Deciphering late Quaternary land snail shell δO and δC from Franchthi Cave (Argolid,Greece)     

André C. Colonese  Giovanni Zanchetta  Catherine Perlès  Russell N. Drysdale  Giuseppe Manganelli  Ilaria Baneschi  Elissavet Dotsika  Hélène Valladas 《Quaternary Research》2013

This paper investigates the stable isotopic composition from late Pleistocene–Holocene (~ 13 to ~ 10.5 cal ka BP) shells of the land snail Helix figulina, from Franchthi Cave (Greece). It explores the palaeoclimatic and palaeoenvironmental implications of the isotope palaeoecology of archaeological shells at the time of human occupation of the cave. Modern shells from around the cave were also analysed and their isotopic signatures compared with those of the archaeological shells. The carbon isotope composition of modern shells depicts the consumption of C₃ vegetation. Shell oxygen isotopic values are consistent with other Mediterranean snail shells from coastal areas. Combining empirical linear regression and an evaporative model, the δ¹⁸Os suggest that modern snails in the study area are active during periods of higher relative humidity and lower rainfall δ¹⁸O, probably at night. Late glacial and early Holocene δ¹⁸Os show lower values compared to modern ones. Early Holocene δ¹⁸Os values likely track enhanced moisture and isotopic changes in the precipitation source. By contrast, lower late glacial δ¹⁸O could reflect lower temperatures and δ¹⁸Op, compared to the present day. Shell carbon isotope values indicate the presence of C₃ vegetation as main source of carbon to late glacial and early Holocene snails.  相似文献   

Centennial-scale Asian monsoon variability during the mid-Younger Dryas from Qingtian Cave,central China     

Dianbing Liu  Yongjin Wang  Hai Cheng  Xinggong Kong  Shitao Chen 《Quaternary Research》2013

The regional climate correlation within the Northern Hemisphere in the cold/dry mid-Younger Dryas event (YD) remains elusive. A key to unraveling this issue is sufficient knowledge of the detailed climate variability at the low latitudes. Here we present a high-resolution (3-yr) δ¹⁸O record of an annually laminated stalagmite from central China that reveals a detailed Asian monsoon (AM) history from 13.36 to 10.99 ka. The YD in this record is expressed as three phases, characterized by gradual onsets but rapid ends. During the mid-YD, the AM variability exhibited an increasing trend superimposed by three centennial oscillations, well-correlated to changes in Greenland temperatures. These warming/wetting fluctuations show a periodicity of ~ 200 yr, generally in agreement with centennial changes in cosmogenic nuclides indicated by the ¹⁰Be flux from the Greenland ice. This relationship implies that centennial-scale climate changes during the mid-YD are probably caused by solar output and rapidly transported over broad regions through atmosphere reorganization.  相似文献   

南京汤山葫芦洞地质雷达勘探洞穴堆积研究     

周春林  袁林旺  刘泽纯  梁中 《江苏地质》2007,31(1):25-29

通过对南京汤山葫芦洞内部东侧地质雷达勘探资料的分析,根据经验值计算,东部洞穴基岩埋深在10m左右,可能为水平状的红色岩系。特殊的地质基础导致葫芦洞成为汤山地区已知规模最大的洞穴。其上的洞穴埋藏堆积可以分为上、中、下三个角砾层,可能反映了该洞穴曾经历过三次较大的崩塌堆积过程。上角砾层可能含有动物化石,是今后古人类考古值得关注的堆积层。  相似文献   

Temporal and spatial variations in the discharge and dissolved organic carbon of drip waters in Beijing Shihua Cave,China   总被引：1，自引：0，他引：1  

Fengmei Ban  Genxing Pan  Jian Zhu  Binggui Cai  Ming Tan 《水文研究》2008,22(18):3749-3758

To detect the causal relationship between cave drip waters and stalagmite laminae, which have been used as a climate change proxy, three drip sites in Beijing Shihua Cave were monitored for discharge and dissolved organic carbon (DOC). Drip discharges and DOC were determined at 0 to 14‐day intervals over the period 2004–2006. Drip discharges show two types of response to surface precipitation variations: (1) a rapid response; and (2) a time‐lagged response. Intra‐annual variability in drip discharge is significantly higher than inter‐annual variability. The content of DOC in all drip waters varies inter‐ and intra‐annually and has good correlation with drip water discharge at the rapid response sites. High DOC was observed in July and August in the three years observed. The flushing of soil organic matter is dependent upon the intensity of rain events. The DOC content of drip water increases sharply above a threshold rainfall intensity (>50 mm d^?1) and shows several pulses corresponding with intense rain events (>25 mm d^?1). The DOC content was lower and less variable during the dry period than during the rainy period. The shape of DOC peak also varies from year to year as it is influenced by the intensity and frequency of rainfall. The different drip sites show marked differences in DOC response, which are dominated by hydrological behaviour linked to the recharge of the soil and karst micro‐fissure/porosity network. The results explain why not all stalagmite laminae are consistent with climate changes and suggest that the structure of the rainy season events could be preserved in speleothems. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

