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High‐resolution pollen and geochemical analyses conducted on a sediment profile from a small lake in County Sligo, Ireland, revealed that human development during the Neolithic was influenced by pronounced climatic oscillations. The primeval woodland around the lake experienced a considerable transformation coinciding with the elm decline at 3810 BC. The subsequent increase in summer temperatures and decrease in precipitation favoured wheat cultivation in the lake's catchment area, which was practised for approximately 140 years. A shift towards pastoral farming took place with the establishment of exceptionally dry conditions between 3650 and 3560 BC, when lake level and influx of allochthonous material were notably low. The onset of cool and wet conditions at the transition from the Early to Middle Neolithic possibly caused the initial decline of human activity in the area. Periods of particularly high precipitation during the Middle and early Late Neolithic contributed to the abandonment of the area by the first farmers. Comparison of the proxy record from the study site with other palynological and archaeological records from Ireland suggests that climatic variability on the decadal to centennial scale represented a primary control on the nature and duration of farming practices during the Neolithic. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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The Condat tufa is a localised deposit, reaching 8.2m in thickness, composed of freshwater carbonates deposited in a complex series of environments which include marsh, spring and stream facies. Five radiocarbon determinations had previously been obtained from different stratigraphic levels within the tufa and had given a consistent series, ranging from 12320 ± 175 BP to 31050 ± 1500BP. Although the youngest two dates, from near the surface of the tufa, had been rejected as being anomalously young, the older dates were regarded as indicating tufa formation during the last cold stage. Biostratigraphic analyses of the molluscan and ostracod faunas, presented here, demonstrate that the tufa formed under fully temperate conditions throughout. The occurrence of certain snails that are either locally extinct (e.g. Belgrandia marginata) or unknown living in western France (e.g. Daudebardia brevipes), together with the geomorphological setting, suggest that the tufa is of interglacial age. New radiocarbon determinations of the Condat tufa all proved to be >33 Ka BP and support this conclusion. 相似文献
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ALBERTO V. REYES GRANT D. ZAZULA SVETLANA KUZMINA THOMAS A. AGER DUANE G. FROESE 《第四纪科学杂志》2011,26(3):345-352
Last interglacial sediments in unglaciated Alaska and Yukon (eastern Beringia) are commonly identified by palaeoecological indicators and stratigraphic position ～2–5 m above the regionally prominent Old Crow tephra (124 ± 10 ka). We demonstrate that this approach can yield erroneous age assignments using data from a new exposure at the Palisades, a site in interior Alaska with numerous exposures of last interglacial sediments. Tephrochronology, stratigraphy, plant macrofossils, pollen and fossil insects from a prominent wood‐rich organic silt unit are all consistent with a last interglacial age assignment. However, six 14C dates on plant and insect macrofossils from the organic silt range from non‐finite to 4.0 14C ka BP, indicating that the organic silt instead represents a Holocene deposit with a mixed‐age assemblage of organic material. In contrast, wood samples from presumed last interglacial organic‐rich sediments elsewhere at the Palisades, in a similar stratigraphic position with respect to Old Crow tephra, yield non‐finite 14C ages. Given that local permafrost thaw since the last interglaciation may facilitate reworking of older sediments into new stratigraphic positions, minimum constraining ages based on 14C dating or other methods should supplement age assignments for last interglacial sediments in eastern Beringia that are based on palaeoecology and stratigraphic association with Old Crow tephra. