200 ka以来澳大利亚西北岸外沉积物源区风化的Mg同位素记录及其对澳洲古季风的响应 您所在的位置:网站首页 澳大利亚的季风气候 200 ka以来澳大利亚西北岸外沉积物源区风化的Mg同位素记录及其对澳洲古季风的响应

200 ka以来澳大利亚西北岸外沉积物源区风化的Mg同位素记录及其对澳洲古季风的响应

2024-06-27 03:19| 来源: 网络整理| 查看: 265

摘要

本文通过对IODP 363航次于澳大利亚西北岸外陆架上钻取的U1483站岩芯进行沉积物粒度、镁同位素以及主量元素成分等分析,重建200 ka以来帝汶海西南部沉积物输入演化及其指示的源区风化和侵蚀历史,探讨海洋沉积物中细粒硅质碎屑组分镁同位素的古环境指示意义。U1483站陆源碎屑组分主要由黏土质粉砂组成,其δ26Mg变化范围超过0.25‰。通过计算化学蚀变指数(chemical index of alteration, CIA)和两种物理侵蚀指标(包括陆源物质堆积速率和Ti/Ca比值),结果显示200 ka以来δ26Mg指标与CIA具有非常一致的曲线形态。本文推测陆源碎屑组分的Mg同位素组成主要反映物源区大陆硅酸盐风化强度的变化,而受矿物学分选、岩性和早期成岩作用的影响较小。结合区域古气候记录,我们发现本研究中的风化和侵蚀记录与同一个站位已发表的澳洲夏季风降水和表层海水温度变化具有较好的耦合关系,而与赤道太平洋海平面变化的相关程度较低,反映了轨道时间尺度上沉积物所记录的物源区风化和侵蚀演化主要受控于澳洲古季风系统,表现为气候驱动型风化模式。本研究δ26Mg指标的应用为我们理解区域大陆风化及其对气候演化的响应和反馈机制提供了全新的同位素视角。

Abstract

We present a new multiproxy dataset of grain size, Mg isotopes and major elemental compositions of sediments from the International Ocean Discovery Program Site U1483, situated in the northwestern Australian margin, in order to reconstruct the terrestrial sediment supply to the southwestern Timor Sea, as well as the continental weathering and erosion history in the source region since 200 ka. A second objective is to explore the potential of δ26Mg values of fine-grained siliciclastic marine sediments in tracing paleoclimate changes. The results demonstrate that terrestrial siliciclastic fraction of sediments at IODP Site U1483 are mainly composed of clay silt, with δ26Mg values ranging larger than 0.25‰. The Chemical index of alteration (CIA) and two physical erosion parameters including mass accumulation rates (MAR) and Ti/Ca ratios are reported. Over the last 200 ka, the δ26Mg index shows a shape of curve in a great similarity with that of the CIA, suggesting that Mg isotope compositions are mostly indicative of weathering intensity changes in the source region, and are little influenced by mineralogical sorting, lithology and early diagenesis. Combined with regional paleoclimate records, we notice that our new weathering and erosion data show nearly synchronous co-variations with published Australian summer monsoonal precipitation and the sea surface temperature records from the same site since 200 ka. However, there is relatively low coherence between our data and the sea level in the equatorial Pacific. By compiling the data, this study suggests that the weathering and erosion evolution of the source region on the orbital timescale were mainly controlled by the Australian paleo-monsoon system during the last 200 ka, pointing to the “climate-driving weathering” pattern. The application of δ26Mg index provides a new isotopic perspective on understanding regional continental weathering and its response as well as feedback mechanisms to the climate evolution.

关键词

粒度 ; 镁同位素 ; 陆源硅酸盐碎屑 ; 帝汶海 ; 澳洲古季风

Keywords

grain size ; Mg isotopes ; terrestrial siliciclastic sediments ; Timor Sea ; Australian paleo-monsoon

硅酸盐风化作用是连接地球外部圈层的重要地质过程,在塑造地表形态和调节生物地球化学循环中起着关键作用,并通过消耗大气CO2调节长时间尺度的全球碳循环和气候变化(Berner,1992; West et al.,2005; Vance et al.,2011)。在这一过程中,大量的沉积物被河流输送到边缘海或深海,可能记录各种时间尺度上的大陆风化和水文气候变化信息(Eiriksdottir et al.,2011)。然而,海洋沉积物大多经历了复杂的“源-汇”沉积过程和物质循环,给我们解读源区古环境演化、理解“硅酸盐风化-气候演化”的响应和反馈机制带来了挑战(Hu Dengke et al.,2012; Wan Shiming et al.,2017)。为了更好地重建古气候古环境演变记录,人们通常需要采用多种代用指标相结合的方法来进行研究,如矿物学指标(黏土矿物组合和重矿物)、沉积物粒度以及地球化学指标(同位素和主微量元素)等。近年来,镁同位素指标(δ26Mg)在示踪季风演化和大陆风化等地质过程中发挥了重要作用(Teng Fangzhen et al.,2010a; Wimpenny et al.,2011,2014a; Huang Kangjun et al.,2016; Ma Long et al.,2019)。

镁元素在岩石圈和水圈中均具有较高的自然丰度。含镁黏土矿物是硅酸岩化学风化过程中的重要产物之一,其形成过程中记录了丰富的气候和环境演化信息。研究发现,Mg同位素体系在岩浆分异过程中分馏有限(Teng Fangzhen et al.,2010b; Teng Fangzhen,2017),在低温地球化学过程中则产生显著分馏(Huang Kangjun et al.,2012; Liu Xiaoming et al.,2014; Wimpenny et al.,2014a; 图1); 硅质碎屑岩的Mg同位素系统不受与低级变质和成岩作用相关改造的影响(Wang Shuijiong et al.,2015)。相对于传统风化指标如化学蚀变指数(chemical index of alteration,CIA)和Sr同位素等,Mg同位素组成受母岩类型和成岩作用的影响较小(Huang Kangjun et al.,2016)。有研究表明,在河流入海过程中Mg属于保守元素不产生分馏(Pogge et al.,2008),陆源沉积岩细粒硅质碎屑组分强烈的δ26Mg正漂移指示极端的化学风化作用(Huang Kangjun et al.,2016)。因此,海洋沉积物硅质碎屑组分的Mg同位素组成可能受“源-汇”沉积过程和物质循环的影响较弱,主要携带了地质历史时期物源区大陆风化演化以及区域古气候古环境演化的信息。

迄今为止,有关海洋沉积物硅质碎屑组分Mg同位素组成的报道较为罕见,轨道时间尺度上深海沉积物Mg同位素与硅酸盐风化以及气候因子之间的联系也尚不清楚,因此制约了该新指标的广泛运用。本文以国际大洋发现计划(International Ocean Discovery Program,IODP)第363航次在帝汶海西南部、澳大利亚西北岸外陆架上钻取的U1483站岩芯为研究对象(图2),开展深海沉积物碎屑组分粒度、Mg同位素和主量元素成分等分析,重建200 ka以来澳大利亚西北岸外沉积物输入和物源区大陆硅酸盐风化历史,继而讨论轨道时间尺度上其与季风降雨、区域海水温度以及海平面升降等因素之间的联系; 旨在探索海洋沉积物中陆源硅酸盐碎屑组分 Mg 同位素示踪大陆风化的潜力,挖掘帝汶海沉积物所承载的区域古气候和古环境信息。

1 区域概况

帝汶海(Timor Sea)是澳大利亚西北部与印度尼西亚群岛之间的边缘海,位于现代印度洋-太平洋暖池(Indo-Pacific Warm Pool,IPWP)的西南部,其北部的帝汶海槽水深可达 3000 m 以上,是印尼穿越流(Indonesian Throughflow,ITF)进入印度洋的主要通道之一(Gordon,2005); 其南部的澳大利亚大陆架,约占该海域面积的2/3,称为Sahul Shelf。澳大利亚大陆架的范围向西南延伸到约22°S,东北约131°E(Mollan et al.,1969),其大地构造环境为开阔大洋的被动边缘,属于陆架边缘张性裂谷盆地,主要包含4个盆地和1个造山带,自西南到东北依次为北卡那封(North Carnarvon)盆地、柔布克(Roebuck)盆地、布劳斯(Browse)盆地、波拿巴(Bonaparte)盆地和帝汶-班达(Timor-Banda)褶皱带,这些地质单元最终构成了西澳巨型盆地,其上沉积了数千米厚的盖层(Mollan et al.,1969; Veevers et al.,1978)。帝汶海北部的印尼群岛与南部的西北澳大利亚岩性差异巨大:印尼群岛主要由新生代较年轻的火山岛弧岩组成,仅有少量古老基岩出露,如苏门答腊岛北部和中部的早—中石炭纪基岩以及巴布亚新几内亚西部的古生代—中生代岩石(Vroon et al.1995; Ehlert et al.,2011); 澳大利亚西北部则主要由古老的太古代和中元古代克拉通岩石以及古生代沉积地层构成(Johnson,2005)。

图1 不同地质储库中镁同位素组成(据Huang Kangjun et al.,2016修改)

Fig.1 The compositions of Mg isotopes (δ26Mg) in major terrestrial materials (modified from Huang Kangjun et al., 2016)

SW—海水(δ26Mg=-0.85‰ ± 0.04‰,据本次研究); UCC—大陆上地壳(δ26Mg =-0.22‰±0.10‰,据Li Wangye et al.,2010); U1483硅酸盐碎屑组分(据本次研究); 高岭石、蒙脱石和伊利石(据Wimpenny et al.,2014b)

SW—seawater (δ26Mg =-0.85‰ ± 0.04‰, after this study) ; UCC—upper continental crust (δ26Mg =-0.22‰±0.10‰, after Li Wangye et al., 2010) ; siliciclastic sediments from U1483 (after this study) ; kaolinite, montmorillonite and illite (after Wimpenny et al., 2014b)

