北京石花洞洞穴滴水中硫酸根浓度的时空变化及其意义

硫是环境地球化学循环中重要的元素之一,是区域及全球性环境变化的重要驱动因子。本文通过对石花洞洞穴4个滴水点（JG,SH,PL1和PL2）硫酸根浓度近3个水文年的分析测定（BL点观测近两年）,结果表明:响应降雨快的滴水点（SH和JG点）滴水SO42-浓度升高幅度最明显,且滴水SO42-浓度与滴率成指数关系;滞后响应降雨的观测点滴水SO42-浓度雨季升高幅度不明显,但在长期观测期间有明显增加的趋势;对降雨没有响应的滴水点,其SO42-浓度低且雨季没有明显变化。通过分析表明,在快速响应降水的滴水点,滴水硫酸根浓度大幅升高可能在一定程度上影响滴水pH值,这也可能是导致雨季时,快速下渗进入洞穴的滴水碳酸钙饱和度降低,从而抑制滴水沉积的一个不可忽略的因素。      

北京石花洞结构特征及发育演化过程研究

北京石花洞是中国北方已探明洞穴中次生碳酸盐沉积规模最大、种类最丰富的洞穴;石花洞的景观美学价值和科学价值,在我国北方岩溶洞穴中占有重要地位。2013年7月,为了获取石花洞发育规模、空间结构等基本数据,采用国际通用洞穴测量方法,运用激光测距仪、罗盘和倾角仪,辅以Onstation洞穴绘图软件和ArcMap10软件对石花洞洞穴开展了全面的调查和测绘。结果显示:(1) 石花洞洞穴系统整体呈北西西-南东东向展布,长度为5 639 m,洞底投影面积为37 096 m2,洞底高差为172 m,洞内最高点海拔约为265 m,最低点海拔约为93 m。洞穴系统的发育演化主要受地层产状与北东向和北西向两组断层控制;(2) 石花洞洞穴系统分为五层,自上而下,各层洞道平均海拔依次为249 m, 211 m, 154 m, 111 m和95 m;(3) 最底第五层季节性地下河洞道长1 638 m,自西北向东南方向贯穿整个洞穴系统,依干湿季水文条件的差别,地下水以季节性涨落为主要特征,有多段有水通道;地下河道下游末端为叉状河道,崩塌明显,洞壁上无明显流纹发育;(4) 综合石花洞地下河走向和流向、洞穴发育控制因素和区域地层产状特征、石花洞与周边洞穴的空间位置关系,推测孔水洞是石花洞洪水期的排泄口。      

Seasonal variation of fatty acids from drip water in Heshang Cave, central China

In order to investigate how lipids in cave water respond to seasonal climate change, drip water samples were collected from 2006 to 2008 in Heshang Cave, central China for fatty acid analysis. These lipids are abundant in the drip water. Their compositions are dominated by lower-molecular-weight nC16:0, nC18:0 and nC14:0 acids, together with mono-unsaturated nC18:1, nC16:1 and nC14:1. Analysis of one water sample revealed marked differences between the dissolved and particulate fractions. The dissolved fraction contains total fatty acids one order of magnitude higher than that of the particulate fraction. The distributional patterns of the fatty acids suggest that microbes living in the overlying soils and/or groundwater system contribute most fatty acids to the drip water. This 2-a monitoring experiment reveals that the abundance of mono-unsaturated fatty acids relative to the saturated homologues (nC16:1/nC16:0 and nC18:1/nC18:0) relate inversely to the changes of synchronous external air temperature. Higher values occur under cold conditions (winter/spring), while lower values appear in warm intervals (summer). Further studies are needed to elucidate the dynamic processes by which the external temperature affects fatty acids in drip water and to confirm the potential application of fatty acid ratios such as nC16:1/nC16:0 and nC18:1/nC18:0 in paleotemperature reconstructions.     

第四纪石笋剖面的初步建立——以北京石花洞为例

北京石花洞位于房山花岗岩体边缘向形带的东北扬起端,与北京猿人遗址南北相望,地层均为奥陶系马家沟组石灰岩.洞内石笋记录了中更新世以来北京西山古环境的变化,可以建立第四纪石笋剖面.钙板的铀系年龄为334.99~366.74 ka,定名钙板组(Qp2g).粗犷石笋的铀系年龄为169 ~ 235 ka,粗犷石笋的电子自旋共振年龄为130~518ka,属中更新世沉积,定名云水洞组(Qp2y).杆状石笋的铀系年龄为14.9±2.1 ~ 100.3±11.1 ka,属晚更新世沉积,定名石花洞组(Qp3sh).在全新世石笋中,微层与微层之间存在厚约1μm的条带状纹线,是划分微层层数的标志,具有微层理的石笋14C年龄为0.58~ 2.50 ka,定名守备支洞组(Qhsh).     

