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轮东1井位于塔里木盆地塔河-轮南古隆起东翼围斜部位.该井在6800～6825m井段上奥陶统发育一高约25m的大型溶洞.第3筒芯取自洞穴顶部.通过对洞穴充填沉积序列及其古生物分析与元素地球化学研究,获以下关键结论:(1)洞穴沉积物中含较多腕足类、腹足类、棘皮类、介形虫和疑源类化石,明显分为洞穴原地生态和异地生屑(洞穴崩塌角砾经溶蚀残存与潜流搬运而来)两类,指示洞穴形成于前石炭纪,并在石炭纪再次沉降时被半充填和埋藏;(2)元素地球化学揭示,洞穴充填泥为钙质古土壤和风化壳残留物,形成于循环不畅的咸水环境;(3)洞穴形成与演化共经历了3期:晚奥陶世良里塔格组沉积后、桑塔木组沉积后和志留系沉积后,其中后两期主要发育顺层承压深潜流岩溶作用.基于洞穴形成历史恢复,可对古岩溶有利区进行预测评价.此外,对古地理学与古岩溶学研究也具有重要意义. 相似文献
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山西侯马—河津一带西汉初期的强烈地震 总被引：1，自引：0，他引：1
1989年至1987年间,在国家地震局招标合同项目《全新世古地震的研究方法和确定标志》工作中,笔者在山西省侯马至河津一带,发现了大规模地震断层和许多古地震遗迹。本文就是在此基础上,对黄土中的古地震遗迹进行了总结,分析研究了古地震的分布和特征,讨论了侯马至河津一带西汉初期强震的规模和震中。 相似文献
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古地震遗迹的研究,无疑是延续历史地震最有效的途径之一。因此,识别其是否是古地震的遗迹,就成了研究古地震的前提。本文提供了一个古地震标志(层理变形构造)研究的实例。通过对河北定兴一带变形构造的分析,认为它确属于一次地震变形构造,並与库南所做的泥沙沉积物振动实验的结果总体上相似。只是其所受的振动要比库南实验结果大得多,振动时间也要长些。 相似文献
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在青藏高原东北缘海原断裂带刺儿沟古地震剖面上不仅保存了地震活动的崩积楔遗迹,还发现多层炭屑以及与人类活动有关的铁渣、陶片等遗物,文中运用14C测年法和经红外释光照射后的绿光释光测年法(Post-IR OSL)分别对剖面上的炭屑、烘烤黏土、沉积物等样品进行年龄测定和比对,获得了各炭屑层和人类活动遗迹的年代。测定的人类活动遗迹年代与海原周缘历史记载的强震发生时间序列比对结果表明,刺儿沟人类活动遗迹的形成可能与历史地震无关,过去以炭屑年代作为地层年代来限定古地震发生的时代,建立的古地震事件时序的结果可能不正确,上述工作为进一步研究海原断裂带的强震复发规律和海原地区考古提供了重要的基础资料 相似文献
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本文对昌马断裂带的大河坝—小东沟梁一段所发现的一些古地震构造剖面及其它古地震地质标志进行了简要描述和分析,並对古地震遗迹所表示的古地震活动事件作了初步讨论,指出昌马断裂带是深入研究古地震活动的良好场所, 相似文献
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K. Gribovszki K. Kovács P. Mónus G. Bokelmann P. Konecny M. Lednická G. Moseley C. Spötl R.L. Edwards M. Bednárik L. Brimich L. Tóth 《Journal of Seismology》2017,21(5):1111-1130
Earthquakes hit urban centres in Europe infrequently, but occasionally with disastrous effects. Obtaining an unbiased view of seismic hazard (and risk) is therefore very important. In principle, the best way to test probabilistic seismic hazard assessments (PSHAs) is to compare them with observations that are entirely independent of the procedure used to produce PSHA models. Arguably, the most valuable information in this context should be information on long-term hazard, namely maximum intensities (or magnitudes) occurring over time intervals that are at least as long as a seismic cycle. The new observations can provide information of maximum intensity (or magnitude) for long timescale as an input data for PSHA studies as well. Long-term information can be gained from intact stalagmites in natural caves. These formations survived all earthquakes that have occurred over thousands of years, depending on the age of the stalagmite. Their ‘survival’ requires that the horizontal ground acceleration (HGA) has never exceeded a certain critical value within that time period. Here, we present such a stalagmite-based case study from the Little Carpathians of Slovakia. A specially shaped, intact and vulnerable stalagmite in the Plavecká priepast cave was examined in 2013. This stalagmite is suitable for estimating the upper limit of horizontal peak ground acceleration generated by prehistoric earthquakes. The critical HGA values as a function of time going back into the past determined from the stalagmite that we investigated are presented. For example, at the time of Jók? event (1906), the critical HGA value cannot have been higher than 1 and 1.3 m/s2 at the time of the assumed Carnuntum event (～340 AD), and 3000 years ago, it must have been lower than 1.7 m/s2. We claimed that the effect of Jók? earthquake (1906) on the location of the Plavecká priepast cave is consistent with the critical HGA value provided by the stalagmite we investigated.The approach used in this study yields significant new constraints on the seismic hazard, as tectonic structures close to Plavecká priepast cave did not generate strong earthquakes in the last few thousand years. The results of this study are highly relevant given that the two capitals, Vienna and Bratislava, are located within 40 and 70 km of the cave, respectively. 相似文献
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Stefan Niggemann Augusto Mangini Detlev K Richter 《Earth and Planetary Science Letters》2003,216(4):539-547
