4Ma来澳大利亚西海岸带的环境变化历史及其与印尼贯穿流的联系

印尼贯穿流在热带甚至全球气候系统的变化中起着重要的作用,而澳大利亚西海岸带（西澳海岸）是研究印尼贯穿流变化历史的理想地区。本次研究通过国际大洋发现计划（IODP）356航次沉积岩芯的基于长链烯酮和正构烷烃指标,重建了4百万年（Ma）来低分辨的西澳海岸南北区域的海表温度、长链烯酮生产藻种属和陆源高等植物输入的演变历史,从而分析区域气候的时空变化趋势,及其与印尼贯穿流强度变化的相关性。结果表明,2~4Ma西澳海岸表现出海表温度逐步下降的趋势以及几个较为明显的降温事件,与临近海域温度数据以及全球底栖有孔虫的δ¹⁸ O曲线有着较好的对应。1Ma以来西澳海岸整体升温,这可能与印尼贯穿流的开启和增强带来的区域升温相关。长链烯酮C₃₇/C₃₈比值表明,1~4Ma西澳海岸南、中、北部站位的长链烯酮生产藻基本没有交流,而0~1Ma交流较为剧烈。这种现象与印尼贯穿流强度的变化相符,表现为贯穿流强度越强交流越明显。4Ma以来,西澳海岸南、北站位的陆源高等植物输入历史表现出相反的变化特征,这种差异性可能由不同环境对不同区域性气候的复杂响应模式所致。通过中部和北部站位的数据,我们进一步探讨了季风影响下的澳大利亚大陆干湿情况和印尼贯穿流变化的关系。结果表明,2~2.5Ma印尼贯穿流的减弱或者关闭降低了整个澳大利亚大陆的湿度,但0~1Ma印尼贯穿流的增强并未导致澳大利亚大陆的湿润,这种现象可能表明了该区域不同时期的气候驱动机制的改变。

     

Examining sediment infill dynamics at Naracoorte cave megafauna sites using multiple luminescence dating signals

Relatively little is known about the long-term sediment accumulation dynamics of Naracoorte Cave Complex (NCC) solution pipe cavities, and many of the megafauna-bearing infill deposits at this globally significant Australian Pleistocene fossil locality remain partially dated or lack any numerical age control. In this study, we assess the suitability of three different luminescence dating signals for improving existing chronologies at six Late and Middle Pleistocene NCC sites (n = 22 samples), and we undertake multi-site examinations of NCC sediment infill dynamics spanning the last 550 thousand years (ka). Modern analogue samples collected from above and beneath two active cave entrances confirm that single-grain OSL, single-grain TT-OSL and multi-grain pIR-IRSL signals can be reset down to insignificant residual levels (<10⁻¹–10⁰ Gy) when compared with the natural dose ranges of interest for most NCC palaeontological applications. Replicate luminescence dating comparisons performed at six NCC fossil sites (n = 15 samples) reveal consistent ages for twenty-eight out of thirty-one paired OSL–TT-OSL, OSL–pIR-IRSL and TT-OSL–pIR-IRSL datasets. Nineteen of the twenty Middle to Late Pleistocene samples analysed from the NCC sites produce homogeneous OSL, TT-OSL and pIR-IRSL D_e datasets suggesting that the NCC solution pipe deposits considered here are generally not affected by syn-depositional mixing complications that can take place within closed karst cavities (i.e., the remobilisation of unbleached grains from pre-existing cave floor sediments, and their subsequent translocation and incorporation into deposits within deeper parts of the cavity along with externally bleached, allochthonous grain populations). Detailed examination of solution pipe dynamics at Smoke Tortoise Cave (SMT) reveals a complex accumulation history focused on the marine isotope stage (MIS) 9 and MIS 7 interglacial complexes, as well as the MIS 8e interstadial. The SMT case study highlights that NCC solution pipes are not simply associated with short-lived opening and sediment accumulation events, but may involve multiple, discontinuous deposition episodes and reactivation events. An initial multi-site examination of all published NCC infill chronologies (n = 70) appears to suggest statistically significant, preferential solution pipe development during the relatively wet parts of interglacial or interstadial cycles. The non-uniform infill age distribution implies that NCC solution pipe dynamics may have exerted taphonomic biases on fossil accumulation, which should be taken into consideration when reconstructing long-term palaeoecological histories from NCC solution pipe cavities.     

