西线调水与区域持续发展

南水北调西线工程(简称西线调水)是从长江上游引水至黄河上游的跨流域调水工程。其重要目标是开发西北,繁荣发展中西部经济和改良生态环境。 本世纪末;下世纪初,我国经济建设的重点将转向大西北,实现区域资源开拓的重点转移。显然这对振兴大西北,实现区域持续发展是一项重大的战略决策。     

Late Holocene relative sea level rise and the Neoglacial history of the Greenland ice sheet

In West Greenland, early and mid Holocene relative sea level (RSL) fall was replaced by late Holocene RSL rise during the Neoglacial, after 4–3 cal. ka BP (thousand calibrated years before present). Here we present the results of an isolation basin RSL study completed near to the coastal town of Sisimiut, in central West Greenland. RSL fell from 14 m above sea level at 5.7 cal. ka BP to reach a lowstand of ?4.0 m at 2.3–1.2 cal. ka BP, before rising by an equivalent amount to present. Differences in the timing and magnitude of the RSL lowstand between this and other sites in West and South Greenland record the varied interplay of local and non‐Greenland RSL processes, notably the reloading of the Earth's crust caused by a Neoglacial expansion of the Greenland Ice Sheet (GIS) and the subsidence associated with the collapse of the Laurentide Ice Sheet forebulge. This means that the timing of the sea level lowstand cannot be used to infer directly when the GIS advanced during the Neoglacial. The rise in Late Holocene RSL is contrary to recently reported bedrock uplift in the Sisimiut area, based on repeat GPS surveys. This indicates that a belt of peripheral subsidence around the current ice sheet margin was more extensive in the late Holocene, and that there has been a switch from subsidence to uplift at some point in the last thousand years or so. Copyright © 2008 John Wiley & Sons, Ltd.     

柴达木盆地北缘侏罗系不同沉积环境烃源岩生物标志物特征及其应用

柴达木盆地北缘地区侏罗系(中下侏罗统)的优质烃源岩主要发育于湖相与三角洲相环境。研究了不同时代、不同沉积环境中烃源岩的生物标志物组成特征,结果发现,有3类化合物的分布与组成差异显著,包括三环萜烷(C19、C20、C21)的分布型式、重排藿烷的丰度以及规则甾烷的相对组成。其中,不同时代的差异主要体现在规则甾烷组成上;而不同沉积环境的差异主要体现为三环萜烷(C19、C20、C21)的分布型式及重排藿烷的丰度。分析认为,这些差异与烃源岩的沉积环境及其生源组成有密切关系。据此,初步将这些参数应用于两方面研究,一是为划分地层沉积环境提供“生物标志物相标志”,二是研究油源对比,取得良好效果。因此,本文研究结果具有重要实用价值与参考意义。     

Zircon U–Pb and Hf isotopic study of gneissic rocks from the Chinese Altai: Progressive accretionary history in the early to middle Palaeozoic

Gneissic rocks in the Chinese Altai Mountains have been interpreted as either Paleozoic metasedimentary rocks or Precambrian basement. This study reports geochemical and geochronological data for banded paragneisses and associated gneissic granitoids collected along a NE–SW traverse in the northwestern Chinese Altai. Petrological and geochemical data suggest that the protoliths of the banded gneisses were possibly immature sediments with significant volcanic input and that the gneissic granitoids were derived from I-type granites formed in a subduction environment. Three types of morphological features can be recognized in zircons from the banded gneisses and are interpreted to correlate with different sources. Zircons from five samples of banded paragneiss cluster predominantly between 466 and 528 Ma, some give Neoproterozoic ages, and a few yield discordant Paleoproterozoic to Archean ages. Zircon Hf isotopic compositions indicate that both juvenile/mantle and crust materials were involved in the generation of the source rocks from which these zircons were derived. In contrast, zircons occur ubiquitously as elongated euhedral prismatic crystals in the four samples of the gneissic granitoids, and define single populations for each sample with mean ages between 380 and 453 Ma. The general absence of Precambrian inheritance and positive zircon ?Hf values for these granitoids suggest insignificant crustal contribution to the generation of the precursor magmas. Our data can be interpreted in terms of a progressive accretionary history in early to middle Palaeozoic times, and the Chinese Altai may possibly represent a magmatic arc built on a continental margin dominated by Neoproterozoic rocks.     

