Reconstruction of the redox environment in Okinawa Trough and its climatic implications since mid-Holocene

Beibei MI; Zhongbo WANG; Xiaohua QIU; Yong ZHANG; Xianhong LAN

doi:10.16562/j.cnki.0256-1492.2019042501

Marine Geology & Quaternary Geology > 2019 > 39(4): 107-115. > DOI: 10.16562/j.cnki.0256-1492.2019042501

Beibei MI, Zhongbo WANG, Xiaohua QIU, Yong ZHANG, Xianhong LAN. Reconstruction of the redox environment in Okinawa Trough and its climatic implications since mid-Holocene[J]. Marine Geology & Quaternary Geology, 2019, 39(4): 107-115. DOI: 10.16562/j.cnki.0256-1492.2019042501

Citation:

PDF (4227 KB)

Reconstruction of the redox environment in Okinawa Trough and its climatic implications since mid-Holocene

1.
The Key Laboratory of Gas Hydrate, Ministry of Natural Resources, Qingdao Institute of Marine Geology, Qingdao 266071, China
2.
Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China
3.
No.1 Institute of Geology and Mineral Resources of Shandong Province, Jinan 250100, China

More Information

Received Date: April 24, 2019
Revised Date: June 03, 2019

Graphical Abstract

Abstract

Abstract

We analyzed grain size, major and trace elements, and AMS¹⁴C for the sediments retrieved from the core GHN056-09 in the Okinawa Trough, where the Kuroshio Current passes through. High resolution curves of grain size and trace elements since mid-Holocene are acquired. The results show that the sedimentary environment in the study area was rather stable since 6235aBP though the three geochemical indices of MnO/Al₂O₃, U/Th and V/Cr of the sediments fluctuated for several times, upon which the cores could be roughly divided into three stages since mid-Holocene: the stage 1 (1830aBP-) characterized by strong fluctuations in productivity and redox, the stage 2 (4000~1830aBP) with low productivity and a weak reduction environment, and the stage 3 (6235~4000aBP) with high productivity and a relatively strong reduction environment. Six extreme high values of productivity and redox are revealed by these geochemical indices since mid-Holocene, which occur at R1 (260aBP), R2 (1200aBP), R3 (2125aBP), R4 (2700aBP), R5 (4250aBP) and R6 (5700aBP) respectively. It is believed that the environmental events are closely related to the sea water temperature and the intensity of Kuroshio Current, suggesting a strong regional response to air-sea interaction in the Okinawa Trough region.
- redox,
- paleoproductivity,
- Kuroshio Current,
- Okinawa Trough,
- Holocene

FullText(HTML)

References (47)

