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1.
隆浩  张静然 《第四纪研究》2016,36(5):1191-1203
在过去的20年里,光释光(optically stimulated luminescence,简称OSL)测年技术发展迅速,已经被广泛应用于第四纪沉积物的测年研究中。近年来,以OSL技术为主要定年手段,利用其测年范围大、测年材料(石英和长石)丰富且易于提取等优势,在我国干旱/半干旱区(腾格里沙漠古湖、内蒙古黄旗海等湖泊)开展了一系列晚第四纪湖泊演化和古气候环境变化的研究工作。高水位湖相阶地的OSL测年结果表明,晚更新世高湖面事件发生时间在MIS 5阶段甚至更老,对基于14C数据建立的“MIS 3a大湖期”假说的年代框架提出了质疑;通过东北兴凯湖晚第四纪连续湖泊沉积物的高分辨率OSL和14C测年对比研究,从年代学机理上揭示晚更新世高湖面的年代学争论主要源自14C技术测定较老样品时的局限性,14C测年手段及易造成老于30000年的沉积物年龄的低估;来自青藏高原东北缘的秦王川盆地和东北地区兴凯湖湖岸的风成沉积也记录了MIS 3a阶段可能不存在气候湿润和高湖面事件;另外,通过对白碱湖古湖岸堤的OSL测年,建立了湖面波动过程和全新世区域湿度变化历史,揭示了季风边缘区早中全新世湿润期和中晚全新世以来逐渐干旱化的气候环境变化过程。综上所述,相较于传统的14C技术,OSL测年技术在湖泊沉积物的应用中具有诸多优势和潜力。尽管如此,OSL测年方法在实际应用过程中会遭遇一些会影响测年结果的潜在的技术问题。因而本文也从石英组分的长石污染、沉积物沉积前OSL信号的曝光程度、铀系不平衡和含水量以及宇宙射线对剂量率的动态影响等多方面,综述了水成沉积释光研究中面临的具体问题,并提出了初步解决方案和建议。  相似文献   

2.
Until recently, little was known about the Quaternary marine sedimentary record in East Greenland. Geophysical and geological investigations in Scoresby Sund were undertaken to characterize the nature and chronology of this record. Seismic records show that almost 70% of the outer fjord system is covered by about 10 m of unlithified sediments, making direct correlation with the Quaternary records on land and the adjacent continental margin difficult. These acoustically unstratified sediments are scoured by icebergs above 550 m water depth. Almost 90% of core material is massive diamicton of Holocene age, deposited mainly from iceberg rafting and turbid meltwater. Sedimentation rates are 0.1 -0.3 m 1000 yr-1. Thicker accumulations of unlithified Quaternary sediments in Scoresby Sund occur as sediment ridges and in two other major depocentres. A low sediment ridge runs across the mouth of Scoresby Sund, and is interpreted as an end moraine of Late Weichselian Flakkerhuk stadial age. The very restricted sediment thickness suggests that grounded ice filled the fjord during the Flakkerhuk and an ice shelf was not present. High inputs of ice rafted debris to the continental margin at about 18 000 BP indicate this as a probable age for the moraine. During the Allerød Interstadial, ice probably retreated from the outer fjord system, since massive diamictons similar to those of Holocene age are present at the base of most cores. A major depocentre of acoustically stratified sediments at the head of Hall Bredning is interpreted to represent ice proximal deposits from a glacier margin extending across the fjord. It is adjacent to dated moraines on land and is inferred to be of Milne Land stadial age (about 10 000 BP). A similar age is interpreted for acoustically laminated sediments and a moraine at the entrance of Vikingebugt, on the south side of Scoresby Sund. Dated kame terraces in the inner fjord system indicate that ice retreated to its present position 6–7000 years ago.  相似文献   

