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1.
李秉成 《吉林大学学报(地球科学版)》2005,35(3):291-295
为了了解黄土高原中部全新世古气候演化特征,通过对陕西富平剖面的地质调查、密集采样和31个样品的孢粉分析,将孢粉图式划分为Ⅰ、Ⅱ、Ⅲ3个带,分别代表早、中、晚3个时期的孢粉带:Ⅰ带为松-菊-香蒲组合带,以草本植物花粉占优势、针叶树植物花粉含量较高为特征;Ⅱ带为松-栎-蒿-环纹藻组合带,以乔木花粉增加、草本植物花粉减少为特征;Ⅲ带为栎-松-蒿组合带,以草本植物花粉增加、乔木花粉减少为特征.结果表明,早全新世植被为森林草原-干草原,气候干凉-干冷;中全新世植被为森林草原与针阔叶混交林草原,气候温暖半湿润;晚全新世植被为森林草原或疏林草原,气候干旱偏暖-温凉干旱. 相似文献
2.
James R. Purdue 《Quaternary Research》1980,13(2):242-258
Eastern cottontail (Sylvilagus floridanus), fox squirrel (Sciurus niger), and gray squirrel (Sciurus carolinensis) were examined for clinal variation during the Holocene. Modern samples of all three species displayed strong east-west patterns along the western edge of the eastern deciduous forest: S. floridanus and S. niger decrease and S. carolinensis increases in size. Archeological samples of S. carolinensis from Rodgers Shelter (23BE125), Benton County, Missouri, and Graham Cave (23MT2), Montgomery County, Missouri, indicated an increase in size from early to middle Holocene. Sylvilagus floridanus from Rodgers Shelter decreased in size from early to middle Holocene and then increased during the late Holocene to modern proportions. A literature survey reveals that clinal variation is a common phenomenon among modern homeotherms. In introduced species, clinal variation has developed after relatively few generations, indicating rapid adaptations to environmental conditions; often winter climatic variables are implicated. Morphological variation in the study species during the Holocene is interpreted as a response to changing climates. Studies of morphological clines may lead to another valuable data source for reconstructing past ecologies. 相似文献
3.
Curtis M. Hudak 《Quaternary Research》1984,21(3):351-368
The faunas and floras from the Dows Local Biota provide an opportunity to compare Holocene taxa without a cultural bias. The Dows Local Biota is located in a large depression on the back side (north) of the Altamont I Moraine complex within the Des Moines Lobe. The Dows Silt Fauna/Flora ( = DSF; ca. 9380 ± 130 yr B.P.), one horizon of the Dows Local Biota, was collected for plant macrofossils, mollusks, and micromammals. DSF terrestrial gastropods are upland mesic forest dwellers although one species, Strobilops affinis, is characteristic of more xeric forests and may represent open woods. The aquatic gastropods reflect both permanent and periodic waters. DSF micromammals prefer an open, mesic, deciduous forest. The micromammal sympatry is restricted to a small area within the tension zone and deciduous forest belt of west-central Wisconsin. DSF plants are characteristic of upland forests, moist meadowlands or disturbed areas, and aquatic habitats. The DSF plant sympatry is large but restricted to the conifer-hardwood and deciduous forests along the Great Lakes-New England regions. Quantitative climatic data for the combined DSF sympatries suggest that Dows (ca. 9380 yr B.P.) was cooler than at present, and is nearly identical to that achieved by pollen analyses at the Cherokee Sewer-Lake West Okoboji sites (ca. 9000 yr B.P.) in northwest Iowa. Based on common habitat interpretations and sympatries, about 9380 yr B.P. north-central Iowa was cooler and moister than at present and was occupied by an open deciduous forest. 相似文献
4.
J. Barry Dawson 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(3):342-34
The African Rift Valleys results from Neogene-Recent breakup up the African Plate due to continental extension. Compared with the western sector, in the eastern or Gregory Rift Valley the fracturing is accompanied by a large amount of volcanic activity and, in northern Tanzania, the volcanic rocks are relatively young compared with those in Ethiopia and Kenya where the products of the earliest stages of mantle melting are buried beneath older, more-extensive volcanic formations. The volcanic rocks vary from Pliocene and early Pleistocene intraplate basalts and trachytes to late Pleistocene/Holocene nephelinites and carbonatites. 相似文献
5.
