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1.
Climatic changes in the Yangtze Delta have played an important role in the emergence, persistence and collapse of civilization. Archaeological excavations in the region over many years have demonstrated that there are several layers of fine sand or organic mud that interrupt the consecutive culture strata in a number of Neolithic culture sites. Continuous biostratigraphical and sedimentological records from the Maqiao cultural site, Shanghai, suggest that the fine sand and organic mud units resulted from expansion of water bodies both by sea-level fluctuations and from increased flooding during cold and humid episodes of Holocene climates. The absence of human settlement from 7240 BP to 5320 BP in the region was mainly caused by higher sea levels resulting from a warm and humid climate. The Neolithic cultures developed under conditions of lower and more stable sea level as well as warmer and dryer climates between about 4410 BP and 3250 BP. A flood-induced lake expansion interrupted the civilization in the region at about 4200 BP. Later, higher water tables and expansion of lakes between 3250 BP and AD 618 under a cold and moist climate temporarily terminated settlement on the delta. Later, during the Tang Dynasty, beginning at about AD 618, the region again became suitable for human settlement under conditions of more favourable climate and lower water tables.  相似文献   

2.
Stobi, a city inhabited from at least the 4th century B.C. to the late 6th century A.D., is at the confluence of the Vardar and Crna Rivers, now in the former Yugoslav Republic of Macedonia. Archaeological and geologic evidence was used in the 1970s by R. L. Folk to develop a scenario of local environmental degradation, resulting from a postulated widespread climate change (4th–8th centuries A.D.), as a major cause of the decline and eventual abandonment of Stobi. The data for increasingly xeric conditions, catastrophic floods, and mudslides along the Crna River are reviewed and other paleoenvironmental evidence is considered. Subsequent archaeological investigations and a refined chronology reveal repeated episodes of rebuilding along the Crna between periods of flooding. After that portion of the city was abandoned in the mid‐5th century, Stobi achieved new prosperity as reflected in the construction of large‐scale ecclesiastical architecture and houses outside the south city wall. Human agency and periodic extreme weather are proposed as causes of environmental degradation at Stobi. The city's demise is attributed mainly to hostile invasions, plague, earthquake, and the collapse of imperial administrative and economic networks. © 2007 Wiley Periodicals, Inc.  相似文献   

3.
The sandstone escarpment of the Dhar Tichitt in South-Central Mauritania was inhabited by Neolithic agropastoral communities for approximately one and half millennium during the Late Holocene, from ca. 4000 to 2300 BP. The absence of prior evidence of human settlement points to the influx of mobile herders moving away from the “drying” Sahara towards more humid lower latitudes. These herders took advantage of the peculiarities of the local geology and environment and succeeded in domesticating bulrush millet – Pennisetum sp. The emerging agropastoral subsistence complex had conflicting and/or complementary requirements depending on circumstances. In the long run, the social adjustment to the new subsistence complex, shifting site location strategies, nested settlement patterns and the rise of more encompassing polities appear to have been used to cope with climatic hazards in this relatively circumscribed area. An intense arid spell in the middle of the first millennium BC triggered the collapse of the whole Neolithic agropastoral system and the abandonment of the areas. These regions, resettled by sparse oasis-dwellers populations and iron-using communities starting from the first half of the first millennium AD, became part of the famous Ghana “empire”, the earliest state in West African history.  相似文献   

4.
The data presented in this paper show that in historical time the Chuy Basin in Kyrgyzstan was repeatedly subjected to strong earthquakes, which affected the inhabitants and the economic and political situation at that time. The deformed buildings in the Novopokrovka site of ancient settlements situated in the central part of the basin unequivocally indicate seismic damage and subsequent abandonment of the settlement. The earthquake happened at the end of the Karakhanid epoch (the end of the 12th century A.D.). The intensity of seismic oscillations (I = VIII–IX) at the site was reinforced by unfavorable engineering geology conditions. The source of the earthquake was probably related to displacements along the piedmont Ysyk-Ata Fault located to the south of the site.  相似文献   

