Publication Date:
2024-07-22
Description:
The Walvis Paradox states that opal accumulation fluctuates in counterphase to general productivity on Walvis Ridge, off northern Namibia. Sediments of early Quaternary age from Site 1085 (Cores 175-1085A-7H to 10H, off South Africa) were studied to check the phase relationships of general productivity and opal deposition in the region off the Oranje River, near the southern end of the Namibia upwelling system. The proxies used are delta18O of Cibicidoides wuellerstorfi, delta13C of C. wuellerstorfi, benthic foraminifers per gram (BF/g), Uvigerina spp. per gram (U/g), estimated diatom abundance (EDA) and sulfide and oxide aggregates (SOA) in the coarse fraction. EDA and BF/g are taken to indicate diatom and organic matter productivity, respectively. Oxygen isotopes were used to determine phase within the glacial-interglacial cycles.
The phase relationships between the different proxies emerge when applying internal stacking methods. For Core 175-1085A-7H, five prescribed 41-k.y. cycles were combined into an average 41-k.y. cycle for the different indices. Productivity indices (BF/g and U/g) tend to follow delta18O in the accustomed manner (with glacial periods showing maximum productivity), but not EDA, whose maximum appears closer to interglacials, offset toward cooling. Thus, phase relationships are similar to those on Walvis Ridge, extending the Walvis Paradox to the southern end of the Namibia upwelling system for the early Quaternary. A tentative reconstruction of the phase of intensity of mixing is given, based on the two productivity indicators EDA and BF/g. Mixing is strongest during the glacial maximum.
Keywords:
175-1085A; AGE; Age, minimum/young; Aggregates; Benguela Current, South Atlantic Ocean; Calculated, see reference(s); Cibicidoides wuellerstorfi, δ13C; Cibicidoides wuellerstorfi, δ18O; Comment; Counting 〉250 µm fraction; Counting 150-250 µm fraction; DEPTH, sediment/rock; Depth, sediment revised; Depth, top/min; Diatom abundance; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Foraminifera, benthic; Joides Resolution; Leg175; Mass spectrometer Finnigan MAT 252; Ocean Drilling Program; ODP; Sample code/label; Sample ID; Size fraction 〉 0.063 mm, sand; Size fraction 〉 0.250 mm; Smear slide analysis; Uvigerina peregrina, δ13C; Uvigerina peregrina, δ18O; Uvigerina spp.; δ13C, carbonate; δ18O, carbonate
Type:
dataset
Format:
text/tab-separated-values, 3184 data points
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