Chinese Journal of Oceanology and Limnology Vol. 32 No. 1, P. 174-186, 2014 http://dx.doi.org/10.1007/s00343-014-3066-x
Assemblage characteristics of clay minerals and its implications to evolution of eolian dust input to the Parece Vela Basin since 1.95 Ma* MING Jie (明洁)1, 2, LI Anchun (李安春)1, **, HUANG Jie (黄杰)1, WAN Shiming (万世明)1, MENG Qingyong (孟庆勇)1, JIANG Fuqing (蒋富清)1, YAN Wenwen (闫文文)3 1
Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
2
University of Chinese Academy of Sciences, Beijing 100049, China
3
First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China
Received Mar. 7, 2013; accepted in principle Apr. 25, 2013; accepted for publication Jul. 6, 2013 © Chinese Society for Oceanology and Limnology, Science Press, and Springer-Verlag Berlin Heidelberg 2014
Abstract To understand the provenance and evolution of eolian input in the last 1.95 Ma in the Parece Vela Basin in the eastern Philippine Sea, the clay mineral assemblage of a gravity core PV090510 from the basin was investigated using paleogeomagnetic dating and X-ray diffraction. The assemblage of the core mainly consisted of smectite (~46%) and illite (~40%), with some chlorite (~10%) and kaolinite (~4%). Analysis of the provenance of these minerals suggested that smectite was mainly derived from volcanic rocks of the Mariana Arc, while illite, chlorite, and kaolinite were mainly transported as eolian dust by the East Asian monsoon from central Asia. We used the ratio of (illite+chlorite+kaolinite)/smectite as a proxy for Asian eolian input to the Parece Vela Basin since 1.95 Ma. This ratio followed glacial and interglacial cycles and was consistent with the intensity of the East Asian monsoon and aridity of central Asia since 1.95 Ma. The changes of the ratio reflected three different stages of the East Asian monsoon and provenance climate. Keyword: eolian dust; East Asian winter monsoon; clay mineral; provenance; Parece Vela Basin
1 INTRODUCTION Eolian dusts are terrestrial particulates transported by atmospheric circulation, and a major source of marine sediments (Rea, 1994). Up to 75% of the nonbiogenic component of North Pacific deep-sea sediment entered as atmospheric dust (Windom, 1969). Wind-borne mineral aerosol can strongly reflect the climate state of its provenance (Maher, 2010). Previous studies have shown that eastern and central Asia are the main sources of dust in the North Pacific Ocean (Hovan et al., 1989; Rea, 1994), and the East Asian monsoon transports a considerable amount of dust over the northwestern Pacific (Pettke et al., 2000). The evolution of the East Asian monsoon has been studied extensively through grain size, susceptibility, and mineral and chemical composition of loess and paleosol measurements (Ding et al., 1999; An et al., 2001; Guo et al., 2002), indicating continued strengthening of the East Asian monsoon
since 2.6 Ma (Xiao and An, 1999; An et al., 2001). Rea et al. (1998) reported eolian flux and grain size distribution in the North Pacific. Proxy records from ocean measurements are relatively simple and limited at present, even though such studies can cover vast space and have great significance. As an important component of marine sediment, the composition of clay minerals can be used to indicate the provenance of marine sediment; in addition, it shows a good response to the change of the East Asian monsoon in recent years. For example, the ratios of clay minerals have been used as a proxy to investigate East Asian monsoon variability in the South China Sea and West Philippine Sea (Liu et al.,
* Supported by the National Basic Research Program of China (973 Program) (No. 2007CB411703) and the National Natural Science Foundation of China (No. 40976026) ** Corresponding author:
[email protected]
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Fig.1 Maps of the study area a. Location of cores discussed in this paper: Core PV090510 from the Parece Vela Basin, Core MD06-3050 from the West Philippine Sea, ODP Site 806 in the West Equatorial Pacific and Core RC11-210 from the central Equatorial Pacific. Ocean currents (red arrows): NEC: Equatorial Counter Current, North Pacific Drift, and Kuroshio Current. The direction of the East Asian monsoon is shown as a gray arrow; b. Topography of the Philippine Sea and bottom currents (white arrows) (Lee and Ogawa, 1998).
