长江三角洲南翼第四纪沉积层序及其与古环境演变的耦合

为研究长江三角洲南翼第四纪地层划分及其与古环境演变的耦合关系,对长江三角洲南翼的第四系BZK02孔(孔深322. 1 m,取芯率大于96%),进行沉积物粒度、孢粉和微体古生物分析,结合岩性地层讨论了上新世以来钻孔揭示的孢粉组合、古环境演化、沉积层序和古气候特征。结果表明,研究区上新世以来经历了多次环境变化,孢粉类型鉴定133种,有孔虫鉴定17属29种,介形类鉴定7属8种。钻孔自下而上揭示岩性第四纪沉积地层依次为上新统嘉兴组一段(299. 8～322. 0 m)、早更新统嘉兴组(160～299. 8 m)、中更新统前港组(87. 3～160. 0 m)、晚更新统东浦组(72. 0～87. 3 m)、晚更新统宁波组(18. 6～72. 0 m)、全新统镇海组(0～18. 6 m)。古环境演化主要表现为上新世以残积坡、河流沉积为主,气候温冷偏湿;早更新世以河流相、河湖相沉积为主,气候经历温暖湿润-寒冷干燥变化的2个旋回;中更新世早期为河流-滨海相沉积,气候温暖湿润,晚期为河湖相沉积为主,气候温凉干燥;晚更新世以河湖、潮坪、河口沉积环境为主,气候经历温暖湿润-温暖偏干-温暖偏湿-寒冷干燥变化;全新世以浅海相、河湖相、湖沼相沉积环境,气候特征早期为干冷,晚期温暖偏干。     

Comparison of paleoclimatic characteristics between monsoon and westerly areas, China

For past decades there have been many studies on the climate features during the last interglacial and glacial periods. A comparison between the loess record of western China with that of monsoon areas shows some regional differences. ( i) Generally, the climate of the Yili region since the late Pleistocene was dry, with fluctuations. Late Pleistocene climate change in the study area can be divided into 5 stages, corresponding to 5 marine isotopic stages (MIS 1-MISS), (ii) Evidence from grain size composition, magnetic susceptibility, carbonate content, pollen assemblage and geochemistry shows that the climate during the last glacial period was instable. During MIS4 the westerly winds were strong and the humidity was relatively high. Compared with the early stage, MIS2 was dry. In MIS3, westerly winds were relatively weak; pedogenesis prevailed, forming paleo-sols. (iii) In contrast to the Loess Plateau the deposition rate of dust at the early stage was higher than at the late stage of the last galical in the Yili region. The strongest wind event occurred at about 24 kaBP instead of 18 kaBP. (iv) Variations in the grain size indicate that the westerly winds decreased since the deglaciation, but dust accumulation continued until the late Holocene. High carbonate contents, low ratio of Rb/Sr and lack of soil development imply that the climate was dry during the early and middle Holocene. Since the late Holocene the climate became relatively wet and the soil was developed.     

黄河源地区晚第四纪环境变迁

在野外考察和１４Ｃ测年的基础上，本文论述了晚更新世至全新世黄河源地区的环境变迁。确定了在末次间冰期、末次冰期和全新世三个时期冰川、冰缘现象、湖泊、河流、植被和土壤的基本状况。最后讨论了近代环境的发展趋势。     

昭通——鲁甸断裂带晚第四纪活动性研究

昭通—鲁甸断裂带是青藏高原东南缘大凉山次级活动块体南部边界的重要组成部分,也是滇东北地区重要的地震构造.为进一步了解断裂活动程度和晚第四纪活动性,开展野外地质地貌调查、探槽工程及样品采集与年代学测试等研究.结果表明：(1)根据野外地质地貌调查结果,昭通—鲁甸断裂带北东向3支次级断裂在晚更新世以来活动强烈,运动性质以逆冲兼具右旋走滑为主.(2)昭通—鲁甸断裂上,新棚子村开挖的探槽揭示出断层错断了晚更新世地层[（32 510±30）a BP];根据黏土层明显的砾石定向排列及砂石层扰动现象,推测断层可能错断全新世地层[（10 880±30）a BP].研究成果对滇东北及川滇交界地区地震趋势及地震危险性预测具有重要意义.     