References

[1]	宋泽华, 万世明, 黄杰, 等.南海西北部表层黏土矿物分布特征及其来源[J].海洋学报, 2017, 39(9):71-82. doi: 10.3969/j.issn.0253-4193.2017.09.007 SONG Zehua, WAN Shiming, HUANG Jie, et al. Distribution and sources of clay minerals in surface sediments of the northwestern South China Sea[J]. Acta Oceanologica Sinica, 2017, 39(9):71-82. doi: 10.3969/j.issn.0253-4193.2017.09.007
[2]	Broecker W, Clark E, Barker S. Near constancy of the Pacific Ocean surface to mid-depth radiocarbon-age difference over the last 20 kyr[J]. Earth and Planetary Science Letters, 2008, 274:322-326. doi: 10.1016/j.epsl.2008.07.035
[3]	Dou Y, Yang S, Li C, et al. Deepwater redox changes in the southern Okinawa Trough since the last glacial maximum[J]. Progress in Oceanography, 2015, 135:77-90. doi: 10.1016/j.pocean.2015.04.007
[4]	王玥铭, 窦衍光, 徐景平, 等.16ka以来冲绳海槽中南部有机质来源及其对上升流演化的指示[J].第四纪研究, 2018, 38(3):769-781. WANG Yueming, DOU Yanguang, XU Jingping, et al. Sources of organic matter in the central and southern Okinawa Trough since 16ka and its Indicators for upwelling evolution[J]. Quaternary Research, 2018, 38(3):769-781.
[5]	Tribovillard N, Algeo T J, Ly Chemic onsT. Armelle Riboulleau Trace metals as paleoredox and paleoproductivity proxies: An update[J]. Geology, 2006, 232:12-32.
[6]	Shaw T J, Gieskes J M, Jahnke R A. Early diagenesis in differing depositional environments: The response of transition meta1s in pore water[J]. Geochimica et Cosmochimica Acta, 1990, 54:1233-1246. doi: 10.1016/0016-7037(90)90149-F
[7]	窦衍光, 陈晓辉, 李军, 等.东海外陆架-陆坡-冲绳海槽不同沉积单元底质沉积物成因及物源分析[J].海洋地质与第四纪地质, 2018, 38(4):24-34. http://hydz.chinajournal.net.cn/WKD/WebPublication/paperDigest.aspx?paperID=aefb73fd-3d88-477d-afed-72d7c6442a0d DOU Yanguang, CHEN Xiaohui, LI Jun, et al. Origin and provenance of the surficial sediments in the subenvironments of the East China Sea[J]. Marine Geology & Quaternary Geology, 2018, 38(4):24-34. http://hydz.chinajournal.net.cn/WKD/WebPublication/paperDigest.aspx?paperID=aefb73fd-3d88-477d-afed-72d7c6442a0d
[8]	李铁刚, 常凤鸣.冲绳海槽古海洋学[M].北京:海洋出版社, 2009:165-172. LI Tiegang, CHANG Fengming. Paleooceanography of the Okinawa Trough[M]. Beijing: China Ocean Press, 2009:165-172.
[9]	南青云. 25kaBP以来黑潮流域古环境演化对高频全球变化事件的响应——来自有机地球化学的证据[D].中国科学院研究生院(海洋研究所)博士论文, 2008. NAN Qingyun. Response of paleoenvironment evolution to high frequency global change events in Kuroshio area since 5kaBP—evidence from organic geochemistry[D]. Doctoral dissertation of Graduate University of Chinese Academy of Sciences (Institute of Oceanography), 2008.
[10]	Ramsey B Christopher. Bayesian analysis of radiocarbon dates[J]. Radiocarbon, 2009, 51(1):337-360. doi: 10.1017/S0033822200033865
[11]	Reimer P J, Bard E, Bayliss A, et al. IntCal 13 and Marine 13radiocarbon age calibration curves 0~50000 years cal BP[J]. Radiocarbon, 2013, 55(4):1869-1887. doi: 10.2458/azu_js_rc.55.16947
[12]	Liu J P, Milliman J D, Gao S, et al. Holocene development of the Yellow Rivers subaqueous delta, North Yellow Sea[J]. Marine Geology, 2004, 209:45-67. doi: 10.1016/j.margeo.2004.06.009