北京石花洞地质遗迹环境和地质灾害问题

通过北京石花洞地质遗迹保护区实地调查和有关资料分析,提出了保护区的环境问题和治理建议。     

The transfer of oxygen isotopic signals from precipitation to drip water and modern calcite on the seasonal time scale in Yongxing Cave,central China

Stable isotope data of precipitation (δ¹⁸O_p and deuterium excess), drip water (δ¹⁸O_d), and modern calcite precipitates (δ¹⁸O_c and δ¹³C_c) from Yongxing Cave, central China, are presented, with monthly sampling intervals from June 2013 to September 2016. Moderate correlations between the monthly variation of δ¹⁸O_p values (from ??11.5 to ??0.7‰) and precipitation amount (r = ??0.59, n?=?34, p?<?0.01) and deuterium excess (r?=?0.39, n?=?31, p?<?0.01) imply a combined effect of changes in precipitation amount and atmospheric circulation. At five drip sites, the δ¹⁸O_d values have a much smaller variability (from ??9.1 to ??7.5‰), without seasonal signals, probably a consequence of the mixing in the karst reservoir with a deep aquifer. The mean δ¹⁸O_d value (??8.4‰) for all drip waters is significantly more negative than the mean δ¹⁸O_p value (??6.9‰) weighted by precipitation amount, but close to the wet season (May to September) mean value (??8.3‰), suggesting that a threshold of precipitation amount must be exceeded to provide recharge. Calculation based on the equilibrium fractionation factor indicates that the δ¹⁸O_c values are not in isotopic equilibrium with their corresponding drip waters, with a range of disequilibrium effects from 0.4 to 1.4‰. The δ¹⁸O_c and δ¹³C_c values generally increase progressively away from the locus of precipitation on glass plates. The disequilibrium effects in the cave are likely caused by progressive calcite precipitation and CO₂ degassing related to a high gradient of CO₂ concentration between drip waters and cave air. Our study provides an important reference to interpret δ¹⁸O_c records from the monsoon region of China.     

北京石花洞空气环境主要因子季节性变化特征研究

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。     

Intra‐messinian gypsum palaeokarst in the Northern Apennines and its palaeogeographic implications

A short intra‐Messinian continental period has been recognised in some North Italian gypsum areas, mostly under the form of palaeokarst deposits. This emersion appears to have occurred only locally, and is explained as caused by the intra‐Messinian tectonic phase and a major sea level lowering. Evidences of this palaeokarst are mostly small, although at some places the palaeontological content of its fillings is of great importance. The discovery near Zola Predosa (Bologna) of a new intra‐Messinian extensive karst system and of its infilling sheds new light on the importance of this karst episode.     

Late Quaternary loess deposition in the southern Chaiwopu Basin of the northern Chinese Tian Shan foreland and its palaeoclimatic implications

The piedmont aeolian sediment in Central Asia is has been widely used for Quaternary palaeoclimatic reconstructions. Here we present detailed sedimentological and rock magnetic investigations on 188 samples from the ~9.4‐m‐thick Urumqi River section (URS) in the southern Chaiwopu Basin of the northern Chinese Tian Shan foreland. Optically stimulated luminescence (OSL) dating constrains the time‐span of the URS loess sedimentation from c. 28 to c. 6.8 ka. This chronology implies that the onset of the URS loess sedimentation is approximately synchronous with the Shangwangfeng Glaciation (MIS 2) in the headwaters of the Urumqi River. Analyses of sediment grain size and rock magnetic parameters indicate that sediment grain‐size composition controls magnetic properties of the URS loess, i.e. the wind intensity model, distinct from the pedogenic model interpreting the variations in magnetic properties of the loess in the Chinese Loess Plateau (CLP). Overall, the variations in sediment grain size and magnetic properties throughout the URS indicate that the present study area was dominated by a climate of strengthened wind associated with gradually intensified aridity during the latest Pleistocene. In contrast, the intensity of aridity and coldness during the early Holocene gradually became relatively weakened.     

