安徽蒙城尉迟寺遗址地层的磁化率与元素地球化学记录研究

通过磁化率和地球化学元素的因子分析法和比值法分析提取出尉迟寺遗址地层记录的环境演变信息。本区5050aBP以前的新石器时期为暖湿的气候环境;大汶口文化阶段气候总体偏干冷,存在数次波动;从大汶口至龙山文化期间,本区气候发生了较为明显的变化,由干冷转向温湿,这为水稻生产提供了有利条件,也促进了龙山文化的繁荣。在5050aBP之前及4620aBP、4700aBP前后可能都发生过冷干事件。     

粤西云开地区中奥陶世双壳类动物群的发现及其意义初探

在粤西云开地区东冲组内发现以双壳类占绝对优势的中奥陶世动物群,包括双壳类:Praenucula cf.sharpei Babin and Gutierrez-Marco,P.sp.,Homilodonta regularis（Portlock）,Similodonta similis（Ulrich）,S.cf.cerys Cope,S.sp.,Trigonoconcha acuta Sanchez,Concavodonta sp.,Arcodonta sp.,Sthenodonta cf.eastii（Tata）,S.sp.,Nuculites cf.cylindricus（Portlock）,N.sp.,Phestia sp.,Cardiolaria? sp.,Inaequidens cf.davisi Pojeta and Gilbert-Tomlinson,I.sp.,Mytilarca? sp.,Cyrtodonta sp.,Modiolopsis spp.,Carminodonta sp.,Famatinodonta sp.等及若干未命名的新属,同层产出的还有三叶虫和腕足类等.双壳类化石个体小、丰度高、分异度高,以古栉齿类占绝对优势,该发现丰富了我国及世界中奥陶世双壳类动物群,为研究区中-上奥陶统的划分对比以及华南板块古地理重建增添了新的古生物学证据,特别是为研究双壳类的早期演化和奥陶纪早期双壳类辐射演化提供了关键信息.      

昆明地区早寒武世关山动物群研究新进展

总结了昆明地区关山动物群自1999年命名以来开展的研究工作和取得的新进展.简要叙述了关山动物群的研究概况、地层位置、生物群组合特征和关山动物群的研究意义.在关山动物群中首次发现了古虫动物门的Vetulicola gangtoucunensis Luo,Fu et Hu,吐卓虫Tuzoia sp.nov.,古蠕虫Palaeoscolex sp.nov.,腕足类Heliomedusa sp.nov.及三叶形虫、海绵动物新属种.指出关山动物群是一个由多门类软躯体后生动物化石组成的伯吉斯页岩型的动物群,时代介于澄江动物群与凯里动物群(或伯吉斯页岩动物群)之间,起到了承前启后的作用,在寒武纪生命大爆发和寒武纪早期生物演化的研究中有重要意义.     

甘肃酒泉盆地早白垩世植物化石及其古气候意义

首次较系统报道了产于甘肃酒泉盆地下白垩统的植物化石,分为两个植物组合。Athrotaxites-Solenites组合产于赤金堡组上段,有Solenites luanpingensis Wang,Pityocladus cf.i waianus(ishi)Chow,Pityocladus sp.,Athrotaxites berryi Bell等,时代大致为早白垩世早期,反映潮湿或半干旱半潮湿气候。Brachyphyllum-Pseudofrenelopsis组合见于中沟组上部,包括Sphenopterissp.,Pseudofrenelopsis dalatzensis(Chowet Tsao)Cao ex Zhou,Cupressinocladus elegans(Chow)Chow,Cupressinocladus sp.,Pagiophyllumyumenense sp.nov.,Pagiophyllumcompressum sp.nov.,Pagiophyllum sp.,Brachyphyllumningshiaense Chow et Tsao,Brachyphyllumobtusum Chow et Tsao,Elatocladus sp.,Podozamites sp.,Carpolithus sp.等12种,时代为Aptian-Albian期,反映干旱型气候。     