The Turkana, Nakuru-Elmenteita, and Naivasha basins in the Rift Valley of East Africa experienced high water levels during the period of 10,000–7000 yr B.P. Analyses of the modern hydrologic and energy budgets for these basins, along with that of Lake Victoria, were used to infer the amount of precipitation that would have been required to maintain the enlarged paleolakes of the early Holocene. Precipitation must have been at least 150–300 mm/yr (15 to 35%) above the modern average. The precipitation estimates were fairly consistent among the various basins, but no quantitative estimate was made for the additional precipitation required to account for overflow from the Rift Valley lake basins. Discharge from the Lake Victoria basin around 1880 A.D. was considerably above the more recent average, and the increased discharge into the White Nile for that period might have been similar to that of the early Holocene. A sensitivity analysis showed that temperature changes were probably not too important for changing the hydrologic-energy budget; changes of albedo, Bowen ratio, and cloudiness were likely to have been of greater importance. 相似文献
6.
Palaeoenvironmental changes inferred from malacofaunas in the Lateglacial and early Holocene fluvial sequence at Conty, northern France 总被引：1，自引：0，他引：1
NICOLE LIMONDIN-LOZOUET PIERRE ANTOINE 《Boreas: An International Journal of Quaternary Research》2001,30(2):148-164
Environmental changes are reconstructed from a Lateglacial and early Holocene sequence at Conty, northern France. The molluscan succession is put into a chronostratigraphic framework supported by numerous radiocarbon dates. Malacofaunas from the Bølling chronozone are reported for the first time in northern France and show progressive expansion of marshy communities within organic deposits. This biozone ended in a calcareous silt with the appearance of several species of arctic-alpine affinities. These sedimentological and malacological data point to colder climatic conditions after 12 220 ± 90 BP, but before 11 640 ± 80 BP, allowing allocation to the Older Dryas event. The first part of the Allerød appears to have been drier and relatively stable. After 11 400 BP, a decline in species richness and diversity in the malacofaunas suggests increasing dryness. During the Younger Dryas, two molluscan biozones are identified in a homogeneous calcareous silt, reflecting an early wet phase followed by a drier episode. At the onset of the Holocene malacofaunas show a higher diversity, suggesting climatic improvement. 相似文献
7.
最近在广西崇左三合大洞发现了步氏巨猿和似人似猿共生的新层位,与之伴生的有52种小哺乳动物,占三合大洞巨猿动物群总数的62%,其中苏门答腊兔（Nesolagus）是东南亚地区首次发现的化石。小哺乳动物群以南方早更新世常见的偏皮氏毛耳飞鼠（Belomys parapearsoni）、中间猪尾鼠（Typhlomys intermedius）、拟低冠竹鼠（Rhizomys brachyrhizomyoides）、硕豪猪（Hystrix magna）、先社鼠（Niviventer preconfucianus）、拟爱氏巨鼠（Leopoldamysedwardioidesi）等为代表,根据小哺乳动物群性质和与其他动物群对比以及磁性地层年代测定,表明其时代应是早更新世中期（约距今120160万年前）。该动物群由树鼩、扁颅蝠、小彩蝠、飞松鼠、笔尾树鼠、猪尾鼠等几乎是旧大陆热带-亚热带森林型动物组成,缺少北方类型,基本上属于热带森林动物群,这表明了当时的自然景观为温暖湿润的热带雨林环境。三合大洞小哺乳动物群是广西地区的首次发现,对华南早更新世巨猿动物群详细划分,探讨步氏巨猿演化和早期人类环境背景等目前科学界关注的问题具有重要的意义。 相似文献
8.
北疆地区早全新世环境演化的湖泊沉积记录 总被引：3，自引：0，他引：3
通过对北疆地区艾比湖沉积物的孢粉组合及其碳酸盐δ^18O,δ^13C,δ^13Corg，TOC，TON和Rb/Sr比等地球化学指标分析，重点对全新世早期气候环境演化特征进行了研究。结果表明，研究时段（8.0-11.cal ka B.P.)温度总体偏低，初期（11.5-10.6cal ka B.P.)较为温湿；早全新世向中全新世转换时期（8.9-8.0cal ka B.P.)气候波动显著。特别是3层泥炭沉积显示了艾比湖地区早全新世气候的强烈不稳定性。泥炭的发育程度及其同位素、孢粉分析数据等都显示，8.2cal ka B.P.,8.6cal ka B.P.,10.5cal ka B.P.的气候状况具有显著的冷湿特征，反映了早全新世的3次冷湿事件。 相似文献
9.