Calcitic stalagmites from caves in the Sauerland, Germany, prove the existence of sub-Milankovitch cycles in precipitation during the last 6000 yr. The δ18O record dated with Th/U is interpreted as an indicator of paleohumidity. Spectral analysis of δ18O from 6000 a BP up to the recent top of a stalagmite from the Atta cave yields statistically significant peaks at 1450, 117, 64 and 57 a. Additionally we find a good correlation of the stalagmite’s δ18O and Δ14C from European tree rings. The 1450 a cycle in the stalagmite probably is analogous to the pervasive millennial scale climate cycle described by Bond et al. [Science 278 (1997) 1257-1266; 294 (2001) 2130-2136] derived from the amount of ice rafted debris in deep sediments from the North Atlantic. Our results suggest that the centennial to millennial shifts observed in the North Atlantic are accompanied by synchronous shifts of the climate in Northern and Central Europe, which most probably can be attributed to solar irradiation variations. 相似文献
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Modern to Holocene tropical Pacific stalagmites are commonly difficult to date with the U-series, the most commonly used dating method for speleothems. When U-series does not provide robust age models, due to multiple sources of 230Th or little U, radiocarbon is, potentially, the best alternative. The 14C content of two stalagmites (Pu17 and Nu16) collected from Pouatea and Nurau caves in the Cook Island Archipelago of the South Pacific were measured to obtain accurate chronology for their most modern parts. The bomb-pulse soil continuum modelling indicates that bomb radiocarbon in Pu17 onsets in 1956 and reaches its maximum in 1966 CE, suggesting a fast transfer of atmospheric carbon to the stalagmite of <1 year. The modelling for Pu17 suggests a 20% contribution from C1 - an instantaneous carbon source, which renders possible an immediate transfer of atmospheric signal into the cave. Nu16 shows a slower transfer of atmospheric carbon to the stalagmite than Pu17, with bomb radiocarbon onsetting in 1957 CE and peaking in 1972 CE. The less negative δ13C values in Nu16 than Pu17, and also the modelling corroborated this, which points out no contribution from the instantaneous carbon source. The radiocarbon age models and laminae counting age models were then spliced to achieve a single master chronology for the top part of each stalagmite. This study is an example of 14C age modelling combined with visible physical and chemical laminae counting and how it can improve the accuracy and precision of dating for otherwise hard-to-date tropical Pacific speleothems. Such accurate and precise age models pave the way to obtain sub-annually resolved paleoclimate records by further improving the calibration of climate proxy data with the current and instrumental weather parameters. 相似文献
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John A. Webb 《地球表面变化过程与地形》2021,46(2):455-464
The maze caves of the Northern Pennines are rectilinear joint-controlled networks of predominantly tall vertical rifts developed on one level towards the top of a ~20 m thick limestone bed; they were all intersected by underground mines and have no relationship to the present landscape. Passage walls commonly have large, non-directional scallops; speleothems are uncommon. The caves were previously identified as hypogene in origin, i.e. formed by groundwater ascending from depth, but reassessment of their origin using published data shows that they lack diagnostic hypogene features (rising wall channels, ceiling channels, ceiling cupolas and dome-pits), and the low permeability strata above and below the limestone bed greatly restrict vertical groundwater flow through the caves. Instead the maze caves were dissolved by the sulphuric acid released by oxidation of iron sulphides (and perhaps chalcopyrite) in the mineralized veins adjacent to all these caves; passage sizes decrease away from the veins and gypsum encrusts the walls of one cave. The maze caves were not formed by vertical groundwater flow, and dissolution was focussed in a relatively