3.
The Late Quaternary ( c . 130,000–10,000 BP) glacial history of the central west coast of Jameson Land, East Greenland, is reconstructed through glacial stratigraphical studies. Seven major sedimentary units are described and defined. They represent two interglacial events (where one is the Holocene). one interstadial event and two glacial events. The older interglacial event comprises marine and fluvial sediments, and is correlated to the Langelandselv interglacial, corresponding to oxygen isotope sub-stage 5e. It is followed by an Early Weichselian major glaciation during the Aucellaelv stade, and subsequently by an Early Weichselian interstadial marine and deltaic event (the Hugin Sø interstade). Sediments relating to the Middle Weichselian have not been recognized in the area. The Hugin Sø interstade deposits have been overrun by a Late Weichselian ice advance, during the Flakkerhuk stade, when the glacier, which probably was a thin, low gradient fjord glacier in Scoresby Sund, draped older sediments and landforms with a thin till. Subsequent to the final deglaciation, some time before 10,000BP, the sea reached the marine limit around 70 m a.s.l., and early Holocene marine, fluvial and littoral sediments were deposited in the coastal areas.  相似文献   

4.
Loess/palaeosol sequences from the Loess plateau in China were investigated by combined infrared optically stimulated luminescence (IRSL) and thermoluminescence (TL) dating techniques in order to study the luminescence properties of the loessic sediments and to provide a direct chronological link for correlation and position of the last interglacial soil in Central Asia and the Loess plateau in China. Sensitivity changes were found for all samples through artificial bleaching of the samples. The greatest sensitivity changes, of up to 50%, were found for very old loess samples designated to be older than the Matu-yama/Brunhes magnetic boundary and hence older than 788,000±1,800 years. The upper dating limit, as investigated by the very old loess samples, ranges from 250,000 to 300,000 years, if the TL additive dose method is applied. The chronological position of the last interglacial soil S1 at the section near Lanzhou indicates luminescence age estimates ranging from 82,000 to 75,000 years for the marine-isotope stage 5 to 4 transition. However, the loess from below S1 yielded luminescence age estimates between 153,200±14,200 and 110,100±20,100 years for TL and IRSL additive dose methods, respectively. Thus, a direct correlation between the S1 and the first intercalated pedocomplex PC1 in Central Asia is most likely. Received: 31 March 1998 / Accepted: 25 October 1998  相似文献   

5.
电子自旋共振(ESR)测年法是近40年来逐步发展起来的第四纪年代学方法。由于它的测年范围宽、测年物质种类多等优点,特别是对于老于20万年的早中更新世没有火山灰等定年物质的样品,有着特殊的优势,引起了第四纪研究者的关注。近年来,随着对ESR法基本原理认识的深入和实验技术的提高,在测年信号心的热稳定性、晒退回零特性、辐射剂量-信号增长特性、测年可靠性等方面的研究均取得了较大进展。本文结合国内外在ESR法基础原理、测年应用等成果,简要回顾了ESR法的历史发展,以及不同信号心在第四纪地质研究中的成功应用。  相似文献   

6.
During the last glacial stage, Washington Land in western North Greenland was probably completely inundated by the Greenland Ice Sheet. The oldest shell dates from raised marine deposits that provide minimum ages for the last deglaciation are 9300 cal. yr BP (northern Washington Land) and 7600 cal. yr BP (SW Washington Land). These dates indicate that Washington Land, which borders the central part of Nares Strait separating Greenland from Ellesmere Island in Canada, did not become free of glacier ice until well into the Holocene. The elevation of the marine limit falls from 110 m a.s.l. in the north to 60 m a.s.l. in the southwest. The recession was followed by readvance of glaciers in the late Holocene, and the youngest shell date from Neoglacial lateral moraines north of Humboldt Gletscher is 600 cal. yr BP. Since the Neoglacial maximum, probably around 100 years ago, glaciers have receded. The Holocene marine assemblages comprise a few southern extralimital records, notably of Chlamys islandica dated to 7300 cal. yr BP. Musk ox and reindeer disappeared from Washington Land recently, perhaps in connection with the cold period that culminated about 100 years ago.  相似文献   