The historical biogeography of highland Mediterranean pines is explored based on Late Pleistocene and Holocene charcoal from Portugal (Iberian Peninsula, SW Europe). The earliest presence of Pinus type sylvestris (including P. nigra, P. sylvestris and P. uncinata) is recorded in archaeological layers dated at ca 23,900 BP, during the Full Glacial. The abundance of remains identified as Pinus type sylvestris suggests that this was a frequent taxon, at least at middle altitudes. Significant occurrences were recorded up until ca 11,000 BP, at the end of the Lateglacial warming period. From the early Holocene onwards the presence of Pinus type sylvestris is recorded only sporadically, but at least up to 2000 years ago. The competition with other tree and shrub species favoured by the Holocene warming may have triggered the decline of highland pines in Portugal. Eventual anthropogenic impact is also considered as playing a role in its regional decline, such as increasing fire frequency resulting from amplified land use since the Neolithic. 相似文献
10.
River mouths on the steep, high-relief coast of the French Riviera exhibit thick sequences of Holocene marine, estuarine, deltaic, and river channel-floodplain sediments that overlie basal fluvial Pleistocene gravel. Gravel is uncommon in most of the early to middle Holocene aggradational-progradational marine, estuarine, deltaic sediments, despite an ample supply from rock units in the steep adjoining uplands. River-mouth gravel is common only in late Holocene river channels and in barrier beaches perched on finer-grained nearshore sediments. Neither downslope grain-size fining on alluvial fans nor sediment stacking patterns during sea-level (base-level) rise readily account for the lack of early to middle Holocene gravel in the river-mouth sediment wedges. Holocene sea-level rise led to the storage of fine-grained sediments in shallow marine, estuarine, and deltaic environments in the present coastal zone. We infer that humid temperate conditions, a dense forest cover, landscape stabilization, and a regular quiescent river flow regime associated with the Atlantic climatic optimum limited gravel supply in the adjoining catchments and gravel entrainment downstream during the early Holocene. Sea-level stabilization in the middle and late Holocene coincided with a marked change in bioclimatic conditions toward the present Mediterranean-type regime, which is characterized by a less dense forest cover, soil erosion, and episodic catastrophic floods. The late Holocene was thus a time of downstream bedload channel aggradation, fine-grained floodplain and paludal sedimentation, and seaward flushing of clasts leading to the formation and consolidation of the gravel barrier beaches that bound the rivermouths and embayments. 相似文献
11.
东北依兰—伊通地堑方正断陷方正组的建立及其意义 总被引：5，自引：0，他引：5
依兰—伊通地堑方正断陷方参 2井 2 10 4.0— 3 45 0 .0 m井段为一套红色碎屑岩 ,产有孢粉化石 Cicatrico-sisporites,Lygodiumsporites,Appendicisporites,Concavissimisporites,Gleicheniidites,Cyathidites,Cibotiumspora,Foraminisporis,Taxodiaceaepollenites,Inaperturopollenites,Triporopollenites和 Tricolporopollenites等。依据岩性及孢粉资料 ,在方正断陷建立方正组 ,并认为方正组时代为晚白垩世早期——赛诺曼期。通过与邻区松辽盆地泉头组、阜新盆地孙家湾组、延吉盆地龙井组等对比 ,认为东北地区这一套红层沉积具有广泛分布的特点 ,它是干热气候事件的产物。 相似文献
12.
Holocene environmental change and environmental archaeology are important components of an international project studying the human-earth interaction system.This paper reviews the progress of Holocene environmental change and environmental archaeology research in the Yangtze River Valley over the last three decades,that includes the evolution of large freshwater lakes.Holocene transgression and sea-level changes,Holocene climate change and East Asian monsoon variation,relationship between the rise and fall of primitive civilizations and environmental changes,cultural interruptions and palaeoflood events,as well as relationship between the origin of agriculture and climate change.These research components are underpinned by the dating of lacustrine sediments,stalagmites and peat to establish a chronology of regional environmental and cultural evolution.Interdisciplinary and other environment proxy indicators need to be used in comparative studies of archaeological site formation and natural sedimentary environment in the upper,middle and lower reaches of the Yangtze River Valley.Modern technology such as remote sensing,molecular bioarchaeology,and virtual reality,should be integrated with currently used dating,geochemical,sedimentological.and palaeobotanical methods of analysis in environmental archaeology macro- and micro-studies,so as to provide a greater comprehensive insight into Holocene environmental and cultural interaction and change in the Yangtze River Valley area. 相似文献
13.
