Diatom-based reconstruction of Holocene hydrological changes along the Colorado River floodplain (northern Patagonia,Argentina)

Diatom assemblages recovered from a Colorado River delta core in northern Patagonia, Argentina were analyzed in order to assess past environmental conditions. A total of 35 samples were selected from a 172-cm core extracted 37 km from the mouth (39°36′19.6″S; 62°29′26.1″W). One-hundred and thirty-eight taxa were recognized and grouped according to life forms. Two diatom zones were identified by cluster analysis. At the base of the sequence, the Diatom Zone I (DZI; 4132 ± 35 ??2919?±?27 ¹⁴C yr BP), consisted of clays, and was characterized by assemblages dominated by aerophilous and benthic taxa and chrysophyte stomatocysts, which led to inferences of a sedimentary environment corresponding to a pond experiencing dry periods. The upper section (DZII) was dominated by fine sands and silts encompassing the last ~?150 yr with abundant planktonic and tychoplanktonic diatoms. Benthic diatoms were abruptly replaced by planktonic forms in this zone indicating a shift to deeper waters. These results characterize the meandering dynamics of a deltaic system. During the Mid-Holocene, more arid periods would have favored the deactivation of meanders and the formation of riverine and oxbow wetlands. In Late-Holocene and historical times, more humid conditions and the hydrological system across the floodplain reactivated the paleochannel. Today, the dominant diatom species are brackish/freshwater fragilaroids. A non-multidimensional scaling analysis showed a lack of analogy between fossil and modern samples. The change in diatom floras in recent historical times was attributed to anthropogenic disturbances, a consequence of the regulation of the river flow. This regulation is evidenced by less discharge, morphological modifications in the floodplain and increased salinity in the last decade.     

Holocene environmental changes and development of Figurnoye Lake in the southern Bunger Hills, East Antarctica

The lithology, radiocarbon chronology, granulometry, geochemistry and distribution of diatoms were investigated in three sediment cores from fresh-water Figurnoye Lake in the southern Bunger Hills, East Antarctica. Our paleolimnological data provide a record of Holocene environmental changes for this region. In the early Holocene (prior to 9.0 ± 0.5 kyr BP), warm climate conditions caused intensive melting of either the floating glacier ice mass or glaciers in the immediate lake surroundings, leading to the accumulation of terrigenous clastic sediments and limiting biogenic production in the lake. From ca. 9.0 ± 0.5 to 5.5 ± 0.5 kyr BP, highly biogenic sediments dominated by benthic mosses formed, indicating more distal glaciers or snowfields. A relatively cold and dry climate during this period caused weaker lake-water circulation and, likely, occurrence of lake ice conditions were more severe than present. The distribution of marine diatoms in the cores shows that, sometime between 8 and 5 kyr BP, limited amounts of marine water episodically penetrated to the lake, requiring a relative sea-level rise exceeding 10–11 m. During the last ca. 5.5 ± 0.5 kyr BP, sedimentation of mainly biogenic matter with a dominance of laminated microbial mats occurred in the lake under warm climatic conditions, interrupted by relative coolings: the first one around 2 kyr BP and then shortly before recent time. Between ca. 5.5 and 4 kyr BP, the drainage of numerous ice-dammed lakes took place in the southern Bunger Hills and, as a result, drier landscapes have existed here from about 4 kyr BP.     