[13]	肖尚斌, 李安春, 蒋富清, 等.近2 ka来东海内陆架的泥质沉积记录及其气候意义[J].科学通报, 2004, 49(21):2232-2237. http://d.old.wanfangdata.com.cn/Periodical/kxtb200421017 XIAO Shangbin, LI Anchun, JIANG Fuqing, et al. The 2ka record and its climate significance of the mud area of inner shelf of the East China Sea[J]. Chinese Science Bulletin, 2004, 49(21): 2232-2237. http://d.old.wanfangdata.com.cn/Periodical/kxtb200421017
[14]	肖尚斌, 李安春, 陈木宏, 等.近8 ka东亚冬季风变化的东海内陆架泥质沉积记录[J].地球科学——中国地质大学学报, 2005, 30(5): 573-581. http://d.old.wanfangdata.com.cn/Periodical/dqkx200505009 XIAO Shangbin, LI Anchun, CHEN Muhong, et al. Mud records from the inner shelf of the East China Sea with the East Asian winter monsoon in recent 8 ka[J]. Earth Science-Journal of China University of Geosciences, 2005, 30(5):573-581. http://d.old.wanfangdata.com.cn/Periodical/dqkx200505009
[15]	Liu J P, Xu K H, Li A C, et al. Flux and fate of Yangtze River sediment delivered to the East China Sea[J]. Geomorphology, 2007, 85:208-224. doi: 10.1016/j.geomorph.2006.03.023
[16]	肖尚斌, 李安春, 刘卫国, 等.闽浙沿岸泥质沉积的物源分析[J].自然科学进展, 2009, 19(2): 185-191. doi: 10.3321/j.issn:1002-008X.2009.02.009 XIAO Shangbin, LI Anchun, LIU Weiguo, et al. Source analysis of mud sediment in the inner shelf of the East China Sea[J]. Progress in Natural Science, 2009, 19 (2): 185-191. doi: 10.3321/j.issn:1002-008X.2009.02.009
[17]	颜文, 古森昌, 陈列忠, 等.南海97-37柱样的主元素特征及其潜在的古环境指示作用[J].热带海洋学报, 2002, 21(2) : 75-83. doi: 10.3969/j.issn.1009-5470.2002.02.009 YAN Wen, GU Senchang, CHEN Liezhong, et al. Characteristics of major elements of sediments incore 97-37 from Southern South China Sea and potential implications to paleoenvironment[J]. Journal of Tropical Oceanography, 2002, 21(2): 75-83. doi: 10.3969/j.issn.1009-5470.2002.02.009
[18]	赵宏樵, 韩喜彬, 陈荣华, 等.南海北部191柱状沉积物主元素特征及其古环境意义[J].海洋学报, 2008, 30(6): 85-93. doi: 10.3321/j.issn:0253-4193.2008.06.010 ZHAO Hongqiao, HAN Xibin, CHEN Ronghua, et al. Characteristics of main elements and their paleoenviromental significance of Core 191 in the northern South China Sea[J]. Acta Oceanologica Sinica, 2008, 30(6):85-93. doi: 10.3321/j.issn:0253-4193.2008.06.010
[19]	Eusterhues K, Heinrichs H, Jürgen Schneider. Geochemical response on redox fluctuations in Holocene lake sediments, Lake Steisslingen, Southern Germany[J]. Chemical Geology, 2005, 222(1-2):1-22. doi: 10.1016/j.chemgeo.2005.06.006
[20]	Nameroff T J, Balistrieri L S, Murray J W. Suboxic trace metal geochemistry in the Eastern Tropical North Pacific[J]. Geochimica et Cosmochimica Acta, 2002, 66(7):1139-1158. doi: 10.1016/S0016-7037(01)00843-2
[21]	Russell A D, Morford J L. The behavior of redox-sensitive metals across a laminated-massive-laminated transition in Saanich Inlet, British Columbia[J]. Marine Geology, 2001, 174(1):341-354. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=74008033691992b2c5132128cd321757
[22]	Tribovillard N, Algeo T J, Lyons T, et al. Trace metals as paleoredox and paleoproductivity proxies: An update[J]. Chemical Geology, 2006, 232(1-2):1-32. doi: 10.1016/j.chemgeo.2006.02.013
[23]	邹建军, 石学法, 刘季花, 等.48ka以来日本海古生产力和古氧化还原环境变化的地球化学记录[J].海洋学报, 2010, 32(4):98-109. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=hyxb201004010 ZOU Jianjun, SHI Xuefa, LIU Jihua, et al. The geochemical records of paleoproductivity and paleoredoxin changing in Japanese Sea since 48ka[J]. Acta Oceanologica Sinica, 2010, 32(4):98-109. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=hyxb201004010