芙蓉洞洞穴水离子浓度和元素比值变化特征及其环境意义

通过对芙蓉洞2006年3月—2009年2月期间泉水和洞穴滴水、池水的地球化学指标监测,结合当地的器测数据,初步认为洞穴滴水的Sr2+、Ca2+、Mg2+浓度及其比值既取决于环境降水和温度的变化,也受到上覆岩土作用的影响。芙蓉洞外山上的6#泉水Ca2+平均浓度为45.81mg/L,洞内1#、3#滴水Ca2+的平均浓度64.59mg/L,2#和4#池水中由于Ca2+沉积,浓度下降到24.74mg/L,下降了大约61.7%。Mg2+和Sr2+的浓度在泉水、滴水和池水中的变化规律与Ca2+基本一致。各种水体中Cl-的浓度变化幅度较小,平均浓度为1.72±0.2mg/L。岩溶水与基岩作用时间长短以及运移过程中Ca2+的前期沉积作用对各元素与离子含量变化具有重要作用。旱季Ca2+的前期沉积作用和雨季基岩的溶蚀及雨水的稀释作用主导着岩溶水中Mg/Ca与Sr/Ca的变化,这些指标能对干旱和洪涝等极端气候事件做出响应。      

Late Quaternary linear dune accumulation and chronostratigraphy of the southwestern Kalahari: implications for aeolian palaeoclimatic reconstructions and predictions of future dynamics

The linear dunes of the Kalahari, now largely inactive, have long been identified as having potential palaeoenvironmental significance. The application of optically stimulated luminescence (OSL) dating to these dunes in the 1990s provided the first chronology of aeolian accumulation in this region, though field methodologies and time-consuming multiple-aliquot laboratory protocols limited both the depth of sampling in dune bodies and the total number of samples dated.In order to permit a more thorough investigation of the potential of these dunes to preserve long chronological records, this intensive study presents 71 OSL ages from the linear dunes of the southwestern Kalahari at Witpan, South Africa, sampled with coring equipment at regular and frequent intervals down to bedrock.The earliest sand accumulation recorded at Witpan is at 104 ka, and in spatially discrete locations, other evidence of dune activity is recorded at 77–76, 57–52 and 35–27 ka. Although an inherently discontinuous archive, the linear dunes of the southwestern Kalahari have the potential to record multiple phases of dune construction. Following the Last Glacial Maximum there is near continuous evidence of dune-building, with a peak of accumulation recorded from 15 to 9 ka at five individual sites. This latter period is generally recognised from other proxy evidence as being unusually arid in this region, and such periods of dune activity are likely to be related to intensification of the continental anticyclone. During the Holocene, accumulation has continued at most sites sampled, albeit at a lesser intensity. This may imply that these dunes are presently not far from thresholds of activation.     

Influences of air CO<Subscript>2</Subscript> on hydrochemistry of drip water and implications for paleoclimate study in a stream-developed cave,SW China

Cave air CO₂ is a vital part of the cave environment. Most studies about cave air CO₂ variations are performed in caves with no streams; there are few studies to date regarding the relationship of cave air CO₂ variations and drip water hydrochemistry in underground stream–developed caves. To study the relationship of underground stream, drip water, and cave air CO₂, monthly and daily monitoring of air CO₂ and of underground stream and drip water was performed in Xueyu Cave from 2012 to 2013. The results revealed that there was marked seasonal variation of air CO₂ and stream hydrochemistry in the cave. Daily variations of cave air CO₂, and of stream and drip water hydrochemistry, were notable during continuous monitoring. A dilution effect was observed by analyzing hydrochemical variations in underground stream and drip water after rainfall. High cave air CO₂ along with low pH and low δ¹³C_DIC in stream and drip water indicated that air CO₂ was one of the dominant factors controlling stream and drip water hydrochemistry on a daily scale. On a seasonal scale, stream flows may promote increased cave air CO₂ in summer; in turn, the higher cave air CO₂ could inhibit degassing of drip water and make calcite δ¹³C more negative. Variation of calcite δ¹³C (precipitated from drip water) was in reverse of monthly temperature, soil CO₂, and cave air CO₂. Therefore, calcite δ¹³C in Xueyu Cave could be used to determine monthly changes outside the cave. However, considering the different precipitation rate of sediment in different seasons, it was difficult to use stalagmites to reconstruct environmental change on a seasonal scale.     