Late Holocene history of the floodplain lakes of the Cauca River, Colombia

We conducted a paleolimnological investigation of late Holocene deposits on a distal, constrained floodplain of the Cauca River, northern Colombia, i.e. the La Caimana sedimentary succession. The record starts sometime between 4,500 and 4,000 cal yr BP, when the first high-energy fluvial events inundated an ancient soil surface. From that time until about 3,260 cal yr BP, a stable and probably seasonal flooding regime was established on the floodplain. From ~3,260 to ~2,800 cal yr BP, ephemeral and shallow swamps developed on the floodplain. Their formation and duration depended on their connection with the Cauca River. From ~2,800 to ~2,400 cal yr BP, fluvial influence became more dominant, establishing a semi-permanent connection between the river and the floodplain. From ~2,400 to 1,400 cal yr BP, episodic formation of ephemeral swamps occurred. During this stage, floodplain lakes displayed high salinity and nutrient concentrations, and possibly alkaline conditions as a consequence of reduced water volume when the connection with the river was reduced or lost completely. A change in the hydrological regime occurred from ~1,400 to ~850 cal yr BP, when high-energy fluvial events were punctuated by periods of reduced flooding that enabled soil formation. Generally, connection with the Cauca River resulted in lake waters with low salinity and nutrient concentration, whereas loss of connection with the river led to lakes with greater salinity and nutrient content. Paleocurrent analyses indicate that flows came predominantly from the Cauca River, suggesting the lakes were formed by the impoundment of La Caimana Creek. The sedimentary succession of La Caimana offers a unique, high-resolution record of the evolution and dynamics of an ancient floodplain of the Cauca River and its aquatic ecosystems.     

Holocene environmental changes on the east coast of Korea

We present a record of Holocene environmental change on the east coast of Korea, inferred using pollen, carbon-isotopic composition (??¹³C), total organic carbon, total sulfur, carbon/nitrogen ratios, particle size analysis and major element geochemistry in a sediment core from Soonpogae Lagoon. A multi-proxy paleoenvironmental approach had not previously been applied in Korea and allowed us to reconstruct climate and vegetation change, sea-level rise, lagoon development, and human impact on the east coast of Korea over the last 8,000?years. Evidence from Soonpogae Lagoon supports the following three conclusions: (1) As a drying trend prevailed on the east coast of Korea after ~5,900?cal?yr BP, chemical weathering weakened and herbaceous plants became more important than during the previous humid phase (Holocene Climate Optimum), (2) Sea-level rise on the east coast slowed dramatically about 6,800?cal?yr BP, resulting in low rates of sedimentation in Soonpogae Lagoon, and (3) Soonpogae Lagoon was almost completely isolated from the sea by sand barriers when human impact intensified ~2,100 BP.     

淮河上游全新世黄土与成壤环境变化

Based on field surveys, soil samples were collected at the YPC site, Yuzhou City, Henan Province for analysis of contents of major and trace elements and their variations with XRF and comparison with the curves of magnetic susceptibility, pH value distribution, loss on ignition and particle-size distribution. It was concluded that the dust source of loess in the upper reaches of the Huaihe River Basin was different from that in the Loess Plateau. And the Holocene pedogenic environmental changes in the upper reaches of the Huaihe River Basin were revealed. Foundation: National Natural Science Foundation of China, No.40571154; No.40471119 Author: Li Xinyan (1978–), Ph.D, specialized in resource exploitation and environmental science.     

Dust source of the Holocene loess-soil and pedogenic environmental changes in the upper Huaihe River

Based on field surveys, soil samples were collected at the YPC site, Yuzhou City, Henan Province for analysis of contents of major and trace elements and their variations with XRF and comparison with the curves of magnetic susceptibility, pH value distribution, loss on ignition and particle-size distribution. It was concluded that the dust source of loess in the upper reaches of the Huaihe River Basin was different from that in the Loess Plateau. And the Holocene pedogenic environmental changes in the upper reaches of the Huaihe River Basin were revealed.     