帝汶海区及其相邻的陆地包括印尼群岛(南部的爪哇-班达岛、帝汶岛等)和澳大利亚西北部的气候受到热带辐合带(intertropical convergence zone,ITCZ)南北迁移的影响呈显著的季节性变化特征(Doupé et al.,2002; Lindsay et al.,2005; Zhang Peng et al.,2020,2021)。现代气候记录表明(图3a、b),南半球夏季(11月~次年1月)时,ITCZ 南移,该地区以湿热的西北季风(澳大利亚夏季风)为主,降水丰沛,该降水量可达到全年降水总量的90%(Spooner et al.,2005; Stuut et al.,2019); 冬季(6~9月)时 ITCZ 北迁,干旱的东南季风(澳大利亚冬季风)盛行,降水稀少,气候干燥(Suppiah,1992)。季风降雨带的迁移调控着区域径流量以及陆源物质输入量的变化,改变着研究区的沉积环境。前人研究发现,在ITF水体和区域海气相互作用的影响下,帝汶海区存在一个显著的NE—SW向温盐梯度,表层海水温度(sea surface temperature,SST)降低、表层海水盐度(sea surface salinity,SSS)增加,而温跃层水团则表现出相反的温盐度梯度(Locarnini et al.,2006; Holbourn et al.,2011)。同时,澳大利亚西北岸外陆架上沉积物的线性沉积速率也呈现出NE—SW向的降低趋势(Keep et al.,2018; Kuhnt et al.,2018),这可能与陆架容纳空间、河口距离以及季风降雨带的位置有关(Pei Renjie et al.,2021)。帝汶海区较大的入海河流主要为澳大利亚西北部的Fitzory河和Ord河(Vorosmarty et al.,1998),二者的年均流量分别约为254 m3/s和636 m3/s; 且这两条河的丰水期均为南半球夏季(12月~次年3月),呈现出极端的季节性特征(图3c; Doupé et al.,2002; Lindsay et al.,2005; Kuhnt et al.,2015)。独特的地理位置以及潜在物源区巨大岩性差异的特征使得帝汶海区沉积物蕴含着丰富的古海洋古气候学信息,是进行物源示踪(Gingele et al.,2001; Ehlert et al.,2011; Stumpf et al.,2015)和研究ITF演化、IPWP范围和波动、ITCZ纬向迁移/纬向范围上膨胀收缩,以及澳洲季风发育程度等古海洋古气候演化的优良场所(Holbourn et al.,2005; Xu Jian et al.,2008; 徐建等,2020; Zhang Peng et al.,2020,2021; Pei Renjie et al.,2021)。

图2 澳大利亚西北岸外的研究站位和沉积物主要陆源元素分布图

Fig.2 Schematic map showing the locations of studied cores and concentrations of main terrigenous elements in sediments from the northwestern Australian margin

(a)—IODP U1483站(红色点)和文中涉及的其他站位(黑色点),以及印尼穿越流(ITF)、鲁汶流(LC)和南赤道流(SEC)示意图;(b)、(c)—钻孔表层沉积物(据Plank et al.,1998; Zhang Peng et al.,2020; Pei Renjie et al.,2020)、河流样品<63 μm细粒组分(据Pei Renjie et al.,2020)以及火山岩样品(据Turner et al.,2001)的主要陆源元素组成(Si,Al,Fe,K,Ti); 蓝色和黑色箭头指示洋流,黑色数字指示ITF出口处流量(单位:1 Sv=106 m3/s)(据Gordon,2005); 底图来自www.maps-for-free.com

(a) —the locations of IODP Site U1483 (red filled circle) and other published coring sites involved in this study (black filled circle) , as well as the Indonesian Throughflow (ITF) , Leeuwin Current (LC) and South Equatorial Current (SEC) ; (b) , (c) —showing locations of coring sites in relation to adjacent main rivers and distribution of main terrigenous elements (Si, Al, Fe, K and Ti) in fine-grained (< 63 μm) fractions of terrigenous materials in marine sediment cores (after Plank et al., 1998; Zhang Peng et al., 2020; Pei Renjie et al., 2020) , river sediments (after Pei Renjie et al., 2020) and volcanic rocks (after Turner et al., 2001) ; blue and black arrows indicate paths of oceanic currents and numbers in black show the transport volumes of the ITF through the individual exits as given in Sverdrup (1 Sv=106 m3/s) (after Gordon, 2005) ; base map was created via www.maps-for-free.com

图3 帝汶海和临近区域现代降水和风场模式图

Fig.3 Modern rainfall and wind pattern of the Timor Sea and nearby region

(a)、(b)—1月和7月研究区1000 hPa风场模式(黑色箭头)和平均陆地降水量(彩色带),底图据Ocean Data View(http://odv.awi.de)绘制,降水数据为1951~2000年月平均值,引自 http://iridl.ldeo.columbia.edu/SOURCES/.DEKLIM/.VASClimO/.PrcpClim,风场数据引自http://iridl.ldeo.columbia.edu/expert/ds:/SOURCES/.NOAA/.NCEP-NCAR/.CDAS-1,红色星号为U1483站所处位置;(c)—1893~2004年Fitzory流域月均降水量和河流流量(据Kuhnt et al.,2015)

(a) , (b) —January and July monthly-mean wind pattern (black arrows) and rainfall (colored shadings) on land in the studied region, base maps were created via Ocean Data View (http://odv.awi.de) , data of monthly rainfall over the period of C.E.1951~2000 from http://iridl.ldeo.columbia.edu/SOURCES/.DEKLIM/.VASClimO/.PrcpClim, data of 1000 hPa wind pattern from http://iridl.ldeo.columbia.edu/expert/ds:/SOURCES/.NOAA/.NCEP-NCAR/.CDAS-1, the red-colored pentagram shows the location of IODP Site U1483; (c) —monthly-mean rainfall and river discharge data at Fitzory River Crossing from 1893 to 2004 (after Kuhnt et al., 2015)

2 材料及方法

U1483站(13°5.24′S,121°48.25′E,水深1733 m)位于澳大利亚西北海域布劳斯盆地西北翼的斯科特(Scott)高原上(图2)。IODP 363航次于2016年在该站位处共获取了A、B、C三根钻孔岩芯; 为避免钻孔取芯间断,根据船测岩芯物性数据将这三根钻孔岩芯拼接成了一根完整的岩芯序列SPLICE。本研究工作样品来自U1483站SPLICE上部的沉积物,其岩性相对均一,主要由富含有孔虫的钙质超微软泥组成(Rosenthal et al.,2017)。由于在同一位置钻取的MD01-2378站(13°04.95′S,121°47.27′E,水深1783 m)具有21个AMS 14C绝对年龄约束以及与冰芯记录对比而建立的高分辨率底栖有孔虫Cibicidoides wuellerstorfiδ18O年代地层框架(Holbourn et al.,2005),U1483站上部41 m岩芯的高分辨率年代地层框架总体上是通过与MD01-2378站记录对比获得。具体为利用QAnalySeries软件将U1483与MD01-2378站两根柱状岩芯以2 cm为间隔进行XRF扫描获得的ln(K/Ca)曲线进行关联(Zhang Peng et al.,2020)。结果显示U1483站沉积物中浮游有孔虫属种Globigerinoidesruber(pink)末次出现的时间约为122.91 ka,与Thompson et al.(1979)记载的该属种生物地层事件发生的时间一致; 同时显示2 cm间隔XRF扫描获得的ln(K/Ca)记录时间分辨率约为0.2 ka(Zhang Peng et al.,2020)。本研究对SPLICE上部19 m以 40 cm 为间隔采样,共计获得47个沉积物样品,时间分辨率约为4 ka,年龄跨度约为 0~200 ka。U1483站的总物质堆积速率(the total mass accumulation rate,g/cm2/ka)根据Rea et al.(1981)的公式MAR = DBD × LSR计算所得,其中DBD为干容重(g/cm3),LSR为线性沉积速率(cm/ka)。

进行粒度分析和Mg同位素测试的样品均为除掉有机质、碳酸盐和Fe-Mn氧化物的陆源硅质碎屑组分。沉积物样品的预处理在西北大学地质学系海洋元素分析实验室进行,提取方法主要参考Simon et al.(2020)建立的海洋沉积物连续相态提取流程。为了避免粗颗粒对样品化学成分的影响,本文以<63 μm的细颗粒酸不溶物质代表陆源碎屑。首先经过63 μm的湿筛,随后烘干称重; 向每个样品加入6%的过氧化氢去除有机质,充分反应后用超纯水清洗至中性; 再加入1 mol/L缓冲醋酸去除碳酸钙,反应完全后加入超纯水清洗数次直到出现抗絮凝状态确保完全去除样品中的酸根离子,除碳酸钙步骤重复3遍; 随后,加入0.05 mol/L盐酸羟胺-15%醋酸反应24 h去除Fe-Mn氧化物,超纯水清洗至中性。最后,烘干称重并将所得重量值与初始重量值相比乘以100%得到陆源物质百分含量。陆源物质组分提取的全过程在室温(约25℃)下进行,避免水浴加热和超声振荡,以防破坏硅酸盐矿物结构。