距今7000年来河南郑州西山遗址古代人类生存环境

对河南郑州西山遗址同期山麓洪积成因的自然沉积剖面样品的有机碳、炭屑含量、碳氮比值和孢粉进行了分析,根据其实验结果,结合平原地貌与物质组成特点,分析了该地区 7000aBP古代人类生存的气候与环境特征,得到如下结论：1）7300 aBP以来气候变化大约以2900aBP为界,在此之前以暖湿为主,当时当地的气候大体与今日的江淮地区的气候相当,台地上宜旱作,有机碳反映出暖湿期内至少存在5个干旱时段。到2900 aBP以近,气候旱化趋势明显,与当地现今气候接近。2）当地的地貌条件是洪积成因的向东向南倾斜的宽阔平原,虽有枯河穿过,因其具有冲沟性质而无泛滥之苦,又平原的组成物质下部是更新世洪积黄土层,顶部为全新世黄土层,很适合古代人类居住和进行旱作农业耕作活动3）以土地氮量供应不足为标准进行判断,至少在7 300 a BP前后这里已开始了旱作农业活动,这种判断与本地区以草本花粉为主的孢粉分析结果是吻合的。在炭屑浓度上,表现为早期D（炭屑长轴直径）＜50μ的具有n×102 片/ 厘米3,D＞50μ的只在近5000 aBP才断续出现,这种变化与耕作施肥技术的进步不无关系。     

浙江杭州萧山跨湖桥遗址发掘中的一些地学问题研究

本文采用高分辨率层序地层学理论,运用气候旋回、基准面升降旋回,以及海平面升降旋回在区域上等时的原理,对研究区46 km2中的23个钻孔及两条全新世剖面进行了高精度的对比研究及沉积环境分析,对跨湖桥人的生态环境进行了深入的研究,得出8000 aBP跨湖桥人生活的地貌环境、植被、动物、气候已与现今基本一致,跨湖桥人突然"消失",是由于海平面上升,遗址被淹而致。直至3000 aBP海水还未从本区退出,所以先人不可能迁回,从而显示出某种"神密"色彩。     

江西九江ZK08钻孔孢粉记录及其反映的古环境信息

根据江西九江永安ZK08孔中的孢粉记录，划分出7个孢粉带和10个亚带，并探讨孢粉源区约12700aBP以来的古环境演化。初步研究表明，约12700-10200aBP，经历寒冷期和温暖期，森林植被为寒温带针阔叶混交疏林、亚热带常绿阔叶林和温带落叶阔叶疏林的演化；约10200-9400aBP为孢粉缺乏带；而后约9400-8600aBP升温期以温带乔木林为主，约8600-3300aBP为大暖期，期间有2个低温期，植被以亚热带乔木林为主，约3300aBP进入新冰期，其中约3300~2100aBP的降温期以温带乔木林为主；约2100-380aBP为寒冷期，约890aBP以前为干冷，其后为湿冷，植被以山地的寒温带针阔叶混交林和温带落叶阔叶林交替变化为特征。约380aBP以来受人类活动影响，孢粉记录小冰期气候特征不明显，但约150aBP以来的气温上升显著。     

吉林辽源地区“呼兰群”的时代及划分对比

辽源地区“呼兰群”模式剖面很可能为倒转向斜构造,因此由下而上层序为石灰窑组石缝组、弯月组.在石缝组产Thamnopora sp., Cladopora sp., Spongophyllum sp. 和Pro-tathyris sp. 及弯月组中产Thamnopora sp., Cladopora sp., Syringopora sp., 和Cirophyl-lum sp.,这些属的组合时代为志留纪,最可能为晚志留世.根据石缝组和弯月组的岩性特征和化石组合性质,大致可与呼兰君北岔屯组,内幕古东部的晒忽苏组和八当山火相对比,但不能与景家台的早志留世桃山组、晚奥陶世放牛沟火山岩和景家台大理岩相对比.这对华北地台北缘地质构造演化研究有重要意义.     