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Pollen‐ and related proxy‐based studies of human–environment interactions during the Norse and later periods within Greenland have primarily involved the investigation of peat, lake and soil deposits, all of which have taphonomic and sampling problems. Many small ponds exist, but they seem to have been relatively ignored in investigations of palaeoecologically based environmental history. To evaluate their usefulness for studies of ecologically related cultural history, especially where sites are in intimate association with the archaeology, a pond in the Norse Eastern Settlement has been examined to investigate three principal questions: (i) Does such a site contain a useful record of environmental history? (ii) Does it offer a record of sufficient resolution and sensitivity for the study of anthropogenic landscape impacts? (iii) Are there any apparent drawbacks to these sequences? Using data obtained from palynological, diatom, sedimentological and radiocarbon analyses, it is concluded that environmental data for each proxy – aside from 14C dating – are clearly capable of being explained in a reasonably straightforward and compatible manner and fulfil the hopes for the sampling medium. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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The behaviour of ice sheets as they retreated from their Last Glacial Maximum (LGM) positions provides insights into Lateglacial and early Holocene ice‐sheet dynamics and climate change. The pattern of deglaciation of the Laurentide Ice Sheet (LIS) in arctic fiord landscapes can now be well dated using cosmogenic exposure dating. We use cosmogenic exposure and radiocarbon ages to constrain the deglaciation history of Clyde Inlet, a 120 km long fiord on northeastern Baffin Island. The LIS reached the continental shelf during the LGM, retreated from the coastal lowlands by 12.5 ± 0.7 ka (n = 3), and from the fiord mouth by 11.7 ± 2.2 ka (n = 4). Rapid retreat from the outer fiord occurred 10.3 ± 1.3 ka (n = 6), with the terminus reaching the inner fiord shortly after 9.4 ka (n = 2), where several moraine systems were deposited between ca. 9.4 and ca. 8.4 ka. These moraines represent fluctuations of the LIS during the warmest summers since the last interglaciation, and this suggests that the ice sheet was responding to increased snowfall. Before retreating from the head of Clyde Inlet, the LIS margin fluctuated at least twice between ca. 7.9 and ca. 8.5 ka, possibly in response to the 8.2 ka cold event. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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Radiocarbon dating of the organic-rich sediments of Lake Illisarvik in the outer Mackenzie Delta indicates that formation of the lake occurred approximately 9500yr BP, with maximum expansion around 6000 yr BP. Sedimentation rates have remained relatively constant at an average of 0.3mm/yr. 13C results on biogenic and inorganic carbonates and organics indicate a change from dominantly terrestrial organics (?27 to ?28%0) to submerged aquatic vegetation or plankton (?18 to ?23%0) upon formation of the lake (9500yr BP), and a dramatic return to dominantly terrestrial organics at 5800yr BP (δ13C = ?27 to ?30%0). This latter shift is accompanied by a drastic reduction in the macroflora and fauna populations. 18O results suggest that a warmer climate than today existed prior to the shift at 5800yr BP. 相似文献
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Artur Sobczyk Ryszard K. Borówka Janusz Badura Renata Stachowicz-Rybka Julita Tomkowiak Anna Hrynowiecka Joanna Sławińska Michał Tomczak Mateusz Pitura Mariusz Lamentowicz Piotr Kołaczek Monika Karpińska-Kołaczek Dariusz Tarnawski Marcin Kadej Piotr Moska Marek Krąpiec Krzysztof Stachowicz Bartosz Bieniek Krzysztof Siedlik Małgorzata Bąk Jan van der Made Adam Kotowski Krzysztof Stefaniak 《第四纪科学杂志》2020,35(4):539-558
