Accumulation rates of volcaniclastic deposits on Loihi Seamount, Hawaii
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AMS radiocarbon age dating of planktonic foraminifera in volcaniclastic deposits on Loihi Seamount yields ages ranging from 590 years before present (y BP) at 10 cm depth to 5,880 y BP at 1,007 cm depth in an 11-m-thick section exposed along inward facing, caldera-bounding faults on the eastern side of Loihi’s summit. The accumulation rate of the deposit was about 0.37 cm/y from 5,880 to 3,300 y BP and it consisted of subequal amounts of alkalic and tholeiitic fragments. The rate slowed dramatically at about 3,300 y BP to an average 0.04 cm/y and the particles that have accumulated since consist mostly of alkalic glass fragments. The decrease in accumulation rate could indicate a decrease in volcanic activity at Loihi beginning about 3,300 y BP. This lower level of activity appears to be continuing today.
KeywordsLoihi Seamount Hawaiian volcanism Volcaniclastic deposits AMS radiocarbon ages
I thank the Lawrence Livermore National Laboratories for producing the AMS radiocarbon age data that form the basis of this paper. Jenny Paduan constructed Fig. 1. The samples were collected during a Hawaii Undersea Research Laboratory Pisces V dive program in 1998 with Rodey Batiza and Jim Head. Terry Kerby’s expert sampling of the stratigraphic section at site G allowed me to attempt this dating project. Helpful reviews by Dick Fiske, Vern Manville, and Associate Editor Jocelyn McPhie improved the presentation significantly.
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