泰安市岩溶塌陷特征及探测方法研究

泰安市岩溶塌陷点主要集中在城区水源地与旧县水源地,对当地居民生产生活造成严重影响,急需查明已知塌陷点范围及隐伏溶洞位置,进行针对性治理。本文通过应用地质雷达、高密度电法与浅层地震,对已知土洞、隐伏溶洞及已知塌陷点进行探测,对东羊娄村与羊西村探测异常进行钻探验证,结果吻合较好。经分析研究认为:地质雷达能较好地分辨浅部土洞的位置;浅层地震探测深度较大,可以较准确地分辨覆盖层厚度与隐伏溶洞的空间位置,但对浅层土洞的分辨率较低;浅层土洞与隐伏溶洞在高密度电法电阻率断面图上有明显的反映,其分辨率不如地质雷达与浅层地震。根据不同物探方法的优点,结合研究区地质情况,提出了综合物探方法探测隐伏岩溶的最优化方案,以供参考。     

基于无人机航摄影像的喀斯特地区裸岩信息提取及景观格局分析

喀斯特地区不同石漠化等级的结构和格局是实现区域石漠化治理的重要基础信息,受技术手段的限制,目前这方面的研究进展仍非常缓慢。随着无人机技术的快速发展,高精度的地表信息获取越来越方便、且成本较低。本研究利用无人机影像,对比了基于像元的非监督和监督分类方法以及面向对象的分类方法在裸岩信息提取中的表现,发现面向对象分类结果具有更高精度。基于获得的裸岩分布信息的研究结果表明：① 岩石平均斑块面积与裸岩率呈负相关的关系,岩石斑块个数与裸岩率呈正相关关系;② 通过对比不同裸岩率（11%、20%、29%和48%）基质的景观斑块指数、景观形状指数和景观破碎度指数对不同裸岩率的景观分布的影响,从而表明了在不同的石漠化地区随着裸岩率的增加,岩石形状指数与岩石破碎度指数均逐渐增加,进而表明石漠化程度越严重;③ 裸岩率不同的地区表现不同的分布形态和斑块特征,裸岩率越高,岩石越破碎,斑块分布较为分散。小尺度斑块景观格局与区域的生态过程有着重要关系,开展小尺度景观格局的研究会深化区域尺度石漠化发展过程的理解。石漠化地区的小尺度斑块景观格局变化影响区域的生态过程,对以后的石漠化过程以及未来石漠化演变的发展有重要的启示作用。     

An inland facies-controlled eogenetic karst of the carbonate reservoir in the Middle Permian Maokou Formation,southern Sichuan Basin,SW China

Carbonate karst is one of the research highlights in the field of carbonate reservoir geology. Here, we report on a new type of karst formed in the Middle Permian Maokou Formation, southern Sichuan Basin, SW China, i.e., inland facies-controlled eogenetic karst, which is different from the previously defined telogenetic karst. This karst is eogenetic as the formation was buried at shallow depths prior to being subaerially exposed for a period of 7–8 Myr, in the paleo-continental region of the Upper Yangtze Uplift. Subaerial exposure may have been caused by a sea level regression during the Tungwu Orogeny, which gave rise to a depositional hiatus over a broad area. The top of the Maokou Formation is commonly marked by a weathered crust and an unconformable relationship with overlying layers. Below the surface, the Maokou Formation contains sediments deposited by an underground drainage. The geological setting can be inferred from an inland karst far from coastline. The subsurface karst interval consists mainly of coarse-grained limestone and micrite, with the former occurring in shoal facies deposited in a high-energy depositional environment, and the latter in non-shoal facies deposited in a low-energy environment. Both of them were interbedded with in variable thicknesses. The coarse-grained limestone layers with high porosity and permeability acted as inception horizons, more favourable for the development of karst than the micritic layers with low porosity and permeability. Therefore, in places where both coarse-grained limestone and micrite are present, the karst is considered to be facies-controlled. The primary permeability of the coarse-grained limestone, combined with the permeability provided by faults and fractures, provides sufficient channels for karst water. Formation of the karst system was characterized by contemporaneous development at multiple levels, as controlled by the stratigraphic position of coarse-grained shoal facies. The karst reservoir therefore developed in both karst highland and karst transitional zone (area between the karst highland and karst basin). According to this model of karstification, hydrocarbon exploration should focus on karst highlands located on palaeohighs and in synclines located far from fault zones.     