《China Geology》2019,2(4):493-500
Due to the unique geographical location and sensitive response to global climate changes, the Antarctic region plays an important role in paleoclimate researches, and attracts great attentions from various scholars. One 324 cm long sediment core (ANT29-P7-09) was obtained from Prydz Bay, Antarctica, during the 29th Chinese National Antarctic Research Expedition. Based on sediment particle size, TOC, δ13C analyses and magnetism data, the authors show that the dominant magnetic minerals are ferrimagnetic pseudo single domain (PSD)-multi domain (MD) magnetite. Variations in the paleoenvironmental records allow us to define 4 zones in the core. These zones outline the climatic variations in the region since the late Early Pleistocene, including a warm period, a transitional period, and a cold period. The magnetic particle assemblage varies with glacial-interglacial cycles. Abrupt changes in particle size, TOC content, and geomagnetism occur at 102–90 cm deep in the core, indicating a sudden warming in the Antarctic region, signaling the onset of the Holocene. The authors identified 3 additional climatic signals in the middle part of the core (232–162 cm) that show unexpected cooling events during the warm period in Prydz Bay, Antarctica. 相似文献
14.
Laura C. Bishop Lawrence Barham Peter W. Ditchfield Sarah Elton William E. H. Harcourt‐Smith Peter Dawkins 《第四纪科学杂志》2016,31(3):178-190
This paper describes a large collection of Quaternary fossil fauna from the Luangwa Rift Valley, Zambia. Stone Age artefacts have been recovered from stratified fluvial contexts, but no in situ fossil faunas have yet been recovered. We report on 500 fossil specimens collected from the surface of point bars exposed seasonally along the banks of the main Luangwa River channel. We used non‐destructive X‐ray fluorescence analysis of the fossils' chemical signatures to determine whether they derive from one or many primary contexts, and the relationship between chemical signature and state of preservation. Specimens are identified to taxon (genus) to reconstruct palaeoenvironments and biochronology. A relatively wide range of taxa is identified, including a fossil hominin talus, described here. None of the fossils is positively attributable to extinct species, except a femur of an extinct Theropithecus reported in 2003. Although no additional extinct taxa were identified, some of the remains were attributable to genera that are not currently found in this region. The results suggest that most of the assemblage derives from sediments which are Middle Pleistocene or later, and that past environments in the Luangwa Valley may have differed from the habitat availability found today. 相似文献
15.
Eric Armynot du Châtelet François GuillotPhilippe Recourt Sandra VentalonNicolas Tribovillard 《Comptes Rendus Geoscience》2010,342(9):710-717
Testate amoebae are increasingly used for environmental monitoring as well as paleoenvironmental reconstructions. Paleoecological interpretations of testate amoebae assemblages depend on the understanding of the ecological processes operating today. We then ask the question of the link between testate structure and its environment. This study analyses both the grain size and mineralogical assemblage of tests of common species belonging to the genus Centropyxis and Difflugia. It is concluded that grain size is a limiting factor for test construction, whereas mineral composition is not. Hence, when analyzing agglutinated testate amoebae for paleoenvironmental reconstructions, it should be taken into account the mean grain size of the sediment. A non-appropriate grain-size probably inhibits the development of a testate amoebae specific assemblage. 相似文献
16.
Phytolith data from Poyang Lake, southern China, indicate that significant natural and human‐induced vegetational changes have occurred in the middle Yangtze River valley, the likely hearth of rice (Oryza sativa L.) domestication, during the Late Pleistocene and Holocene periods. During the Late Pleistocene (from >13,500 to ca. 10,500 yr B.P.) the climate was cooler and drier than today's. Oryza appears to have been a natural component of the vegetation at that time, but may not have been well adapted to the glacial climatic conditions. The early Holocene climate may have been wetter and more markedly seasonal that at present, and wild Oryza species may have been distributed further north than seen today. By 4000 yr B.P., rice agriculture appears to have been well developed in the middle Yangtze River Valley. Environmental factors such as atmospheric CO2 concentrations and the seasonality of precipitation and temperature in addition to overall cooler and drier Pleistocene climates may have significantly influenced human exploitation of Oryza during the Late Pleistocene and early Holocene in southern China. © 2000 John Wiley & Sons, Inc. 相似文献
17.