Aeolian origin and palaeoclimatic implications of the ‘red clay’ (north China) as evidenced by grain‐size distribution

The ‘Red Clay’ is an important deposit underlying the Quaternary loess–palaeosol sequence in the Chinese Loess Plateau, being regarded as an excellent record of palaeoclimate changes in the late Tertiary. Several properties of the ‘Red Clay’ have been measured previously in order to derive climatic information. However, the sedimentary processes involved and the origin of the materials remain controversial. Here we present results of grain‐size analyses of the ‘Red Clay’ from four representative sites in the Chinese Loess Plateau. In particular their grain‐size distribution is compared with that of typical Quaternary aeolian loess–palaeosol, as well as lacustrine and fluvial sediments. It appears from the sedimentological evidence that the major part of the ‘Red Clay’ is of aeolian origin. It is rather similar in some of its properties to the Quaternary loessic palaeosols. The dust forming the ‘Red Clay’ was transported by a wind system that was weaker than that involved in the accretion of the Quaternary loess. Furthermore, the ‘Red Clay’ sediment has been modified by post‐depositional weathering. Copyright © 2001 John Wiley & Sons, Ltd.     

Relationship between the variation of water quality in rivers and the characteristics of watershed at Miyun,Beijing, China

Based on the characteristics of land use and drainage network of the upper watershed of the Miyun Res-ervoir, Beijing, 26 monitoring and sampling sites were selected in different sub-catchments. Temporal and spatial variations in nutrient loss were dealt with in this paper in terms of the monitoring data on the water quality of the main tributaries flowing into the Miyun Reservoir. In combination with the monitoring data on water quality, the impacts of watershed characteristics including land-use type, landscape pattern, and drainage density were assessed, The concentrations of nutrients in the rainy season are higher than those in other seasons, and the concentrations of NO3--N are linearly related to those of total N which is the main form of nitrogen present in the fiver water. The concentrations of nitrogen become higher toward the reservoir along the main rivers. The seasonal variation of ni-trogen in the watershed affected by intensive human activities is very obvious; in the watershed with steady or low water flow, the seasonal variation of nitrogen is less obvious. Forest land and grassland can trap and filter nitrogen effectively. Land-use pattern also has important impacts on the loss of nitrogen. The concentrations of nitrogen and phosphorus in the water bodies show great temporal and spatial variations. On a temporal scale, the concentrations of TN and TP in the rainy reason are higher than those in other seasons. On a spatial scale, the concentrations of TN and NO3--N in the Qingshui River and Chaohe River are highest all the time. The spatial variation of TP is distinct, being obvious at sampling sites near villages. The form of nitrogen and phosphorus loss varies in different hydrological seasons. Dissolved nitrogen and phosphorus are the main forms in streams in non-rainy seasons, the dissolved nitro-gen and total nitrogen decrease in percentage in the rainy season. Particulate nitrogen and phosphorus are the main forms in some rivers. The concentrations of TN and NO3--N from orchards and villages are high whereas those from forest land are lowest. Land-use pattern has impacts on TN and NO3--N losses, at the sampling sites near the source landscape, the concentrations are higher than those at the sampling sites near the sink landscape. Water quality of the rivers which flow into the Miyuan Reservior is influenced by the composition of adjacent soils.     

Nature and origin of the J‐magnetic anomaly offshore Iberia–Newfoundland: implications for plate reconstructions

The nature and origin of the J‐magnetic anomaly along the Iberia–Newfoundland margins are controversial and its validity for plate kinematic reconstructions questioned. At present, it is interpreted as either an oceanic isochron or an edge effect of oceanic crust corresponding to lithosphere breakup. Both interpretations result in restorations that are in conflict with the current knowledge from Pyrenean and North Atlantic geology. We combine seismic interpretations and dating of magmatic additions with magnetic data to examine the nature and formation process of this anomaly and discuss its value for plate restorations. We show that the J‐anomaly is the result of polygenic and multiple magmatic events occurring during and after the formation of the first oceanic crust. Therefore, we conclude that the J‐anomaly cannot be used for plate kinematic studies and, more generally, we question the validity of using ill‐defined magnetic anomalies outside unequivocal oceanic domains for plate reconstructions.     