5.
This article focuses on local paleohydrological changes experienced by the Las Pitas and Miriguaca Rivers in the south‐central Andes of Argentina and their impacts on hunter‐gatherers as they transitioned to food‐producing communities 7000–3000 cal. yr B.P. Paleoenvironmental reconstruction based on geomorphology, alluvial sedimentology, and diatom evidence indicates a dry phase of reduced streamflow between ca. 6700 and 4800 cal. yr B.P. for the Las Pitas River, and 6600 and 3000 cal. yr B.P. for the Miriguaca River. A phase of more humid environmental conditions commenced after ca. 4900 cal. yr B.P. along the Las Pitas River, and after 3000 cal. yr B.P. along the Miriguaca River. Differences in the chronology and magnitude of hydrological changes along both rivers are related to topographic and hydrological characteristics of their respective watersheds. Higher catchment elevation and enhanced orographic precipitation favored greater sensitivity for the Las Pitas River to short humid events during the middle‐to‐late Holocene. The archaeological evidence suggests that the paleohydrological changes within these catchments played a significant role in human occupational dynamics such that the Las Pitas River offered better environmental conditions for human occupation relative to the Miriguaca River as foragers increasingly relied on plant and animal domestication.  相似文献   

6.
北京天竺晚上新世以来植被演替与气候变迁   总被引：4，自引：2，他引：4  
研究了北京天竺TZ01钻孔岩心孢粉样品239块，孢粉组合反映了北京天竺晚上新世以来(约3.580 Ma BP)植被演替和气候变迁大致经历了10个发展阶段：(1) 3.580～3.050 Ma BP：以针叶林植被为主，气候寒冷偏湿；(2) 3.050～2.555 Ma BP：植被为落叶阔叶和常绿阔叶混交林-草原类型，该阶段开始升温，但气候较为温暖湿润；(3)2.555～2.300 Ma BP：植被为温凉偏干的疏林草原，湿度开始下降；(4) 2.300～1770 Ma BP：植被类型仍为疏林草原，该阶段温度上升，但幅度并不大，湿度基本不变，气候温凉干爽；(5) 1.770～1.070 Ma BP：植被类型为针阔混交林-草原，气候温暖湿润；(6) 1.070～0.922 Ma BP：植被演替为较暖湿略干的针阔混交林-草原；(7)0.922～0.800 Ma BP：植被为较寒冷干燥的疏林草原，温度降低，降水减少；(8) 0.800～0.650 Ma BP：植被为温暖偏干的以松为主的疏林草原，温度有所上升，但湿度变化较小；(9)0.650～0.160 Ma BP：植被为温凉湿润的针阔叶混交林-草原；(10) 0.160 Ma BP至今：植被以针阔叶混交林-草原为主，前期气候冷湿，后期较为温暖湿润。  相似文献   

7.
柴达木盆地北缘中侏罗世晚期沉积的大煤沟组七段页岩（J2d7）记录了该地质历史时期的物源、风化作用及对应的气候和构造特征信息。对钻井岩芯样品进行元素地球化学分析,结果显示,较高的Al2O3/TiO2,La/Sc,Th/Co,较低的TiO2/Zr,以及TiO2-Zr、La/Sc-Th/Co、La/Th-Hf、La-Th-Sc组成表明大煤沟组七段页岩物源主要为长英质花岗闪长岩。A-CN-K组成特征指示钾交代作用对页岩的影响有限,整体较高化学蚀变指数（CIA）、化学风化指数（CIW）、斜长石蚀变指数（PIA）表明物源区经历了中等-强烈的化学风化作用,且自下而上,风化作用逐渐减弱,结合逐步降低的古气候指数C值及增高的Sr/Cu值,可得出在中侏罗世晚期柴北缘地区的古气候条件由温暖潮湿向干旱炎热明显转变,为该时期我国西北地区"干热化"事件在柴北缘的具体表现,同期构造沉降幅度大于因气候变干导致的湖平面下降速率,为有机质的富集提供了有利条件。  相似文献   