7.
Wagner, B., Bennike, O., Cremer, H. & Klug, M. 2010: Late Quaternary history of the Kap Mackenzie area, northeast Greenland. Boreas, Vol. 39, pp. 492–504. 10.1111/j.1502‐3885.2010.00148.x. ISSN 0300‐9483. The Kap Mackenzie area on the outer coast of northeast Greenland was glaciated during the last glacial stage, and pre‐Holocene shell material was brought to the area. Dating of marine shells indicates that deglaciation occurred in the earliest Holocene, before 10 800 cal. a BP. The marine limit is around 53 m a.s.l. In the wake of the deglaciation, a glaciomarine fauna characterized the area, but after c. one millennium a more species‐rich marine fauna took over. This fauna included Mytilus edulis and Mysella sovaliki, which do not live in the region at present; the latter is new to the Holocene fauna of northeast Greenland. The oldest M. edulis sample is dated to c. 9500 cal. a BP, which is the earliest date for the species from the region and indicates that the Holocene thermal maximum began earlier in the region than previously documented. This is supported by driftwood dated to c. 9650 cal. a BP, which is the earliest driftwood date so far from northeastern Greenland and implies that the coastal area was at least partly free of sea ice in summer. As indicated by former studies, the Storegga tsunami hit the Kap Mackenzie area at c. 8100 cal. a BP. Loon Lake, at 18 m a.s.l., was isolated from the sea at c. 6200 cal. a BP, which is distinctly later than expected from existing relative sea‐level curves for the region.  相似文献   

8.
释光测年是可对冰川地貌进行直接定年的一种测年技术,已被广泛应用于冰川沉积测年中,推动了第四纪冰川研究的深入发展。但冰川沉积释光测年还没有达到标准化的程度,实际应用中仍有不少问题需要探究,其中最受关注的是冰川沉积物释光信号晒退不完全的问题,即样品在埋藏前因曝光机会有限导致信号没有归零或仅部分归零。冰川沉积释光信号晒退程度与地貌部位和沉积环境密切相关。冰川沉积释光采样需注意几个方面:(1)详细的地貌学和沉积学调查及对采样点的选择;(2)较适合释光测年的冰水沉积和冰缘风成沉积采集及其与冰川作用期次的联系;(3)冰碛夹层中的冰水砂透镜体的选取;(4)冰碛垄采样时垂直与水平方向上的考量;(5)岩石释光测年的发展使砾石成为当前第四纪冰川释光测年采样的一种选择。室内进行释光等效剂量测试时,也有几个关键的选择:(1)粗颗粒石英光释光测年是末次冰期以来冰川作用的首选方法;(2)如果样品年代老于石英测年上限,或者石英不适合测试,则可考虑钾长石后红外高温释光测年方法;(3)单颗粒、小测片和岩石释光埋藏测年技术可以鉴别样品的晒退情况,是目前最适合冰川沉积释光测年的几种选择;(4)如有条件,尝试用不同矿物、不同粒径、不同方法进行测试对比和交叉检验。要获得第四纪冰川释光测年的最佳年代学结果,地貌学、沉积学和年代学的结合是非常必要的。  相似文献   

9.
《Quaternary Science Reviews》2003,22(10-13):1111-1121
This paper presents a case study in the analysis of anthropogenically reset sedimentary materials, through work undertaken to identify and date sediments in an ancient canal in the Mekong Delta, Cambodia. The emergence of rice cultivating communities, utilising canals for both hydraulic management and transport, represents an important stage in the social evolution of southeast Asia. The emergence of complex polities in the region, which may have depended on both international trade and intensified agriculture, led ultimately to the formation of the famous Khmer empires which dominated the region on several occasions through the 1st and 2nd millennia AD. French colonial scholars identified possibly ancient canals in the region that may have played roles in trade, agriculture, or both. This series of ancient canal features near Angkor Borei has been the subject of recent investigations in a collaboration between the Universities of Glasgow and Hawaii. Luminescence profiling measurements were used to identify the canal bed, by exploiting the contrast between a regional substrate of some 50 ka depositional age and more recent archaeological sediments. In this manner it has been possible to identify the sedimentary substrate, undisturbed canal sediments, and redeposited material. Ages have been estimated for substrate and canal infill sediments. The work represents the first convincing demonstration of luminescence dating of one of these important regional features, and indeed the first confirmation of the presumed antiquity of the canal system around Angkor Borei.  相似文献   

