桂林市芦笛岩、大岩洞穴环境特征   总被引：13，自引：5，他引：8  

陈伟海  邓亚东  韩道山  房锋保  刘学 《中国岩溶》2004,23(2):113-119

对桂林市西郊的芦笛岩和大岩洞穴环境长期观测的结果表明,作为游览洞穴的芦笛岩与洞外空气交换频繁,洞穴CO2 的含量较低,温、湿度变化频繁而且幅度大。游览活动导致洞内CO2 含量显著增加,但是回落十分迅速,不会引起洞内温度、CO2 的累积效应。作为非游览洞穴的大岩与外界交换弱且缓慢,保持着相对恒定的原始环境,有较好的洞穴气候分带,空气温度、湿度比较稳定, CO2 的含量呈规律性季节变化;最近20多年来,洞内气温、湿度有明显的降低。   相似文献   

爪哇犀(Rhinoceros sondaicus,Rhinocerotidae)化石在中国更新统的首次发现     

严亚玲  张阳  金昌柱  张颖奇  王元 《地质论评》2020,66(1):198-206

犀类是我国华南地区更新世地层中最为常见的化石哺乳动物类群之一。本文对广西崇左三合大洞中发现的犀牛化石材料进行了形态特征描述,并与我国华南地区第四纪相关属种以及东南亚地区所发现的化石和现生种进行了比较,从牙齿形态特征和大小等方面来看,认为三合大洞中的标本应该归入爪哇犀(Rhinoceros sondaicus)。此次所发现的爪哇犀(Rhinoceros sondaicus)化石根据相关文献记录,应该是爪哇犀化石在我国更新世地层中的首次报道,并且是我国有关爪哇犀的最早记录。形态学研究表明,该地区早更新世早期的扶绥岩亮洞、鲤鱼山百孔洞以及泊岳山巨猿洞发现的扶绥犀(Rhinoceros fusuiensis)可能是爪哇犀的直接祖先。三合大洞中爪哇犀的发现进一步丰富了我国华南地区独角犀的种类,填补了该种类在我国更新世地层中缺乏化石记录的空白。  相似文献   

早全新世季风演化的高分辨率石笋δ18O记录研究--以河南老母洞石笋为例   总被引：1，自引：0，他引：1  

张银环  杨琰  杨勋林  殷建军  黄帆  任小凤  赵景耀  刘肖  聂旭东 《沉积学报》2015,33(1):134-141

基于豫西老母洞LM2石笋8个高精度230Th年龄,449个氧碳同位素,建立了达十年际分辨率的8.2~10.9 ka B.P.亚洲季风变化的δ18O记录序列.老母洞石笋δ18O值最为偏负达-12.0‰,最偏正为-8.2‰,振幅达3.8‰.早全新世10.13~10.9 ka B.P.时段内,河南西部老母洞石笋和东石崖石笋,陕西九仙洞C996-2石笋δ18O曲线揭示该时段内季风稳定,而中国南方的衙门洞石笋、三宝洞石笋和极地冰芯GRIP记录揭示该时段季风逐渐增强;同时季风达到顶峰的时期也不相同,进一步说明中国南北方早全新世10.13~10.9 ka B.P.时段季风演变过程的差异,可能与中国南北方气候的响应机制有关.从早全新世平均分辨率10年的LM2石笋记录中识别出8.2 ka,9.5 ka,10.2 ka和10.9 ka显著弱季风事件,尤其是8.2 ka和9.5 ka事件.对比分析老母洞与已发表的高分辨率石笋δ18O记录发现:石笋所揭示的某些冷事件发生时间在亚洲季风区存在差异,主要表现在事件内部变化特征及趋势上.LM2石笋δ18O曲线并没有明显记录9.3 ka弱季风事件,而是在9.3~9.6 ka B.P.左右记录了一个弱季风事件,与DSY09(2009)、Y1、HS-4记录相似,表明在该时段内存在季风的减弱事件,但是氧同位素传输的复杂性,使其在南北方表现不同.此外,在LM2石笋δ18O的8.2 ka B.P.开始时段,氧同位素曲线阶段性下降,且变幅达3‰,与Zhang等研究万象洞石笋提出的“中国8 200阶段”吻合,表明中国北方地区的8.2 ka事件是阶段性的事件,而南方的石笋氧同位素记录揭示的8.2 ka事件并未表现出阶段性特征,其原因有待于更多北方高精度石笋记录来进一步研究.LM2石笋氧同位素记录进行功率谱分析发现:在短尺度上季风变化与太阳活动密切相关,这与近年来对早全新世极端气候变化研究的驱动机制是一致的,早全新世亚洲季风的演化与太阳活动变化引起的太阳辐射能量的变化和北半球高纬气候的变化状况有关.  相似文献   