2003; Wan et al., 2008, 2012). However, although equally important, the Parece Vela Basin in the Philippine Sea, which is located downwind of the East Asian monsoon, has been paid little attention. We therefore used a 6.37-m long core from the Parece Vela Basin to study Asian eolian input. The Parece Vela Basin is located in the east of the Philippine Sea (Fig.1a), and is one of the largest backarc basins in the world (Ren and Li, 2000). More specifically, it is a nearly closed marginal basin lying to the west of the Mariana Trough, south of the Shikoku Basin, east of the Palau Ridge and north of a complex system of island arc-trench-fault zones, with an average water depth of 4 800 m. The main ocean current flowing through the Parece Vela Basin is the North Equatorial Current (NEC) from east to west, and the bottom current is a branch of the Antarctic Intermediate Water (AAIW) that travels counterclockwise around the Shikoku and Parece Vela Basin (Lee and Ogawa, 1998) (Fig.1b). Because of the great depth, complex seafloor topography, and difficulty dating because of the lack of calcium and extremely low deposition rate (a few millimeters/ka) (Loren and Robert, 1981; Xu et al., 2008; Meng et al., 2010), research on the sediments and paleoenvironment in this area is rare, and mostly focuses on the surface sediment (Jin et al., 2007; Xu et al., 2008; Zhai et al., 2009; Xiong et al., 2012). There is a lack of study on the variation of sediment in this area over time.
Moreover, because the Parece Vela Basin is located downwind of the East Asian monsoon and is a nearly closed marginal basin free of fluvial substance supply, it is an ideal place to reconstruct the history of Asian eolian input. The characteristics of clay minerals from the Parece Vela Basin were analyzed using a paleogeomagnetic dating method to: (1) determine the sediment source of the study core and present a proxy for eolian input to the Parece Vela Basin over the last 1.95 Ma, and (2) focus on the time variation of eolian input to the Parece Vela Basin. Our work provides a reference for the changes of eolian dust input to the Pacific over the last ~2 Ma.
2 MATERIAL AND METHOD Sediment Core PV090510 analyzed in this study was collected from the Parece Vela Basin during a cruise by R/V Science No.1 in 2004. The core was 6.37 m long, and located at 16°47.79′N, 138°5.55′E at a water depth of 5 152 m (Fig.1). This sample is primarily composed of siliceous organisms (radiolarian and diatoms), volcanic materials (volcanic glass and debris), terrigenous materials (quartz, feldspar, and clay minerals) and authigenic materials. Core PV090510 can be divided into three parts according to its lithology and physical properties. The upper part (0–200 cm) is composed of olive-gray and
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Smectite (001)
Illite (001)
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Illite (003) +Quartz (101)
Chlorite (001) Kaolinite (001) +Chlorite (002) Illite (002)
Chlorite (004) Kaolinite (002)
Feldspar (110)
Chlorite (003) Ethylene-glycolated curve
Heated curve (550°C)
Nature curve
17 14
10
7
5
4.7
3.5
3.3
2.8
Fig.2 Typical XRD patterns of clay minerals from Core PV090510 (unit: Å)
gray laminated diatom mats, which are dominated by fragmented valves of the mat-forming diatom Ethmodiscus rex in near monospecific assemblages (Zhai et al., 2009). The water content of this part is so high that it has a flow shape. The middle part (200– 245 cm) is characterized by gray diatomaceous clays. The bottom part (245–637 cm) contains large red pelagic clays, with no obvious sedimentary discontinuity. Samples used for clay mineral analysis were taken at 4-cm intervals for the upper 245 cm and at 2-cm intervals for 245–637 cm, so 262 samples were collected and analyzed from Core PV090510. Clay mineral analysis was carried out on the fraction of the sediment with a size of