陆源碎屑样品粒度和Mg同位素测试均在西北大学大陆动力学国家重点实验室完成。粒度分析所使用的仪器为英国MALVERN公司生产的MS-2000型激光粒度仪,该仪器的测量范围为0.02~2000.00 μm,重复测量相对误差小于3%。Mg同位素地球化学测试前,首先对样品和标样(BCR-2、BHVO-2、SW)进行化学消解:称取约10 mg样品于Savillex Teflon © beaker中,加入1 mL HNO3∶ H2O(1∶1)、3 mL HF和两滴HClO4,密封后置于电热板(150℃)上加热48 h消解样品; 完全溶解后的样品蒸干,加入1 mL高纯HNO3,随后继续蒸干,此步骤重复2遍; 最后用2%的HNO3将部分样品稀释100倍用于Mg含量测试。Mg的纯化采用Bao Zhian et al.(2019)建立的阳离子交换色谱法流程进行:定量吸取满足50 μg 上样量的样品后,首先加入4 mol/L NaOH溶液进行共沉淀反应去除基体元素K; 随后对转换为HCl介质的样品进行上柱分离,包括充填2 mL AG50W-X12的大柱子和充填0.5 mL AG50W-X12的小柱子。为了确保Mg纯度,每份样品至少上柱分离2遍,且纯化过程保证样品回收率>99%,空白样Mg<10 ng。过滤后收集的Mg溶液在80℃的电热板上蒸干,最终用2% HNO3溶液溶解待测试。Mg同位素上机测试,采用“标样-样品”交叉法校正质量歧视效应,消除长期仪器信号波动的影响(Galy et al.,2001; Teng Fangzhen et al.,2007)。每份样品的Mg同位素比值在Nu plasma II多接收器电感耦合等离子体质谱仪(MC-ICP-MS)上至少测定4次(Bao Zhian et al.,2019),法拉第杯H5、Ax、L5分别接收26Mg、25Mg和24Mg信号,Mg同位素比值进行国际标准DSM3归一化。Mg同位素组成用测定值与DSM3的千分偏差δ(‰)表示,公式如下:

δxMg=[(xMg/24Mg)sample/(xMg/24Mg)DSM3-1]×1000,其中x为25或26。

为了进一步保证数据的准确性,将本研究所测得BHVO-2、BCR-2、SW和实验室长期标准样品alfa Mg的δ25Mg、δ26Mg值与先前报道数据进行了比较,所得标准样品的分析结果与先前发表的值较为一致(表1)。同时,3份随机重复样的测试结果表明误差在2SD不确定度范围内。此外,本研究所测得样品和标样的δ25Mg、δ26Mg值均落在斜率为0.5121(R2=0.9998)的单一质量分馏线上(图4),分析精度为0.03‰,进一步支持了测试结果的可信度。

表1 本研究的标准样品Mg同位素组成测试结果和前人测试数据的对比

Table1 Comparison of Mg isotopic compositions of standards analyzed in this study with published data

注:2SD表示同一次测试过程中获得的多个重复数据的2倍标准偏差。

图4 U1483站样品和分析标样的Mg同位素图解

Fig.4 Mg isotopic composition of samples from IODP Site U1483 and standards analyzed in this study

图中黑色虚线代表镁同位素质量相关平衡分馏线(斜率为0.5121)

The black dashed line represents the Mg equilibrium mass-dependent fractionation curve with a slope of 0.5121

3 结果

本研究中所得分析数据均在表2中列出。200 ka以来,U1483站的沉积速率较高,平均线性沉积速率约为9.97 cm/ka(Zhang Peng et al.,2020),平均总物质堆积速率约为7.07 g/cm2/ka。研究时段内,该站沉积物中陆源物质百分含量为29.28%~43.88%,平均35.74%。陆源物质堆积速率由陆源物质百分含量乘以总物质堆积速率获得,其变化范围为1.16~4.17 g/cm2/ka,平均2.53 g/cm2/ka。U1483站陆源物质堆积速率呈现明显的冷-暖期变化特征,即冷期时较高(平均值2.74 g/cm2/ka)、暖期时相对较低(平均值2.36 g/cm2/ka),与总物质堆积速率变化趋势一致,但与全样CaO含量(Zhang Peng et al.,2020)变化相反(图5,图中CaO、黏土和细砂的反向标尺)。根据不同粒度组分的贡献,U1483站的陆源物质主要由粉砂(65.14%~77.74%,平均70.49%)、随后是黏土(21.94%~34.46%,平均28.77%)和少量细砂(0%~3.35%,平均0.74%)组成,平均粒径(mean grain size,Mz)在8.08~14.59 μm范围变化(平均10.73 μm)。研究时段内,细砂含量绝对值的变化整体较小,冷-暖期对比不明显; 粉砂含量在暖期(70.81%)略高于冷期(70.09%); 黏土含量则在冷期(29.76%)略高于暖期(28.95%)。此外,粉砂组分的变化趋势和平均粒径相同,而黏土组分与平均粒径相反(图5)。整体而言,200 ka以来U1483站记录了冷期时海洋生产力降低,而陆源物质输入增加,主要表现为粒径较小的黏土含量增多、粉砂含量相对减少; 暖期时则与之相反。

图4显示U1483站陆源碎屑组分的δ25Mg和δ26Mg值之间呈明显的正相关关系(斜率为0.5121),并与Mg同位素质量相关平衡分馏线相吻合。在研究时段内,δ26Mg值的变化范围在-0.06‰±0.04‰到0.19‰±0.02‰之间,平均值和中间值均为0.08‰,最高值0.19‰出现在海洋氧同位素 7期(MIS 7)。总体上,U1483站δ26Mg的绝对值相对集中,且冷-暖期差异不太明显(冷期0.0767‰,暖期0.0764‰),但与陆源物质堆积速率呈现较为一致的曲线形态(图5)。

4 讨论 4.1 U1483站沉积物物源

沉积物的矿物、元素和同位素组成变化可以反映边缘海沉积物物源和古环境的变迁(杨守业等,2015)。目前,帝汶海区物源识别的研究比较薄弱,该海区沉积环境复杂、缺乏大量潜在陆地端元以及长时间尺度海洋沉积物的黏土矿物、主要陆源元素和Sr-Nb-Pb同位素组成等记录,帝汶海区仅有的少量短时间尺度的研究之间存有争议(Gingele et al.,2001; Ehlert et al.,2011; Stumpf et al.,2015; Zhang Peng et al.,2020)。就本次研究U1483站(与MD01-2378站几乎相同位置)而言(图2),前人分别利用沉积物黏土组分Sr-Nb-Pb同位素和全样稀土元素(rare earth elements,REE)模式研究沉积物来源所获得的结论截然不同(Stumpf et al.,2015; Zhang Peng et al.,2020; 图6)。Stumpf et al.(2015)基于MD01-2378站MIS 3期的20份黏土放射性Sr-Nb-Pb同位素数据,根据87Sr/86Sr值的差异判断爪哇-班达对沉积物的贡献远高于澳洲西北部,认为澳大利亚西北部大陆架上沉积的细粒陆源碎屑主要来源于ITF路径上的印尼群岛(图6a~d)。Zhang Peng et al.(2020)通过对比U1483站(MIS 11~MIS 1期)和位于其东北部的DSDP 262站(10°52.19′S,123°50.78′E,2315 m)“沉积物/UCC”标准化REE模式,发现两个钻孔的沉积物具有相似的“轻稀土略微亏损,中、重稀土相对富集”特征,判断两者的陆源物质来源非常相似(图6e)。DSDP 262站位于帝汶海槽的最西边(图2),受到ITF的影响要远强于U1483站所处区域。Vroon et al.(1995)通过对比东印度洋沉积物的Sr-Nb-Pb同位素组成以及REE模式,判断DSDS 262站的陆源物质主要来自澳洲北部,因此位于其南部且更靠近澳大利亚的U1483站也主要接受来自澳洲的陆源物质输入(Zhang Peng et al.,2020)。

表2 U1483站样品深度和年龄(据Zhang Peng et al.,2020),以及陆源物质组分百分含量、陆源物质堆积速率、平均粒径、各粒级百分含量、δ25Mg和δ26Mg值

Table2 Depth and age (after Zhang Peng et al., 2020) , percentage of terrestrial contents, mass accumulation rate of the terrestrial materials, mean grain size, percentage of different-sized grains, δ25Mg and δ26Mg data of sediment samples from IODP Site U1483

注:2SD表示同一次测试过程中获得的多个重复数据的2倍标准偏差。

图5 U1483站200 ka以来沉积地球化学记录

Fig.5 Geochemical records of sediment samples from IODP Site U1483 since 200 ka

(a)—底栖有孔虫C. wuellerstorfi δ18O(据Zhang Peng et al.,2020);(b)—线性沉积速率;(c)—全样CaO百分含量(据Zhang Peng et al.,2020);(d)—总物质堆积速率;(e)—陆源物质堆积速率;(f)—陆源组分的平均粒径;(g)~(i)—分别为黏土、粉砂和细砂的百分含量;(j)—硅质碎屑组分δ26Mg值; 灰色条带为冷期; 底栖有孔虫δ18O曲线上的数字标号为海洋氧同位素期(Marine Isotope Stage,MIS); MIS界限年龄数据引自Lisiecki et al.(2005); T-I和T-II分别为冰期终止期I和II; 请注意临近每条曲线坐标轴的箭头指示数值增大; δ26Mg曲线上线段为测试误差2SD

(a) —benthic foraminiferal C. wuellerstorfi δ18O (after Zhang Peng et al., 2020) ; (b) —linear sedimentation rate; (c) —percentage of CaO content in bulk sediments (after Zhang Peng et al., 2020) ; (d) —total mass accumulation rate; (e) —mass accumulation rate of terrestrial materials; (f) —mean grain size; (g) ~ (i) —percentage of clay, silt and fine-sand; (j) —δ26Mg of terrestrial siliciclastic fraction; the gray color bars mark cold periods; numbers alongside the δ18O curve indicate the marine isotope stage (MIS) ; boundary ages of the MISs are according to Lisiecki et al. (2005) ; T-I and T-II are glacial terminations I and II, respectively; please note the arrows aside the scale bars point to larger values; the error bars of δ26Mg curve are 2SD

