Publication Date:
2013-09-06
Description:
ABSTRACT We present an SiF 4 separation line, coupled to a laser fluorination system, which allows for an efficient combined silica δ 18 O and δ 30 Si analysis (50 min per sample). The required sample weight of 1.5–2.0 mg allows for high-resolution isotope studies on biogenic opal. Besides analytical tests, the new instrumentation set-up was used to analyse two marine diatom fractions (〉63 µm, 10–20 µm) with different diatom species compositions extracted from a Bølling/Allerød–Holocene core section [MD01-2416, North-West (NW) Pacific] to evaluate the palaeoceanographic significance of the diatom isotopic signals and to address isotopic effects related to contamination and species-related isotope effects (vital and environmental effects). While δ 30 Si offsets between the two fractions were not discernible, supporting the absence of species-related silicon isotope effects, systematic offsets occur between the δ 18 O records. Although small, these offsets point to species-related isotope effects, as bias by contamination can be discarded. The new records strengthen the palaeoceanographic history during the last deglaciation in the NW Pacific characterized by a sequence of events with varying surface water structure and biological productivity. With such palaeoceanographic evolution it becomes unlikely that the observed systematic δ 18 O offsets signal seasonal temperature variability. This calls for reconsideration of vital effects, generally excluded to affect δ 18 O measurements.
Print ISSN:
0267-8179
Electronic ISSN:
1099-1417
Topics:
Geography
,
Geosciences
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