Stable carbon isotope ratios of n-alkane in ODP Hole 175-1083A in the South Atlantic Ocean (Table 1)

• Main Authors: Denison, S M, Maslin, Mark, Boot, C, Pancost, Richard D, Ettwein, V J
• Format: Dataset
• Language: English
• Published: PANGAEA 2005
• Subjects: 175-1083A; Amplitude; Benguela Current; South Atlantic Ocean; DEPTH; sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Isotope ratio mass spectrometry; Joides Resolution; Leg175; n-Alkane C27; δ13C; n-Alkane C29; n-Alkane C31; n-Alkane C33; Ocean Drilling Program; ODP; Sample code/label
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.694036; https://doi.org/10.1594/PANGAEA.694036

The intensification of Northern Hemisphere Glaciation (iNHG) is one of the critical climate thresholds in the Cenozoic. This study focuses on marine sediments recovered from Marine Isotope Stages 101/100 at the Ocean Drilling Program Site 1083 to assesses the impact of the iNHG on continental southern African vegetation through n-alkane (straight-chain hydrocarbon) abundance and delta13C values. The n-alkane abundance data yield a convoluted signal due to the number of controlling factors such as the source area, transportation routes and vegetation type. The C31 n-alkane delta13C values, however, exhibit a cyclic pattern with a periodicity of c. 20 ka, and are not correlated to the abundance data. It is inferred that the signal does not represent a change in the geographical source of n-alkanes. Instead, we suggest that the variations are caused by water-stress-induced changes in either carbon isotope fractionation during C3 photosynthesis or subtle changes in the proportion of C3 and C4 plants. These changes, unlike variations in oceanographic proxies, closely track precessional forcing factors and are independent of the prevailing obliquity-forced glacial/interglacial cycles. We conclude that the varying monsoon strength, rather than pCO2 or temperature change, forced changes in southern African vegetation during this period.