Impact of water source dynamics on dissolved reactive phosphorus loadings in heterogenous karst agroecosystems with phosphatic limestones

Karst landscapes underlain with phosphatic limestones are now recognized to be an important contributor of fluvial phosphorus (P) to coastal waters. Specifically, karst agroecosystems may be a hotspot for dissolved reactive P (DRP) due to chronic over-application of organic and inorganic fertilizers that create legacy P accumulation in surface soils. Nevertheless, few studies have assessed the hydrologic controls on DRP transport in these systems at the watershed scale, which is the focus of this study. We analysed soil moisture, soil water extractable P, and storm event hydrologic and water quality data from a small heterogenous karst watershed (10.7 km²) in the Inner-Bluegrass Region of Central Kentucky, USA. Four storm events were sampled in winter, 2020 and were analysed for flow pathways using hydrograph recession analysis and water source connectivity using a tracer-based unmixing model. Based on hydrograph separation results, multiple linear regression analysis was performed to assess drivers of DRP concentrations and loadings. Soil water extractable P results showed stark vertical gradients with greater concentrations at both the surface and deeper soil zones, and minimum concentrations in the root zone. Results for the storm event analysis showed that water source connectivity provided superior prediction of DRP concentrations over the flow pathway analysis, which reflected the heterogeneity of karst maturity masking intermediate flow pathways. Findings from the MLR and loading analysis suggest waters sourced from the soil/epikarst produced significantly higher loadings compared with phreatic and precipitation water source in the three largest events, although concentrations fell between the phreatic (low) and precipitation (high) sources. Findings highlight variable activation of matrix-macropore exchange at different depths throughout the event. Collectively these results suggest existing models and approaches to assess karst hydrology need revision to improve management strategies in this critical landscape.     

Anomalous drip in the Punkva caves (Moravian Karst): relevant implications for paleoclimatic proxies

The anomalous drip in the Punkva caves (Moravian Karst) shows specific hydrogeochemical properties such as low SI_calcite ~ 0.14 ± 0.11 (standard deviation), low mineralization (4.53 ± 0.42) × 10^?3 mol l^?1, and enhanced values of δ¹³C (?7.85 to ?8.35‰ VPDB), Mg/Ca × 1000 ratio (45.7 ± 3.3), and Sr/Ca × 1000 ratio (0.65 ± 0.06). By these properties, the anomalous drip significantly differs from other regular drips in the same cave and other caves in the region. The study suggests that the anomalous drip properties are a consequence of prior calcite precipitation or/and water mixing along the water flow path. As the former processes are spatially controlled, the knowledge of dripwater flow path seems to be necessary for correct paleoclimatic/paleoenvironmental reconstructions. Copyright © 2015 John Wiley & Sons, Ltd.     

Time series and stochastic analyses to study the hydrodynamic characteristics of karstic aquifers

The regional study of hydrodynamic characteristics of karstic aquifers is challenging because of the great variety of lithology and the structural complexity found in carbonate formations. In order to improve this situation, a combined approach of time series and stochastic analyses was adopted to assess the hydrodynamic behaviour of the karstic aquifers. To achieve this, daily flow rates of 20 springs were taken from the 11 most significant aquifer units of the Basque Country. The results demonstrate the presence of memory effects, which modulated the input rainfall for short‐, medium‐ and long‐term storage capacity, resulting in hydrodynamic properties such as system memory, response time and mean delay between input and output. They reflect the storage and the manner in which these are filled and emptied, thus indicating the karstification of the aquifer. Likewise, the hydrodynamic and hydraulic classification obtained from the stochastic analysis provides a complementary approach to characterize the hydraulic behaviour of the studied karstic aquifers. The discussed examples indicate that this approach provides an excellent method to research hydrological karst systems. It is also shown that the use of hydrologic time series, alone, does not lead to a satisfactory classification of the hydrodynamic characteristics. Therefore, the general approach to hydrological regionalization in karst areas should take into account the structural complexity, heterogeneity of the lithology and the degree of karstification. Only in this case will the regionalization be physically founded, leading to a regional understanding of the hydrodynamic characteristics and flow conditions in a karst aquifer. Copyright © 2009 John Wiley & Sons, Ltd.     