Accelerator mass spectrometry radiocarbon ages of amino acid extracts from Californian palaeoindian skeletons

A decade ago, aspartic acid racemization ages were determined for some skeletal remains found in California, near La Jolla, Del Mar and Sunnyvale, suggesting that people were present in North America during the Upper Pleistocene. These ages were obtained from the aspartic acid racemization rate, which was calibrated using a radiocarbon date of 17,150 +/- 1,470 yr BP determined for a skeleton found in Laguna Beach, California. These studies generated an intense controversy not only about the antiquity of human beings in the New World but also about the validity of racemization-based ages, and prompted efforts to date the finds by other means. Here we have used accelerator mass spectrometry (AMS) to determine the radiocarbon ages of the amino acid extracts used in the original racemization studies. Our studies indicate that some of the controversial Californian skeletons, which had been assigned to the Upper Pleistocene, are in fact Holocene.     

Millennial-scale paleoceanography in Okinawa Trough during Late Quaternary period

Based on the analyses of foraminifer and accelerator mass spectrometer radiocarbon dating in DGKS9603 core from mid-Okinawa Trough close to bottom, oscillation curve, which expressed the relation between the surface water temperature and the depth, has been obtained by using foraminifer analysis and calculation of FP-12E transfer function. The whole core indicated seven cold phases and eight warm phases. Obvious expression of low temperature event during Middle and Late Holocene, YD,H1,H2,H3 and H4 events, as well as the short cold phase during the middle last glacial period, implied that short shifts since 50 kaBP would have been global significance. Sedimentation rate during cold phases is usually faster than that in warm stages, with the lowest rate in Holocene, which may be connected with rising sea level and principal axial of Kuroshio Current moving to west. Volcanic activities highly developed in Okinawa Trough during the Quaternary period, thus abundant volcanic glass and pumice were well preserved.     

Radiocarbon evidence of mid-Holocene mammoths stranded on an Alaskan Bering Sea island

Island colonization and subsequent dwarfing of Pleistocene proboscideans is one of the more dramatic evolutionary and ecological occurrences, especially in situations where island populations survived end-Pleistocene extinctions whereas those on the nearby mainland did not. For example, Holocene mammoths have been dated from Wrangel Island in northern Russia. In most of these cases, few details are available about the dynamics of how island colonization and extinction occurred. As part of a large radiocarbon dating project of Alaskan mammoth fossils, I addressed this question by including mammoth specimens from Bering Sea islands known to have formed during the end-Pleistocene sea transgression. One date of 7,908 +/- 100 yr bp (radiocarbon years before present) established the presence of Holocene mammoths on St Paul Island, a first Holocene island record for the Americas. Four lines of evidence--265 accelerator mass spectrometer (AMS) radiocarbon dates from Alaskan mainland mammoths, 13 new dates from Alaskan island mammoths, recent reconstructions of bathymetric plots and sea transgression rates from the Bering Sea--made it possible to reconstruct how mammoths became stranded in the Pribilofs and why this apparently did not happen on other Alaskan Bering Sea islands.     

广州地区晚第四纪孢粉气候研究

 利用广州地区南北2个不同沉积地貌区的钻孔进行孢粉分析,结合测年和沉积信息,分析了广州所代表的珠江三角洲地区晚更新世以来的沉积环境和气候变化。孢粉分析结果显示：在晚更新世珠江三角洲地区气候经历了偏冷干-偏凉干-暖湿-热湿-偏凉干-冷干的变化过程,末次冰期对本区具有明显影响,使全新世和晚更新世孢粉组合表现出一定的差异;全新世气候明显转暖湿,整体上以暖湿为主,但出现了一些小的气候波动事件,最明显的是在2 250 a BP 前后偏凉干的变化;该区在晚更新世和全新世各经历过一次海侵,两孔反映的气候期和海平面变化较为一致,气候和海平面变化也有很好的对应。两孔在地层、沉积相和孢粉特征上的差异是地理位置、沉积环境和基座地貌等差异造成的。     

近2000年来太白山高山带不同海拔植被对气候变化的响应

根据西佛爷池(海拔3410 m)剖面的有机地球化学指标, 重建太白山高山带过去2000年的气候变化。对采自该剖面的样品进行孢粉分析, 并结合太白山跑马梁(海拔3556 m)、三清池(海拔3080 m)和芳香寺(海拔3000 m)剖面的孢粉数据, 进行聚类分析, 探讨高山带不同海拔植被对气候变化响应规律。结果表明, 不同海拔植被对相对冷干气候的响应有更好的一致性, 且林线过渡带内这种一致性更明显。随着现代升温期的到来, 植被对气候的响应主要受高程影响。研究结果可为认识晚全新世以来高山环境系统的气候?植被耦合关系提供一定的参考。     

