Radiocarbon dating of charcoal from tropical sequences: results from the Niah Great Cave,Sarawak, and their broader implications     

Thomas F. G. Higham  Huw Barton  Chris S. M. Turney  Graeme Barker  Christopher Bronk Ramsey  Fiona Brock 《第四纪科学杂志》2009,24(2):189-197

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Origin of the sedimentary deposits of the Naracoorte Caves, South Australia   总被引：1，自引：0，他引：1  

M.S. Forbes  E.A. Bestland   《Geomorphology》2007,86(3-4):369-392

The origin of the sediments located in the Naracoorte Caves (South Australia) was investigated via the analysis of strontium isotope ratios (⁸⁷Sr/⁸⁶Sr), elemental geochemistry, and mineralogy. Sedimentary deposits located in Robertson, Wet, Blanche and several other chambers in Victoria Cave are all variable mixes of fine sand and coarse silts, which display similar and consistent strontium isotope ratios (0.717–0.725). This suggests that over the 400 ka time frame that these deposits span there has been minimal variation in the source of the clastic sediments. Increased strontium concentrations for these cave sediments correspond with increasing silt content, yet there is no correlation between ⁸⁷Sr/⁸⁶Sr ratios and silt content. This implies that the silt-sized component of the sediments is the main contributor of strontium to the cave sediments. Comparisons of ⁸⁷Sr/⁸⁶Sr with regional surficial deposits show a significant correlation between the cave sediments (avg: 0.7228; n = 27), the fine silt lunettes of the Bool Lagoon area (avg: 0.7224; n = 4), the sandy A horizons of the Coonawarra Red Brown Earths (RBEs; avg: 0.726; n = 5), and Holocene age podsolic sand deposits (0.723). These data suggest that there has been substantial flux from this group of deposits to the caves, as would be expected considering prevailing winds. This relationship is further supported by a strong correlation between many trace elements, including Ti, Zr, Ce, and Y; however, variations in clay mineralogy suggest that the fine silt-dominated lunettes and Padthaway RBEs were not significant contributors to the cave deposits. Hence, the detritus entering the caves was more than likely from areas proximal to the cave entrance and was dominated by medium grain-sized materials. Major regional deposits, including the coarser-grained, calcite-rich Bridgewater Formation sands, basalts from the lower SE, Padthaway Horst granites, Gambier limestone, and metamorphics from the Adelaide geosyncline show minimal correlation in ⁸⁷Sr/⁸⁶Sr ratios, elemental geochemistry, and mineralogy with the cave sediments, and are discounted as significant sources. In comparison, ⁸⁷Sr/⁸⁶Sr ratios for the Coorong silty sands (0.717–0.724), Lower Murray sands (0.727–0.730), and the medium size silt component of the Murray–Darling River system (0.71–0.72), compare favourably with the cave sediments. This relationship is further supported by similarities in elemental chemistry and mineralogy. Thus, much of the strontium-rich silt that is now located in the Naracoorte Cave sediments likely originated from the Murray–Darling basin. Over time, this material has been transported to the SE of South Australia, where it mixed with the medium sand component of the regressive dune ridge sequence, locally derived organic matter, limestone fragments, and fossil material to produce the unique deposits that we see evident in many of the chambers of the Naracoorte Cave system today.  相似文献   

岭南东江流域晚更新世哺乳动物化石的新发现   总被引：5，自引：1，他引：5       下载免费PDF全文

李保生边戈果  张韦温小浩  牛东风杜恕环李后信  欧先交 《地质学报》2007,81(9):1195-1199

近年在南岭以南的广东东江流域河源地区东源县上莞镇的碧寿洞中发现较丰富的古哺乳动物牙齿化石。经鉴定为6个目5属5种,称之为碧寿动物群。根据碧寿动物群指示的古生态、化石层位、热释光测试结果和生物地层对比初步认为,该动物群与西江流域的罗沙岩动物群一样,都属于晚更新世时期的大熊猫—剑齿象动物群,生活在MIS5a时的间冰期,但罗沙岩动物群的时代略早,为(79.0±15)kaBP,而碧寿动物群则存在于末次冰期/末次间冰期之交的MIS5a之末叶。此动物群为广东东江流域历年首现,代表了当时的热带北缘森林草原的自然环境。  相似文献   

文山普者黑机场地下溶洞裂隙稳定性分析     

段乔文  李正江  吴继明  唐耀明 《云南地质》2007,26(3):335-340

对工程场区溶洞、溶隙的埋深、充填物及其性能、顶板厚度与洞跨、荷载作用形式及大小等因素进行综合分析，判断溶洞、溶隙的稳定性及其对工程建设运营的影响，提出相应的处治方案。  相似文献   

Geological risk assessment of the area surrounding Altamira Cave: A proposed Natural Risk Index and Safety Factor for protection of prehistoric caves     

Miguel A. Snchez  Alberto Foyo  Carmen Tomillo  Eneko Iriarte 《Engineering Geology》2007,94(3-4):180-200