长江流域全新世环境考古研究进展

长江流域是我国重要的经济区和人类文明孕育、诞生和发展区,也是水旱等自然灾害频繁发生的地区,在该区开展全新世环境考古研究,对弄清全新世10.0~3.0 ka BP无文字记载期的环境演变和人地关系互动影响有着重要的科学意义。近年来,长江流域全新世环境考古主要以古洪水和海面变化事件地层学为依据和线索,从遗址时空分布学研究、典型遗址考古地层学研究,以及区域内自然沉积地层记录的环境演变背景特征研究这三个方面入手,在长江流域的上、中、下游地区均获得了有重要意义的进展,表明长江流域全新世环境考古正在向更深更广的领域发展。同时,国际环境考古研究也在不断深入发展,新出版的PAGES Magazine杂志就特别关注了分辨率高达一年至数月的过去沉积记录;遥感、GIS等技术和DNA等分子生物学技术正不断在环境考古领域得到应用。     

Holocene floodplain metamorphosis in the Midlands, United Kingdom

Many lowland rivers in the United Kingdom, including the Nene, Soar and Severn, have layered floodplains with a basal gravel of Pleistocene or Late glacial age and a structureless silty clay superficial unit burying the entire former floodplain. This burial is illustrated by the existence of variable, mixed and pedologically disturbed sediments and palaeo landsurfaces between the basal gravels and superficial silty clay. This paper presents a comparison of the pre- and post-late Holocene palaeo landsurfaces and palaeochannels using data from the Nene, Soar and Severn valleys. From this comparison it is argued that during the mid to late Holocene (ca 4500 yr BP to 2500 yr BP) floodplains and river channels underwent a metamorphosis. This is indicated by accelerated vertical accretion, a reduction in floodplain relative relief, changed floodplain soil conditions, a reduction in channel W/D ratios and a resultant increase in the silty clay proportion of channel perimeter sediments. There are indications that hydrological change preceded this metamorphosis but the primary cause was an increase in fine sediment supply during the later Holocene and a disequilibrium between channel bed and floodplain aggradation rates resulting in relative incision. This metamorphosis, which is explained in this paper by the proposed stable-bed aggrading-banks model (SBAB), is the key factor in the Holocene evolution of low-energy floodplain systems in the United Kingdom, upon which more subtle short-term fluctuations are superimposed.     

Holocene environmental changes in the Gebel Umm Hammad, Eastern Desert, Egypt

Gebel Umm Hammad in the Red Sea Mountains east of Quseir, Egypt, today enjoys small but irregular amounts of winter rain, enabling the widening of joint controlled openings in the Thebes Limestone. Cavities are especially affected by flaking, while rock fragmentation is more active on the outside. The sedimentological and botanical study of fan deposits at the outlet of a karstic shaft in the Tree Shelter showed the local Holocene environmental evolution. Three periods of different degree of aridity can be considered: (i) Before 8120±45 BP (UtC-5389), bedload aggradation points to rare but occasionally heavy rains, lasting for several hours, attaining intensities of more than 76 mm/h and covering some 20 km². Wadi flash floods occasionally attained bankfull stage. (ii) Since 8120±45 BP (UtC-5389), such heavy rains have not occurred in the Egyptian Red Sea Mountains. Instead, a more moderate but maybe wetter precipitation regime was established. The karstic shafts were active, and there was water and life in the desert. Two humid pulses can be distinguished within this period. The first occurs at ±8000 BP, the second between 6630±45 (GrN-22560) and 6770±60 BP (GrN-22562). (iii) After the last wet culmination, there was a gradual shift to drier conditions. Shortly after ±5000 BP, modern climatic conditions are believed to have been attained. Today, the occasional rain storms are less heavy than before ±8000 BP. Bankfull stage river floods do not occur. Instead, secondary channels are eroded in the wadi beds. The general arid character during the whole period and the inherent local and temporal variations in precipitation patterns might explain apparent aberrations between the palaeoenvironmental evolution of the Tree Shelter site and other remote study areas in Egypt and Sudan.     

