shows clear G-IG variations for the past 800 kyr, but the amplitude of δ18O was too small to capture MIS in earlier intervals. Therefore, there are few δ18O age constraints in the 0.8-2.2 Ma inverval. On the other hand, the stable carbon isotope ratios (δ13C) show a clear G-IG variation, the pattern of which is very similar to that in the western tropical Pacific IODP Site U1488, but with smaller amplitude. In this presentation, we will discuss the possibility of stratigraphic correlation between PC05 and U1488 based on δ13C of planktonic foraminifera.