Altamira Cave occurs in a carbonate sequence-dated as middle to upper Cenomanian, being characterized by tabular bedding. This sequence has been studied in detail and mapped in an attempt to delimit the beds in which the cave was formed. The cave forms part of a karstic complex developed in the Altamira Formation, which consists of eight stratigraphic units characterized by karstic forms and landslides as the main geomorphologic elements. The strong relationship between sinkholes and faults within the area was also revealed, with sinkholes of oval morphology aligned along the faults. Inside the cave, the subhorizontal bedding is intersected by subvertical joints, generating geometrical blocks prone to falling down. This is the main process of the present evolution of the cave in addition to the dissolution and precipitation of carbonates in local zones. We used this geological characterization as the basis for the definition of protection areas around prehistoric caves, applied in this article to the Altamira Cave. Landslides, water flow towards the cave, rock falls within cave and karstic features are the main geological risks affecting the karstic complex. Two semi-quantitative indexes were proposed, the Natural Risk Index (NRI) and Safety Factor (SF), with the main aim of determining the risk level in different zones of the study area. The information provided by geological studies as well as the results obtained using the proposed indexes allowed definition suitable protection areas around the cave.  相似文献   

四川雷波马湖地质公园景观资源     

曹俊  陈斌  张慧利  郭建强 《四川地质学报》2007,27(2):134-138

马湖地质公园以高山湖泊景观为主,马湖湖岸呈锯齿状,水域面积7.32 km2,为我国已知的第四大深水湖泊。此外还有岩溶洞穴、丹霞地貌、火山熔岩、金沙江峡谷地貌、三国文化遗址景观——孟获庙。构成了地质遗迹景观成因类型多样、组合独特、功能齐全、互补性强的综合性景观。该地质公园,具有重要的科考价值、美学价值、观赏价值和保护价值。  相似文献   

Dung, diet, and the paleoenvironment of the extinct shrub-ox (Euceratherium collinum) on the Colorado Plateau, USA     

Manny Kropf  Jim I. Mead  R. Scott Anderson 《Quaternary Research》2007,67(1):143-151

Fossil remains of Euceratherium collinum (extinct shrub-ox) have been found throughout North America, including the Grand Canyon. Recent finds from the Escalante River Basin in southern Utah further extend the animal's range into the heart of the Colorado Plateau. E. collinum teeth and a metapodial condyle (foot bone) have been recovered in association with large distinctively shaped dung pellets, a morphology similar to a ‘Hershey's Kiss’ (HK), from a late Pleistocene dung layer in Bechan Cave. HK dung pellets have also been recovered from other alcoves in the Escalante River Basin including Willow and Fortymile canyons. Detailed analyses of the HK pellets confirmed them to be E. collinum and indicate a browser-type diet dominated (> 95%) by trees and shrubs: Artemisia tridentata (big sagebrush), Acacia sp. (acacia), Quercus (oak), and Chrysothamnus (rabbit brush). The retrieval of spring and fall pollen suggests E. collinum was a year-round resident in the Escalante River Basin.  相似文献   

Contribution of stable isotopes to the understanding of the unsaturated zone of a carbonate aquifer (Nerja Cave, southern Spain)     

Francisco Carrasco  Bartolom Andreo  Cristina Lin  Jacques Mudry 《Comptes Rendus Geoscience》2006,338(16):1203-1212

We analysed the stable isotopes (¹⁸O and ²H) of rainwater and drip water within a cave (Nerja Cave) located in the unsaturated zone of a carbonate aquifer. Rainfall is more abundant and presents lower isotopic content in winter, while the volume of drip water is greater and its isotopic content is lower in summer. The flow analysis of ¹⁸O through the unsaturated zone confirms the seasonal lag between rainfall and the appearance of drip water in the cave and reveals that the unsaturated zone of the aquifer, in the sector of the cave, behaves like an inertial system with a strong capability to modulate the input signal. To cite this article: F. Carrasco et al., C. R. Geoscience 338 (2006).  相似文献   

中国洞穴石笋信息管理系统的开发与应用     

杨琰  袁道先  覃嘉铭  林玉石  张美良 《中国岩溶》2004,23(4):328-334

随着全球气候变化研究的逐步深入,洞穴化学沉积物在重建古环境中的作用受到越来越多学者的重视,它是一种不可多得的古环境信息载体。我国学者从事洞穴沉积物古环境重建工作已有20多年,已取得大量的石笋记录数据。本信息管理系统主要收集中国南方、北方已有的石笋记录数据,并分析汇总成库,可以较方便地满足国内外从事洞穴石笋古环境重建研究者进行数据查询分析,以实现科技资源共享。   相似文献   

云南寻甸地区最近八千年气候环境变迁   总被引：2，自引：0，他引：2  

张会领  袁道先  覃嘉铭  林玉石  张美良  王华 《中国岩溶》2004,23(4):293-298

通过对云南寻甸白石岩仙人洞1号石笋进行高精度TIM S-U系测年和氧碳稳定同位素分析,重建了寻甸地区中全新世8. 0ka 以来高分辨率古气候演化序列。石笋剖面的碳氧同位素记录揭示,云南寻甸地区自8. 0kaB. P.以来的气候演化可以分为三个气候期: (1) 8000～6000aB. P.为温暖湿润期,夏季风强盛,气温较高,降水丰沛,石笋的氧碳同位素偏负; ( 2) 6000～5200 a B. P.为季风气候衰退期,在这期间气温和降水都发生了较大变化,气候由温湿变为冷干,石笋氧碳同位素持续偏正; ( 3) 5200～2100aB. P.凉干气候期,这一时期气候基本稳定,东亚季风对气候影响较大,但气温和降水都低于第一个气候稳定期。   相似文献