Observed and simulated Lagrangian and eddy characteristics of the East Australian Current and the Tasman Sea

New insights into the Lagrangian and eddy dynamical processes within the East Australian Current (EAC) and the Tasman Sea are presented. We briefly discuss the past campaigns undertaken to observe the EAC and the Tasman Sea eddies as well as the motivation to renew the deployment of drifting buoys into the EAC and the Tasman Sea. The specific features discussed are motivated by the recent observing campaigns using drifting buoys and the availability of high spatial- and temporal-resolution estimates of the ocean state and circulation from eddy resolving models. The interpretation of these features is also aided by other components of the ocean observing system. The dynamics presented includes: (a) transient EAC separation through a vortex dipole, (b) stratified vortex mergers and secondary circulation of EAC eddies, (c) eddy networks in the Tasman Sea and (d) formation and propagation of the EAC separation point. The importance of these dynamical features to the EAC and the Tasman Sea and their implications for the observing system and modelling are discussed.     

An oceanographic survey of the Tasman Front

Results of a detailed expendable bathythermograph survey in the northern Tasman Sea are presented. The Tasman Front, with its origin in the edge of an East Australian Current eddy, extended throughout the survey region. The front marked a coherent, meandering, zonal jet which crosses the Tasman Sea and hence links at least part of the East Australian Current to the other western boundary currents in the subtropical gyre. The frontal meandering derives from both the variability of the East Australian Current system and the topographic effects of the major ridge systems in the north Tasman Sea. The front is less distinct over the crests of these ridges. The flow field in the survey area contained a number of anticyclonic eddies, and current records show that the oceanic eddies are long‐lived features similar to the eddies in the East Australian Current.     

Long-term marine litter monitoring in the remote Great Australian Bight, South Australia

The Anxious Bay beach litter clearance is the longest running annual survey of ocean-based litter in Australia. It's remoteness from centres of human population and location (with respect to prevailing winds and currents) make it an ideal place for monitoring ocean or ship-based litter in Australia's southern oceans and particularly, the Great Australian Bight. Over the 1991-1999 period, a large but gradual decline in the amount of beach washed litter was recorded (with minor peaks recorded during the 1992 and 1994 surveys). Beach washed litter decreased by approximately 86%, from 344 kg recorded in 1991 (13.2 kg/km) to 49 kg in 1999 (i.e. 1.9 kg/km), reaching a maximum of 390 kg in 1992 (or 15 kg/km of beach). However, a sharp increase in litter was recorded in 2000 (i.e. 252 kg or 9.7 kg/km). This increase in litter yield in 2000 is probably due to stronger than average onshore surface flow (or Ekman Transport) in the western Eyre Peninsula and Bight region. Prior to the survey in 2000, the results appeared to indicate that ocean litter on Anxious Bay beach was beginning to level out at around 50-70 kg/year (i.e. 2-3 kg/km). As the beach surveys involve the assumption that the beach is completely cleared of litter, this may represent a baseline level for ocean-based litter in the region. The yields and type of litter collected from the annual survey indicates that the majority of litter washed ashore originates from commercial fishing activities within the Great Australian Bight. Most of the fishing-related litter was directly sourced to the Southern Rock Lobster Fishery (i.e. bait buckets, baskets, pots), the Great Australian Bight Trawl Fishery (i.e. codends, trawl nets) and the Southern Shark Fishery (i.e. monofilament gillnets and longlines). Between 1994 and 1999, large reductions were observed in the amount of bait straps (77% reduction), lobster bait baskets/buckets (86% reduction), nets/ropes (62% reduction) and floats/buoys (83% reduction). Significantly, fishing-related litter in the Bight has reduced at a slower rate than domestic litter. While the level of glass and soft plastics on the beach have both reduced by almost 93% (i.e. 103-7 kg and 119-8 kg, respectively), the level of hard plastics, has diminished at a slower rate, with reductions of only 75% (i.e. 122-30 kg). Some fisheries (i.e. rock lobster, Southern Shark Fishery) have shown marked reductions in fishing-related litter. This is probably due, to some extent, to significant reductions in fishing effort in the region, although this requires further investigation. The information from the Anxious Bay beach litter survey is crucial in monitoring trends in ocean litter in Australia's southern oceans and compliance with international litter regulations. While fishing-related litter remains the major source of ship-based or ocean litter in Australia's southern oceans, the continued reduction in ship-based litter since 1991 supports increasing compliance to MARPOL (Annex V) by commercial fisheries and shipping in the Great Australian Bight. While Australia participates in marine debris monitoring programs in the Antarctic (under CCAMLR), there is currently no national program or management framework to assess, manage and monitor ocean-based litter along Australia's coasts, and monitor compliance with MARPOL. Apart from the commitments under CCAMLR for Antarctic (and sub-Antarctic) marine environments, there are no other regional programs, guidelines or monitoring protocols or to assess and manage ocean litter in the Southern Ocean.     