8.
Social responses to climate change over human history have been widely discussed in academia over the last two decades. However, the transformation of the human–environment nexus crossing prehistoric and historic periods and the processes associated with it are not yet clearly understood. In this study, based on published works on radiocarbon dating, archaeobotany, zooarchaeology, and archaeological sites, together with a synthesis of historical documents and highresolution paleoclimatic records, we trace the extent to which human settlement patterns in the Hexi Corridor in northwestern China evolved in conjunction with climate change over the last 5,000 years. A total of 129 Neolithic, 126 Bronze Age, and 1,378 historical sites in the Hexi Corridor(n=1,633) were surveyed. Our results show that, in the Late Neolithic and Bronze Age periods(～2800–100 BC), climate change contributed to the transformation of subsistence strategies and the subsequent changes in human settlement patterns in the Hexi Corridor. The warm-humid climate in ～2800–2000 BC promoted millet agriculture and helped the Majiayao, Banshan, and Machang Cultures to flourish. The cold-dry climate in ～2000–100 BC resulted in the divergence and transformation of subsistence strategies in the Xichengyi–Qijia–Siba and Shajing–Shanma Cultures and in a shift in their settlement patterns. However, in the historical period(121 BC–AD 1911), human settlement patterns were primarily determined by geopolitics related to the alternating rule of regimes and frequent wars, especially in the Sui–Tang dynasties. We also find that trans-Eurasian cultural exchange since ～2000 BC improved social resilience to climate change in the Hexi Corridor, mediating the human–environment nexus there. Our findings may provide insights into how human societies reacted to climate change in arid and semi-arid environments over the long term.  相似文献   

9.
The stratigraphy of Scandinavian open‐air archaeological settlements is usually characterized as homogeneous, highly enriched in decomposing organic matter and poor in biogenic carbonates such as shells or bones. As a result, stratigraphies are often difficult to read in the field and settlement sequences may pass unnoticed by archaeologists. Here we show how the integration of bulk analyses, soil micromorphology, X‐ray fluorescence (XRF) core scanning and multivariate statistics can help in overcoming such limitations. We use the case study of Håkonshella 8, a Mesolithic hunter‐fisher‐gatherer settlement located in Bergen (W Norway). Fluctuations in the organic matter content, geochemical proxies (mainly P, Ga, Ti and the Si/Al ratio) and redoximorphic features highlight four cycles of site occupation and abandonment in an otherwise massive anthropogenic deposit. Following these settlement sequences, the site was covered by colluvium from nearby slopes over which a waterlogged soil formed. The approach used in Håkonshella has the potential to improve our capacity to interpret organically enriched anthropic deposits formed in coastal Scandinavia and in similar climatic regions.  相似文献   

10.
An 8400 cal yr record of vegetation change from the northern Peten, Guatemala, provides new insights into the environmental history of the archaeological area known as the Mirador Basin. Pollen, loss on ignition, and magnetic susceptibility analyses indicate warm and humid conditions in the early to mid-Holocene. Evidence for a decrease in forest cover around 4600 cal yr B.P. coincides with the first appearance of Zea mays pollen, suggesting that human activity was responsible. The period between 3450 cal yr B.P. and 1000 cal yr B.P. is characterized by a further decline in forest pollen types, includes an abrupt increase in weedy taxa, and exhibits the highest magnetic susceptibility values since the early Holocene, all of which suggest further agricultural disturbance in the watershed. A brief drop in disturbance indicators around 1800 cal yr B.P. may represent the Preclassic abandonment of the area. Changing pollen frequencies around 1000 cal yr B.P. indicate a cessation of human disturbance, which represents the Late Classic collapse of the southern Maya lowlands.  相似文献   