东昆仑北缘都兰县巴隆一带人类活动遗迹的发现及其环境背景

青海都兰县巴隆乡朝火鹿陶勒盖含有人类活动遗迹黄土剖面的孢粉和环境磁学分析结果表明,该地区自中全新世以来气候经历了3个阶段:4080aBP以前气候温干偏湿;4080～3500aBP气候温干与温干偏湿交替;3500aBP以来气候以温干为主,气候逐渐恶化。其中2890～1810aBP相对降温和变干,是本地区环境最为恶劣时期。反映人类活动遗迹的木炭层14C年龄为(3970±90)aBP,相当于黄河上游发现的齐家文化时期,比在昆仑山垭口发现的人类活动遗迹早400多年。     

博斯腾湖碳酸盐和同位素组成的全新世古环境演变高分辨记录及与冰川活动的响应

本文通过对在新疆南部塔里木盆地北缘博斯腾湖采集的一根953cm的岩心进行了早全新世以来的古气候重建。对BSTC2000岩心进行了碳酸盐矿物组成、Ca/1000Sr,有机质TOC,C/N和C/S分析,并结合BSTC2000岩心附近的一个沉积物剖面的孢粉资料,利用多指标重建了8500aBP以来的古气候变化特征。在2个平行岩心中对保存的植物叶片、草籽,以及全有机质进行了9个AMS14C年代测定。8500～8100aBP气候冷湿,钻孔位置为河流-滨湖相环境,沉积物中有3层泥炭层。从8100～6400aBP,气温升高,湖泊扩张,气候暖湿,湖泊可能为最高湖面时期。而从6400～5100aBP湖泊稍微下降,气候变冷。在中全新世晚期从5100～3100aBP气候变得高温干旱,但其间的4400～3800aBP有短暂的气候变冷,早期大量的冰雪融水补给博斯腾湖,使得湖泊水位上升。湖泊的第二个高湖面期是5200～3800aBP。在3100～2200aBP气候冷湿,由于蒸发减弱而湖泊有所扩张,湖泊在3100至2800aBP期间是最后一次短暂的高湖面期。这次短期高湖面后,湖泊由于较长时期的低温而引起的供水减少,湖泊收缩。从2200～1200aBP,气候变得干热,湖泊收缩。尽管从1200aBP以来,温度有所下降,气候变得暖干,湖泊又开始有所上升,但是没有达到博斯腾湖出水口孔雀河的海拔高度。     

First post-glacial establishment of forest trees: early Holocene vegetation, mollusc settlement and climate dynamics in central Troms, North Norway

Sediments from two limnic basins in a sub-continental region of northern Norway are investigated for pollen, plant macrofossils and bivalves at a high stratigraphical resolution. The basins are located at 280 and 400 m a.s.l. on the S-SW slope of Mt. Skrubben (848 m a.s.l.). The bio- and lithostratigraphical records are interpreted in terms of immigration and establishment of forest tree species and climate. The mountain was deglaciated at both sites at c . 9200-9100 BP ( c . 10200-10100 cal. BP). Betula pubescens forest stands established at c . 8900 BP ( c . 9900 cal. BP). The first Pinus sylvestris individuals may have established at or near the lowermost investigation site at c . 8700-8600 BP ( c . 9700-9600 cal. BP), while P. sylvestris forest stands were present at 400 m a.s.l. c . 7700 BP ( c . 8500 cal. BP) and expanded in area and/or density from c . 7200 BP. Macrofossils of P. sylvestris occur in strata with a pine pollen influx as low as c . 200 grains cm -2 yr -1 . The immigration of P. sylvestris to the western part of northern Fennoscandia may thus have happened earlier than formerly interpreted from pollen analyses alone, where influx values as low as c . 200 grains cm -2 yr -1 would not be considered as indicative of local presence. Alnus incana established at approximately the same time as P. sylvestris . During the period from deglaciation to c . 6600 BP ( c . 7300 cal. BP), calcareous limnic sediments were deposited in the basins, with Chara species and a Sphaeriidae fauna consisting of Pisidium hibernicum , P. lilljeborgii , P. milium , P. nitidum , P. waldeni and P. casertanum . During the period c . 8800-8500 BP, P. nitidum prevailed, and almost pure CaCO 3 sediments were formed. We interpret the environment as dry with a low influx of both minerogenic particles and humic substances. The period 8800-8500 BP (9800-9500 cal. yr BP) is interpreted as a period with warm and dry summers and cold and dry winters.     