柴达木盆地北缘侏罗系两类不同有机质丰度泥岩的 生物标志物特征对比研究

在柴达木盆地北缘地区,分别选取有机碳含量很低和较高的侏罗系泥岩样品,对比分析了它们在生物标志物组成上的差异。结果发现,高有机质丰度泥岩的生标组成与我国西北地区侏罗纪煤系有机质的特征差异不大,相比而言,低有机质丰度泥岩的正烷烃以前主峰为特征,Pr/Ph比值在1.0左右,三环萜烷和伽马蜡烷丰度较高,并在部分样品中检出了25 降藿烷系列。结合泥岩的有机岩石学特征,认为这些差异可能反映了泥岩沉积环境和生烃母质的不同:高有机质丰度泥岩的有机显微组分以相对弱还原条件下的形态有机质为主,包括藻类体、孢子体和角质体等,而低有机质丰度泥岩的有机显微组分以相对强还原条件下的矿物沥青基质为主,其母质可能来源于低等显微菌藻类。进一步通过对比不同有机质丰度泥岩,以及区内原油生标组成之间的相互关系,讨论了研究区的油源问题。     

南海温跃层基本特征及一维预报模式

根据现有1907—1990年南海大面调查资料,按1°×1°网格进行逐月的标准水层的温度统计。在此基础上采用3次样条函数的插值方法计算出整个南海温跃层的深度、厚度和强度并予以相应分析。分析表明,南海温跃层主要分为两种类型:第一类为辐射型,主要分布在南海北部的陆架区内,季节变化显著;第二类为不同水体叠置型,主要分布在广大深水区,它长年存在,季节变化较小。一种温跃层的一维积分预报模式,该模式是基于忽略热平流作用和水平热扩散的前提下,从局部热平衡方程出发,建立了受海面热收支及风混合作用下求解温度垂直分布及温跃层的时空变化。在南海北部水深约300m处进行了单站温跃层后报,结果表明,温跃层的深度、厚度和强度的相对误差均在30％以下。     

A method to estimate the forces exerted by internal solitons on cylindrical piles

Internal soliton is the large amplitude wave existing in the pycnocline, induced by internal tide in the condition of special bottom topography. During its propagation process, the induced disturbance can bring about strong convergence of sea water and sudden strong current (wave-induced-current), which can cause severe threat to the ocean engineering structures, such as oil drilling platform and pipeline. In this paper, Morison’s empirical method, modal separation and regression analyses are introduced to estimate the forces and torques exerted by internal soliton on cylindrical piles. As an example, a limited set of observational data recording a passage of the internal soliton near Dongsha Islands is used to estimate the horizontal velocity and its acceleration in a vertical section for computing the force and torque on a supposed pile, and the estimation results are reasonable. It is shown that, the higher number of the modes retained in the calculation, the better the estimation of velocity profile fits the observational one. A better overall approximation to the real solution can be reached if there are more observational current data acquired in a whole vertical profile.     

Images of the seabed in the Faroe-Shetland Channel from commercial 3D seismic data

A large number of 3D deep seismic surveys in the Faroe-Shetland Channel gives continuous coverage over most of the region. These surveys were designed primarily to image depths in excess of 4 km, use low frequency sources and are recorded at low temporal sample rates. However, commercial 3D data can generate highly detailed images of the seabed due to the high spatial sample rate, typically 12.5 m. This is particularly true in waters below 200 m. Despite geophysical artefacts, the images reveal that there are a number of sedimentary processes at work adjacent to and within this channel. On the West Shetland Shelf, iceberg scouring and moraines reflect the impact of glaciation. On the West Shetland slope there is clear evidence for down-slope processes, such as debris flows, linear erosion channels, basal fans and (one case) slope failure. Along-slope processes are also active as indicated by the presence of sediment waves and contourite mounds. On the floor of the basin, polygonal cracking can be observed. The most spectacular feature appears to be the Judd Deeps, a system of cliffs approximately 200 m high and 40 km across. Traditionally, seabed investigation has been performed using high-resolution surveys. This study shows that deep exploration data can also provide useful images of the seafloor.     

珠江三角洲晚第四纪沉积特征

本文主要研究珠江三角洲的第四纪地层;晚更新世玉木亚间冰期、全新世中期(大西洋期)海侵阶段的地貌景观及珠江三角洲晚第四纪以来的沉积形成过程。