笔者发现Stumpf et al.(2015)研究中的MIS 3期样品黏土组分206Pb/204Pb和εNd与爪哇-班达以及澳洲西北部两个潜在源区均有重叠,且在ITF路径上更靠近MD01-2378站的两份表层样品也处于这两个潜在源区范围内(图2a和图6b、d中的3-阿拉弗拉海和4-帝汶海站位)。同时,Sr同位素的对比也似乎存在潜在的问题:① 该站的黏土组分与潜在源区的87Sr/86Sr值差异均相对较小(爪哇-班达:0.7069<87Sr/86Sr<0.7282; 澳大利亚西北部:0.7352<87Sr/86Sr<0.8299; MD01-2378站:0.7189<87Sr/86Sr<0.7222); ② 用来对比的澳大利亚区域样品多为更远离帝汶海峡出口的澳洲陆架上表层沉积物(Ehlert et al.,2011),可能受到澳洲风尘输入以及西澳流的影响,从而显著区别于MD01-2378(U1483)站所处沉积环境; ③ 缺少相邻陆上入海河流的样品对比,且有一份来自澳洲西北部Fitzory河的样品87Sr/86Sr值(0.7209; Harrington et al.,2011)与MD01-2378站样品非常接近(图6a、c)。因此,笔者认为Stumpf et al.(2015)提出的“MD01-2378站沉积物以印尼群岛陆源输入为主”的结论需要更多潜在源区的同位素证据支撑,并且MIS 3期与地质历史上的其他时期存在显著差异,对该研究区的物源识别需要更长时间尺度的黏土矿物组合以及同位素指标的研究。

目前由于缺乏更多潜在源区的黏土矿物组合、同位素数据等传统物源识别指标的报道,对于研究区长时间尺度上源区的明确厘定仍然存在很大困难。就现有轨道尺度上的主量元素以及REE模式结果而言,更多证据支持U1483站沉积物来源以澳洲西北部河流供应为主。本文对比了U1483站(Zhang Peng et al.,2020)、相邻SO257-18548站(Pei Renjie et al.,2021)和ODP765站(Plank et al.,1998)的顶部样品,以及来自潜在物源区的澳洲西北部河流<63 μm沉积物细粒组分(Pei Renjie et al.,2021)和爪哇-班达岛弧玄武岩样品(Turner et al.,2001)的主要陆源元素组成(表3,图2b、c),发现U1483站的陆源元素组成与相邻SO257-18548站、ODP765站以及澳洲西部海岸Derby地区和在此处入海的Fitzroy河的两份现代细粒黏土组分陆源元素组成非常接近(Fitzroy河样品高的Si元素含量是由于粉砂组分中含较多石英),且与来自印尼群岛的样品差异明显。这一结果支持了Kuhnt et al.(2015)和Zhang Peng et al.(2020)的研究,即U1483(MD01-2378)站的陆源碎屑物质主要来自于澳大利亚西北部的河流输入,印尼群岛的远洋碎屑对研究站位的贡献相对有限。同时,200 ka以来U1483站沉积物主量元素和稀土元素组成较为稳定(Zhang Peng et al.,2020; 图6e),陆源碎屑δ26Mg值相对集中(图1),且陆源堆积速率与指示ITF强度变化的参数ΔTWTSO18460-MD01-2378(Holbourn et al.,2011)也缺乏相关性(R=0.09; 图7a)。由此,笔者认为U1483站在研究时段内处于相对稳定且物源较单一的沉积环境,ITF搬运来源微乎其微,而澳洲西北部的河流输入是其主要物源供应,可以用来重建区域大陆风化强度的演变。

图6 U1483站(MD01-2378站)沉积物物源判定

Fig.6 Determination of provenance for sediments at the location of Site U1483 (MD01-2378)

(a)~(d)—MD01-2378站和ITF路径上表层沉积物黏土组分放射性Sr-Nd-Pb同位素组成与潜在端元同位素特征对比(据Ehlert et al.,2011; Stumpf et al.,2015修改),其中Fitzory河样品87Sr/86Sr值据Harrington et al.(2011);(e)—U1483站和DSDP 262站沉积物全样UCC标准化REE模式图(据Vroon et al.,1995; Zhang Peng et al.,2020修改)

(a) ~ (d) —radiogenic Sr-Nd-Pb isotope series of the clay-sized fraction from core MD01-2378 and marine core top sediments within the ITF pathway in comparison with potential endmembers (modified from Ehlert et al., 2011; Stumpf et al., 2015) , the 87Sr/86Sr data of Fitzory river sample after Harrington et al. (2011) ; (e) —distribution patterns of UCC-normalized rare earth elements in bulk sediments from IODP Site U1483 and DSDP Site 262 (modified from Vroon et al., 1995; Zhang Peng et al., 2020)

4.2 U1483站沉积物源区风化强度与澳洲古季风 4.2.1 风化指标及其影响因素

海洋沉积物中的陆源碎屑组分主要形成于大陆硅酸盐风化作用,是源区特定母岩、构造背景和气候等因素共同影响下的风化产物(Nesbitt et al.,1982; Clift et al.,2002)。尽管其组成可能受到入海后洋流及沉积分异等因素的影响,但一定程度上仍继承了研究区累积风化演变的平均信号。本文采用传统化学风化指标CIA和潜在化学风化指标硅酸盐δ26Mg值来指示化学风化强度,同时计算陆源物质堆积速率和Ti/Ca值用于指示物理侵蚀以及径流输入量。CIA值为通过校正U1483站沉积物主量元素含量(Zhang Peng et al.,2020),利用Nesbitt et al.(1982)提出的公式CIA=Al2O3/(Al2O3+CaO*+Na2O+K2O)×100计算所得。其中,氧化物含量为摩尔含量,CaO*为硅酸盐组分中的含量。由于海水盐类中富集Na组分,沉积物的Na含量需要校正海水,即:Naxs=Na-(0.1×Al),0.1为页岩Na/Al平均值(Wedepohl,1971); Na含量校正值 Na2Ocorr=Na2O-Na2Oxs。基于Naxs值,Al和K也通过海水组成进行校正(Hu Dengke et al.,2012)。对于硅酸盐组分CaO*含量,在不明确碳酸盐和磷酸盐含量的情况下,本文根据McLennan(1993)提出的间接法进行计算:CaO剩余=CaO-P2O5×10/3。硅酸盐中CaO与Na2O通常以1∶1比例存在,因此比较CaO剩余和Na2Ocorr摩尔浓度,以较低值作为硅酸盐组分的CaO*含量。

图7 U1483站沉积物多种指标相关性图解

Fig.7 Cross plots of multi-proxies for Site U1483

(a)—陆源物质堆积速率与ΔTWTSO18460-MD01-2378相关性(0~140 ka,据Holbourn et al.,2011);(b)~(e)—平均粒径与陆源物质堆积速率、Ti/Ca、δ26Mg以及化学蚀变指数(CIA)相关性(0~200 ka)

(a) —correlation of mass accumulation rate of terrestrial materials to ΔTWTSO18460-MD01-2378 (0~140 ka, after Holbourn et al., 2011) ; (b) ~ (e) —correlation of mean grain size to mass accumulation rate of the terrestrial material, Ti/Ca, δ26Mg and CIA, respectively (0~200 ka)

表3 澳大利亚西北岸外海洋表层沉积物和邻区河口以及陆地样品的主要元素含量

Table3 Concentration of main terrigenous elements of adjacent marine sediment cores, river sediments and land samples to the northwestern Australian margin

注:a据 Zhang Peng et al.,2020; b据 Pei Renjie et al.,2021; c据Plank et al.,1998; d据Turner et al.,2001。

沉积物陆源组分的元素和同位素组成会受到化学风化、物源变化、粒级分选作用以及成岩作用等的影响(Fralick et al.,1997; Kump et al.,2000; Clift et al.,2008; West,2012; Garzanti et al.,2014)。前文有述U1483站具有相对稳定且单一的沉积环境,因此物源变化不是控制该站风化和侵蚀指标变化的主要因素。对于粒级分选作用的影响,一般采用相关性图解来进行分析(Wan Shiming et al.,2007; Xu Zhaokai et al.,2018)。图7b~e显示,至少在U1483站沉积物所处的环境中,风化和侵蚀指标与平均粒径之间的相关性均非常低,表明运输过程或水动力分选作用对研究区陆源组分的元素和同位素组成影响较小。碱金属元素如Na、K在沉积物成岩过程中可以发生迁移(Nesbitt et al.,1982),Al2O3-(CaO* + Na2O)-K2O图解一直以来被用于检验沉积物成岩作用(Fedo et al.,1995)。未发生交代的沉积岩投点应该落在平行于A-CN轴的风化趋势线上; 如果有外来Na、K加入,投点将会偏移风化趋势线与A-CN轴呈斜交状态(Fedo et al.,1995)。图8显示,U1483站样品点均平行于A-CN轴,表明并未有成岩作用发生。对于Mg同位素指标,成岩作用的潜在影响可能与海水中Mg(δ26Mgsw =-0.85‰ ± 0.04‰)的吸收有关,从海水中产生的自生黏土δ26Mg值通常比大陆风化产物更轻(Higgins et al.,2015),此过程可能会导致U1483站细粒硅酸盐δ26Mg值随成岩作用的进行而发生变化; 然而U1483站硅质碎屑δ26Mg值并无系统地随钻孔深度或沉积物年龄的变化,且图1所示大多数δ26Mg数据点非常接近页岩、泥岩以及黏土矿物(伊利石和蒙脱石)等端元。综上所述,成岩作用可能不足以改变U1483站沉积物从大陆过程中继承的硅酸盐碎屑元素及同位素组成。因此,U1483站陆源碎屑组分风化和侵蚀指标应当主要反映区域气候和环境等因素的变化。

图9e和9f显示,U1483站200 ka以来CIA值(58%~65%)和δ26Mg值(-0.06‰~0.19‰)的变化趋势较为相似、变幅较小,并且没有明显的冷-暖期对比。与物源分析结果相对应,图8中U1483站沉积序列的CIA值与澳洲西北部ODP765站沉积物(全样校正值; Plank et al.,1998)非常接近,但明显小于位于其南部的SO257-18571站(硅酸盐组分计算值; Pei Renjie et al.,2021)。这可能由于SO257-18571站位于澳洲风尘带内、且其CIA值是通过直接计算硅酸盐组分而获得的,从而显著高于利用沉积物全样元素组成校正所得CIA值。同时,U1483站CIA值也显著区别于来自印尼群岛爪哇的玄武岩和DSDP261站沉积物(全样校正值; Plank et al.,1998; Turner et al.,2001),进一步支持了上述的物源区示踪结果。