Quantitative climate and vegetation trends since the late glacial on the northeastern Tibetan Plateau deduced from Koucha Lake pollen spectra

Quantitative information on vegetation and climate history from the late glacial-Holocene on the Tibetan Plateau is extremely rare. Here, we present palynological results of a 4.30-m-long sediment record collected from Koucha Lake in the Bayan Har Mountains, northeastern Tibetan Plateau. Vegetation change has been traced by biomisation, ordination of pollen data, and calculation of pollen ratios. The application of a pollen-climate calibration set from the eastern Tibetan Plateau to Koucha Lake pollen spectra yielded quantitative climate information. The area was covered by alpine desert/steppe, characteristic of a cold and dry climate (with 50% less precipitation than today) between 16,700 and 14,600 cal yr BP. Steppe vegetation, warm (∼ 1°C higher than today) and wet conditions prevailed between 14,600 and 6600 cal yr BP. These findings contradict evidence from other monsoon-influenced areas of Asia, where the early Holocene is thought to have been moist. Low effective moisture on the northeastern Tibetan Plateau was likely due to high temperature and evaporation, even though precipitation levels may have been similar to present-day values. The vegetation changed to tundra around 6600 cal yr BP, indicating that wet and cool climate conditions occurred on the northeastern Tibetan Plateau during the second half of the Holocene.     

A multiproxy environmental investigation of Holocene wood from a submerged conifer forest in Lake Huron, USA

Remains of a Holocene drowned forest in southern Lake Huron discovered in 12.5 m of water (164 m above sea level), 4.5 km east of Lexington, Michigan USA (Sanilac site), provided wood to investigate environment and lake history using several proxies. Macrofossil evidence indicates a forest comprised primarily of conifers equivalent to the modern “rich conifer swamp” community, despite generally low regional abundance of these species in pollen records. Ages range from 7095 ± 50 to 6420 ± 70 ¹⁴C yr BP, but the clustering of stump dates and the development of 2 floating tree-ring chronologies suggest a briefer forest interval of no more than c. 400 years. Dendrochronological analysis indicates an environment with high inter-annual climate variability. Stable-carbon isotope composition falls within the range of modern trees from this region, but the stable-oxygen composition is consistent with warmer conditions than today. Both our tree-ring and isotope data provide support for a warmer environment in this region, consistent with a mid-Holocene thermal maximum. This drowned forest also provides a dated elevation in the Nipissing transgression at about 6420 ¹⁴C yr BP (7350 cal yr BP) in the southern Lake Huron basin, a few hundred years before reopening of the St. Clair River drainage.     

Lateglacial and Holocene terrestrial and marine proxies reflecting climate changes in the Malangen fjord area, Norway, northeast North Atlantic

A high-resolution Younger Dryas–late Holocene record of climate and environment from the Malangen fjord has been established on the basis of two marine sediment cores. Five pollen-spore assemblage zones have been defined covering the period c . 11 500 cal. yr BP (10 200 ¹⁴C yr BP) to c . 1600 cal. yr BP (1600 ¹⁴C yr BP) with a hiatus of c . 2000 cal. years between c . 10 200 and 8100 cal. yr BP (9000 and 7300 ¹⁴C yr BP). The Holocene vegetation development from pioneer vegetation to forest development, identified in the marine pollen record, correlates well with pollen records from terrestrial sections of northern Norway. The marine pollen record was also correlated directly with marine proxy records of the bottom water temperature investigated in the same sediment cores. Correlation between the marine and terrestrial proxies suggests that changes in the influx of warm Atlantic Water to the fjord led to an instant change in the vegetation of the surrounding land area. The results thus support a strong link between marine and atmospheric mean climatic states in the North Atlantic region throughout the Holocene.     