26Al/10Be埋藏测年及其在洞穴沉积年代学研究中的应用     

邵庆丰  高斌 《中国岩溶》2006,25(3):195-200

长期暴露于地表的石英砂被快速搬入洞穴或埋藏,不再接受宇宙射线辐射,埋藏前所积累的陆地宇生核素26 Al 和10 Be 随时间指数衰减。据此用加速器质谱计测定沉积物中石英样品现存的26 Al /10 Be可计算其埋藏年代。用此方法本文对周口店第一地点的下部地层年代作了初探。此次研究表明自第10层以下的沉积物其年代很可能≥ 1 Ma。   相似文献   

洞穴石笋沉积速率研究中值得注意的几个问题   总被引：12，自引：5，他引：7  

林玉石  张美良  覃嘉铭 《中国岩溶》2001,20(2):131-136

众多大型石笋纵剖面观测、测年和纹层沉积计率(沉积速率计算)表明,速率差异是石笋沉积特征的重要数据,也是古气候环变化的重要反映,但以往诸多资料不好引用、无从对比。通过筛选石笋的全(正)心纵剖面,沿纹层轴(中)部采样,测年值和计率可信度大,具时空对比意义。为提高精度和分辨率,提倡按石笋沉积特征段,特别是纹层组测年计率。   相似文献   

重庆丰都雪玉洞群的洞穴特征和洞穴沉积物   总被引：15，自引：11，他引：4  

朱学稳  张远海  韩道山  文汝平  陈炳清 《中国岩溶》2004,23(2):85-168

重庆市丰都县的雪玉洞群,由水洞子(雪玉洞群主洞)、水鸣洞和羊子洞组成,发育于三叠系下统的嘉陵江灰岩中,均为沿单斜构造地层走向发育的纵向洞穴系统,集中分布在龙河峡谷左岸2km 内高、中、低不同的相对高度,但洞穴发育特征差异甚大。在该洞穴群的次生物理— 化学沉积物( speleo thems )中碳酸盐类(方解石、文石)和硫酸盐类(石膏)并存,而且其形态的多样与完美,类型的稀有而珍贵,质地的纯粹而白净,在国内已发现的洞穴中是不多见的,其中尤以地石盾、塔珊瑚、钙膜晶锥、卷曲石等生成物为代表。   相似文献   

Dolomite in caves: Recent dolomite formation in oxic, non-sulfate environments. Castañar Cave, Spain     

Ana M. Alonso-Zarza  Andrea Martín-Prez 《Sedimentary Geology》2008,205(3-4):160-164

Dolomite is a common mineral in the rock record but rare in recent superficial environments. Where it does occur, it is related to anoxic, sulfate-rich environments and microbial activity. The occurrence of some dolomite deposits in caves, however, indicates that dolomite formation is also possible in oxic, non-sulfate settings. Dolomite is forming at 17 °C and in oxic-vadose conditions on the host rocks and aragonite speleothems of the Castañar Cave, Cáceres, Spain. It appears as spheroids and dumbbells 50–300 μm in diameter that internally consist of micron-sized rhombic to rounded crystals. Initially this dolomite is Ca-rich, non-stoichiometric and poorly ordered. Mg-rich solutions allow the precipitation of metastable Mg-rich carbonates, such as huntite. This soon transforms into this Ca-rich dolomite, which later “ages” to form a more stoichiometric dolomite. These dolomites show similarities to those grown under anoxic, sulfate-rich conditions and their presence in caves provides a different setting that may contribute to the understanding of the “dolomite problem”, including their initial formation and later recrystallization processes.  相似文献   

富源刺托洞旧石器遗址初探     

张子雄  戴兴乾  刘肃昆  刘经仁  杨正纯 《云南地质》2001,20(1):99-117

富源刺托洞的旧石器文化是适应岩溶地貌发育环境的产物,形成以小型石片、刮削器为主体的石器工业;当时的气候总体上是在热带、亚热带气候至暖温带之间波动,形成的动物群为非典型的大熊猫-剑齿象动物群(Ailuroooda-Stegodon fauna)可与晚更新世的柳江动物群(西畴动物群)对比;遗址时代为晚更新世,地质年龄测定(14C)＞4×104a.  相似文献   

褒禅山华阳洞的形成机理及保护意义     

张春雷  夏琼  高雅  胡晨  查世新  马国明 《安徽地质》2016,26(2):132-134

褒禅山华阳洞主体发育于二叠系栖霞组灰岩中,是含山地区重要的地质遗迹之一。笔者从区域地质演化过程入手,针对岩溶洞穴发育的物质基础、局部构造条件、水流的定向溶蚀及新构造运动等方面进行综合研究,简要分析了华阳洞的形成机理,并从地学研究、旅游价值等方面阐述了对其保护的重要意义。  相似文献