Paleoenvironmental change in the middle Okinawa Trough since the last deglaciation : evidence from the sedimentation rate and planktonic foraminiferal record
Figure 1: Locations of cores A7 and E017 and other coring sites in the middle and southern Okinawa Trough. (195.9Kb)
Figure 2: Age model construction of core E017 with 5 additional comparative age control points (hollow triangle) obtained by lithological and biostratigraphic correlation with core A7, which has been detailed AMS14C dated. (312.1Kb)
Figure 4: Variations of percentage abundance of cold water foraminiferal species and warm/cold species ratio in core A7 (A) and core E017 (B) during the last 17-18 cal. Kyr B.P. (465.9Kb)
Figure 5: Variations of Percentage abundance of warm water foraminiferal species in core A7 (A) and core E017 (B) during the last 17-18 cal. Kyr B.P. (472.9Kb)
Figure 6: Abundance profiles of deep and shallow-dwelling species and deep/shallow species ratio in cores A7 and E017. (244.6Kb)
Figure 7: Time plot of δ18O, warm water species and warm/cold species ratio in cores A7 and E017 and Mg/Ca-based SST in core A7. (306.4Kb)
Oppo, Delia W.
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KeywordOkinawa Trough; Last deglaciation; Holocene; Planktonic foraminifera; Sedimentation rate; Kuroshio Current; Millennial- scale climate changes; Oxygen isotope
Well-dated, high-resolution records of planktonic foraminifera and oxygen isotopes from two sediment cores, A7 and E017, in the middle Okinawa Trough reveal strong and rapid millennial-scale climate changes since ~18 to 17 thousand years before present (kyr B.P.). Sedimentation rate shows a sudden drop at ~11.2 cal. kyr B.P. due to a rapid rise of sea-level after the Younger Dryas (YD) and consequently submergence of the large continental shelf on the East China Sea (ECS) and the retreat of the estuary providing sediment to the basin. During the last deglaciation, the relative abundance of warm and cold species of planktonic foraminifera fluctuates strongly, consistent with the timing of sea surface temperature (SST) variations determined from Mg/Ca measurements of planktonic foraminifera from one of the two cores. These fluctuations are coeval with climate variation recorded in the Greenland ice cores and North Atlantic sediments, namely Heinrich event 1 (H1), Bølling-Allerød (B/A) and YD events. At about 9.4 kyr B.P., a sudden change in the relative abundance of shallow to deep planktonic species probably indicates a sudden strengthening of the Kuroshio Current in the Okinawa Trough, which was synchronous with a rapid sea-level rise at 9.5-9.2 kyr B.P. in the ECS, Yellow Sea (YS) and South China Sea (SCS). The abundance of planktonic foraminiferal species, together with Mg/Ca based SST, exhibits millennial-scale oscillations during the Holocene, with 7 cold events (at about 1.7, 2.3-4.6, 6.2, 7.3, 8.2, 9.6, 10.6 cal. kyr BP) superimposed on a Holocene warming trend. This Holocene trend, together with centennial-scale SST variations superimposed on the last deglacial trend, suggests that both high and low latitude influences affected the climatology of the Okinawa Trough.
Author Posting. © The Authors, 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Palaeogeography, Palaeoclimatology, Palaeoecology 243 (2007): 378-393, doi:10.1016/j.palaeo.2006.08.016.
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