Platform margins, reef facies, and microbial carbonates; a comparison of Devonian reef complexes in the Canning Basin, Western Australia, and the Guilin region, South China     

Jian-Wei Shen  Gregory E. Webb  John S. Jell 《Earth》2008,88(1-2):33-59

Devonian reef complexes were well developed in Western Australia and South China, but no detailed direct comparison has been made between reef building in the two regions. The regions differ in several respects, including tectonic, stratigraphic and palaeoceanographic–palaeogeographic settings, and the reef building styles reflect minor differences in reef builders and reef facies. Similarities and differences between the two reef complexes provide insights into the characteristics of platform margins, reef facies and microbial carbonates of both regions. Here we present a comparison of platform margin types from different stratigraphic positions in the Late Devonian reef complex of the Canning Basin, Western Australia and Middle and Late Devonian margin to marginal slope successions in Guilin, South China. Comparisons are integrated into a review of the reefal stratigraphy of both regions. Reef facies, reef complex architecture, temporal reef builder associations, 2nd order stratigraphy and platform cyclicity in the two regions were generally similar where the successions overlap temporally. However, carbonate deposition began earlier in South China. Carbonate complexes were also more widespread in South China and represent a thicker succession overall. Platforms in the Canning Basin grew directly on Precambrian crystalline basement or early Palaeozoic sedimentary rocks, but in South China, carbonate complexes developed conformably on older Devonian siliciclastic strata. Pre-Frasnian reef facies in South China had more abundant skeletal frameworks than in Canning Basin reefs of equivalent age, and Famennian shoaling margins containing various microbial reefs may have been more common and probably more diverse in South China. However, Late Devonian platform margin types have been documented more completely in the Canning Basin. Deep intra-platform troughs (deep depressions containing non-carbonate pelagic sediments — Nandan-type successions) that developed along syndepositional faults characterize Devonian carbonate platforms in South China, but have no equivalent on the Lennard Shelf, Canning Basin where inter-reef areas were more shallow. The South China platform-to-depression pattern was generally continuous from the Lower to Upper Devonian, indicating that many pre-Devonian tectonic features continued to exercise considerable effect through deposition. Localized, fault-controlled subsidence was an important factor in both regions, but similarities in 2nd order aggradation–progradation cycles suggest that eustasy was also an important control on the larger scale stratigraphic development of both regions.  相似文献   

Daytime deposition and nighttime dissolution of calcium carbonate controlled by submerged plants in a karst spring-fed pool: insights from high time-resolution monitoring of physico-chemistry of water   总被引：6，自引：0，他引：6  

Zaihua Liu  Xiangling Liu  Changjun Liao 《Environmental Geology》2008,55(6):1159-1168

Water temperature, dissolved oxygen (DO), pH, and specific conductivity (spc) were measured in a time interval of 15 min in a karst spring and the spring-fed pool with flourishing submerged plants in Guilin, SW China under dry weather for periods of 2 days. Measurements allowed calculation of calcium and bicarbonate concentrations ([Ca²⁺] and [HCO₃ ⁻]), and thus CO₂ partial pressure ( ) and saturation index of calcite (SIc). Results show that there were not any diurnal variations in the physico-chemical parameters of the water for the spring. However, during daytime periods, pool water decreased to far less than the spring water in a few hours, pH and SIc increased to greater than the spring, and [Ca²⁺] and [HCO₃ ⁻] decreased to less than the spring. During nighttime periods, pool water returned to or even increased to greater than the spring, pH and SIc decreased to less than the spring, and [Ca²⁺] and [HCO₃ ⁻] increased to greater than the spring. The decrease in [Ca²⁺] and [HCO₃ ⁻] to less than the spring during daytime periods implies daytime deposition of calcium carbonate, while the increase in [Ca²⁺] and [HCO₃ ⁻] to greater than the spring during nighttime periods implies nighttime dissolution of calcium carbonate. The direction of the observed changes depended essentially on the illumination, indicating that daytime photosynthetic and nighttime respiratory activities in the pool aquatic plant ecosystem, which were further evidenced by the increase and decrease in DO during daytime and nighttime periods respectively, were the main processes involved. The large variations of the components of the carbonate system imply considerable changes of the capacities of CO₂ and O₂ in water. The finding has implications for water sampling strategy in slow-flowing karst streams and other similar environments with stagnant water bodies such as estuaries, lakes, reservoirs, and wetlands, where aquatic plant ecosystem may flourish.  相似文献   

桂林岩溶洼地生态系统中大气CO2动态及环境意义   总被引：17，自引：1，他引：16  

曹建华  潘根兴 《地质论评》1999,45(1):105-111

对桂林岩溶试验场岩溶洼地生态系统中大气ＣＯ２动态的昼夜观测结果说明,岩溶洼地对大气ＣＯ２具有一定的调蓄作用,并促进岩溶发育;植被的光合呼吸作用是制约大气ＣＯ２日动态直接的因素,而土壤ＣＯ２向大气的排放居次要地位。  相似文献   