中国东部季风区与西北干旱区 降水变化的石笋记录对比          下载免费PDF全文

胡超涌  汪颖钊  李骜扬  廖金  谢树成 《地球科学》2015,40(2):268-274

中国东部季风区和西北干旱区分别受控于季风和西风环流,是全球变化响应的敏感区域.过去50年全球升温,西北干 旱区降水显著增加,而东部季风区的降水变化不明显.在未来全球继续变暖的情况下,两个地区降水将如何变化尚不清楚.利 用湖北神农架三宝洞和新疆特克斯科桑洞的石笋生长速率记录,考察它们对降水变化的响应,研究冰期-间冰期旋回中两地 的降水变化及其差异,为未来气候变暖下的中国降水模型预测提供一个验证实例.研究表明,500ka以来中国东部季风区和西 部干旱区降水呈现冰期-间冰期波动变化,气温偏高的间冰期降水量大.但是,中国西北干旱区降水的响应滞后于东部季风 区,指示两地降水对温度变化的响应可能并非完全同步.   相似文献   

北京石花洞空气环境主要因子季节性变化特征研究   总被引：13，自引：6，他引：7  

班凤梅  蔡炳贵 《中国岩溶》2011,30(2):132-137

洞穴大气CO2浓度不仅是影响洞穴沉积物沉积（或者溶蚀）的重要因素之一,而且在旅游洞穴,它关系到沉积物景观的稳定性以及旅游环境的舒适性。本文通过对石花洞洞穴大气温度、湿度及CO2浓度近4个水文年的观测,结果表明：（1）洞穴温度在15℃上下波动,夏季约高1℃,主要与洞内外温差的季节性变化和旅游活动有关;（2）洞穴CO2浓度随着大气温度上升而缓慢升高,至每年的7月上旬雨季来临时,气温、降水及土壤中CO2大幅提高,降水溶解大量的土壤CO2并渗入洞穴中,导致洞穴CO2浓度迅速上升,8月观测到的最高浓度可达到4 334ppm,在雨季结束后,随着大气温度降低,CO2浓度缓慢下降,2月份平均值达到最低,为360~458 ppm。另外,在5月份和10月份的旅游黄金周,旅游人数的增加,洞穴CO2浓度异常增高。在进行洞穴管理与规划时,应综合考虑自然和人为因素对洞穴的影响。  相似文献   

Comparison of 14C and 210Pb - 137Cs - 241Am dating methods of a recent bat guano deposit (Lot,SW France)     

《Quaternary Geochronology》2022

Bat guano deposits are increasingly used as records of past environmental changes, an approach that requires a precise chronology of the guano layers. This paper presents a comparison between the well-established ¹⁴C dating method and methods based on natural ²¹⁰Pb excesses, (²¹⁰Pb)_ex, and artificial radionuclides ¹³⁷Cs and ²⁴¹Am. The studied example is a bat guano deposit from a cave in SW France (the Brantites III cave), which is currently investigated for paleo-environmental reconstructions using stable isotopes. ¹⁴C data show that the upper part of the guano deposit accumulated during the last 150 years with a marked increase in accumulation rates after around 1960 AD. While the incorporation of atmospheric ¹⁴C in guano is a well-understood process, the origin of ²¹⁰Pb excesses is more complex. Based on consideration of ¹³⁷Cs and (²¹⁰Pb)_ex inventories recorded in undisturbed soils in France, and the measured inventories in the guano deposit, we suggest that most of the ²¹⁰Pb excess is produced by ²²²Rn decay in the cave air and then adsorbed onto the guano. As Radon concentrations in caves can vary significantly on both short and long-term timescales, one needs to be cautious before applying the often-used CRS (constant rate of supply of ²¹⁰Pb excess) model to guano dating. Our (²¹⁰Pb)_ex data are best interpreted by two successive periods of roughly constant, but widely different accumulation rates (0.3 cm/y and 2.6 cm/y before and after 1960, respectively) and (²¹⁰Pb)_ex fluxes. We suggest that these relatively abrupt variations result from a change in cave ventilation leading to a more favourable shelter for bats after 1960. The upper 40 cm of the deposit shows evidence of ²¹⁰Pb mobility, adding a further complexity to the interpretation of (²¹⁰Pb)_ex profiles in guano deposits. However, the existence of well-defined ¹³⁷Cs and ²⁴¹Am peaks allows a precise identification of the year of maximum atmospheric fallouts (∼1963–1964). When the ages provided by artificial radionuclides are combined with the ²¹⁰Pb-derived accumulation rates, an age model can be built, which is in good agreement with the ¹⁴C age model. This example shows that the (²¹⁰Pb)_ex method, when associated with ¹³⁷Cs (²⁴¹Am) data, can be used to date recent guano deposit, although its application is not as straightforward as the ¹⁴C method.  相似文献   

New chronological constraints on the Plio-Pleistocene uplift of the Guizhou Plateau,SE margin of the Tibetan Plateau     