11.
The northern Tien Shan is the northern front of the Himalayan mountain belt, which resulted from the collision between the Indian and Eurasian Plates. This region encompasses the most active seismic zones of the orogen, which generated the strongest (M > 8) earthquakes. Since there are scarcely any written accounts, the only way to trace back strong earthquakes is the paleoseismologic method. Since 1984 we have been studying the northwestern Issyk Kul’ basin, where there are differently directed anticlines, which constitute the Kungei meganticline. Here, several active tectonic structures (faults, folds) are located, whose development was accompanied by strong earthquakes. Our field studies of 2008 in the Iiri-Taldybulak Valley, along the adyrs (foothills) of the Kungei-Ala-Too Range, revealed two unknown historical earthquakes. The first one, which occurred along the southern rupture in the late 7th century A.D., gave rise to a seismic scarp; the latter broke through the river floodplain and a tash-koro (ancient settlement). The second one, which occurred along the northern rupture in the late 9th century A.D., increased the height of the seismic scarp, existing on the Early Holocene and older terraces. Note that this region already records a strong seismic event around 500 A.D. Archeologic data have revealed one more strong earthquake, which took place in the 14th century A.D. Note that the above-mentioned strong seismic events are coeval with the decline of the nomadic cultures (Wusun, Turkic, Mogul) in the northern Tien Shan and Zhetysu (Semirech’e).  相似文献   

12.
We investigated the long-term reclamation settlement of Chek Lap Kok Airport, Hong Kong, one of the largest reclamation projects worldwide. An advanced InSAR technique was applied to two independent ASAR data sets along ascending (25 scenes) and descending (22 scenes) orbits acquired between 2003 and 2008, and allowed us to generate deformation velocity maps and displacement time series for the investigated area. Intercomparison of deformation velocity results from the two ASAR data sets and their validation against leveling survey measurements were carried out in order to assess accuracy and reliability of the InSAR observations. The intercomparison and validation results demonstrated the potential of elaborate InSAR processes on local-scale areas to monitor and detect a long-term residual settlement in such complex reclamation area. The InSAR-derived deformation velocity maps showed a fair stability in areas of the two original rocky islands of Chek Lap Kok and Lam Chau, and on most of the buildings at the site due to foundation on piles reaching the granite bedrock, whereas a generally moderate (3–7 mm/year) to strong (> 10 mm/year) and spatially variable settlement trend was detected in the majority of reclamation areas of the airport. The consistent relationship we found between the observed settlement pattern and the underlying geological conditions suggested that this recoded differential settlement was mainly related to the variations in thickness and soil properties of both the fill materials and the alluvial deposits below the reclamation. A geological and geotechnical interpretation of the lithostratigraphy of the alluvial deposits beneath the reclamation implied that the relatively large settlement rate measured up to 2008 was resulted from a still active primary consolidation process.  相似文献   

13.
The Deccan Trap region exhibits an erosional landscape over a relatively ancient and stable Deccan shield. The Quaternary history of the area has been reconstructed on the basis of evidence from alluvial deposits occurring along the major rivers. However, recent investigations have revealed that evidence for geo-environmental change during the Quaternary Period is also contained in the colluvial deposits that occur in the foothill zones. The colluvial deposits, ranging in thickness from 1 to 10 m, invariably occupy gently inclined pediment slopes. The sediments are presently deeply dissected by gullies, and the process of colluviation has almost ceased. These deposits are best preserved in the semi-arid parts of the region. Detailed textural, geochemical and stratigraphical studies at four different sites reveal similar input processes, the slight variations being attributed to local environmental factors. Scanning electron microscopy studies of some grains indicate marginal contribution of aeolian processes at the time of deposition. Mesolithic artefacts and a few U/Th dates indicate that the colluviation took place during the Late Quaternary. The properties of the deposits suggest relatively high energy conditions as well as a remarkable variability in the intensity of hillslope processes. These properties are indicative of semi-arid conditions during which the regolith was stripped from devegetated hillslopes and was deposited on the pediments. A variety of evidence indicates that the period of colluviation coincided with arid conditions during the Last Glacial Maximum. The geomorphological and archaeological evidence also indicates that incision by gully systems was initiated during the early Holocene humid phase. The environmental conditions deduced for the study area are similar to those reported for other parts of the intertropical zone. © 1997 John Wiley & Sons, Ltd.  相似文献   