[24]	李军.冲绳海槽中部A7孔沉积物地球化学记录及其对古环境变化的响应[J].海洋地质与第四纪地质, 2007, 27(1):37-45. http://hydz.chinajournal.net.cn/WKD/WebPublication/paperDigest.aspx?paperID=3941811e-fa13-49bd-984c-e7cfc7c324d8 LI Jun. Geochemical records of sediments from A7 core in the middle Okinawa Trough and their response to the paleoenvironmental changes[J]. Marine Geology & Quaternary Geology, 2007, 27(1):37-45. http://hydz.chinajournal.net.cn/WKD/WebPublication/paperDigest.aspx?paperID=3941811e-fa13-49bd-984c-e7cfc7c324d8
[25]	蒋富清, 李安春, 李铁刚, 等.冲绳海槽南部柱状沉积物地球化学特征及其古环境意义[J].海洋地质与第四纪地质, 2002, 22(3): 11-18. http://hydz.chinajournal.net.cn/WKD/WebPublication/paperDigest.aspx?paperID=d943eabf-48c9-4b9c-98ca-9fdf16cfa45c JIANG Fuqing, LI Anchun, LI Tiegang, et al. Geochemical characteristics of the core sediments from southern Okinawa Trough and its paleo-environmental implication[J]. Marine Geology & Quaternary Geology, 2002, 22(3):11-18. http://hydz.chinajournal.net.cn/WKD/WebPublication/paperDigest.aspx?paperID=d943eabf-48c9-4b9c-98ca-9fdf16cfa45c
[26]	Delaney M L, Linn L J, Druffel R M. Seasonal cycles of manganese and cadrnium in coral from the Galapagos Islands[J]. Geochimicaet Cosmochimica Acta, 1993, 57: 347-354. doi: 10.1016/0016-7037(93)90436-Z
[27]	Shen G T, Campbell R B, Dunbar R B, et al. Paleochemistry of manganese in corals from the Galapagos Islands[J]. Coral Reefs, 1991, 10 (2): 91-100. doi: 10.1007/BF00571827
[28]	阎军, 何丽娟, 薛胜吉.西太平洋边缘海区元素地层学研究及其古海洋学意义[J].海洋地质与第四纪地质, 1991, 11(2):57-68. http://hydz.chinajournal.net.cn/WKD/WebPublication/paperDigest.aspx?paperID=77537802-2520-4912-bb0d-86a9f4890f0b YAN Jun, HE Lijuan, XUE Shengji. Characteristics of elements in the marginal-sea strata of west Pacific ocean and their paleo-oceanographical significance[J]. Marine Geology & Quaternary Geology, 1991, 11(2): 57-68. http://hydz.chinajournal.net.cn/WKD/WebPublication/paperDigest.aspx?paperID=77537802-2520-4912-bb0d-86a9f4890f0b
[29]	郭丽芬, 陈婉颜, 陈丽虹.南沙群岛永暑礁区近百万年来的古气候变化——南永井的锰含量分析[J].热带海洋, 1993, 12(4): 39-46. GUO Lifen, CHEN Wanyan, CHEN Lihong. The paleoclimatic change of Yong-Shu reef area of Nansha Islands in recent million years—the Mn content analysis of Nanyong well[J]. Tropical Oceanology, 1993, 12(4): 39-46.
[30]	Jian Z, Wang P, Saito Y, et al. Holocene variability of the Kuroshio Current in the Okinawa Trough, northwestern Pacific Ocean[J]. Earth and Planetary Science Letters, 2000, 184:305-319. doi: 10.1016/S0012-821X(00)00321-6
[31]	翦知湣.南海冰期深部水性质的稳定同位素证据[J].中国科学D辑, 1998, 28(3): 250-256. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=QK199800269857 JIAN Zhimin, Stable isotope evidence of Deep Water Properties in South China Sea during the Glaciation Period[J]. Science China(Series D), 1998, 28(3): 250-256. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=QK199800269857
[32]	CHANG Fengming, LI Tiegang, ZHUANG Lihuan, et al. A Holocene paleotemperature record based on radiolariafrom the northern Okinawa Trough (East China Sea)[J]. Quaternary International, 2008, 183(1):115-122. doi: 10.1016/j.quaint.2006.12.007