10.
11.
Carbonate content and faunal composition of two gravity cores from the coastal Arabian sea provide evidence of a major environmental change in surface ocean waters about 13,000 yr B.P. Radiocarbon dating indicates that deposition rates ranged from 1.8 to 9.8 cm/103 yr, with a major change in rate occurring in one core at about 7500 yr B.P.  相似文献   

12.
The pyroxenes of the upper zone of the Skaergaard layered seriesconsist of an iron-rich series of brown and green clinopyroxenes.Five new analyses are presented, together with a revised trendline which includes the full range of clinopyroxenes believedrepresentative of the Skaergaard fractionation sequence. Therange for the augite-ferroaugite-ferrohedenbergite series isfrom Ca42?4 Mg47?9 Fe9?7 to Ca42?5 Mg0?4 Fe57?1, the most ferriferousvariety coexisting with a pure fayalite. A re-study of the compositionsand textures of certain green ferrohedenbergites supports thebelief that they are the product of sub-solidus inversion offerriferous ß-wollaston?tes, which crystallized asa temporary phase between the periods when brown ferrohedenbergitescrystallized directly from the magma. A consideration of thecompositional and textural relationships between green and brownpyroxenes, and the significance of the mosaic inversion texture,have led to an interpretation of the crystallization and inversionsequence for these minerals. Four new analyses of ferrohedenbergitesfrom the downward-crystallized upper border group rocks provideevidence for a trend which differs slightly from that for thelayered series ferrohedenbergites.  相似文献   

13.
杭州湾晚第四纪沉积与古环境演变   总被引:6,自引:1,他引:6  
通过对杭州湾第四系钻孔的年代地层学、沉积学、古环境学等多学科综合分析,认为XZK169孔全新世沉积始于孔深17.35m处(年代约为10~9kaBP),其下至孔深86.40m沉积属晚更新世。整个沉积层中可分出3个海进—海退旋回晚更新世早期以陆相沉积为主,出现河湖相—滨海湖泊相—河湖相沉积,气候为温凉干燥—温暖湿润—温凉干燥;晚更新世中晚期出现河湖相—潮滩湖相—浅海相—河口湾相沉积,气候为温凉干燥—寒冷干燥—温凉—暖热湿润—温热湿润;经历了末次冰期侵蚀后,全新世出现浅海相—河口湾相沉积,气候以暖热湿润—温暖湿润为主。约在5kaBP,杭州湾与长江口分离。  相似文献   

14.
Only Ulleung and Baegdusan volcanoes have produced alkaline tephras in the Japan Sea/East Sea during the Quaternary. Little is known about their detailed tephrostratigraphy, except for the U–Oki and B–Tm tephras. Trace element analysis of bulk sediments can be used to identify alkaline cryptotephra because of the large compositional contrast. Five sediment cores spanning the interval between the rhyolitic AT (29.4 ka) and Aso-4 (87 ka) tephras were analyzed using an INAA scanning method. Source volcanoes for the five detected alkaline cryptotephra were identified from major element analyses of hand-picked glass shards: Ulleung (U–Ym, and the newly identified U–Sado), and Baegdusan (B–J, and the newly identified B–Sado and B-Ym). The eruption ages of the U–Ym, U–Sado, B–J, B–Sado, and B–Ym tephras are estimated to be 38 ka, 61 ka, 26 ka, 51 ka, 68–69 ka, and 86 ka, respectively, based on correlations with regional-scale TL (thinly laminated) layer stratigraphy (produced by basin-wide changes in bottom-water oxygen levels in response to millennium-scale paleoclimate variations). This study has allowed construction of an alkaline tephrostratigraphical framework for the late Quaternary linked to global environmental changes in the Japan Sea/East Sea, and improves our knowledge of the eruptive histories of Ulleung and Baegdusan volcanoes.  相似文献   