14.
Lathrap introduced the concept of lateral channel migration of the meandering rivers as a potential factor for human community dynamics in the Upper Amazon. Nevertheless, the dynamics considered by Lathrap is restricted to particular floodplains. He payed no attention to a large scale fluvial phenomenom: the sudden river relocations (avulsion), which also profoundly affected the Upper Amazon cultures. We present here a historical case study analyzing a river floodplain avulsion at the Middle Ucayali River during the late 1700s, causing the abandonment of a settlement called San Miguel de Cunibos and probably leading to the massive migration of the Cunibos Indians. Furthermore, we argue that similar situations have frequently occurred during the human history of the Upper Amazon, and thus these fluvial phenomena should be taken into consideration in future archaeological and ethnohistorical studies. © 1996 John Wiley & Sons, Inc.  相似文献   

15.
 The historic processing of precious metal ores mined from the Comstock Lode of west-central Nevada resulted in the release of substantial, but unquantified amounts of mercury-contaminated mill tailings to the Carson River basin. Geomorphic and stratigraphic studies indicate that the introduction of these waste materials led to a period of valley-floor aggradation that was accompanied by lateral channel instability. The combined result of these geomorphic responses was the storage of large volumes of mercury-enriched sediment within a complexly structured alluvial sequence located along the Carson River valley. Much of the contaminated sediment is associated with filled paleochannels produced by the cutoff and abandonment of meander loops, and their subsequent infilling with contaminated particles. Geochemically, these deposits are characterized by variations in mercury levels that exceed three orders of magnitude. Continued lateral instability, coupled with an episode of channel-bed incision, followed the decline of Comstock mining, and has reexposed contaminated debris within the banks of the river. Erosion of bank sediments reintroduces mercury-enriched particles to the modern channel bed. It is suggested on the basis of geochemical and sedimentological data that during the bank erosion process, much of the mercury associated with fine (<63 μ) valley-fill deposits are carried downstream without being incorporated to any appreciable extent within the channel-bed sediments. In contrast, mercury associated with larger and denser particles, particularly mercury-gold-silver amalgam grains, are accumulated in the channel-bed sediments as the river traverses polluted reaches of the Carson River valley. Concentration patterns developed along the modern channel indicate that the valley fill is the primary source of mercury to the river today. Thus, these data imply that efforts to reduce the influx of mercury to the aquatic environment should examine methods for reducing bank erosion rates. Received: 13 December 1996 · Accepted: 15 April 1997  相似文献   

16.
ABSTRACT To better understand the linkage between climate and ocean circulation under greenhouse conditions we have studied calcareous nannofossils, palynomorphs and benthic foraminifera from the Early Albian Oceanic Anoxic Event 1b black shale (OAE 1b) in the Vocontian Basin (SE France). We propose that monsoonal activity resulting from precessional forcing and modulated by eccentricity-driven temperature changes represents the driving factor of OAE 1b formation in low latitudes. With the onset of OAE 1b, increasingly warm and humid conditions, stronger winds and enhanced terrestrial input led to higher surface water productivity. Therefore, increased productivity is an important factor for OAE 1b formation in the Vocontian Basin. However, monsoonally forced productivity changes are a regional climate signal only. The supraregional occurrence of the OAE 1b is probably due to a reduction of deep water formation in the low latitudes under extremely warm and humid conditions, leading to enhanced preservation of organic matter.  相似文献   

17.
Michael Feige 《GeoJournal》2001,53(3):323-333
Kiryat-Arba and Jewish Hebron are communities planted in the most heated front of the Israeli-Palestinian conflict. This paper examines how the Hebron Jewish settlers' collective memory interprets the `truth' of Hebron as a typical Israeli Place that reveals Zionism in its purest form. Today the populations of Kiryat-Arba and of the Hebron Jewish enclaves number about 5,000 and 500, respectively. Kiryat-Arba functions as an economic and educational centre for the nearby Jewish settlements in the region. Rejecting the segregative concept of a separate Jewish settlement overlooking Hebron, the settlers treat Kiryat-Arba as part of Hebron. Some 70,000 Palestinians live in Hebron, many more residing in neighbouring towns and villages, cutting Hebron – Kiryat–Arba off from the nearest Jewish urban centres of Jerusalem and Beer-Sheva. The settlers initiated the narrative of `Return' to the city after the massacre of Jews in 1929 in the city, as the key symbol Symbolically, the first place Hebron Jews reidentified with was its ancient Jewish graveyard. Today, IDF soldiers protect settlers and their visitors who want to tour Hebron. The huge gulf between `metaphorical Hebron' as a symbolic centre and `actual Hebron' as a poor development town creates tensions fuelling violent events. The Jews in Hebron take the Israeli logic of `Place' making to its extreme, thus testing concepts of Israeli territoriality. If Israeli society rejects Hebron as a `Place' constructed from intense memories and violent national encounters, it would leave the Hebron Jews out of the so-called Israeli normalcy.  相似文献   