Application of multivariate analysis to suspended matter particle size distribution in a karst aquifer

Numerous quantitative and qualitative variables control suspended sediment dynamics in karst systems. The objective of this study was to identify the hydrodynamic variables controlling the transport properties of particles in a karst aquifer (western Paris basin). The particle size distribution of suspended sediment infiltrating via a swallow hole was compared to that in discharge from a spring, allowing identification of the particle transport properties of the karst system. Hill and Smith analysis, a type of multivariate analysis that allows joint examination of quantitative and qualitative variables, was used to identify the hydrodynamic parameters controlling the transport properties of the suspended matter. The results demonstrate that the particle size distribution discharging at the karst spring is controlled by spring discharge and the hydraulic gradient of the system. The hydraulic gradient is defined by the piezometric level and the stage of the Seine River, which is in turn controlled by the tide. This study illustrates the use of Hill and Smith analysis to identify those variables which control suspended sediment transport. It also illustrates the application of this analysis to identify boundary conditions and evaluate variables which control the behaviour of the hydrologic system. Copyright © 2007 John Wiley & Sons, Ltd.     

西南岩溶区生态地质环境特点及其重建策略

西南岩溶区生态地质环境具有水热充沛、矿产和旅游资源丰富,但存在地上地下双层岩溶空间结构和山高水深、地形陡峻、土壤贫瘠等两重性的特点,在人为活动的干扰影响下很容易导致生态退化,产生水土流失和石漠化等生态环境问题。本文在充分论述了西南岩溶区生态地质环境的这种特点的基础上,通过生态系统退化过程的机理分析,提出了岩溶生态系统退化是脆弱的岩溶生态地质环境和人类活动共同作用的结果的成因观点,以及以将人为活动限制在岩溶生态系统环境承载允许的范围之内作为前提条件,并辅以因地制宜开发水资源、合理利用土地资源、发展立体化生态农业、挖掘地方经济增长潜力、改善农村能源结构及生态移民等工程措施的生态系统恢复重建策略。      

贵州岩溶区镶嵌景观上覆土层的粒度分布特征及其指示意义

通过对贵州岩溶区喀斯特镶嵌景观中碳酸盐岩与碎屑岩相互接触部位剖面的粒度分布特征综合对比、分析研究,结果表明:不同岩石上覆土层之间的粒度频率曲线和粒度参数存在明显的差异,仅在两种岩石类型的接触过渡带显示出一定混合特征,且与区域其它岩类上覆土层没有关联性;各土层粒度分布特征与下伏基岩有着密切的联系,显示出继承性。同时,进一步肯定了粒度分布特征在贵州岩溶区上覆土层的物源指示意义。      

Influence of partial confinement and Holocene river formation on groundwater flow and dissolution in the Florida carbonate platform

Much of what is known about groundwater circulation and geochemical evolution in carbonate platforms is based on platforms that are fully confined or unconfined. Much less is known about groundwater flow paths and geochemical evolution in partially confined platforms, particularly those supporting surface water. In north‐central Florida, sea level rise and a transition to a wetter climate during the Holocene formed rivers in unconfined portions of the Florida carbonate platform. Focusing on data from the Santa Fe River basin, we show river formation has led to important differences in the hydrological and geochemical evolution of the Santa Fe River basin relative to fully confined or unconfined platforms. Runoff from the siliciclastic confining layer drove river incision and created topographic relief, reorienting the termination of local and regional groundwater flow paths from the coast to the rivers in unconfined portions of the platform. The most chemically evolved groundwater occurs at the end of the longest and deepest flow paths, which discharge near the center of the platform because of incision of the Santa Fe River at the edge of the confining unit. This pattern of discharge of mineralized water differs from fully confined or unconfined platforms where discharge of the most mineralized water occurs at the coast. Mineralized water flowing into the Santa Fe River is diluted by less evolved water derived from shorter, shallower flow paths that discharge to the river downstream. Formation of rivers shortens flow path lengths, thereby decreasing groundwater residence times and allowing freshwater to discharge more quickly to the oceans in the newly formed rivers than in platforms that lack rivers. Similar dynamic changes to groundwater systems should be expected to occur in the future as climate change and sea level rise develop surface water on other carbonate platforms and low lying coastal aquifer systems. Copyright © 2012 John Wiley & Sons, Ltd.