15.
Nioghalvfjerdsfjorden in North-East Greenland is at present covered by a floating glacier. Raised marine deposits in the surrounding area contain shells of marine molluscs, bones of marine mammals and pieces of driftwood. A fairly systematic sampling of such material has been conducted, followed by extensive radiocarbon dating. We suggest that the Greenland ice sheet extended onto the shelf offshore North-East Greenland during isotope stage 2, perhaps even reaching the shelf break. During the subsequent recession of the ice sheet, the entrance of Nioghalvfjerdsfjorden had become ice-free by 9.7 cal. ka BP. The recession culminated between 7.7 and 4.5 cal. ka BP, during which time the fjord was glacier-free along its entire 80 km length. No dates younger than 4.5 cal. ka BP are available on marine material from the fjord, and it seems probable that the fjord has been continuously covered by the floating glacier since this time. The maximum glaciation was attained around AD 1900, after which thinning and recession took place. The marine limit increases from c. 40 m above sea level near the present margin of the Inland Ice to c. 65 m above sea level at the outer coast. These figures fit into the regional pattern of the marine limit for areas both to the south and north. The marine fauna comprise two bivalves, Macoma calcarea and Serripes groenlandicus, that may represent a southern element present during the Holocene temperature optimum. Remains of three taxa of southern extralimital terrestrial and limnic plants were dated to 5.1 cal. ka BP, and remains of another extralimital plant were dated to 8.8 and 8.5 cal. ka BP. The known Holocene time ranges of the willow Salix arctica and the lemming Dicrostonyx torquatus have been extended back to 8.8 and 6.4 cal. ka BP, respectively, providing minimum dates for their immigration to Greenland.  相似文献   

16.
A detailed magnetostratigraphic and rock magnetic study was conducted on Tertiary lacustrine/fluvial sediments from Jiyang, Shandong, East China. High temperature susceptibility variation and thermal demagnetization show that magnetite is the main magnetic remanence carrier. The characteristic remanent magnetization (ChRM) was isolated above 150 °C by thermal demagnetization, and a detailed magnetic polarity sequence was established. The lacustrine/fluvial sediments were dated from polarity chron C18n.1r to polarity chron C15n, i.e., within the interval 39.631–34.655 Ma. The results of this study indicate the likelihood that either no hydrocarbon-bearing fluids were present after 34.655 Ma or, if there was any such fluid flow, the fluids must have gone through the section very quickly, without having any significant influence on the magnetic signal.  相似文献   

17.
A 54-m long core was raised from the bed of the Nal Sarovar, a large shallow lake located in the middle of the low-lying region linking the Gulfs of Kachchh and Khambhat, in western India. A three-layer sequence comprising: Zone-1 (top 3 m), predominantly silty-clay/clayey; Zone-2 (3–18 m), sandy; and Zone-3 (18–54 m), dominated by sticky silty-clay/clayey-silt with occasional thin sand layers and basalt fragments was identified. Smectite and illite are the dominant clay minerals with minor amounts of kaolinite and chlorite. Very high content of smectite (53–97%) in the clays of the lowermost zone (18–54 m) and the geomorphic features of the surrounding region suggested that the sediments were derived from the basaltic terrain of Saurashtra and/or via the Gulf of Khambhat. The clay content in the middle zone (3–18 m), dominantly sandy, is very low. Therefore, provenance for this zone was derived using heavy minerals in the sand fraction. The heavy mineral species in this zone suggested the mixed metamorphic and igneous terrain of Aravallis as the major source. The grain-size distribution of this zone closely matched with the sediments underlying the modern Sabarmati riverbed at Ahmedabad, suggesting fluvial depositional environment. Clays also dominate sediments of the topmost (0–3 m) zone with illite as the dominant (74–81%) specie followed by smectite suggesting derivation from the mixed metamorphic and igneous terrain of Aravallis.  相似文献   

