Browsing Radiocarbon, Volume 28 (1986) by Subjects
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AMS Radiocarbon Dates on Foraminifera from Deep Sea Sediments14C ages were determined on samples of foraminifera separated from cores from three areas of the tropical Pacific (Fast Pacific Rise, Oontong Java Plateau, and South China Sea). Analyses were made on four planktonic species and on mixed benthics. The purpose of the multiple analysis on planktonic species is to assess the importance of artifacts resulting from the bioturbation-abundance change couple, from the bioturbation-partial dissolution couple and from redeposition by bottom currents. The goal is to use the benthic-planktonic age difference as a means of establishing changes in deep sea ventilation rate over the past 25,000 years. Results of a part of this work are presented in this paper.
Radiocarbon in Particulate Matter from the Eastern Sub-Arctic Pacific Ocean: Evidence of a Source of Terrestrial Carbon to the Deep SeaCarbon isotope ratios were measured in organic and inorganic carbon of settling particulate matter collected with a sediment trap at Ocean Station "P" in the Gulf of Alaska from March to October, 1983. Dissolved inorganic carbon (DIG) in surface sea water collected during two different seasons in 1984 were analyzed using large gas proportional counters and revealed a minimum seasonal Delta-14C variation of 14 per mil. Results show that the 14C of calcium carbonate sedimenting to the deep sea is the same as that measured in surface water DIG. In contrast, particulate organic carbon (POC) had significantly higher Delta-14C values (by 25-70 per mil) than that in surface water DIG. Also, the delta-13C of the POC was markedly lower than previously reported values from other trap stations and marine particulate matter in general. Results from this study suggest that a significant amount of the POC settling to the deep sea at this pelagic station is of terrestrial origin, not strictly of marine origin as had previously been believed.