small area of limestone beneath an impermeable confining layer. The caves began to form when river incision due to the probably Late Cenozoic uplift of northern England exposed the iron sulphides to weathering and oxidation. The process that formed the maze caves is here termed supergene sulphuric acid speleogenesis, because generation of the acidity was due to near-surface supergene sulphide oxidation, and differentiated from hypogene sulphuric acid speleogenesis, where the source is at depth beneath the cave. To clarify usage of the term hypogene, it should be restricted to Palmer's geochemical definition (Speleogenesis: Evolution of Karst Aquifers, eds Klimchouk et al., National Speleological Society: Huntsville, AL, 2000; 77–90): dissolution by a deep-seated source of acidity. Caves dissolved by ascending groundwater containing carbonic acid with a near-surface origin, e.g. on the rising limb of a phreatic loop, are better identified as epigene. © 2020 John Wiley & Sons Ltd 相似文献
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CHEN Shitao WANG Yongjin KONG Xinggong LIU Dianbing CHENG Hai & R.L. Edwards . College of Geography Science Nanjing Normal University Jiangsu Key Laboratory of Environmental Change Ecological Construction Nanjing China . Department of Geology Geophysics University of Minnesota Minneapolis MN USA 《中国科学D辑(英文版)》2006,49(9):982-990
1 Introduction The Younger Dryas (YD) cold spell is one of the most prominent abrupt climate change events in the past and a key feature of the last glacial termination. A great agreement has been attained in terms of the tim- ing and geographic extent of… 相似文献
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Győző Szeidovitz Gergely Surányi Katalin Gribovszki Zoltán Bus Szabolcs Leél-Őssy Zsolt Varga 《Journal of Seismology》2008,12(1):21-33
The examination of speleothems in the Hajnóczy and Baradla caves (northeastern Hungary) allows estimating an upper limit for
horizontal peak ground acceleration generated by paleoearthquakes. The density, the Young’s modulus and the tensile failure
stress of the samples originating from a broken speleothem have been measured in a laboratory, whereas the natural frequency
of intact speleothems was determined by in situ observations. The value of horizontal ground acceleration resulting in failure,
the natural frequency and the inner friction coefficient of speleothems were assessed by theoretical calculations. The ages
of the samples taken from a stalagmite 5.1 m in height (Baradla cave) have been determined by inductively coupled plasma mass
spectrometry analysis and alpha spectrometry. The measured ages fall between 140,000 and 70,000 years; therefore, we assume
the speleothem has not been changed since the end of this time interval. According to our modeling results, this speleothem
has not been excited by a horizontal acceleration higher than 0.05 g during the last 70,000 years. 相似文献
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选取上海地铁交通9号线沿线近车站典型区段为对象,以基于LabVIEW2010开发平台的振动测试系统进行数据采集。根据现场实测数据,分析了地铁运行时隧洞中心线对应的地表处3个方向,以及距中心线不同距离地表处垂直地面方向的振动响应实况和振动特性及传播规律。结果表明,地面振动以垂直地表方向振动为主,振动幅值距离隧洞中心线越远越小,在15m左右存在放大区,且放大的敏感频率为15~25Hz。本次实验地点靠近9号线某车站,实验数值具有一定的典型性和特殊性,可为完善该领域的研究提供借鉴和参考。 相似文献
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The stalagmite chronological table is established based on the definition of annual character of microlayers of a stalagmite
by comparing the laminated rhythm to natural cyclic processes. Climatic anomalies lasting over ten years and rapid climatic
changes such as abrupt changes of mean value, of variability, of trend and of cycles are discovered from the stalagmite chronological
table. Stalagmites which record interannual to century scale climatic changes are excellent
This work is a part of PANASH/PEP-II Project, and supported by the National Natural Science Foundation of China (Grant Nos.49672134,
49894170), Chinese Academy of Sciences (Grant No.KZ951-A1-402-06-02), and State Science & Technology Commission of China. 相似文献
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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