Paleolimnological evidence of Holocene climatic changes in Lake Blanca, southern Uruguay

Paleolimnological data are presented on Holocene climatic changes in Lake Blanca, a small (0.6 km²), coastal fresh waterbody in southern Uruguay. Using a sediment core that extended to 7,300 year BP, analyses of pooid, panicoid and chloridoid phytoliths (Poaceae) allowed us to identify 16 Opal Phytoliths Association Zones (OPAZ). Both temperature and humidity indices were calculated from relative percentages of opal phytoliths and the climatic trends were inferred. During the early Holocene, prior to the first Holocene marine transgression (∼ ∼8,000–7,000 yr BP), cool-arid climatic conditions were inferred. After the first Holocene transgression, predominance of cool-humid conditions was registered until about 4,000 yr BP. A transition from cool-semiarid/arid to alternate warm-temperate and humid-very-humid conditions was detected for ∼∼4,000–1,000 yr BP. Increases in trophic state were observed because of such a climatic amelioration. After ∼ ∼1,000 yr BP, a shift from warm to temperate and cool temperatures was inferred. Such a cooling episode was assigned to a “LIA” which took place by the end of the 18th century and the beginning of the 19th century. A decrease in trophic state was observed during this climatic deterioration. After such a little ice age, present temperate humid conditions were established. The humidity indices calculated from relative percentages of opal phytoliths for the last ∼ ∼70 years were compared to annual rainfall data. Such a comparison showed that opal phytoliths are reliable indicators of humidity.     

Holocene environmental changes of the Hwajinpo Lagoon on the eastern coast of Korea

Lithologic and geochemical data of a core from the Hwajinpo Lagoon, located on the eastern coast of Korea, provided the evolutionary history of the lagoon related to Holocene sea-level changes of the East Sea (Sea of Japan). Grain size analysis, water content analysis, and soft X-ray analysis of core samples were used to reconstruct sedimentary environments, as were total organic carbon, C/N, S and C/S chemical records. Assemblages of mollusc and diatom remains also provided paleoenvironmental information. The reconstruction of paleoenvironments from these multi-proxy data allows the establishment of an evolutionary model of the Hwajinpo Lagoon. The environmental changes of the Hwajinpo Lagoon can be divided into seven different depositional facies: (l) Exposed basement rock; (2) Estuarine; (3) Stagnant brackish lagoon (isolated); (4) Oxic condition lagoon (organic activity); (5) Fresh water lake; (6) Oxic brackish lagoon (recent condition); (7) Prograding river delta. These environmental changes can be related to sea-level change during the Holocene. The trends of sea-level change in the Hwajinpo Lagoon from this study can be compared to those of the Japanese coastal areas located on the other side of the East Sea such as Lakes Shinji and Nakaumi.     

青藏高原北部孢粉记录的全新世以来环境变化

根据青藏高原北部同纬度地区,同一个垂直自然带内的西藏羊湖的湖相沉积、青海昆仑河河流相沉积、青海豆错(苦海)湖的湖相沉积记录的全新世以来孢粉(spore-pollen)资料的对比分析,表明:①极度干旱荒漠区的代表植被麻黄属(Ephedra)花粉平均百分含量,三个地区分别为:7.7%,4.2%,7.5%,总体上,羊湖地区的数值高于昆仑河地区与苦海地区。②代表气候湿润的禾本科(Gram ineae)花粉平均百分含量,三个地区分别为:1.2%、4.9%、12.0%,从西向东数值逐渐升高。③代表气候湿润的蒿属(Artem isia)花粉平均百分含量,三个地区分别为:22.2%,43.6%,48.8%,从西向东数值逐渐升高。④代表气候干旱的藜科(Chenopod iaceae)花粉平均百分含量,三个地区分别为:52.1%,42.4%,11.5%,从西向东数值逐渐降低。⑤依据蒿属、藜科花粉百分含量,计算出环境变化指标,蒿属/藜科(A/C)值,三个地区的平均值分别为:0.45,1.23,5.59,从西向东比值逐渐升高,⑥麻黄属/蒿属值,在全新世晚期,三个地区都呈上升趋势,但幅度存在差异,分别为:0.45,0.34,0.28,从西向东数值逐渐降低。综观上述6个方面的变化规律,青藏高原北部全新世以来,干旱的程度从西向东逐渐降低;对青藏高原北部东西方向现今植被和环境的实际考察并结合上述变化规律,未来高原北部干旱变化的趋势将继续由西向东推移。     

