右江盆地晚古生代白云岩特征及成因研究

右江盆地在晚古生代沉积演化过程中，在各个时代、各层位均有白云岩形成，但不同层位白云岩发育的规模有明显差异。宏观上在剖面上产出的形态有层状、斑块状、透镜状、角砾状、裂缝状等；微观上白云石的形态可以分为：自形-半自形密集状、自形星散状、半自形-他形不规则状、自形-半自形缝合线状、他形生物腔充填状、自形-他形生物组织状和他形的脉状等。在上述基础上讨论了白云岩的岩石学特征，主要包括有结构残余的白云岩、无结构残余的白云岩、强烈交代的白云岩和含(泥)硅质白云岩四大类，其中无结构残余的白云岩又包括粉晶白云岩、中-细晶白云岩和粗晶白云岩三类。论述了白云岩产出的环境从台→地台地边缘→斜坡→盆地均有产出。正是由于沉积环境的关系，也导致白云岩产出的宏观产状特征从厚层块状大套(台地)→中厚层(台缘)→角砾状(斜坡)→薄层或夹层(台盆)，进而建立了白云岩的成因模式。通过对研究区内白云岩的上述特征研究可以看出，区内白云岩为成岩交代的产物，但不同宏观特征的白云岩其成因机制和过程是不同的。可以分为两种类型，一种为深水白云石化作用形成的白云岩，另一种为浅水白云石化作用形成的白云岩。     

3H/3He age data in assessing the susceptibility of wells to contamination

Regulatory agencies are becoming increasingly interested in using young-ground water dating techniques, such as the 3H/3He method, in assessing the susceptibility of public supply wells (PSWs) to contamination. However, recent studies emphasize that ground water samples of mixed age may be the norm, particularly from long-screened PSWs, and tracer-based "apparent" ages can differ substantially from actual mean ages for mixed-age samples. We present age and contaminant data from PSWs in Salt Lake Valley, Utah, that demonstrate the utility of 3H and 3He measurements in evaluating well susceptibility, despite potential age mixing. Initial 3H concentrations (measured 3H + measured tritiogenic 3He) are compared to those expected based on the apparent 3H/3He age and the local precipitation 3H record. This comparison is used to determine the amount of modern water (recharged after approximately 1950) vs. prebomb water (recharged before approximately 1950) samples might contain. Concentrations of common contaminants were also measured using detection limits generally lower than those used for regulatory purposes. A clear correlation exists between the potential magnitude of the modern water fraction and both the occurrence and concentration of contaminants. For samples containing dominantly modern water based on their initial 3H concentrations, potential discrepancies between apparent 3H/3He ages and mean ages are explored using synthetic samples that are random mixtures of different modern waters. Apparent ages can exceed mean ages by up to 13 years for these samples, with an exponential age distribution resulting in the greatest discrepancies.     

Temporal changes in the vertical distribution of flow and chloride in deep wells

The combination of flowmeter and depth-dependent water-quality data was used to evaluate the quantity and source of high-chloride water yielded from different depths to eight production wells in the Pleasant Valley area of southern California. The wells were screened from 117 to 437 m below land surface, and in most cases, flow from the aquifer into the wells was not uniformly distributed throughout the well screen. Wells having as little as 6 m of screen in the overlying upper aquifer system yielded as much as 50% of their water from the upper system during drought periods, while the deeper parts of the well screens yielded 15% or less of the total yield of the wells. Mixing of water within wells during pumping degraded higher-quality water with poorer-quality water from deeper depths, and in some cases with poorer-quality water from the overlying upper aquifer system. Changes in the mixture of water within a well, resulting from changes in the distribution of flow into the well, changed the quality of water from the surface discharge of wells over time. The combination of flowmeter and depth-dependent water quality data yielded information about sources of high-chloride water to wells that was not available on the basis of samples collected from nearby observation wells. Changing well design to eliminate small quantities of poor-quality water from deeper parts of the well may improve the quality of water from some wells without greatly reducing well yield.     

Comparing bleaching and mortality responses of hard corals between southern Kenya and the Great Barrier Reef, Australia

We compared the bleaching and mortality response (BMI) of 19 common scleractinian corals to an anomalous warm-water event in 1998 to determine the degree of variation between depths, sites, and regions. Mombasa corals experienced a greater temperature anomaly than those on the Great Barrier Reef (GBR) sites and this was reflected in the greater BMI response of most taxa. Comparing coral taxa in different sites at the same depth produced high correlation coefficients in the bleaching response in Kenya at 2 m (r=0.86) and GBR at 6 m depth sites (r=0.80) but less in the GBR for shallow 2 m sites (r=0.49). The pattern of taxa susceptibility was remarkably consistent between the regions. Coral taxa explained 52% of the variation in the response of colonies to bleaching between these two regions (Kenya BMI=0.90 GBR BMI+26; F(1,19) - 18.3; p < 0.001; r2 = 0.52). Stylophora and Pocillopora were consistently susceptible while Cyphastrea, Goniopora Galaxea and Pavona were resistant in both regions. Three taxa behaved differently between the two regions; Acropora, and branching Porites were both moderately affected on the GBR but were highly affected in Kenya while the opposite was true for Pavona. These results suggest that a colonies response to bleaching is phylogenetically constrained, emphasizing the importance of features of the host's physiology or morphology in determining the response to thermal stress.     

龙门山国家地质公园地质遗迹的保护

为了更好地保护龙门山国家地质公园地质遗迹,在进行多次野外考察和室内分析总结的基础上,指出推覆构造是地质公园最典型、珍贵的地质遗迹,也是必须重点保护的地质遗迹。包括：典型的推(滑)覆构造体、与推覆构造相伴形成的区域性大型断裂及典型的构造和地层剖面、在区域上具有特殊性或者较为典型的其它类型的地质遗迹、“冰川漂砾”学说的学者所确认的有关重要地质遗迹等。还对重点保护的地质遗迹进行保护级别和范围的规划,提出了地质遗迹保护策略和措施。