A fossiliferous fissure filling at Les Alleveys, Mormont (Canton de Vaud, Switzerland), sampled in 1986 and representing part of the same fissure system as that excavated by Chavannes and Morlot in 1852, contains an Eocene mammal fauna of 27 species-group taxa, dominated by micromammals. Unlike the 1852 collection, thanks to screenwashing techniques, there is an abundance of rodents, especially theridomyids, which provide new information on the early radiation of the family. The homogeneity of the new assemblage suggests that the Les Alleveys fauna is entirely Bartonian in age and not as previously thought mixed with Priabonian elements. Bartonian faunas rich in a diversity of micromammals are relatively uncommon in Europe outside the Quercy region of France and this is the first such fauna from Mormont and from Switzerland. The rodents are here treated systematically and a new species of Elfomys, E. engesseri sp. nov. is described. A few teeth of an undescribed species tentatively referred to ‘Protadelomys’ provide an archaic element, whereas a single milk premolar of Patriotheridomys? suggests a considerable range for the genus prior to the middle Priabonian. The Les Alleveys theridomyids, together with a range of other early family members are analysed cladistically. The analysis confirms both the distinctness of the subfamily Remyinae and that the genus Estellomys is a primitive theridomyine; it shows Paradelomys to be a primitive member of the Columbomyinae, but finds no dental synapomorphies to support the Issiodoromyinae as represented by Elfomys and Pseudoltinomys. 相似文献
18.
丽蚌动物群的分布受气候和地理环境控制,研究地层中的丽蚌动物群可以恢复当时的古环境。在河北省白洋淀地区全新统共发现13种珠蚌科(Unionidae)的化石,属 Lamprotula-Cuneopsis-Unio 组合,称为白洋淀丽蚌动物群。该动物群与长江中下游流域太湖、鄱阳湖、洞庭湖及其周围水域的现代丽蚌动物群和山东王因、河南西水坡中全新世丽蚌动物群相比,虽然分异度低,但其组合特征相似,同属东洋界中印亚界动物地理区,生活于亚热带湿热气候下的河湖环境中。推测白洋淀丽蚌动物群的生活时代应为中全新世早期,当时北亚热带和东洋界的北界应在白洋淀以北的京津-河套一带。 相似文献
19.
This paper presents a Holocene pollen record from an ombrotrophic bog in Southland, New Zealand, together with multiproxy data (testate amoebae, peat humification and plant macrofossils) from the same core to establish an independent semiquantitative record of peatland surface moisture. Linkages between reconstructed peatland surface moisture and regional forest composition are investigated using redundancy analysis of the forest pollen data constrained with predicted bog water‐table depths. Over 32% of the pollen data variance can be explained by surface moisture changes in the bog, suggesting a common cause of water‐table and regional vegetation change. Water tables were higher during the early to mid‐Holocene when the forest was dominated by podocarp taxa. Water tables lowered after about 3300 cal. yr BP coevally with the expansion of Nothofagus species, culminating with the dominance of Nothofagus subgenus Fuscospora in the past 1200 cal. yr BP. This is in apparent opposition to the warm/dry to cool/wet trend suggested by subjective interpretation of pollen data alone, from this and other studies. We suggest that during the late Holocene, drier summers associated with shifts in solar insolation caused reduced surface wetness and summer humidity, which together with a trend to cooler winters, apparently favoured the regeneration of Nothofagus species. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
20.
Anna Stepanova Ekaterina Taldenkova Henning A. Bauch 《Boreas: An International Journal of Quaternary Research》2012,41(4):557-577
Fossil ostracod assemblages were investigated in five AMS 14 C‐dated cores from various water depths of the Laptev and Kara seas ranging from the upper continental slope (270 m) to the present‐day shelf depth (40 m). Six fossil assemblages were distinguished. These represent the varying environmental conditions at the North Siberian continental margin since about 18 ka. In the cores from the shelf the ostracod assemblages reflect the gradual transition from an estuarine brackish‐water environment to modern marine conditions since 12.3 ka, as induced by the regional early Holocene transgression. The core from the upper continental slope dates back to c. 17.6 ka and contains assemblages that are absent in the shelf cores. The assemblage older than 10 ka stands out as a specific community dominated by relatively deep‐water Arctic and North Atlantic species that also contains euryhaline species. Such an assemblage provides evidence for past inflows of Atlantic‐derived waters from as early as c. 17.2 ka, probably facilitated by upwelling in coastal polynyas, and a considerable riverine freshwater influence with enhanced surface water stratification owing to the proximity of the palaeocoastline until early Holocene times. In all studied cores, relative increases in euryhaline species dominant in the inner‐shelf regions are recorded in the mid–late Holocene sediments (<7 ka), which otherwise already contain modern‐like ostracod assemblages with relatively deep‐water species. This observation suggests euryhaline species to be largely sea‐ice‐ and/or iceberg‐rafted and therefore may provide evidence for a climate cooling trend. 相似文献