桂林境外游客结构特征及时空动态模式研究   总被引：27，自引：3，他引：24  

张红  李九全 《地理科学》2000,20(4):350-354

通过对桂林境外游客的实地抽样调查,利用Ｖｉｓｕａｌ ＦｏｘＰｒｏ软件,建立桂林境外游客时间和空间变化数据库,经过统计分析,探讨桂林境外游客市场结构特征、客流量的时间变化规律及其与１１个旅游热点城市之间流动模式。  相似文献   

桂林地区4万年来气候变化及其动力机制浅析   总被引：6，自引：0，他引：6  

李彬  袁道先  林玉石  覃嘉铭  张美良 《地球学报》2000,21(3):313-319

通过桂林灌阳响水岩1号石笋的测年和O、C同位素的详细研究,得出了桂林地区4万a来高分辨率的古气候变化的连续记录,并揭示了由末次冰期向全新世的突变过程和3次与Heinrich事件(H1、H2、H3)对应的气候突变事件。在此基础上,通过与GISP2冰芯记录、古海水表面温度记录、深海海底生物的O同位素记录和苏禄海沉积物O同位素记录的对比,认为我国古季风环流变化的直接动力机制是全球冰量的变化。  相似文献   

桂林喀斯特石山苔藓植物生态分布的初探   总被引：8，自引：0，他引：8  

黄雅丹  谢强 《中国岩溶》2003,22(4):299-305

通过以桂林喀斯特石山地区苔藓植物为研究对象进行取样调查,选择植被比较完整的样地进行典型样点取样,共选取样地15处,样点34个,采集鉴定苔藓植物40种,分属19科32属,其中苔类8科8属8种,藓类11科24属32种。以山顶、山腰、山脚和土生、石生、树生以及干湿状态环境因子组合共划分出18种不同的样点环境类型,应用数学生态学等级分划分类方法的组分析技术,以苔藓植物种在某一样点环境中存在与否的二元数据进行样点类型分划和确定临界种; 并通过样点共有种或相异种的分析,探讨不同环境条件下苔藓植物生态分布特点。研究结果表明: ( 1)运用等级分划分类法组分析技术进行桂林喀斯特石山地区苔藓植物生态分布的研究是可行且有效的; ( 2)桂林喀斯特石山地区的苔藓植物分布与湿度状态关系最为密切; ( 3)桂林喀斯特石山地区苔藓植物与环境最佳适应可依次以小凤尾藓( Fissidens bryoides [ L. ] Hedw . )、尖叶提灯藓( Mnium cuspidatumHedw . )和灰羽藓( Thuidium glaucinum Mit t )作为分划特征种。   相似文献   

桂林热带岩溶地貌特点及其科学价值   总被引：3，自引：2，他引：1  

刘金荣  袁道先  梁耀成  闭萧萧 《中国岩溶》2001,20(2):137-139

桂林热带岩溶地貌的特点及其科学价值是举世闻名的,甚至是世界独一无二的。本文从七个方面进行了阐述,以期桂林人、国人对之有一个粗略的认识,并尽快申请将桂林岩溶列入世界自然遗产名录。   相似文献   

桂林市环境问题及综合防治对策   总被引：1，自引：0，他引：1  

钱建平  叶军 《矿产与地质》2009,23(2)

桂林市存在的主要环境问题有岩溶塌陷、漓江水资源、酸雨、土壤汞污染、石漠化、滑坡、崩塌等。文章阐述了桂林市所存在的各种环境问题的特征、现状、危害、成因和影响因素,并提出了综合防治对策。  相似文献   

数值预报产品在桂林暴雨预报中的应用研究     

周文志  薛荣康 《气象研究与应用》2004,25(1):1-3

利用1998～2002年4～7月间欧洲、日本,2002年5～7月我国数值预报产品进行统计分析,总结出以数值预报产品为主的暴雨预报模式指标。这一模式指标,为日常预报工作中以天气学预报为主转向以数值预报为主奠定良好基础,也为预报员提供客观简捷的预报方法。通过一年的试报探索和一年的实际业务应用,其预报准确率较为理想。  相似文献   

酸碱及可溶盐溶液对桂林红黏土压缩性影响实验研究   总被引：2，自引：1，他引：1  

顾展飞  刘琦  卢耀如  刘之葵 《中国岩溶》2014,33(1):37-43

为探讨水环境对红黏土工程地质性质的影响,以桂林岩溶地区典型地段的红黏土为研究对象,对浸泡于不同浓度的 HCl、NaOH、Fe（NO3）3和 Al（NO3）3溶液中的试样进行固结实验。结果显示：（1）在 HCl 和 NaOH 溶液中浸泡后,红黏土的压缩模量都降低,压缩系数都增大,且溶液浓度越大其值降低或增大的幅度越大;（2）浸泡在 NaOH 溶液中的红黏土的压缩模量比浸泡在 HCl 溶液中的大,且压缩模量值随着溶液浓度的增加而减小,压缩系数则相反;（3）在 Fe（NO3）3和Al（NO3）3溶液中浸泡后,红黏土的压缩模量会随着溶液浓度的增大而增大,压缩系数随着溶液浓度的增大而降低,且 Fe（NO3）3溶液对红黏土的压缩性影响作用比 Al（NO3）3溶液的大。  相似文献