Holocene environmental changes around Xiaohe Cemetery and its effects on human occupation,Xinjiang, China

The Xiaohe Cemetery archaeological site (Cal. 4–3.5 ka BP) is one of the most important Bronze Age sites in Xinjiang, China. Although the surrounding environment is an extremely arid desert now, abundant archaeological remains indicate that human occupation was common during certain periods in the Holocene. Field investigations and laboratory analyses of a sediment profile near the Xiaohe Cemetery indicate that while the regional environment was arid desert throughout the Holocene there were three episodes of lake formation near the site in the periods 4.8–3.5 ka BP, 2.6–2.1 ka BP and 1.2–0.9 ka BP. Geomorphic and hydrological investigations reveal that a lake or lakes formed in a low-lying area when water was derived initially from the Kongque River and then shunted into the Xiaohe River basin. Low amounts of active chemical elements in lacustrine sediment between 4.8–3.5 ka BP indicate abundant and continuous water volume in the lake; the content of active chemical elements increased between 2.6–2.1 ka BP but was still at a relatively low level, suggesting a declining amount of water and diminished inflow. Between 1.2–0.9 ka BP there was a very high content of active elements, suggesting decreased water volume and indicating that the lake was stagnate. In contrast, the general climate condition shows that there had a warm-humid stage at 8–6 ka BP, a cool-humid stage at 6–2.9 ka BP and a warm-dry stage at 2.9–0.9 ka BP in this region. The hydrological evolutions around Xiaohe Cemetery did not have one-to-one correspondence with climate changes. Regional comparison indicates that broad-scale climatic conditions played an important role through its influences on the water volume of the Tarim River and Kongque River. But, the formation of the lakes and their level were controlled by geomorphic conditions that influenced how much water volume could be shunted to Xiaohe River from Kongque River. Human occupation of the Xiaohe Cemetery and nearby regions during the Bronze Age and Han-Jin period (202 BC–420 AD) corresponded to the two earlier lake periods, while no human activities existed in the third lake period because of the decreased water volume.     

Mineral magnetic record of Holocene environmental changes in Sägistalsee, Switzerland

The Holocene magnetic signature due to environmental change has been investigated in sediments from Sägistalsee, a small alpine lake in the Bernese Alps, Switzerland. The environmental signal in the mineral magnetic parameters of the sediments was compared with palynological and geochemical data. The types of magnetic minerals and their grain size reflect changes in the lake catchment, vegetation, and degree of erosional input. The concentration of the magnetic minerals, as expressed by isothermal and anhysteretic remanent magnetizations also reflect changes in vegetation, but may also be related to redox conditions during sedimentation. Climate influence on the mineral magnetic record has been recognized and interpreted as a consequence of the production of an authigenic mineral with particularly uniform magnetic properties during warmer stages and the influx of heterogeneous detrital magnetic mineral during cooler stages and under increased human activity.     

Late Holocene environmental changes inferred from diatoms in a lake on the western Taimyr Peninsula, northern Russia

Changes in the diatom assemblages preserved in a sediment core taken from a small lake located north of arctic treeline on the western Taimyr Peninsula, Russia, were examined in order to investigate late Holocene (i.e., ca 5000 cal yr BP to present) climatic and environmental changes within the region. Early diatom assemblages were dominated by benthic Fragilaria taxa and indicate a transitional phase in the lake history, most likely reflecting lake development and environmental change associated with treeline retreat to the south of the study site. Concurrent with pollen and macrofossil evidence of a vegetation shift to shrub tundra in the catchment basin at ca 4200 cal yr BP, an increase in cold-water taxa, followed by little change in diatom assemblages until ca 2800 cal yr BP, suggests that conditions were relatively cool and stable at this time. The last 2000 years of the Middendorf Lake record have been marked by fluctuating limnological conditions, characterized by striking successional shifts between Fragilaria pinnata and Aulacoseira distans var. humilis. Recent conditions in Middendorf Lake indicate an increase in diatom taxa previously rare in the record, possibly associated with twentieth-century climatic warming. The Middendorf Lake record indicates that significant limnological change may occur in the absence of catchment vegetation shifts, suggesting late-Holocene decoupling of aquatic and terrestrial responses to climatic and hydrological change. Our study results represent one of the few paleoecological records currently available from northern Russia, and highlight the need for further development of calibration data sets from this region.     