[33]	徐海, 洪业汤, 林庆华, 等.红原泥炭纤维素氧同位素指示的距今6 ka温度变化[J].科学通报, 2002, 47(15): 1181-1186. doi: 10.3321/j.issn:0023-074X.2002.15.014 XU Hai, HONG Yetang, LIN Qinghua, et al. The temperature Change indicated by Peat Cellulose Oxygen Isotope in Hongyuan since 6 Ka[J]. Chinese Science Bulletin, 2002, 47(15): 1181-1186. doi: 10.3321/j.issn:0023-074X.2002.15.014
[34]	刘升发, 石学法, 刘焱光, 等.近2ka以来东海内陆架泥质区记录的高分辨率古气候演化[J].海洋学报, 2011, 33(3):85-93. http://d.old.wanfangdata.com.cn/Periodical/hyxb201103010 LIU Shengfa, SHI Xuefa, LIU Yanguang, et al. Environmental record from the mud area on the inner continental shelf of the East China Sea since 2ka[J]. Acta Oceanologica Sinica, 2011, 33(3):85-93. http://d.old.wanfangdata.com.cn/Periodical/hyxb201103010
[35]	江波.末次冰盛期以来黑潮流域的古环境演化[D].中国科学院研究生院(海洋研究所)硕士论文, 2007. http://cdmd.cnki.com.cn/article/cdmd-80068-2008033872.htm JIANG Bo, Palaeoenvironmental Evolution of the Kuroshio Region since the Last Maximum Glacial[D]. Master's thesis of Graduate University of Chinese Academy of Sciences (Institute of Oceanography), 2007. http://cdmd.cnki.com.cn/article/cdmd-80068-2008033872.htm
[36]	竺可桢.中国近五千年来气候变迁的初步研究[J].中国科学, 1973, 2: 168-189. http://d.old.wanfangdata.com.cn/Periodical/xsj201210011 ZHU Kezhen. A preliminary study of climate change in China since the past 5000 Years[J]. Science China, 1973, 2:168-189. http://d.old.wanfangdata.com.cn/Periodical/xsj201210011
[37]	施雅风, 孔昭宸, 王苏民, 等.中国全新世大暖期的气候波动与重要事件[J].中国科学B辑, 1992, 22(12): 1300-1308. doi: 10.3321/j.issn:1006-9240.1992.12.003 SHI Yafeng, KONG Zhaochen, WANG Sumin, et al. Climate fluctuation and important events during Holocene warm period in China[J]. Science China (Series B), 1992, 22(12): 1300-1308. doi: 10.3321/j.issn:1006-9240.1992.12.003
[38]	葛全胜, 郑景云, 满志敏, 等.过去2000a中国东部冬半年温度变化序列重建及初步分析[J].地学前缘, 2002, 9 (1): 169-181. doi: 10.3321/j.issn:1005-2321.2002.01.021 GE Quansheng, ZHENG Jingyun, MAN Zhimin, et al. Reconstruction and preliminary analysis of temperature variation series half of year in winter in East China during the past 2000 years[J]. Earth Science Frontiers, 2002, 9 (1): 169-181. doi: 10.3321/j.issn:1005-2321.2002.01.021
[39]	葛全胜, 郑景云, 满志敏, 等.过去2000a中国温度变化研究的几个问题[J].自然科学进展, 2004, 14 (4): 449-455. doi: 10.3321/j.issn:1002-008X.2004.04.014 GE Quansheng, ZHENG Jingyun, MAN Zhimin, et al. Several problems of the research of temperature variation in China[J]. Natural Science Progress, 2004, 14 (4): 449-455. doi: 10.3321/j.issn:1002-008X.2004.04.014
[40]	向荣, 杨作升, Satio Y, 等.济州岛西南泥质区近2300a来环境敏感粒度组分记录的东亚冬季风变化[J].中国科学D辑, 2006, 36(7): 654-662. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=zgkx-cd200607006 XIANG Rong, YANG Zuosheng, Satio Y, et al. East Asia Winter Monsoon changes inferred from environmentally sensitive grain-size component records during the last 2300 years in mud area southwest off Cheju Island[J], Science in China(Series D), 2006, 49(6):604-614. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=zgkx-cd200607006
[41]	徐军, 石学法, 刘升发, 等.晚全新世东亚季风高分辨率沉积记录:来自东海内陆架泥质区的证据[J].海洋科学进展, 2018, 36(2):216-228. doi: 10.3969/j.issn.1671-6647.2018.02.007 XU Jun, SHI Xuefa, LIU Shengfa, et al. High-resolution sedimentary record of East Asian monsoon during Late Holocene: evidence from the inner shelf mud area of East China Sea[J]. Advances in Marine Science, 2018, 36(2):216-228. doi: 10.3969/j.issn.1671-6647.2018.02.007