日喀则—吉隆铁路活动断裂特征及其工程影响分析

日喀则至吉隆铁路位于藏南地区板块碰撞的构造边界带上,跨越定结、岗嘎和佩枯错三条大的第四纪活动裂谷,各裂谷内分布的活动断层对铁路的选线及工程设计具有重要影响。通过对日吉铁路沿线各裂谷内共25条断裂的现场调查测试,查明工程共穿越晚更新世活动断裂10条,其中有全新世活动断裂4条,分别为定结裂谷中的定结、郭家、登么错断裂和佩枯错裂谷中的岗彭庆断裂。对于定结、郭家断裂,可选择其活动性相对较弱的南段以简易工程通过,而对全线全新世活动性最强的登么错断裂,建议以路基形式通过。岗彭庆断裂带因未来地震危险性高,应避免以隧道工程通过。     

Slip rate variations on normal faults during glacial-interglacial changes in surface loads

Geologic and palaeoseismological data document a marked increase in the slip rates of the Wasatch fault and three adjacent normal faults in the Basin and Range Province during the Late Pleistocene/Early Holocene epochs. The cause of this synchronous acceleration of fault slip and the subsequent clustering of earthquakes during the Holocene has remained enigmatic, although it has been suggested that the coincidence between the acceleration of slip and the shrinkage of Lake Bonneville after the Last Glacial Maximum may indicate a causal relationship. Here we use finite-element models of a discrete normal fault within a rheologically layered lithosphere to evaluate the relative importance of two competing processes that affect fault slip: postglacial unloading (the removal of mass), which decreases the slip rate, and lithospheric rebound, which promotes faster slip. We show that lithospheric rebound caused by regression of Lake Bonneville and deglaciation of adjacent mountain ranges provides a feasible mechanism for the high Holocene rates of faulting in the Wasatch region. Our analysis implies that climate-controlled changes in loads applied to Earth's surface may exert a fundamental control on the slip history of individual normal faults.     

Coupling controls of neotectonism and paleoclimate on the Quaternary sediments of the Yangtze （Changjiang） coast

1 Introduction The Quaternary sediments of the Yangtze coast, re-garding their distribution and origin, have been intensively discussed over the last decades since they are deeply in-volved into many aspects of Quaternary study, such as sea-level fluctuations, paleoclimate change and sediment facies evolution[1―6]. A painstaking effort has been made on the sediment study, which tends to elucidate what the primary control on sediment deposition and sedimentary facies formation is. Of note, nu…     

Pleistocene to Holocene extinction dynamics in giant deer and woolly mammoth

The extinction of the many well-known large mammals (megafauna) of the Late Pleistocene epoch has usually been attributed to 'overkill' by human hunters, climatic/vegetational changes or to a combination of both. An accurate knowledge of the geography and chronology of these extinctions is crucial for testing these hypotheses. Previous assumptions that the megafauna of northern Eurasia had disappeared by the Pleistocene/Holocene transition were first challenged a decade ago by the discovery that the latest woolly mammoths on Wrangel Island, northeastern Siberia, were contemporaneous with ancient Egyptian civilization. Here we show that another spectacular megafaunal species, the giant deer or 'Irish elk', survived to around 6,900 radiocarbon yr bp (about 7,700 yr ago) in western Siberia-more than three millennia later than its previously accepted terminal date-and therefore, that the reasons for its ultimate demise are to be sought in Holocene not Pleistocene events. Before their extinction, both giant deer and woolly mammoth underwent dramatic shifts in distribution, driven largely by climatic/vegetational changes. Their differing responses reflect major differences in ecology.     

洞庭盆地第四纪气候演变的沉积物地球化学记录

对洞庭盆地安乡凹陷东南部两护村ZKC1孔上新世末—第四纪沉积物的主量、微量和稀土元素以及粒度进行了分析,进而探讨洞庭盆地第四纪气候演变。曲线协变性及相关系数表明,ZKC1孔沉积物化学蚀变指数(CIA)与Cr、Ga、V、Nb、Be、Li、Sc、Th等微量元素含量呈明显的正相关。从陆相沉积物CIA及微量元素含量与温度和湿度正相关的概念出发,结合其他资料,重塑洞庭盆地第四纪气候演变过程:早更新世为冷干→暖湿→冷干→暖湿,中更新世为冷干→暖湿→冷干—温湿→暖湿,晚更新世为寒冷→温湿→寒冷,全新世总体为温湿—暖湿。这一结论与ZKC1孔孢粉组合特征反映的气候演变过程及中国东部第四纪气候演化基本吻合,说明沉积物CIA和微量元素含量较好地记录了第四纪气候演变信息。相关性分析表明洞庭盆地沉积物粒度对CIA无明显影响;CIA与沉积物粘土含量呈弱的正相关关系,应与湿热气候条件下有更强烈的风化和更多粘土矿物形成有关。     