18.
《Quaternary Science Reviews》2003,22(2-4):407-421
Along the southeastern coastline of the Korean peninsula, well-developed marine terraces are found at various elevations. The ages of these terraces, and the time of deposition of the terrace sediments are important to our understanding of the geological history of this area during the Quaternary period, and represent a unique record of the regional tectonic activity. Previous efforts to establish a chronology using optically stimulated luminescence (OSL) methods have produced controversial results, particularly because of stratigraphic inconsistency and poor reproducibility. In this paper, the application of OSL dating based on the single-aliquot regenerative-dose (SAR) protocol for quartz is investigated. The dependence of equivalent dose on the preheat and cut-heat temperatures (thermal treatment of the regeneration and test-doses, respectively) are examined. Linearly modulated luminescence signals from chemically cleaned quartz samples are used to identify the presence of a thermally unstable component with a large optical cross-section (component A′), which in part affects the ability to correct for sensitivity changes during measurements, and thus the reliability of the equivalent dose estimates. In some samples, a higher heat treatment after the test-dose is shown to improve our ability to measure a dose given in the laboratory before any heat treatment (dose recovery test). This higher temperature treatment effectively removes component A′, and hence improves sensitivity correction. Furthermore, the samples were broadly divided into poorly sorted and well-sorted, based on field evidence. The poorly sorted samples contain friable, weathered gravel clasts, which is a likely post-depositional source of quartz grains. In general, these grains will not have been zeroed prior to deposition, and so the poorly sorted samples are rejected from further age studies. Results obtained from the well-sorted samples are reproducible at each sampling location, and give ages grouping broadly into 50–70 and 110–120 ka, but laterally discontinuous on a scale of tens of km. Our OSL results for the younger group are supported by radiocarbon ages from overlying terrestrial deposits. It is concluded that these results point to considerable tectonic activity in the southeast of Korea during the Late Pleistocene.  相似文献   

19.

中国南方地区一些旧石器考古遗址的沉积物因遭受强烈化学风化而粒径较细、长石含量低,难以单独提取长石颗粒进行测年。本研究利用从湖南省北部赤山岛枫树嘴旧石器遗址剖面第2、第3和第4考古层位采集的3个沉积物样品中提取的细粒混合矿物,尝试对其红外释光(IRSL)信号进行研究。实验表明,虽然长石IRSL信号很弱,但仍可以测得信噪比足够高的红外激发后高温红外激发释光(post-IR IRSL)信号。与此同时,样品存在明显的红外激发后蓝光释光(post-IR OSL)信号,并且样品的IRSL与post-IR OSL信号均以快组分为主,这为该地区沉积物利用长石光释光信号定年提供了新的可能。鉴于长石IRSL信号较弱,根据剂量恢复实验结果,本研究采用post-IR IRSL SAR法(50℃红外激发后270℃高温红外激发,pIRIR270℃)进行等效剂量测量,同时也应用post-IR OSL SAR法定年进行比较。实验结果表明,细粒混合矿物的pIRIR270℃等效剂量分别为418.8±13.2 Gy、562.3±18.2 Gy和694.8±17.9 Gy,相对应的post-IR OSL SAR等效剂量结果为345.0±29.4 Gy、409.6±33.7 Gy和424.7±32.2 Gy。假设强烈化学风化未对沉积物的剂量率造成很大影响,基于长石pIRIR270℃信号的释光年龄为89±6 ka、118±8 ka和152±9 ka,比前人所得的石英OSL SAR法年龄老30%~55%(约20~55 ka)。通过对比不同测量条件下获得的等效剂量值来评估长石IRSL信号是否存在晒退问题,没有发现长石post-IR IRSL信号存在晒退不完全的证据。根据本研究post-IR IRSL SAR法测年结果,赤山岛枫树嘴旧石器遗址似阿舍利技术类型的石器出现在倒数第二次冰期(MIS 6)后期至末次间冰期(MIS 5)前期,比湖南道县福岩洞现代人类牙齿化石年龄(80~120 ka)稍老。作为似阿舍利技术石器制造者的赤山岛古人与福岩洞现代人的关系将是我国旧石器时代考古学和古人类学研究的一个重要课题。

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20.
凌联海 《地质通报》2001,20(4):366-367
新余市南英地区第四纪冲积物发育齐全,属侵蚀阶地保存(图1),由老到新划分为赣县组、进贤组、莲塘组和联圩组。最近对各组底部砾石层填隙物分别进行了石英粉砂的电子自旋共振(ESR)年龄测定。1岩石地层单位简介(1)赣县组(Qpg):原称赣县砾石层,系陈国达、刘辉泗于1939年创立的,创名地是赣县江口镇三团。本组下部为灰白色砾石层;中部为桔红色含砾粉砂;上部为桔黄色粘土。下与老第图1新余市南英袁河Ⅰ至Ⅳ级阶地地貌剖面图Fig.1GeomorphologicalprofileofterracesItoIV…  相似文献   

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