[42]	Yu S Y. Quantitative reconstruction of mid- to late-Holocene climate in NE China from peat cellulose stable oxygen and carbon isotope records and mechanistic models[J]. Holocene, 2013, 23(11):1507-1516. doi: 10.1177/0959683613496292
[43]	刘升发, 石学法, 刘焱光, 等.中全新世以来东亚冬季风的东海内陆架泥质沉积记录[J].科学通报, 2010, 55(14):1387-1396. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=kxtb201014014 LIU Shengfa, SHI Xuefa, LIU Yanguang, et al. Records of the East Asian winter monsoon from mud area in the inner shelf of the East China Sea since the mid-Holocene[J]. Chinese Science Bulletin, 2010, 55(14):1387-1396. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=kxtb201014014
[44]	翦知湣, 孟翊.长江口区全新世古环境变化及其对黑潮变化的响应[J].海洋地质与第四纪地质, 2002, 22(3): 77-82. http://hydz.chinajournal.net.cn/WKD/WebPublication/paperDigest.aspx?paperID=b4e5ea19-28b1-4513-8970-c3b2ce400b30 JIAN Zhimin, MENG Yi. Holocene paleoenvironment changes in the Yangtze River mouth and their responses to the variations in the Kuroshio Current[J]. Marine Geology & Quaternary Geology, 2002, 22(3): 77-82. http://hydz.chinajournal.net.cn/WKD/WebPublication/paperDigest.aspx?paperID=b4e5ea19-28b1-4513-8970-c3b2ce400b30
[45]	何华春, 王颖, 李书恒.长江南京段历史洪水位追溯[J].地理学报, 2004, 59(6):938-47. doi: 10.3321/j.issn:0375-5444.2004.06.017 HE Huachun, WANG Ying, LI Shuheng. Retrospect of historical flood level in Nanjing section of Yangtze River[J]. Acta Geographica Sinica, 2004, 59(6):938-47. doi: 10.3321/j.issn:0375-5444.2004.06.017
[46]	朱诚, 于世永, 张兵, 等.南京宝华山地区全新世沉积环境研究[J].地理科学, 1997, 17(3):253-258. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=QK199700940315 ZHU Cheng, YU Shiyong, ZHANG Bing, et al. Holocene sedimentary environment research in Baohuashan area of Nanjing[J]. Scientia Geographica Sinica, 1997, 17 (3): 253-258. http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=QK199700940315
[47]	李文宝, 王汝建, 陈建芳, 等.南海表层沉积物与水柱中沉降颗粒物对比研究及其古环境再造意义[J].海洋地质与第四纪地质, 2008, 28(4):73-83. http://hydz.chinajournal.net.cn/WKD/WebPublication/paperDigest.aspx?paperID=1b4416e2-9a1c-4e31-be97-3eea6b663186 LI Wenbao, WANG Rujian, CHEN Jianfang, et al. Correlation of surface sediments with sinking particulate matters in the south China Sea and implication for reconstructing paleoenvironment[J]. Marine Geology & Quaternary Geology, 2008, 28(4):73-83. http://hydz.chinajournal.net.cn/WKD/WebPublication/paperDigest.aspx?paperID=1b4416e2-9a1c-4e31-be97-3eea6b663186

Cited By

Cited by

Periodical cited type(3)

1.	密蓓蓓，张勇，梅西，王忠蕾，窦衍光. 南黄海表层沉积物稀土元素分布特征及其物源指示意义. 海洋地质与第四纪地质. 2022(06): 93-103 . 本站查看
2.	岳保静，刘金庆，刘健，廖晶，张军强. 渤海西缘YRD-1101孔晚更新世以来沉积物粒度特征及其环境变迁. 中国地质. 2020(03): 853-867 .
3.	田旭，胡邦琦，王飞飞，黄威，丁雪，宋维宇，徐方建. 末次冰消期（1.9万年）以来冲绳海槽中部黏土矿物来源及其环境响应. 中国地质. 2020(05): 1501-1511 .

Other cited types(2)

Get Citation

PDF

XML

Article views (4097) PDF downloads (138) Cited by(5)

Turn off MathJax

Article Contents

Abstract

References

Reconstruction of the redox environment in Okinawa Trough and its climatic implications since mid-Holocene