The sedimentary succession exposed in the Gorzów Wielkopolski area includes Eemian Interglacial (MIS 5e) or Early Weichselian (MIS 5d–e) deposits. The sedimentary sequence has been the object of intense interdisciplinary study, which has resulted in the identification of at least two palaeolake horizons. Both yielded fossil remains of large mammals, alongside pollen and plant macrofossils. All these proxies have been used to reconstruct the environmental conditions prevailing at the time of deposition, as well as to define the geological context and the biochronological position of the fauna. Optically stimulated luminescence dating of the glaciofluvial layers of the GS3 succession to 123.6 ± 10.1 (below the lower palaeolake) and 72.0 ± 5.2 ka (above the upper palaeolake) indicate that the site formed during the Middle–Late Pleistocene (MIS 6 – MIS 5). Radiocarbon-dating of the lacustrine organic matter revealed a tight cluster of Middle Pleniglacial Period (MIS 3) ages in the range of ~41–32 ka cal bp (Hengelo – Denekamp Interstadials). Holocene organic layers have also been found, with 14C ages within a range of 4330–4280 cal bp (Neolithic). Pollen and plant macrofossil records, together with sedimentological and geochemical data, confirm the dating to the Eemian Interglacial. 相似文献
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环渤海泥质海岸带近30年来获得的600余个放射性碳测年数据,确定了该地区晚更新世晚期以来的基本年代地层序列。但是,对14C数据的系统校正,迄未得到应有的重视,致使在应用14C数据解释地层和地质现象的年代时,存在着一定程度的混乱。文章对作者自己所采集和由国内外有关实验室测定的126个14C数据进行了系统校正,主要步骤包括分馏效应、地区性海洋贮存库效应及大气14C含量变化校正等。建议以-2.68‰PDB作为环渤海晚更新世晚期以来半咸水和开放浅海区(潮间带与潮下带上部)贝壳的地区性δ13C平均值。另外,讨论了在地区性海洋贮存库效应值获得之前的1990年代,以MARINE93与INTCAL93程序的平均校正年龄近似地视作该地区贝壳的校正值,以抵消这一类地区小型水体与大气迅速进行14CO2交换而对年龄值的影响。CALIB4.4校正结果表明,前述近似校正是可行的,其结果仍可沿用。文章经统一校正的年龄,最大限度地接近其太阳历纪年的"真实"年龄,从而有助于更加准确地重建该地区的晚更新世晚期以来的地质年代史,并可与考古纪年及其他测年方法获得的绝对年龄直接对比。 相似文献
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Chris D. Clark Richard C. Chiverrell Derek Fabel Richard C. A. Hindmarsh Colm Ó Cofaigh James D. Scourse 《第四纪科学杂志》2021,36(5):673-680
Motivated to help improve the robustness of predictions of sea level rise, the BRITICE-CHRONO project advanced knowledge of the former British–Irish Ice Sheet, from 31 to 15 ka, so that it can be used as a data-rich environment to improve ice sheet modelling. The project comprised over 40 palaeoglaciologists, covering expertise in terrestrial and marine geology and geomorphology, geochronometric dating and the modelling of ice sheets and oceans. A systematic and directed campaign, organised across eight transects from the continental shelf edge to a short distance (10s of kilometres) onshore, was used to collect 914 samples which yielded 639 new ages, tripling the number of dated sites constraining the timing and rates of change of the collapsing ice sheet. This special issue synthesises these findings of ice advancing to the maximum extent and its subsequent retreat for each of the eight transects to produce definitive palaeogeographic reconstructions of ice margin positions across the marine to terrestrial transition. These results are used to understand the controls that drove or modulated ice sheet retreat. A further paper reports on how ice sheet modelling experiments and empirical data can be used in combination, and another probes the glaciological meaning of ice-rafted debris. 相似文献
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作为晚更新世与全新世地层年代测定的一种重要手段,14C测年被广泛应用于地质样品的年代测定。但对于14C数据的系统校正,迄今未得到应有的重视。文章在环渤海海岸带14C数据集(Ⅰ)的基础上,对所收集的421个由其他研究者获得的环渤海海岸带14C数据进行了系统校正。并讨论了百年、千年与万年尺度的14C数据校正效果。结果表明,直接测定值与系统校正值之间的差值常有数百年至两千年的差别。经统一校正的14C年龄,最大限度地接近样品太阳历纪年的“真实”年龄,从而有助于更加准确地重建该地区的晚更新世晚期以来的地质年代史,并可与考古纪年及其他测年方法获得的绝对年龄直接对比。 相似文献
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渤海湾牡蛎礁平原中部兴坨剖面全新世地质环境变迁 总被引：9，自引：8，他引：9
渤海湾牡蛎礁平原中部兴坨剖面的有孔虫组合划分为5种沉积环境7个带(亚环境)，从下向上依次为晚更新世陆相(Ⅶ带)、早全新世海陆过渡相(Ⅵ带：沿海低地与潮间带)、中晚全新世海相(Ⅴ带：潮下带-浅海，Ⅳ带：低潮线附近)、晚全新世海陆过渡相(Ⅲ带：开放潮间带，Ⅱ带：渴湖)和河流泛滥相(Ⅰ带：古土壤及洪积层)。^14C确定了全新世底泥炭始于9486 cal BP，Ⅳ带始于约4696 cal BP。Ⅱ带所处的渴湖环境，从约4000 cal BP直至隋唐温暖期之前，历时约2700年。隋唐暖期古土壤发育向南东减弱至逐渐消失，说明在比兴坨更靠近渤海湾的地方，潟湖持续的时间更长。广泛存在的潟湖，是牡蛎礁平原晚全新世的重要地貌景观。 相似文献