18.
《Quaternary Science Reviews》2007,26(19-21):2598-2616
Linear dunes occupy more than one-third of the Australian continent, but the timing of their formation is poorly understood. In this study, we collected 82 samples from 26 sites across the Strzelecki and Tirari Deserts in the driest part of central Australia to provide an optically stimulated luminescence chronology for these dunefields. The dunes preserve up to four stratigraphic horizons, bounded by palaeosols, which represent evidence for multiple periods of reactivation punctuated by episodes of increased environmental stability. Dune activity took place in episodes around 73–66, 35–32, 22–18 and 14–10 ka. Intermittent partial mobilisation persisted at other times throughout the last 75 ka and dune activity appears to have intensified during the late Holocene. Dune construction occurred when sediment was available for aeolian transport; in the Strzelecki and Tirari Deserts, this coincided with cold, arid conditions during Marine Isotope Stage (MIS) 4, late MIS 3 and MIS 2, and the warm, dry climates of the late Pleistocene–Holocene transition period and late Holocene. Localised influxes of sediment on active floodplains and lake floors during the relatively more humid periods of MIS 5 also resulted in dune formation. The timing of widespread dune reactivation coincided with glaciation in southeastern Australia, along with cooler temperatures in the adjacent oceans and Antarctica.  相似文献   

19.
Accurate chronological records are critical for studying the alluvial fan sequences emplaced during local/global climatic changes but, in general, there are no satisfactory, quantitative dating methods available. In situ -produced 10Be concentrations have been measured in quartz boulders exposed on Sulawesian late Quaternary fan surfaces. These concentrations suggest that the two fan units evidenced by geomorphic study were emplaced during two distinct major climatic events. The calculated minimum exposure ages imply abandonment ages of 11 kyr and 120 kyr, for the younger and older units, respectively. This study demonstrates that using both the neutron and muon components implicated in the in situ 10Be production, surficial erosion rates can be estimated and alluvial fans dated. In particular, it shows that in situ 10Be may be used to date fan emplacement during the last 120 kyr under humid tropical conditions, significantly helping to constrain continental palaeoclimatology.  相似文献   

20.
中国北方风沙沉积物气候代用指标对比研究   总被引：2，自引：0，他引：2  
在浑善达克沙地和巴丹吉林沙漠各选择近NS走向的大断面采集表层样品,用筛析法对样品进行粒度分析,用Eijkelkamp碳酸钙测定仪测定其碳酸钙含量。两地沙质沉积物的粒度参数对比结果显示,巴丹吉林沙漠沙总体上比浑善达克沙地沙粗,分选性比浑善达克沙地沙好,同时在粒度分布频率曲线上表现出明显的双峰,这应与其地处冬夏季风交替地带、冬季风和夏季风搬运营力上的差别有关。巴丹吉林沙漠和浑善达克沙地沙质沉积物粒度参数上的差别反映了两地不同的风动力条件和下垫面性质。浑善达克沙地的沙粒较细在一定程度上也与该地区较湿润条件下的成土作用有关。气候差异应是导致两地沙质沉积物粒度参数区别的主导因素。碳酸钙测量结果说明,浑善达克沙地的碳酸钙含量明显低于巴丹吉林沙漠。巴丹吉林沙漠沙的碳酸钙含量从北往南呈增加趋势,与该地区年降水量的南北方向变化相一致。从对这两个地区沙质沉积物的碳酸钙含量对比中可以看出,即使在干旱背景下,当多年平均降雨量达到一定临界值时,地表碳酸钙含量将达到一最大值,随后则呈降低趋势  相似文献   

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