图8 U1483站与其他来源沉积物Al2O3-(CaO* + Na2O)-K2O图解

Fig.8 Al2O3- (CaO* + Na2O) -K2O diagram of sediments from IODP Site U1483 and potential endmembers

爪哇玄武岩(据Turner et al.,2001); DSDP 261站(据Plank et al.,1998); SO257-18571站(据Pei Renjie et al.,2021); ODP 765站(据Plank et al.,1998); 大陆上地壳(UCC,据Rudnick et al.,2014); 澳大利亚后太古宙页岩(PAAS,据Taylor et al.,1985)

Java basalt (after Turner et al., 2001) ; DSDP 261 (after Plank et al., 1998) ; SO257-18571 (after Pei Renjie et al., 2021) ; ODP 765 (after Plank et al., 1998) ; UCC (after Rudnick et al., 2014) ; Post-Archean Australian shale (PAAS, after Taylor et al., 1985)

图9 U1483站化学风化和物理侵蚀指标与区域古气候记录对比

Fig.9 Comparison of chemical weathering and erosion intensity records from IODP Site U1483 with regional paleoclimate records

(a)—赤道太平洋海平面变化(据Waelbroeck et al.,2002);(b)—MD01-2378站表层海水温度(SST)(据Holbourn et al.,2011); 季风降水记录:(c)—SO18548-U1482站Log(Terr/Ca),其中Terr为Al、Si、K、Fe和Ti(据Pei Renjie et al.,2021)和(d)—U1483站Ln(K/Ca)(据Zhang Peng et al.,2020);(e)—硅质碎屑组分δ26Mg;(f)—CIA;(g)—陆源物质堆积速率;(h)—Ti/Ca; 灰色阴影指示冷期

(a) —the sea level in the equatorial Pacific (after Waelbroeck et al., 2002) ; (b) —SST from core MD01-2378 (after Holbourn et al., 2011) ; monsoonal precipitation records from (c) —core SO18548-U1482 (Terr represent Al, Si, K, Fe and Ti; after Pei Renjie et al., 2021) and from (d) —IODP Site U1483 (after Zhang Peng et al., 2020) ; (e) —δ26Mg of terrestrial siliciclastic fractions; (f) —CIA; (g) —mass accumulation rate of the terrestrial materials; (h) —Ti/Ca; the gray color bars indicate cold periods

4.2.2 U1483站沉积物风化作用记录指示的澳洲古季风演化

图9e~h显示,U1483站陆源碎屑组分δ26Mg、CIA、陆源物质堆积速率以及Ti/Ca具有非常一致的曲线形态。本文利用SPSS软件对上述指标进行了4 ka等间距插值以及R型因子分析。根据特征值大于1的原则,经方差极大正交旋转后共获取了1个主成分,其累计方差贡献为55%。指标均为F1主因子的正载荷,其中F1δ26Mg=0.39、F1CIA=0.82、F1陆源物质堆积速率=0.83、F1Ti/Ca=0.83,虽然δ26Mg指标的F1值相对较低但仍具有统计意义。这些结果表明U1483站沉积物风化和侵蚀指标具有一个共同的调控因素,即F1主因子。

研究发现区域季风气候系统(即温度和降水)和全球海平面变化可能是轨道尺度热带侵蚀和风化的关键调控机制(Colin et al.,1999; Tamburini et al.,2003; Liu Zhifei et al.,2005; Hartmann et al.,2009; Vance,2011; Xu Zhaokai et al.,2012; Phillips et al.,2014; Wan Shiming et al.,2017)。区域季风气候系统的变化可能会影响邻近陆地的大陆风化和径流输入(Clift et al.,2008; Wang Yongjin et al.,2008; Goudie et al.,2012); 而明显的海平面波动则控制着东印度洋边缘海岸线的位置,影响了河口到研究站位的距离以及陆架古河道的发育,从而改变了物质供应和沉积速率(Lambeck et al.,2001; Waelbroeck et al.,2002; Kuhnt et al.,2015)。在轨道尺度和更短的千年乃至百年时间尺度上,帝汶海沉积环境的演化始终与澳洲古季风相伴(Holbourn et al.,2005; Kawamura et al.,2006; Denniston et al.,2013; Kuhnt et al.,2015; Zhang Peng et al.,2020,2021; Pei Renjie et al.,2021)。研究时段内,邻近帝汶海的陆地构造活动相对稳定,大陆风化强度主要与区域气候相关,考虑到该地区典型的季风气候(雨热同期),我们可以合理地假设帝汶海沉积物记录的化学风化、物理侵蚀演化与澳洲古季风的变化应当密切相关。气候变化主要表现为风力和降水,以及其他参数,如:海水和大气温度等的变化(White et al.,1995)。本文将风化和侵蚀记录与区域内SST(Holbourn et al.,2011)、季风降水(Zhang Peng et al.,2020; Pei Renjie et al.,2021)等记录进行对比,发现上述记录在200 ka以来呈现出较为同步的演化趋势,可能反映了轨道尺度上气候因素对风化的驱动作用(图9)。

较高的温度与较多的降水相伴可以加速水岩相互作用,从而对元素迁移和同位素分馏产生影响,如增强活动性元素Ca、Na、K等的迁移以及造成轻Mg同位素的分馏; 相反的过程则发生在寒冷和干燥的条件下(Clift et al.,2002; Tipper et al.,2006a; Wimpenny et al.,2011; Pogge von Strandmann et al.,2012)。本文特别关注U1483站沉积物风化和侵蚀指标的峰值时期:~200 ka(MIS 7a)、~126 ka(T-II/MIS 5e)、~65 ka(MIS 4)和~10 ka(T-I/早全新世)。这些高值通常出现在冰期终止期或间冰期的开始阶段,伴随着全球海平面快速上升、表层海水温度迅速增加以及径流输入量指示的澳洲夏季风降雨显著增强(图9)。来自澳洲北部的陆源花粉记录(Torgersen et al.,1988)、MD01-2378站孢粉记录(Kawamura et al.,2006)、澳洲Eyre湖古水文记录(Magee et al.,2004)以及数值模拟结果(Otto-Bliesner et al.,2003; Wyrwoll et al.,2007)均支持上述峰值时期研究区温暖潮湿的气候条件。相反,在200~160 ka、126~95 ka和65~20 ka阶段,区域季风降水和温度的逐步降低,导致U1483站δ26Mg、CIA、陆源物质堆积速率和Ti/Ca值减小(图9)。其中,126~95 ka的下降阶段出现在MIS 5期,Pei Renjie et al.(2021)研究发现MIS 5a~d期间澳洲季风强度非常弱。尽管此阶段为间冰期且海平面保持相对较高的水平,但是该时期的ITCZ被锁定在更靠北的区域(Zhang Peng et al.,2020),可能由于澳大利亚西北部陆地和相邻海区的温度未到达阈值,导致研究区在此期间始终保持相对干燥的气候状态(Pei Renjie et al.,2021),此时U1483站的化学风化和侵蚀记录也表现出了较低值,进一步支持了区域气候因素对风化和侵蚀起着显著的调控作用。

前人研究发现,海平面变化会对热带地区海洋沉积物记录的风化强度产生显著影响。例如在南海(Wan Shiming et al.,2017)、西菲律宾海吕宋陆架(Xu Zhaokai et al.,2018; Xiong Zhifang et al.,2018)和东海沉积记录(Zhao Debo et al.,2018)中,冷期低海平面时沉积物风化强度呈现异常的高值,被解释为由于暴露的热带陆架松散沉积物在适宜的温湿条件下再次经历风化,然后被搬运并沉积导致。然而,U1483站虽处热带陆架,但其沉积物的风化程度并没有出现低海平面时显著增加的趋势。这可能是由于该陆架在冷-暖期始终稳定地接受来自西澳河流的物质输入,尽管海平面降低会缩短河口与站位的距离,并且可能会剥蚀陆架上的松散沉积物,但是澳洲季风系统仍是控制径流输入量和沉积物风化程度的主要因素。在U1483站风化记录的3个显著下降阶段(200~160 ka、126~95 ka和65~20 ka),海平面变化均呈现出逐步降低的趋势(图9),可能指示在轨道尺度上低海面时暴露的陆架“老物质”对U1483站的贡献相对有限,不足以掩盖经河流输入的陆地物源区同时期由气候因素调控的风化和侵蚀信号。同时,该站沉积物410 ka以来的Ln(K/Ca)频谱分析结果显示出明显的岁差周期(23 ka、19 ka)和斜率周期(41 ka),而没有海平面变化的信号(100 ka)(Zhang Peng et al.,2020),说明其所指示的径流输入主要与澳洲夏季风降雨密切相关、而受海平面变化的影响较小。综上所述,在轨道时间尺度上,U1483站沉积物风化和侵蚀指标的F1因子主要代表了澳洲古季风的影响,风化侵蚀指标与季风降水和区域表层海水温度在不同氧同位素期的协同性演化表明研究区为“气候驱动型风化”模式。

