武夷山南段前寒武纪浅变质岩系的划分与时代     

张利民 《地层学杂志》1996,20(1):16-22

武夷山南段前寒武纪地层分布较广。从下至上分为楼子坝群、丁屋岭组、南岩组和黄连组。过去因缺乏可靠的微古植物化石证据和同位素地质年龄资料,对其时代归属分歧颇大。为此,作者对该区的前寒武系进行了系统的微古植物取样、分析,参考最近的Nd同位素模式年龄资料,认为:楼子坝群为前震旦系,大致相当于蓟县系与青白口系;丁屋岭组为下震旦统;南岩组和黄连组为上震旦统;江西东南部的"下寒武统炭质板岩"应归入老虎塘组,属上震旦统。  相似文献   

上扬子区(四川盆地)寒武系的含盐性与地质背景          下载免费PDF全文

黄建国 《沉积与特提斯地质》1993,(5):44-56

据记载,分布于上扬子区寒武系的石膏岩仅有零星资料。如今,大量蒸发岩如溶蚀角砾岩、硬石膏、石盐岩及富钾卤水等已被发现。沉积相经历了从盆地相、台地相到蒸发岩相的演化过程。在中、下寒武统中找到海退沉积序列。古构造-古地理背景是蒸发岩沉积的重要控矿条件之一。周边板块运动及塑性基底的褶皱,导致台缘隆起及台内坳陷的形成。岩相古地理图展示从碳酸盐、硫酸盐到氯化物盐类的“泪滴式”沉积相带。蒸发岩沉积于台缘隆起及礁生长进入堰塞潟湖至盐湖阶段。在稳定坳陷区沉积盆地中蒸发岩系发育;石盐岩较厚,其溴氯比值为0.2—0.4;古气候炎热、干燥;在蒸发岩体周围有沉积(封层)水及溶滤水,其含钾(K~+)量为0.10—4.76g/L;水文地球化学比值(如钾氯比值、钾盐比值及钾溴比值等)指示含钾异常;盐湖浓缩卤水达到氯化物盐类沉积阶段及相应的构造封闭程度;含盐地质标志广泛分布等等。鉴于上述,估计该区可能具备钾盐成矿条件。然而目的层埋藏太深,因此笔者建议,应在浅埋部位进行有效的成矿预测,为普查指出远景区。  相似文献   

钻孔灌注桩施工对邻近运营隧道变形影响研究     

周志良  仇欢  黄晓东  杜平  杨平  吕伟华 《岩土工程技术》2021,(1)

桩基施工将引起周边地层位移和邻近隧道结构变形,以南京龙津桥改建项目桩基工程为背景,通过现场实测,分析研究钻孔灌注桩施工全过程各工况条件对地层位移场和邻近既有隧道结构变形的影响规律。结果表明:由于钢套管的护壁作用,钻孔灌注桩施工过程中产生的最大地层位移和隧道结构变形较小,说明采用“钢套管边旋压边取土”、“群桩间跳施工”等工艺,对周围土体扰动影响程度较小,建议近隧桩基工程采用全套管灌注桩的施工方法,监测分析结果可为类似工程提供技术参考。  相似文献   

Real Time Analysis and Forecasting of Strata Caving Behaviour during Longwall Operations     

S. Tadisetty  K. Matsui  H. Shimada  R. N. Gupta 《Rock Mechanics and Rock Engineering》2006,39(4):383-393

Summary. Discontinuous manual observations and irregular caving characteristics of roof rocks often lead to improper decisions resulting in accidents and production loss. Hence, systematic monitoring of the hanging roof behind the chock shields is necessary for safe and productive mining operations. A real-time application was successfully implemented in an Indian mine for forecasting of hanging roof behaviour to enhance safety and productivity. This paper reports the functioning of real-time TWAP (time weighted average pressure) analysis in the forecasting of hanging roof behaviour in real time.  相似文献   

Lake-Level Fluctuations and Small-Scale Vegetation Patterns During the Late Glacial in The Netherlands     

Johanna A. A. Bos  Sjoerd J. P. Bohncke  C. Roel Janssen 《Journal of Paleolimnology》2006,35(2):211-238

Late glacial changes in the vegetation were studied in and around a former lake on the southeastern side of a coversand ridge near Milheeze (southern Netherlands). Analyses of microfossils and macroremains and AMS ¹⁴C dating were performed on four sediment cores along a transect from sand ridge to the lake centre. Small-scale vegetation patterns and lake-level fluctuations were reconstructed in detail based on the information provided by the transect. For the first time in The Netherlands, cores along a transect within one lake were used to reconstruct the amplitude of late glacial lake-level fluctuations. Near Milheeze, a small and shallow lake was formed during the Bølling. The large increase in the water level during the Bølling and early Allerød, and the transition to more eutrophic conditions at the start of the Allerød, were probably related to the disappearance of permafrost. During the Allerød, open birch and pine woodlands developed in the area. In the lake, organic deposits accumulated, and the lake size and depth fluctuated. At the start of the Younger Dryas, higher lake water levels were recorded and woodlands became more open as a result of both a drop in the temperature and an increase in the effective precipitation. During the late Younger Dryas the lake water level dropped as the climate became drier and temperatures slightly increased. Accumulation of organic deposits in the lake ceased at the end of the Younger Dryas, which was caused by a drop in the water level in combination with the hydroseral succession process within the lake itself. The climatic signal reflected in the late glacial flora and lake-level fluctuations agree well with other published data from The Netherlands.  相似文献   