Holocene environmental changes in the Whitefish Dunes Area, Door Peninsula, Northern Lake Michigan Basin, USA

A two meter sediment core taken from an inter-dune pond in Whitefish Dunes State Park, Door Peninsula, Wisconsin, provides a record of paleoenvironmental changes in the area from approximately 3600 RCYBP to 5100 RCYBP. The hydrology of the Whitefish Dunes pond is now apparently dependent on ground water recharge from local precipitation that infiltrates into the dunes and from Clark Lane, making it very sensitive to low magnitude, short term climate fluctuations.Changes in lithology, molluscan species diversity, oxygen isotopes from gastropod shells, and sediment organic content permit division of the core into several intervals representing different environmental regimes. The basal sediments are older than 5130 RCYBP and resemble those of the Liberty Grove Member of the Pleistocene Horicon Formation. The oldest Holocene sediments recorded in the core are an organic rich layer dated at 5130 RCYBP, which accumulated in a depression on the surface of a sand bar. Continued rise in the local water table during the Nipissing Transgression produced paludal conditions in the area, which were followed by the onset of lacustrine conditions. During this interval, the area supported a diverse molluscan fauna. Minor, short term climate fluctuations are reflected in sediment and oxygen isotope changes which are absent from the record in deep water cores from Lake Michigan. This phase in the history of the area ended with the eutrophication of the pond and the development of dunes. Information from Whitefish Dunes pond and other onshore sites within the Lake Michigan basin are an important source of data for reconstructing the history of water levels and climate changes for this area of the Great Lakes drainage.     

Late Pleistocene: Holocene record of environmental changes in Lake Zirahuen,Central Mexico

Geochemical data obtained from X-ray fluorescence, physical properties, total organic and inorganic carbon content (TOC/TIC), and diatom analysis from a 6.61-m-long sedimentary sequence near the modern northern shore of Lake Zirahuen (101° 44′ W, 19° 26′ N, 2000 m asl) provide a reconstruction of lacustrine sedimentation during the last approximately 17 cal kyr BP. A time scale is based on ten AMS ¹⁴C dates and by tephra layers from Jorullo (AD 1759-1764) and Paricutin (AD 1943-1952) volcanoes. The multiproxy analyses presented in this study reveal abrupt changes in environmental and climatic conditions. The results are compared to the paleo-record from nearby Lake Patzcuaro. Dry conditions and low lake level are inferred in the late Pleistocene until ca. 15 cal kyr BP, followed by a slight but sustained increase in lake level, as well as a higher productivity, peaking at ca. 12.1 cal kyr BP. This interpretation is consistent with several regional climatic reconstructions in central Mexico, but it is in opposition to record from Lake Patzcuaro. A sediment hiatus bracketed between 12.1 and 7.2 cal kyr BP suggests a drop in lake level in response to a dry early Holocene. A deeper, more eutrophic and turbid lake is recorded after 7.2 cal kyr BP. Lake level at the coring site during the mid Holocene is considered the highest for the past 17 cal kyr BP. The emplacement of the La Magueyera lava flows (LMLF), dated by thermoluminiscence at 6560 ± 950 year, may have reduced basin volume and contributed to the relative deepening of the lake after 7.2 cal kyr BP. The late Holocene (after 3.9 cal kyr BP) climate is characterized by high instability. Extensive erosion, lower lake levels, dry conditions and pulses of high sediment influx due to high rainfall are inferred for this time. Further decrease in lake level and increased erosion are recorded after ca. AD 1050, at the peak of Purepechas occupation (AD 1300–1521), and until the eighteenth century. Few lacustrine records extend back to the late Pleistocene—early Holocene in central Mexico; this paper contributes to the understanding of late Pleistocene-Holocene paleoclimates in this region.     