High-precision U-series dating of Holocene corals from South China Sea by thermal ionization mass spectrometry (TIMS)

Using the isotopic diluting and thermal ionization mass spectrometric (TIMS) technique, the U-series dating procedure was established on the basis of measurement of national standard GBW04412. With this highly precise technique the Holocene corals from the South China Sea were dated. Comparison between this method and α-spectrometry was made. The results show that a thriving period of corals in the South China Sea appeared at 6 800-5 800 a BP, during which the paleosea level was the higher than at present in the Holocene.     

闽江河口第四纪地层划分和地质年代研究

本文系统地研究了闽江河口琅岐岛钻孔揭示的第四纪地层。根据孢粉、微古、硅藻和~(14)C测年等资料分析了沉积物形成时的气候波动、沉积相和沉积物年代,将闽江河口第四纪地层划分为上更新统上段(厚>15米)和全新统(厚49.80米)。全新统又可分为下全新统下段和上段、中全新统和上全新统。气候演化为:冷干→温暖略干→温暖湿润→炎热潮湿→温暖略干。沉积相演化为:冲积相、冲洪积相、湖沼相→冲积相、湖沼相→河口相、湖沼相→海湾相→河口相。     

闽江河口第四纪地层划分和地质年代研究

本文系统地研究了闽江河口琅岐岛钻孔揭示的第四纪地层。根据孢粉、微古、硅藻和~(14)C测年等资料分析了沉积物形成时的气候波动、沉积相和沉积物年代,将闽江河口第四纪地层划分为上更新统上段(厚>15米)和全新统(厚49.80米)。全新统又可分为下全新统下段和上段、中全新统和上全新统。气候演化为:冷干→温暖略干→温暖湿润→炎热潮湿→温暖略干。沉积相演化为:冲积相、冲洪积相、湖沼相→冲积相、湖沼相→河口相、湖沼相→海湾相→河口相。     

Precise timing of lacustrine gypsum in Luobubo, Xinjiang using the thermal ionization mass spectrometry U-series method

Dating techniques including gypsum dissolution in water, iron hydroxide co-precipitation with uranium and thorium and mass spectrometric determination have been investigated in this note. The ages of the gypsum samples in a CK core from Luobubo lacustrine sediments are in the range of (12.85±0.21) kaBP (4 m distance from the top core) to (153.2±7.2) kaBP (49 m distance from the top core) with the relative errors of ±1.6%–±4.7%. It indicates that the sedimental environment of the CK core was situated in the middle-late Pleistocene and Holocene periods, corresponding to 1–6 stages of oxygen isotopes in the abyssal sediments and included much information from last interglacial to Holocene warm periods.     

Evolution of drainage systems and its developing trend in connection with tectonic uplift of Eastern Kunlun Mt.

The Eastern Kunlun Mt. had been subjected to uplift together with the Qinghai-Xizang (Tibet) Plateau before the Early Pleistocene, and yet the Mt, did not protrude out of the Plateau surface. During that period lakes spread all over the studied region, with the drainage systems being all short rivers flowing into the lakes. At the end of the Early Pleistocene, intensive tectonic uplift led to the rising of the Eastern Kunlun Mt. and made the Mt. protrude onto the Plateau surface. As a result, a fault depression valley formed extending nearly from west to east along the fault belt of the Southern Kunlun Mt. Lakes in this region died out, surface runoffs joined into the valley of the Southern Kunlun Mt. resulting in a large river streaming nearly from west to east. Around 150 kaBP, because of the strong differential movement, rivers, such as the Jialu River and the Golmud River, retrogressively eroded seriously, cutting through the Burhan Budai Mt. Then they pirated the large river and divided it into four portions. Owing to the uplift of the Eastern Kunlun Mt., strongly retrogressive erosion of the upper reaches of the Jialu River has made the watershed of the Buqingshan Mt. migrate 6–10 km southward since Holocene. At present, it remains a stronger trend of retrogressive erosion developing upward to the basin of the Yellow River Source and it seems that the Jialu River is scrambling for the streamhead of the Yellow River.