4.3 海洋沉积物细粒硅酸盐组分Mg同位素的古海洋学意义

近20年来,Mg同位素体系作为新兴的地球化学示踪剂,凭借其活跃的流体迁移特性、较为简单的地球化学特征以及在低温地球化学过程中分馏显著的优势,被广泛地应用于探索古海洋古环境演化的研究。目前已基本勾勒出海洋储库Mg同位素组成的“源”与“汇”(Tipper et al.,2006b; 董爱国等,2016),也初步阐明了碳酸盐沉淀过程(Galy et al.,2002; Tipper et al.,2006a,2006b; Rustad et al.,2010; Geske et al.,2015)、水岩反应过程的Mg同位素分馏机制(Holland et al.,2005; Wimpenny et al.,2010),以及部分海洋生物体(如珊瑚、有孔虫、棘皮动物等)的Mg同位素组成(Chang et al.,2001; De Villiers et al.,2005; Pogge von Strandmann,2008; Saenger et al.,2014),但是对海洋沉积物陆源碎屑组分的研究则相对较少,导致其Mg同位素组成及其所承载的古海洋古气候学信息在很大程度上仍然属未知。本文以<63 μm细粒硅酸盐物质作为陆源碎屑组分,恢复其200 ka以来δ26Mg指标的时间演化序列。本文在解读Mg同位素记录的环境指示意义前,考虑了物源、粒径分选以及早期成岩作用等非风化效应可能造成的影响,并在排除上述因素后与传统化学蚀变指标CIA进行了对比。结果显示,陆源碎屑组分δ26Mg指标的采样密度虽然较低(时间分辨率为4 ka),但其曲线形态忠实地记录了风化演变,并且Mg同位素分馏程度与风化强度呈正相关关系,即:风化强度越高,δ26Mg值越大。与区域古气候记录的对比(Ln(K/Ca)、Ln(Terr/Ca)、SST)结果,也反映出δ26Mg所承载的物源区大陆硅酸盐风化信号主要响应了澳洲古季风的调控。因此,本文显示U1483站海洋沉积物细粒硅质碎屑组分的δ26Mg值可以很好地指示物源区在轨道时间尺度上的“气候驱动型风化”演化。δ26Mg指标的应用为我们理解区域大陆风化及其对气候演化的响应和反馈机制提供了全新的同位素视角。

5 结论

本文分析了澳大利亚西北岸外帝汶海U1483站沉积物陆源碎屑组分的粒度、Mg同位素和主量元素地球化学组成,结合区域研究背景以及古气候参数,首次开展了该区域轨道尺度上化学风化演化及其控制因素的研究,取得了以下主要结论:

(1)200 ka以来U1483站所处的帝汶海西南部在冷期时海洋生产力较低、陆源物质输入量增加,主要表现为粒径较小的黏土含量增多,粉砂含量相对减少; 暖期时则与之相反。物源示踪结果表明,研究时段内U1483站的陆源物质供应较为稳定,主要来自于澳大利亚西北部的河流输入,其径流量的大小受到澳洲夏季风降雨量的强烈控制。

(2)U1483站沉积物细粒硅质碎屑组分Mg同位素组成受物源区岩性、粒径分选和早期成岩作用的影响较小,主要反映了澳大利亚西北部大陆硅酸盐风化强度的演化,且δ26Mg与CIA值呈正相关关系。

(3)在轨道时间尺度上,CIA和δ26Mg指标与物理侵蚀、澳洲季风强度、表层海水温度记录有很好的耦合关系,表明季风降雨、温度等气候条件是控制研究区大陆化学风化以及物理侵蚀作用的主要因素。研究区沉积物的元素和同位素组成受到海平面波动以及水动力分选的影响较小,主要表现为“气候驱动型风化”模式。

(4)本研究彰显了深海沉积物细粒硅质碎屑组分Mg同位素组成对沉积物“源-汇”过程的指示及其古气候学意义,或可成为第四纪古海洋古气候研究中新的气候-环境变化替代性指标。

致谢:IODP 363 航次科学家及工作人员为本研究提供了宝贵的样品,西北大学大陆动力学国家重点实验室雷丹博以及地质学系乔江华和Muhammad Sarim在样品测试过程中提供众多指导和帮助,在此一并感谢。

参考文献

Bao Zhian, Huang Kangjun, Huang Tianzheng, Shen Bing, Zong Chunlei, Chen Kaiyun, Yuan Honglin. 2019. Precise magnesium isotope analyses of high-K and low-Mg rocks by MC-ICP-MS. Journal of Analytical Atomic Spectrometry, 34: 940~953.

Berner R A. 1992. Weathering, plants, and the long-term carbon cycle. Geochimica et Cosmochimica Acta, 56: 3225~3231.

Chang V T C, Galy A, O'Nions R K. 2001. Mg isotopic compositions of modern Planktonic foraminifera. Hot Springs, Virginia: Eleventh Annual V. M. Goldschmidt Conference, abstract No. 3426.

Clift P D, Lee J I, Clark M K, Blusztajn J. 2002. Erosional response of South China to arc rifting and monsoonal strengthening: A record from the South China Sea. Marine Geology, 184: 207~226.

Clift P D, Plumb R A. 2008. The Asian Monsoon: Causes, History and Effects. Cambridge: Cambridge University Press.

Colin C, Turpin L, Bertaux J, Desprairies A, Kissel C. 1999. Erosional history of the Himalayan and Burman ranges during the last two glacial-interglacial cycles. Earth and Planetary Sciences Letters, 171(4): 647~660.

Denniston R F, Asmerom Y, Lachniet M, Polyak V J, Hope P, Ni An, Rodzinyak K, Humphreys W F. 2013. A Last Glacial Maximum through middle Holocene stalagmite record of coastal Western Australia climate. Quaternary Science Reviews, 77: 101~112.

De VilliersS, Dickson J A D, Ellam R M. 2005. The composition of the continental river weathering flux deduced from seawater Mg isotopes. Chemical Geology, 216: 133~142.

Dong Aiguo, Zhu Xiangkun. 2016. Mg isotope geochemical cycle in supergene environment. Advances in Earth Science, 31(1): 43~58(in Chinese with English abstract).

Doupé R G, Pettit N E. 2002. Ecological perspectives on regulation and water allocation for the Ord River, Western Australia. River Research and Applications, 18(3): 307~320.

Ehlert C, Frank M, Haley B A, Boniger U, De Deckker P, Gingele F X. 2011. Current transport versus continental inputs in the Eastern Indian Ocean: Radiogenic isotope signatures of clay size sediments. Geochemistry Geophysics Geosystems, 12: Q06017.

Eiriksdottir E S, Gislason S R, Oelkers E H. 2011. Does runoff or temperature control chemical weathering rates? Applied Geochemistry, 26: S346~S349.

Fedo C M, Nesbitt H W, Young G. 1995. Unraveling the effects of potassium metasomatism in sedimentary rocks and paleosols, with implications for paleoweathering conditions and provenance. Geology, 23(10): 921~924.

Fralick P W, Kronberg B I. 1997. Geochemical discrimination of clastic sedimentary rock sources. Sedimentary Geology, 113(1-2): 111~124.

Galy A, Belshaw N S, Halicz L, O'Nions R K. 2001. High-precision measurement of magnesium isotopes by multiple-collector inductively coupled plasma mass spectrometry. International Journal of Mass Spectrometry, 208: 89~98.

Galy A, Bar-Matthews M, Halicz L, O'Nions R K. 2002. Mg isotopic composition of carbonate: Insight from speleothem formation. Earth and Planetary Sciences Letters, 201: 105~115.

Garzanti E, Padoan M, Setti M, Galindo A L, Villa I M. 2014. Provenance versus weathering control on the composition of tropical river mud (southern Africa). Chemical Geology, 366: 61~74.

Geske A, Goldstein R H, Mavromatis V, Richter D K, Buhl D, Kluge T, John C M, Immenhauser A. 2015. The magnesium isotope (δ26Mg) signature of dolomites. Geochimica et Cosmochimica Acta, 149: 131~151.

Gingele F X, De Deckker P, Hillenbrand C D. 2001. Clay mineral distribution in surface sediments between Indonesia and NW Australia—source and transport by ocean currents. Marine Geology, 179: 135~146.

Gordon A L. 2005. Oceanography of the Indonesian seas and their throughflow. Oceanography, 18(4): 14~27.

Goudie A S, Viles H A. 2012. Weathering and the global carbon cycle: Geomorphological perspectives. Earth-Science Reviews, 113(1-2): 59~71.

Harrington G A, Stelfox L, Gardner W P, Davies P, Doble R, Cook P G. 2011. Surface water-groundwater interactions in the lower Fitzroy River, Western Australia. Water for a Healthy Country Flagship Report series, 54.

Hartmann J, Jansen N, Durr H H, Kempe S, Kohler P. 2009. Global CO2 consumption by chemical weathering: What is the contribution of highly weathering active weathering regions? Global and Planetary Change, 69(4): 185~194.

Higgins J A, Schrag D P. 2015. The Mg isotopic composition of Cenozoic seawater-evidence for a link between Mg-clays, seawater Mg/Ca, and climate. Earth and Planetary Science Letters, 416: 73~81.

Holbourn A, Kuhnt W, Kawamura H, Jian Zhimin, Grootes P M, Erlenkeuser H, Xu Jian. 2005. Orbitally paced paleoproductivity variations in the Timor Sea and Indonesian Throughflow variability during the last 460 kyr. Paleoceanography, 20: PA3002.

Holbourn A, Kuhnt W, Xu Jian. 2011. Indonesian Throughflow variability during the last 140 ka: The Timor Sea outflow. London: Geological Society, 355(1): 283~303.

Holland HD. 2005. Sea level, sediments and the composition of sea- water. American Journal of Science, 305(3): 220~239.

Hu Dengke, Böning P, Köhler C M, Hillier S, Pressling N, Wan Shiming, Brumsack H J, Clift P D. 2012. Deep sea records of the continental weathering and erosion response to East Asian monsoon intensification since 14 ka in the South China Sea. Chemical Geology, 326-327: 1~18.

Huang Kangjun, Teng Fangzhen, Wei Gangjian, Ma Jinlong, Bao Zhengyu. 2012. Adsorption- and desorption-controlled magnesium isotope fractionation during extreme weathering of basalt in Hainan Island, China. Earth and Planetary Science Letters, 359-360: 73~83.

Huang Kangjun, Teng Fangzhen, Shen Bing, Xiao Shuhai, Lang Xianguo, Ma Haoran, Fu Yong, Peng Yongbo. 2016. Episode of intense chemical weathering during the termination of the 635 Ma Marinoan glaciation. Proceedings of the National Academy of Sciences, 113(52): 14904~14909.

Huang Kangjun, Teng Fangzhen, Plank T, Staudigel H, Hu Yan, Bao Zhengyu. 2018. Magnesium isotopic composition of altered oceanic crust and the global Mg cycle. Geochimica et Cosmochimica Acta, 238: 357~373.

Johnson D. 2005. The Geology of Australia. Cambridge, U. K: Cambridge University Press.