Mid–late Holocene hydrological changes in the Mahi River, arid western India

This paper attempts to quantify contemporary and palaeo-discharges and changes in the hydrologic regime through the mid–late Holocene in the alluvial reach of the arid Mahi River basin in western India. The occurrence of terraces and pointbars high above active river levels and change in the width/depth ratio can be regarded as geomorphic responses to changes in discharge. Discharge estimates are made based on the channel dimensions and established empirical relations for the three types of channels: mid–late Holocene, historic (the channel that deposited extensive pointbars above the present-day average flow level) and the present ones. The bankfull discharge of the mid–late Holocene channel was  55 000 m³ s^− 1 and that of the historic channel was  9500 m³ s^− 1, some  25 times and  5 times greater than that of the present river (2000 m³ s^− 1), respectively. Since the mid–late Holocene, the channel form has changed from wide, large-amplitude meanders to smaller meanders, and decreases in the width/depth ratio, unit stream power and the bed shear stresses have occurred. It can be inferred that there has been a trend of decreasing precipitation since the mid–late Holocene.     

淮河上游全新世风成黄土与成壤环境变化研究

在野外考察研究的基础上,在河南禹州全新世黄土-古土壤剖面系统采样,利用X-荧光光谱仪测定了常量元素的含量,并与磁化率、粘粒含量及碳酸钙含量变化曲线对比发现:常量元素氧化物(Al2O3、Fe2O3、K2O、MgO)含量随土壤地层呈现有规律变化,即在古土壤层(S0)中含量最高,表土层(MS)中次之,在黄土层(L1、Lt、L0)中最低;Na2O在古土壤层淋失,在黄土层相对富集。深入分析表明,淮河上游全新世黄土为风力沉积物,来源于黄河下游泛滥平原的风沙活动和沙尘暴沉积。在古土壤层和表土层形成时期,气候温暖湿润,虽然仍然有沙尘暴发生,但是成壤作用和次生粘化作用较强;在黄土层堆积时期,气候干旱寒冷,黄河下游泛滥平原植被稀疏,风沙活动和沙尘暴强烈,风化成壤作用极其微弱。这些化学成分含量与磁化率相关性很强,表明它们主要受全新世气候与成壤环境变化的控制。     

Impact of Holocene environmental change on temporal-spatial distribution of Neolithic sites in Huaihe River Basin, Anhui Province

The Huaihe River basin of Anhui is not only a transitional zone of physical geography, but also a convergent area of many cultures in China. It is one of the sensitive ecotones to global changes and the birthplace of Chinese civilization. Using the field archaeological data and the sporo-pollens and the age data of the drilling cores, we analysed Neolithic cultural development and environmental evolution in the Huaihe River basin of Anhui. According to the combination of some research results in archaeology with environmental evolution research, this paper discusses the relationship between culture and environment in the Huaihe River basin of Anhui. The Neolithic cultural development was strongly impacted by the environmental change. The primitive culture (Shishanzi) was developed in the beginning of the Holocene Megathermal Period with distinct regional feature of the culture. From 6.5 kaBP to 5.5 kaBP, the climate changed warmer and wetter. The frequent occurrence of flood and waterlog due to such a climate regime and high sea level caused the earth’s surface environment deteriorated in the Huaihe River basin of Anhui and the interruption of the Neolithic cultural development, hence a lack of archaeological sites. From 5.5 kaBP to 4.0 kaBP, the climate changed from wet to dry, the natural environment was propitious to human survival. Dawenkou Culture and Longshan Culture flourished in this period. The Neolithic cultural development, the number of the sites and their distribution characteristics of the sites in the study area differed apparently from those in Central China and Shandong Province.