Isotopic measurements in the Cape York Peninsula area,North Qeensland

K‐Ar and Rb‐Sr isotopic measurements have been made on the north‐south belt of igneous and metamorphic rocks from the Peninsula Ridge and Yambo Inlier of Cape York Peninsula. Four periods of Palaeozoic igneous activity appear to have been denned. These are (⁸⁷’Rb^λ = 1.39 X 10^–11y–1) about 415 m.y., about 400 m.y., 385–390 m.y., and 255–280 m.y., with the youngest dates to the north and northeast. The largest volume of magma, the Kintore Adamellite was emplaced during the 285–390 m.y. period. Initial ⁸⁷Sr/⁸⁶Sr ratios range from 0.715 (a granodiorite) through 0.72–0.74 (muscovite adamellite) to 0.76 (leuco‐adamellite), which suggests a high component of old crustal material in the latter types.

The host metamorphics grade from greenschist facies in the west to almandine‐amphibolite facies in the centre and south. Limited direct data suggest that the greenschists are older than 1400 m.y. This is supported by intrusive dolerite dating greater than 1800 m.y. Rocks possibly 2000 m.y. old are thus adjacent to the Australian northeast coast and place drastic limitations on the possibility of continual continental growth to the east.

Rb/Sr measurements on minerals of the almandine amphibolite rocks record the major Kintore event. Total rock measurements have high uncertainties but give only slightly older figures. Initial ⁸⁷Sr/⁸⁶Sr ratios of these apparent total rock isochrons are high, 0.735–0.745. Gross isotopic redistribution must have occurred during the Palaeozoic metamorphism.

The Rb/Sr isotopic and geochemical relationships suggest that some of the granitic rocks have been derived from the equivalent of the present greenschist facies suite, and that the almandine amphibolite facies was, in part, remetamorphosed during the Palaeozoic and is possibly partly residual after metamorphic segregation.

The region has been examined from the plate tectonic point of view and shows that many of the requirements of a cordilleran‐type mountain belt of Dewey & Bird (1970) existed during the mid‐upper Palaeozoic. The Palmerville Fault and the Hodgkinson Basin are key units in this interpretation.

Dolerite, possibly 2000 m.y. old, could be contemporaneous with voluminous dolerites of similar age from the Kimberley region (Australia) and of Venezuela and Guyana. They may be a useful continental breakup indicator, as are the Gondwana dolerites.     

The Relationship between the Aleutian Low and the Australian Summer Monsoon at Interannual Time Scales

The relationship between the boreal winter(December,January,February) Aleutian Low(AL) and the simultaneous Australian summer monsoon(ASM) is explored in this study.A significant correlation is found between the North Pacific index(NPI) and ASM index,the bulk of which is attributed to the significant correlation after late 1970s.Significant differences in precipitation and outgoing long-wave radiation between typical negative and positive NPI years appear over the ASM area.A regression analysis of the circu...     

最后两个冰期旋回季风-沙漠系统不稳定性的高分辨率黄土记录

黄土高原西北部黄土沉积的粒度变化同时受控于沙漠进退和冬季风强度波动,因此,此区粒度可视为季风-沙漠系统变迁的替代性指标。本研究以2cm为间隔,对李家塬和新庄源S2以上部分做了粒度分析。结果表明,倒数第二次冰期中的冰阶时段与末次冰期类似,存在着频繁的千年尺度的气候波动;而末次间冰期这类变化并不明显。