北京密云环斑花岗岩的锆石SHRIMP U-Pb 年龄及其构造意义

密云环斑花岗岩与华北克拉通的破坏、燕辽裂谷的启动同期,其年代学研究一直令人关注,已获得的一些数据虽然具有参考意义,但缺乏高质量的SHRIMP定年的制约.利用西澳大利亚科庭大学离子探针中心进行远程测试,首次在该花岗岩体中获得锆石SHRIMP U-Pb加权平均年龄1685Ma±15Ma.这一年龄表明燕辽裂谷最早启动于1700Ma,为准确地标定长城系底界的年龄提供了重要的参考依据.     

Assessing cave internal aerology in understanding carbon dioxide (CO<Subscript>2</Subscript>) dynamics: implications on calcite mass variation on the wall of Lascaux Cave (France)

Carbon dioxide gas is a key component in dissolution and precipitation of carbonates in karst and cave systems. Therefore, characterizing the internal aerology of a cave is essential to obtain the spatiotemporal distribution of temperature and CO₂ level. In this research, Lascaux Cave (France), an important adorned cavity, was studied. First, the spatiotemporal distribution of CO₂ and temperatures were examined using continuous monitoring at a per minute basis. High-resolution spatial measurements (14 PCO₂ locations and 27 locations for temperature) were carried out for a year in the epikarst and the cave (February 2015 to February 2016). The spatiotemporal analysis presents that air and rock temperatures vary for less than a degree Celsius (12.4–12.9 °C). These are controlled by the conduction of the external thermal waves through the overlying calcarenite massif. As a consequence, two seasonal internal aerologic regimes were identified: stratification and convection. These regimes govern the spatiotemporal distribution of the CO₂ levels (1.1–3.7%), showing that this parameter is a good natural marker of the internal air movements. Second, a method was proposed to estimate the calcite mass potentially affected by condensation water (dissolution process) and exfiltration water (precipitation process). This method, based on numerical simulations, relies on CO₂ and air and rock temperature spatiotemporal distributions in the cave. Third, the method was applied using the case of the left wall of the Hall of the Bulls (one of the most adorned part of the cave). Results showed that the calcite mass, possibly dissolved, varies from 0.0002 to 0.006 g when the mass potentially precipitated is higher (from 0.013 to 0.067 g) depending on the aerologic conditions. This method allows determining which alteration process (e.g., precipitation or dissolution) could eventually lead to the largest variation of calcite on the wall. The results can serve as useful data to the cave experts of the French Ministry of Culture and Communication in terms of Lascaux Cave management policies.     

Cyclic nature of lamination in the Tithonian Solnhofen Plattenkalk of southern Germany and its palaeoclimatic implications

In the Tithonian Solnhofen Plattenkalk (Malm + 2) of southern Germany, layers of purely micritic limestone are rhythmically interbedded with ones of marly micritic limestone. It appears that this alternation was formed under control of the Tithonian orbital variations. The Fourier spectral analysis shows that, on a decimetric to metric scale, the long-term cyclicities in the number of laminae per centimetre are in agreement with those found in the bed-thickness series, varying from 0.7 to 1.3 m cycles. The number of laminae of the Solnhofen Formation ranges from about 5,800 to about 12,800 laminae per main cycle. This indicates that, under an assumption that the main cycle of the Solnhofen Formation corresponds to the Tithonian precessional one, a single lamina represents a multi-year time interval. Particularly, in the short-term cyclic domain, the laminated sequence contains clearly millimetric cycles consisting of about two to three cyclic components. It implies that laminae formation may result from the composite effect of two or three distinct climatic processes.     

北京西山侏罗纪盆地演化及其构造意义

沉积盆地的形貌、充填及变受区域大地构造的影响和控制。北京西山株罗纪盆地是在三叠末开阔谷地的基础上发展起来的。三叠纪末或早株罗世初,开阔的谷底沉积了山间河流相的杏石口组。早侏罗世中期,盆地被溢流和喷发的南大岭组玄武安山岩充填。北京西山株罗纪盆地早期沉积是恢复其原型盆地的重要依据。中株罗世早期是全区重要的成煤期,下窑坡组为湖泊－三角洲及沼泽相。中株罗世中期,北京西山盆地逐渐封闭,上窑坡组上部沉积已经在宁静中孕育着风暴。中株罗世中－晚期,燕山运动主幕强烈爆发,盆地在接受了龙门组粗碎屑快速充填后,开始在九龙山期分化,盆地沉积中心向北迁移,在晚株罗世期间消亡。北京西山株罗纪盆地的演化及其变形的动力学背景与西伯利亚地块和华北地块在中－晚株罗世的碰撞拼合密切相关。