Deglacial and Holocene conditions in northernmost Baffin Bay: sediments, foraminifera, diatoms and stable isotopes

A multiproxy study of palaeoceanographic and climatic changes in northernmost Baffin Bay shows that major environmental changes have occurred since the deglaciation of the area at about 12 500 cal. yr BP. The interpretation is based on sedimentology, benthic and planktonic foraminifera and their isotopic composition, as well as diatom assemblages in the sedimentary records at two core sites, one located in the deeper central part of northernmost Baffin Bay and one in a separate trough closer to the Greenland coast. A revised chronology for the two records is established on the basis of 15 previously published AMS ¹⁴C age determinations. A basal diamicton is overlain by laminated, fossil-free sediments. Our data from the early part of the fossiliferous record (12 300–11 300 cal. yr BP), which is also initially laminated, indicate extensive seasonal sea-ice cover and brine release. There is indication of a cooling event between 11 300 and 10 900 cal. yr BP, and maximum Atlantic Water influence occurred between 10 900 and 8200 cal. yr BP (no sediment recovery between 8200 and 7300 cal. yr BP). A gradual, but fluctuating, increase in sea-ice cover is seen after 7300 cal. yr BP. Sea-ice diatoms were particularly abundant in the central part of northernmost Baffin Bay, presumably due to the inflow of Polar waters from the Arctic Ocean, and less sea ice occurred at the near-coastal site, which was under continuous influence of the West Greenland Current. Our data from the deep, central part show a fluctuating degree of upwelling after c . 7300 cal. yr BP, culminating between 4000 and 3050 cal. yr BP. There was a gradual increase in the influence of cold bottom waters from the Arctic Ocean after about 3050 cal. yr BP, when agglutinated foraminifera became abundant. A superimposed short-term change in the sea-surface proxies is correlated with the Little Ice Age cooling.     

Late Quaternary vegetational changes on the east side of Yellowstone park,Wyoming

A bog pond 4 km east of Yellowstone Lake has a pollen record starting with an Artemisia spruce assemblage, implying alpine vegetation. A layer of volcanic ash, dated as 14,360 ± 400 BP (probably Glacier Peak or Mt. St. Helens J), occurs within the zone, which terminates at 11,630 ± 180 BP. The rest of the pollen sequence is dominated by lodgepole pine, with reappearance of spruce pollen in modest quantities about 4500 BP, according to dating provided by a layer of Mt. Mazama ash (6600 BP). The present vegetation of the area is marked by forests of lodgepole pine with some stands of spruce and fir. The pollen sequence suggests that the upper treeline before 11,600 y. a. was perhaps 500 m lower than today. The climate then became warmer and/or drier than today (Altithermal interval). About 4500 y. a., a slight climatic reversal took place, roughly contemporaneous with the regrowth of glaciers in the western mountains (neoglaciation).     

Postglacial diatom stratigraphy in relation to the recession of Glacial Lake Agassiz

The sediment and diatom stratigraphy of a small pond on The Pas moraine, near Grand Rapids, Manitoba, reveals a change in sedimentary environment related directly to the last stages of Glacial Lake Agassiz. Beach sands were replaced by clay 7300 ¹⁴C y. a., then by organic silt and, at 4000 ¹⁴C y. a. by coarse organic detritus; the corresponding diatom assemblages were (I) a predominantly planktonic spectrum in beach sands, (II) a rich assemblage of nonplanktonic forms, and (III) a distinctly nonplanktonic acidophilous spectrum. These results confirm Elson's (1967) reconstruction of the extent and chronology of the final (Pipun) stage of Glacial Lake Agassiz. The sedimentary environments change from a sandy beach of a large lake at 7300 BP to a small, shallow eutrophic pond with clay and silt deposition from 7000 to 4000 BP. From 4000 BP to the present, organic detritus was deposited in a shallow pond that tended toward dystrophy.     