《Quaternary Geochronology》2022

The Guizhou Plateau represents a geomorphic transition between the Tibetan Plateau and the Yangtze River Plain. It likely formed in response to the propagation of surface uplift in southeastern Tibet during India-Eurasia continental collision. However, the uplift history of the region is unclear largely due to a lack of datable material. The bedrock geology is dominated by carbonate rocks, which contains numerous multi-level caves in the main river valleys that are linked to the river incision history. Cosmogenic ²⁶Al and ¹⁰Be burial dating of sediments in caves and river terraces from the northwestern and southern plateau reveals the fluvial chronology and provides the first direct determination of long-term river incision rates. The caves and terraces on the Liuchong River in NW Guizhou yield burial ages of between 0.41 ± 0.12 Ma and 2.85 ± 0.21 Ma, indicating an average incision rate of 57 ± 3 m/Ma. Four level caves at Libo in southern Guizhou yield burial ages of between 0.56 ± 0.16 Ma and 3.54 (+0.25/-0.22) Ma, indicating slightly slower incision rate (47 ± 5 m/Ma). These new results imply that the high elevation of the Guizhou Plateau had developed before the Late Pliocene, and that surface uplift during the Late Cenozoic was largely uniform across the region.  相似文献   

The role of inherited Pb in controlling the quality of speleothem U-Pb ages     

《Quaternary Geochronology》2022

Over two decades of technical and application-based advances to the speleothem U-Pb chronometer have cemented this terrestrial archive at the forefront of landscape reconstruction, palaeoclimatology, and palaeoanthropology. The ability to access speleothem palaeoclimate records beyond the 650 ka limit of the U-Th system has opened many avenues to such ‘deep-time’ considerations. Yet still this chronometer remains a challenging analytical exercise, more-so as the technique becomes routinely applied to carbonates with less-than-ideal U/Pb ratios. In this contribution, we review the vadose speleothem U-Pb system, as revealed by 68 previously published isochrons produced from 474 solution-mode analyses across three separate geographical regions. We develop a new statistical parameter of ‘average distance’ to quantify the dispersion or ‘spread’ along the previously published isochrons and compare this with available U and Pb elemental concentrations. Our findings highlight the importance of regional geology and karst morphology in controlling the speleothem's overall U/Pb ratio. Furthermore, we show that variability in the amount of inherited Pb across the sampling layer (average variability of 63% relative to sample average) – not uranium (23% variability) or by extension radiogenic Pb – is a main factor controlling the resulting isochron's quality. This is demonstrated using Z-score distributions of the U and Pb concentrations and isochron average distance values. By making this distinction we hope to initiate further research into Pb-specific transportation vectors through the karst, in addition to physical/chemical processes that fractionate inherited Pb at the speleothem precipitation site. We go on to extend the use of Tera-Wasserburg common Pb anchors to the ‘classical’ U-Pb isochrons as an example of the utility gained by considering the role of inherited Pb within speleothems. Finally we argue that an improved theoretical understanding of inherited Pb distributions within speleothems would greatly benefit solution mode sampling strategies, especially for poor-to-moderate U/Pb speleothems.  相似文献   

神农架石笋记录的近200年东亚季风变化及其ENSO响应   总被引：2，自引：0，他引：2  

赵侃  陈仕涛  崔英方  汪永进  程海 《地理研究》2015,34(1):74-84

通过湖北省神农架永兴洞石笋(编号:YX92)230Th年龄和纹层计数年代学研究,建立了1788AD-1956AD时段年际分辨率石笋氧同位素序列。该序列δ18O值变化范围为-9.70‰~-7.87‰,最大振幅约达1.83‰,呈现显著的年代际尺度振荡旋回特征。功率谱分析结果揭示存在显著的60~70年准周期信号。该记录与同区域和尚洞石笋δ18O曲线具有很好的重现性,说明其可能受控于共同的气候因子,指示了东亚夏季风大尺度环流特征。将石笋重建的东亚夏季风指标与全印度夏季降水量指示的印度夏季风指数对比,结果显示两者在年代际旋回特征上具有很好的相似性,但是呈反相位关系。进一步与ENSO指数对比,发现东亚夏季风年代际尺度变化与ENSO存在密切联系,表现为东亚夏季风增强,对应于ENSO暖期,反之亦然。因此,东亚季风与印度季风在年代际尺度上的反相位关系可能源于两者对ENSO机制的不同响应。  相似文献   

Condensation water in heritage touristic caves: Isotopic and hydrochemical data and a new approach for its quantification through image analysis     

Cristina Liñán  José Benavente  Yolanda del Rosal  Iñaki Vadillo  Lucía Ojeda  Francisco Carrasco 《水文研究》2021,35(5):e14083

Condensation water is a major factor in the conservation of heritage caves. It can cause dissolution of the rock substrate (and the pigments of rock art drawn on it) or covering thereof with mineral components, depending on the chemical saturation degree of the condensation water. In show caves, visitors act as a source of CO₂ and thus modify the microclimate, favouring negative processes that affect the conservation of the caves. In spite of their interest, studies of the chemical composition of this type of water are scarce and not very detailed. In this work we present research on the condensation water in the Nerja Cave, one of the main heritage and tourist caves in Europe. The joint analysis of isotopic, hydrochemical, mineralogical and microbiological data and the use of image analysis have allowed us to advance in the knowledge of this risk factor for the conservation of heritage caves, and to demonstrate the usefulness of image analysis to quantify the scope of the possible corrosion condensation process that the condensation water could be producing on the bedrock, speleothem and rock art. To our knowledge, this application of image analysis (relative to the condensation water in caves) is the first one of this type that has been documented.  相似文献