Effects of mode coupling and location of rotational axis on glacial induced rotational deformation in a laterally heterogeneous viscoelastic earth     

Patrick Wu  Hansheng Wang 《Geophysical Journal International》2006,167(2):853-859

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Evidence of reworking and resuspension of carbonates during last glacial maximum and early deglacial period along the southwest coast of India     

Kamlesh Verma  M Sudhakar 《Journal of Earth System Science》2006,115(6):695-702

A gravity core collected from the upper slope of southwest of Quilon at a water depth of 776 m (Lat: 8°12′263″N, Long: 76°28′281″E) was analysed for texture (carbonate free), calcium carbonate and organic carbon. Variation in silicic fraction seems to be controlled by silt, i.e., enrichment from 15 ka BP to 10 ka BP and then constant in Holocene. Below 15 ka BP, the silicic fraction gets depleted compared to the Holocene section with a minimum around 21 ka BP. Clay content remains nearly constant except in the Holocene where it shows an enrichment. Carbonate content of less than 63 micron when computed by subtracting coarse fraction content from the total carbonate suggests that the total carbonates are mainly concentrated in the finer fraction. All these carbonate phases show an inverse relationship with silicic fraction except in Holocene. Below 15 ka BP, CaCO₃ dominates in sediments comprising more than 65%, such an increase is also seen in the coarse fraction. Coarse fraction from these sections contains abundant nodular type aggregates encrusting small forams. This period is marked by a high sedimentation rate comparable to Holocene. These parameters suggest that the productivity and precipitation have increased in the Holocene due to the intensification of the southwest monsoon. During the last glacial maximum and early deglacial period the high sedimentation rate indicates redeposition of the carbonates from the existing carbonate lithofacies situated between Quilon and Cape Comorin probably due to the slope instability.  相似文献   

致密砂岩孔隙度计算方法     

董建刚  范晓敏 《吉林大学学报(地球科学版)》2006,(Z1)

鄂尔多斯盆地北部下二叠系下石盒子组为纵横向变化大,岩性、孔隙结构等复杂的河流相地层,很难用统一的计算公式来完成对孔隙度的计算。采用多元统计分析、散点图和孔隙度对比图来确定其孔隙度。运用上述方法,比较精确地确定鄂尔多斯盆地北部下二叠系下石盒子组的孔隙度,对鄂尔多斯盆地油气储量的估计,提供一个很好的基础资料。  相似文献   

青藏高原唐古拉山口第四纪冰碛层划分及其地质环境意义   总被引：4，自引：1，他引：4       下载免费PDF全文

段志明  李勇  李亚林  张毅王谋 《中国地质》2005,32(1):128-134

在对唐古拉山口现代冰川和古冰川考察研究的基础上，结合定位观测资料和TL、^10B-^26Al-^21Ne及^14C测年数据，对区内第四纪冰川遗迹进行了深入讨论，划分出二次冰期(即中更新世晚期的倒数第二次冰期、晚更新世中一晚期的末次冰期)和二次全新世冰进(即新冰期和小冰期)。提出在早更新世时，由于山体未达到当时冰川发育的雪线高度，所以未发育冰川。但在唐古拉山口地区，截止目前还未找到中更新世早期的倒数第三次冰期的冰川遗迹，由于高原隆升的滞后性和冰川发育的延滞效应及“亚洲干极”的耦合，推测仍只发育局部冰川作用。进一步研究表明，古今雪线由高原边缘向腹地升高，唐古拉山地区高出边缘1500m左右，生动表现了“亚洲干极”的作用；广泛分布的湖群说明羌塘地区是一个大江大河尚未伸入的内流地区，意味着青藏高原是个年青的高原。由于青藏高原的隆升，对高原腹地引起的干旱化过程和水分严重不足，使唐古拉山地区的冰川自倒数第二次冰期以来，冰川规模一次比一次明显地减小。  相似文献   

淄博市洪山、寨里煤矿地下水串层污染形成原因及防治     

吕华刘洪量  马振民徐品 《中国煤田地质》2005,17(4):24-27,31

淄博市洪山、寨里煤矿区隐伏的奥陶系灰岩裂隙岩溶水污染严重。水质污染突发于矿坑全面闭坑以后，污染范围与矿坑水区一致，地下水污染组份与矿坑水的高含量组份相同。水质恶化主要由矿坑水串层污染所致。在此针对串层污染形成原因及影响因素，提出了防治对策。  相似文献