青藏高原秋里南木湖盐类沉积韵律

盐类沉积韵律对研究湖泊环境及气候变迁有重要意义。对青藏高原秋里南木湖发现的芒硝、粘土和原生硼砂的韵律沉积进行了沉积速率和沉积韵律的分析。从物质来源、地貌和气候变化3个方面讨论了韵律形成的机制。在此基础上，利用矿物组成、年代、孢粉资料讨论了沉积物所反映的气候环境变化。结果表明，充足的物源和封闭的地貌环境是沉积韵律形成的物质条件，气候变化是主要外部动力。沉积韵律所反映的气候环境变化为：20.6~20.5 ka BP无芒硝，植被发育，气候相对温暖湿润；20.5~11.4 ka BP芒硝层很厚，植被类型过渡至以蒿为主的荒漠草原，气候干冷。其中，20.5~17.5 ka BP气候极端干旱寒冷，17.5~17.1 ka BP，15.9~15.2 ka BP和14.1~13.4 ka BP气温回升；11.4~10.1 ka BP芒硝层很薄，植物种类丰富，气候显著变暖；10.1~7.5 ka BP芒硝层厚度增加，木本植物花粉进一步降低，盘星藻消失，气候变冷；7.5~4.97 ka BP芒硝层厚度减小，但厚薄不一，植被过渡到以蒿为主的典型草原，气候相对暖湿，但冷暖交替频繁，其中7.0~6.2 ka BP蒿含量下降，湿生植物含量增加，气候冷湿，6.2~5.2 ka BP耐干旱、盐碱植物增加，禾本科消失，湖水盐度增加，气候冷干。     

坝上高原安固里淖全新世沉积地球化学特征与环境变化

湖泊沉积物是记录过去气候变迁的自然档案，分析湖泊沉积物的地球化学特征可以恢复湖区的古环境。在安固里淖湖心区钻取一沉积剖面，并以1cm为间隔分样，测得剖面各段的化学元素组成。根据岩心化学元素组成的变化和元素比值指标的变化，结合岩心纹层年代，获得湖区全新世以来的环境变化信息： 8507～7543a BP气候略干冷,但向暖湿方向发展；7453～4617a BP以湿润气候为主，但是存在相对干旱的时段(5137～4617a BP);4617～574a BP以干冷气候为主，在4617a BP和2494～1924a BP期间出现强干冷气候突变事件；574a BP以来，前期气候向湿润方向发展，但是在383a BP以后又转为干旱。安固里淖湖区全新世的环境变化状况与我国北方同期的气候状况具有很好的可比性。     

太湖平原碟形洼地沉积物记录的距今8000年以来植被、气候与地貌演变

利用DGY孔沉积物的岩性、粒度及孢粉分析资料,探讨了太湖平原碟形洼地沉积物记录的8000年以来植被演化、气候波动,流域地貌环境的演变及其对海平面波动的响应。孢粉记录表明:本区距今8000~5000年木本植被由以落叶阔叶乔木和针叶乔木为主变为落叶阔叶乔木和常绿阔叶乔木为主,气候由温和略干转为暖热湿润;距今5000~4000年森林退缩,气候温和偏干;距今4000年左右出现低温事件;距今4000~3,000年木本植被以常绿阔叶乔木为主,气候温暖湿润;距今3000年以来木本植被主要为常绿阔叶乔木、落叶阔叶乔木和针叶乔木,气候总体温暖湿润,有波动变凉干趋势。岩性、粒度及孢粉记录综合显示本区距今8000~5000年发育潟湖相泥质粉砂,反映流域环境开放、与海连通;距今5000~4000年发育淡水沼泽,未受海水作用,反映水域缩小、流域环境封闭;距今4000~3000年水域扩大,并出现海水倒灌,反映内低外高的碟形洼地已经形成;距今3000年以来,发育湖沼平原,发生数次海水倒灌,反映碟形洼地地貌的进一步发育。