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Jayde N. Hirniak Eugene I. Smith Racheal Johnsen Minghua Ren Jamie Hodgkins Caley Orr Fabio Negrino Julien Riel-Salvatore Shelby Fitch Christopher E. Miller Andrea Zerboni Guido S. Mariani Jacob A. Harris Claudine Gravel-Miguel David Strait Marco Peresani Stefano Benazzi Curtis W. Marean 《第四纪科学杂志》2020,35(1-2):199-212
Chemical characterization of cryptotephra is critical for temporally linking archaeological sites. Here, we describe cryptotephra investigations of two Middle–Upper Paleolithic sites from north-west Italy, Arma Veirana and Riparo Bombrini. Cryptotephra are present as small (<100 µm) rhyolitic glass shards at both sites, with geochemical signatures rare for volcanoes in the Mediterranean region. Two chemically distinct shard populations are present at Arma Veirana (P1 and P2). P1 is a high silica rhyolite (>75 wt.%) with low FeO (<1 wt.%) and a K2O/Na2O > 1 and P2 is also a high silica rhyolite (>75 wt.%) but with higher FeO (2.33–2.65 wt.%). Shards at Riparo Bombrini (P3) are of the same composition as P1 shards at Arma Veirana, providing a distinct link between deposits at both sites. Geochemical characteristics suggest three possible sources for P1 and P3: eruptions from Lipari Island (56–37.7 ka) in Italy, the Acigöl volcanic field (200–20 ka) in Turkey and the Miocene Kirka-Phrigian caldera (18 Ma) in Turkey. Eruptions from Lipari Island are the most likely source for P1,3 cryptotephra. This study highlights how cryptotephra can benefit archaeology, by providing a direct link between Arma Veirana and Riparo Bombrini as well as other deposits throughout the Mediterranean. 相似文献
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Masaki Yamada Shigehiro Fujino Takashi Chiba Kazuhisa Goto James Goff 《Sedimentology》2020,67(3):1354-1372
The Hyuga-nada Sea, south-eastern Kyushu, Japan, is located between a strong (Nankai Trough) and a weak interplate coupling zone (Ryukyu Trench). Over the past 400 years this area has only experienced Magnitude 7·5 earthquakes or smaller and associated small-scale tsunamis. However, this short historical record most likely does not include the full range of high magnitude, low frequency giant earthquakes that might have occurred in the region. Thus, it is still unclear whether giant earthquakes and their associated tsunamis have occurred in this region. This paper reports on a prehistoric tsunami deposit discovered in a coastal lowland in south-eastern Kyushu facing the Hyuga-nada Sea. There is a reddish-brown pumiceous layer preserved in a non-marine, organic-rich mud sequence obtained from onshore sediment cores. This layer is recognized as the ca 4600 year old Kirishima-Miike tephra (that is now placed around 4500 years ago) sourced from Mount Kirishima, southern Kyushu. Another whitish pumiceous layer is evident below the Kirishima-Miike tephra in almost all of the sediment cores. A relatively high percentage of marine and brackish diatoms is recorded within this lower pumiceous layer (but not in the surrounding muds or in the overlying Kirishima-Miike tephra), indicating a marine or beach sediment source. Plant material obtained from organic-rich mud immediately below the event layer was dated to ca 4430 to 4710 cal yr bp , providing a limiting-maximum age for this marine incursion event. The presence of marine diatoms below the event layer is probably explained by pre-seismic subsidence. An absence of the resting spore of the planktonic brackish diatom Cheatoceros and the appearance of the freshwater diatom Eunotia serra immediately above the event layer probably represents a marked change to a relatively low-salinity environment. Assuming that there were no significant local geomorphological changes, such as drainage obstruction caused by formation of a new barrier spit, it is considered that co-seismic or immediate post-seismic uplift are the most likely explanations for this notable environmental change. Based on the crustal movements noted before and after the marine incursion, this event is interpreted here as an earthquake-generated tsunami. Moreover, because of these notable seismic crustal movements the tsunamigenic earthquake probably occurred immediately offshore of the study site. 相似文献