Kawamura H, Holbourn A, Kuhnt W. 2006. Climate variability and land-ocean interactions in the Indo Pacific warm Pool: A 460-ka palynological and organic geochemical record from the Timor Sea. Marine Micropaleontology, 59 (1): 1~14.

Keep M, Holbourn A, Kuhnt W, Gallagher S J. 2018. Progressive Western Australian collision with Asia: Implications for regional orography, oceanography, climate and marine biota. Journal of the Royal Society of Western Australia, 101: 1~16.

Kuhnt W, Holbourn A, Xu Jian, Opdyke B, De Deckker P, Rohl U, Mudelsee M. 2015. Southern Hemisphere control on Australian monsoon variability during the late deglaciation and Holocene. Nature Communications, 6(1): 1~7.

Kuhnt W, Holbourn A, Schonfeld J, Lindhorst K, Gallagher S, Keep M, Sadekov A, Dunlea A, Clemens S, Wilkens R, Sarnthein M, Leutert T, Zhang P, Maicher D, Manceau R, Dillon A, Gonzalez J-L, Fabian S, McCaffrey J, Kochhann K, Lübbers J, Johnck J, Hingst J, Parplies K, Koppe M, Steffen S, Schultz J, Heinrich S, Averes T, Evers F. 2018. Cruise Report Sonne 257, WACHEIO-Western Australian Climate History from Eastern Indian Ocean Sediment Archives, Darwin-Fremantle, May 12, 2017~June 04, 2017. Christian-Albrechts-Universitat Kiel, Institut für Geowissenschaften, 260.

Kump L R, Brantley S L, Arthur M A. 2000. Chemical Weathering, Atmospheric CO2, and Climate. Annual Review of Earth and Planetary Sciences, 28(1): 611~667.

Lambeck K, Chappell J. 2001. Sea level change through the last glacial cycle. Science, 292 (5517): 679~686.

Li Wangye, Teng Fangzhen, Ke Shan, Rudnick R L, Gao Shan, Wu Fuyuan, Chappell B W. 2010. Heterogeneous magnesium isotopic composition of the upper continental crust. Geochimica et Cosmochimica Acta, 74(23): 6867~6884.

Lindsay R P, Commander D P. 2005. Hydrogeological assessment of the Fitzroy alluvium. Western Australia, Department of Water, Hydrogeological Record Series HG 16.

Lisiecki L E, Raymo M E. 2005. A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records. Paleoceanography, 20(1): PA1003.

Liu Xiaoming, Teng Fangzhen, Rudnick R L, McDonough W F, Cummings M L. 2014. Massive magnesium depletion and isotope fractionation in weathered basalts. Geochimica et Cosmochimica Acta, 135: 336~349.

Liu Zhifei, Colin C, Trentesaux A, Siani G, Frank N, Blamart D, Farid S. 2005. Late Quaternary climatic control on erosion and weathering in the eastern Tibetan Plateau and the Mekong Basin. Quaternary Research, 63(3): 316~328.

Locarnin R A, Mishonov A V, Antonov J I, Boyer T P, Garcia H E. 2006. World Ocean Atlas 2005, Volume 1: Temperature. Washington: U. S. Government Printing Office, NOAA Atlas NESDIS 61.

Ma Long, Sun Youbin, Jin Zhangdong, Bao Zhi'an, Zhang Pan, Meng Zekun, Yuan Honglin, Long Xiaoping, He Maoyong, Huang Kangjun. 2019. Tracing changes in monsoonal precipitation using Mg isotopes in Chinese loess deposits. Geochimica et Cosmochimica Acta, 259: 1~16.

Magee J W, Miller G H, Spooner N A, Questiaux D G. 2004. Continuous 150 k. y. monsoon record from Lake Eyre, Australia: Insolation-forcing implications and unexpected Holocene failure. Geology, 32(10): 885~888.

McLennan S M, Hemming S, McDaniel D K, Hanson G N. 1993. Geochemical approaches to sedimentation, provenance and tectonics. Special Paper of Geological Society of America, 284: 21~40.

Mollan R G, Craig R W, Lofting M J W. 1969. Geological framework of the continental shelf off northwest Australia. Australian Petroleum Exploration Association Journal, 9(1): 49~59.

Nesbitt H W, Young G M. 1982. Early proterozoic climates and plate motions inferred from major element chemistry of lutites. Nature, 299: 715~717.

Otto-Bliesner B L, Brady E C, Shin S-I, Liu Zhensheng, Shields C. 2003. Modeling El Nino and its tropical teleconnections during the last glacial-interglacial cycle. Geophysical Research Letters, 30(23), doi: 10. 1029/2003GL018553.

Pei Renjie, Kuhnt W, Holbourn A, Hingst J, Koppe M, Schultz J, Kopetz P, Zhang Peng, Andersen N. 2021. Monitoring Australian Monsoon variability over the past four glacial cycles. Palaeogeography, Palaeoclimatology, Palaeoecology, 568: 110280.

Phillips S C, Johnson J E, Giosan L, Rose K. 2014. Monsoon-influenced variation in productivity and lithogenic sediment flux since 110 ka in the offshore Mahanadi basin, northern bay of Bengal. Marine and Petroleum Geology, 58 (Part A): 502~525.

Plank T, Langmuir C H. 1998. The chemical composition of subducting sediment and its consequences for the crust and mantle. Chemical Geology, 145 (3-4): 325~394.

Pogge von Strandmann P A E. 2008. Precise magnesium isotope measurements in core top planktic and benthic foraminifera. Geochemistry Geophysics Geosystems, 9: Q12015.

Pogge von Strandmann P A E, James R H, Calsteren P, Gislason S R, Burton K W. 2008. Lithium magnesium and uranium isotope behaviour in the estuarine environment of basaltic islands. Earth and Planetary Science Letters, 274(3-4): 462~471.

Pogge von Strandmann P A E, Elliott T, Marschall H R, Coath C, Lai Y J, Jeffcoate A B, Ionov D A. 2011. Vatiations of Li and Mg isotope ratios in bulk chondrites and mantle xenoliths. Geochimica et Cosmochimica Acta, 75(18): 5247~5268.

Pogge von Strandmann P A E, Opfergelt S, Lai Y J, Sigfusson B, Gislason S R, Burton K W. 2012. Lithium, magnesium and silicon isotope behaviour accompanying weathering in a basaltic soil and pore water profile in Iceland. Earth and Planetary Science Letters, 339-340: 11~23.

Rea D K, Janecek T R. 1981. Mass-accumulation rates of the non-authigenic inorganic crystalline (eolian) component of deep-sea sediments from the Western Mid-Pacific mountains, Deep Sea Drilling Project Site 463. Initial reports of the Deep Sea Drilling Project, 62.

Rosenthal Y, Holbourn A, Kulhanek D, Expedition 363scientists. 2017. Expedition 363 preliminary report: Western Pacific Warm Pool. International Ocean Discovery Program.

Rudnick R L, Gao Shan. 2014. Composition of the continental crust. Treatise on Geochemistry (Second Edition), 4: 1~51.

Rustad J R, Casey W H, Yin Qingzhu, Bylaska E J, Felmy A R, Bogatko S A, Jackson V E, Dixon D A. 2010. Isotopic fractionation of Mg2+(aq), Ca2+(aq), and Fe2+(aq) with carbonate minerals. Geochimica et Cosmochimica Acta, 74(22): 6301~6323.

Saenger C, Wang Zhengrong. 2014. Magnesium isotope fractionation in biogenic and abiogenic carbonates: Implications for paleoenvironmental proxies. Quaternary Science Reviews, 90(474): 1~21.

Simon M H, Babin D P, Goldstein S L, Cai M Y, Liu Tanzhuo, Han Xibin, Haws A A, Johns M, Lear C, Hemming S R. 2020. Development of a protocol to obtain the composition of terrigenous detritus in marine sediments—a pilot study from International Ocean Discovery Program Expedition 361. Chemical Geology, 535: 119449.

Spooner M I, Barrows T T, De Dekker P, Paterne M. 2005. Palaeoceanography of the Banda Sea, and Late Pleistocene initiation of the Northwest Monsoon. Global and Planetary Change, 49(1-2): 28~46.

Stumpf R, Kraft S, Frank M, Haley B, Holbourn A, Kuhnt W. 2015. Persistently strong Indonesian Throughflow during Marine Isotope Stage 3: Evidence from radiogenic isotopes. Quaternary Science Reviews, 112: 197~206.

Stuut J W, Deckker P D, Saavedra-Pellitero M, Bassinot F, Drury A, Walczak M H, Nagashima K, Murayama M. 2019. A 5. 3-million-year history of monsoonal precipitation in northwestern Australia. Geophysical Research Letters, 46: 6946~6954.

Suppiah R. 1992. The Australian summer monsoon: A review. Progress in Physical Geography: Earth and Environment, 16(3): 283~318.

Tamburini F, Adatte T, Föllmi K, Bernasconi S M, Steinmann P. 2003. Investigating the history of East Asian monsoon and climate during the last glacial-interglacial period (0~140000 years): Mineralogy and geochemistry of ODP Sites 1143 and 1144, South China Sea. Marine Geology, 201(1-3): 147~168.

Taylor S R, McLennan S H. 1985. The continental crust: Its composition and evolution. United States.

Teng Fangzhen. 2017. Magnesium isotope geochemistry. Reviews in Mineralogy and Geochemistry, 82(1): 219~287.

Teng Fangzhen, Wadhwa M, Helz R T. 2007. Investigation of magnesium isotope fractionation during basalt differentiation: Implications for a chondritic composition of the terrestrial mantle. Earth and Planetary Science Letters, 261(1-2): 84~92.

Teng Fangzhen, Li Wangye, Rudnick R L, Robert G. 2010a. Contrasting lithium and magnesium isotope fractionation during continental weathering. Earth and Planetary Science Letters, 300(1-2): 63~71.

Teng Fangzhen, Li Wangye, Ke Shan, Bernard M, Nicolas D, Huang Shichun, Wu Fuyuan, Ali P. 2010b. Magnesium isotopic composition of the Earth and chondrites. Geochimica et Cosmochimica Acta, 74(14): 4150~4166.

Thompson P R, Bé AWH, Duplessy J C, Shackleton N J. 1979. Disappearance of pink-pigmented Globigerinoides ruber at 120000 yr BP in the Indian and Pacific Oceans. Nature, 280: 554~558.

Tipper E T, Galy A, Bickle M J. 2006a. Riverine evidence for a fractionated reservoir of Ca and Mg on the continents: Implications for the oceanic Ca cycle. Earth and Planetary Science Letters, 247(3-4): 267~279.

Tipper E T, Galy A, Gaillardet J, Bickle M J, Elderfield H, Carder E A. 2006b. The magnesium isotope budget of the modem ocean: Constraints from riverine magnesium isotope ratios. Earth and Planetary Science Letters, 250(1-2): 241~253.

Torgersen T, Luly J, De Deckker P, Jones M R, Searle D E, Chivas Allan R, Ullman W J. 1988. Late Quaternary environments of the Carpentaria basin, Australia. Palaeogeography, Palaeoclimatology, Palaeoecology, 67(3-4): 245~261.

Turner S, Foden J. 2001. U, Th and Ra disequilibria, Sr, Nd and Pb isotope and trace element variations in Sunda arc lavas: Predominance of a subducted sediment component. Contributions to Mineralogy and Petrology, 142(1): 43~57.

Vance D. 2011. Isotopic tracers of chemical weathering and consequences for marine geochemical budgets. Applied Geochemistry, 26(Supplement): S311~S313.

Veevers J J, Cotterill D. 1978. Western margin of Australia-evolution of a rifted arch system. Geological Society of America Bulletin, 89: 337~355.

Vorosmarty C J, Fekete B M, Tucker B A. 1998. Global River Discharge, 1807-1991, V. 1. 1 (RivDIS)[DS/OL]. Oak Ridge, Tennessee, USA: ORNL Distributed Active Archive Center.

Vroon P Z, van Bergen M J, Klaver G J, White W M. 1995. Strontium, neodymium, and lead isotopic and trace-element signatures of the East Indonesian sediments: Provenance and implications for Banda Arc magma genesis. Geochimica et Cosmochimica Acta, 59(12): 2573~2598.

Waelbroeck C, Labeyrie L, Michel E, Duplessy J C, McManus J F, Lambeck K, Balbon E, Labracherie M. 2002. Sea-level and deep water temperature changes derived from benthic foraminifera isotopic records. Quaternary Science Reviews, 21(1-3): 295~305.

Wan Shiming, Li Anchun, Clift P D, Stuut J B W. 2007. Development of the East Asian monsoon: Mineralogical and sedimentologic records in the northern South China Sea since 20 Ma. Palaeogeography, Palaeoclimatology, Palaeoecology, 254(3-4): 561~582.

Wan Shiming, Clift P D, Zhao Debo, Hovius N, Munhoven G, France-Lanord C, Wang Yinxi, Xiong Zhifang, Huang Jie, Yu Zhaojie, Zhang Jin, Ma Wentao, Zhang Guoliang, Li Anchun, Li Tiegang. 2017. Enhanced silicate weathering of tropical shelf sediments exposed during glacial lowstands: A sink for atmospheric CO2. Geochimica et Cosmochimica Acta, 200: 123~144.

Wang Yongjin, Cheng Hai, Edwards R L, Kong Xinggong, Shao Xiaohua, Chen Shitao, Wu Jiangyin, Jiang Xiouyang, Wang Xianfeng, An Zhisheng. 2008. Millennial- and orbital-scale changes in the East Asian monsoon over the past 224, 000 years. Nature, 451(7182): 1090~1093.

Wang Shuijiong, Teng Fangzhen, Rudnick R L, Li Shuguang. 2015. The behavior of magnesium isotopes in low-grade metamorphosed mudrocks. Geochimica et Cosmochimica Acta, 165: 435~448.

Wedepohl K. 1971. Environmental influences on the chemical composition of shales and clays. Physics and Chemistry of the Earth, 8: 305~333.

West A J. 2012. Thickness of the chemical weathering zone and implications for erosional and climatic drivers of weathering and for carbon-cycle feedbacks. Geology, 40: 811~814.

West A J, Galy A, Bickle M. 2005. Tectonic and climatic controls on silicate weathering. Earth and Planetary Science Letters, 235: 211~228.

WhiteA F, Blum A E. 1995. Effects of climate on chemical weathering rates in watersheds. Geochimica et Cosmochimica Acta, 59(9): 1729~1747.

Wimpenny J, Gislason S R, James R H, Gannoun A, Pogge Von Strandmann P A E, Burton K W. 2010. The behaviour of Li and Mg isotopes during primary phase dissolution and secondary mineral formation in basalt. Geochimica et Cosmochimica Acta, 74(18): 5259~5279.

Wimpenny J, Burton K W, James R H, Gannoun A, Mokadem F, Gislason S R. 2011. The behavior of magnesium and its isotopes during glacial weathering in an ancient shield terrain in West Greenland. Earth and Planetary Science Letters, 304(1): 260~269.

Wimpenny J, Yin Qingzhu, Tollstrup D, Xie Liewen, Sun Jimin. 2014a. Using Mg isotope ratios to trace Cenozoic weathering changes: A case study from the Chinese Loess Plateau. Chemical Geology, 376: 31~43.

Wimpenny J, Colla C A, Yin Qingzhu, Rustad J R, Casey W H. 2014b. Investigating the behaviour of Mg isotopes during the formation of clay minerals. Geochimica et Cosmochimica Acta, 128: 178~194.

Wyrwoll K H, Liu Zhengyu, Chen Guangshan, Kutzbach J E, Liu Xiaodong. 2007. Sensitivity of the Australian summer monsoon to tilt and precession forcing. Quaternary Science Reviews, 26(25-28): 3043~3057.

Xiong Zhifang, Li Tiegang, Chang Fengming, Algeo T J, Clift P D, Bretschneider L, Lu Zhengyao, Zhu Xiao, Frank M, Sauer P E, Jiang Fuqing, Wan Shiming, Zhang Xu, Chen Shuangxi, Huang Jie. 2018. Rapid precipitation changes in the tropical West Pacific linked to North Atlantic climate forcing during the last deglaciation. Quaternary Science Reviews, 197: 288~306.

Xu Jian, Holbourn A, Kuhnt W G, Jian Zhimin, Kawamura H. 2008. Changes in the thermocline structure of the Indonesian outflow during Terminations Ⅰ and Ⅱ. Earth and Planetary Science Letters, 273 (1-2): 152~162.

Xu Jian, Ke Fei, Kuhnt W, Holbourn A, Zhang Peng, Cui Rui, Liu Heng, Sun Jinliang. 2020. Stacked records of Timor Sea cores over the last 21 ka and their paleoceanographic significance. Quaternary Sciences, 40(6): 1562~1576 (in Chinese with English abstract).

Xu Zhaokai, Li Tiegang, Wan Shiming, Nan Qingyun, Li Anchun, Chang Fengming, Jiang Fuqing, Tang Zheng. 2012. Evolution of East Asian monsoon: Clay mineral evidence in the western Philippine Sea over the past 700 kyr. Journal of Asian Earth Sciences, 60: 188~196.

Xu Zhaokai, Li Tiegang, Clift P D, Wan Shiming, Qiu Xiaohua, Lim D. 2018. Bathyal records of enhanced silicate erosion and weathering on the exposed Luzon shelf during glacial lowstands and their significance for atmospheric CO2 sink. Chemical Geology, 476: 302~315.

Yang Shouye, Wei Gangjian, Shi Xuefa. 2015. Geochemical approaches of tracing source-to-sink sediment processes and environmental changes at the East Asian Continental Margin. Bulletin of Mineralogy, Petrology and Geochemistry, 34(5): 902~910 (in Chinese with English abstract).

Zhao Debo, Wan Shiming, Clift P D, Tada R, Huang Jie, Yin Xuebo, Liao Renqiang, Shen Xingyan, Li Anchun. 2018. Provenance, sea-level and monsoon climate controls on silicate weathering of Yellow River sediment in the northern Okinawa Trough during late last glaciations. Palaeogeography, Palaeoclimatology, Palaeoecology, 490: 277~239.

Zhang Peng, Xu Jian, Holbourn A, Kuhnt W, Beil S, Li Tiegang, Xiong Zhifang, Dang Haowen, Yan Hong, Pei Renjie, Ran Yazhou, Wu Hanning. 2020. Indo-Pacific hydroclimate in response to changes of the Intertropical Convergence Zone: Discrepancy on precession and obliquity bands over the last 410 kyr. Journal of Geophysical Research: Atmospheres, 125(14), DOI: 10. 1029/2019JD032125.

Zhang Peng, Xu Jian, Beil S, Holbourn A, Kuhnt W, Li Tiegang, Xiong Zhifang, Yan Hong, CuiRui, Liu Heng, Wu Hanning. 2021. Variability in Indonesian Throughflow upper hydrology in response to precession-induced tropical climate processes over the past 120 kyr. Journal of Geophysical Research: Oceans, 126, e2020JC017014.

董爱国, 朱祥坤. 2016. 表生环境中镁同位素的地球化学循环. 地球科学进展, 31(1): 43~58.

徐建, 可菲, Kuhnt W, Holbourn A, 张鹏, 崔瑞, 刘恒, 孙金梁. 2020. 21ka以来帝汶海区钻孔堆叠记录的古海洋学意义. 第四纪研究, 40(6): 1562~1576.

杨守业, 韦刚健, 石学法. 2015. 地球化学方法示踪东亚大陆边缘源汇沉积过程与环境演变. 矿物岩石地球化学通报, 34(5): 902~910.



【本文地址】

公司简介

联系我们

今日新闻

    推荐新闻

    专题文章
      CopyRight 2018-2019 实验室设备网 版权所有