A Discussion of Concavo-Convex Contacts between Oolites and Quartz Grains in Mixed Siliciclastic-Carbonate Rocks in Huanghua Basin, China

Concavo-convex contacrs between oolites and quartz grains are observed in mixed siliciclastic-carbonate rocks of the lower part of number 1 of Shahejie Formation, beach area, Dagang. Thin sections observation shows that oolite is convex in quartz grain, and oolite is complete. A possible explanation for it is pressure dissolution under alkaline fluid.     

Diagenetic Sequences Analysis of Fuyu Reservoir in Qijia - Gulong Depression, Northern Songliao Basin

Five paragenetic associations are recognized in Fuyu reservoir of Qijia - gulong depression of Daqing oil field: 1 )detrital illite permeation, glauconite and pyrite precipitation; 2 ) feldspar dissolution, kaolinite precipitation and the incipient quartz overgrowths; 3 ) early calcite cements; 4 ) postdate quartz overgrowths and pore - filling quartz, authigenetic illite and chlorite formation, feldspar overgrowths, petroleum injections, K - feldspar and calcite cement dissolution; 5) pore - filling calcite and calcite replacement.     

Episodic orogeny deduced from coeval sedimentary sequences in the foreland basin and its implication for uplift process of Longmen Mountain, China

Longmen Mountain located at the boundary between the Sichuan Basin and Tibetan Plateau,representing the steepest gradient of any edges of the plateau.Three endmember models of uplift process and mechanism have been proposed,including crustal thickening,crustal flow,and crustal isostatic rebound.Here we use coeval sedimentary sequences in the foreland basin to restraint uplift process and mechanism in the Longmen Mountain.The more than 10,000 m thick Late TriassicQuaternary strata filled in this foreland basin and can be divided into six megasequences that are distinguished as two distinct types.The first type is the wedge-shaped megasequences which are sedimentary response of strong active thrust loading events,characterized by a high rate of subsidence and sediment accumulation,coarsening-upward succession and a dual-sourced sediment supply.This type includes Late Triassic,Late Jurassic to Early Cretaceous and Late Cretaceous to Paleogene megasequences.The second type is the tabular megasequences,characterized by the low rate of subsidence and sediment accumulation,finingupward succession,and a single-sourced sediment supply,which is sedimentary response of isostatic rebound and erosion unloading.This type includes the Early to Middle Jurassic,Middle Cretaceous and Neogene to Quaternary megasequences.Basing on sedimentary,active tectonic,geomorphic evidence,we infer that the direction has been reversed from SSWdirected sinistral strike-slip to NNE-directed dextral strike-slip during 40-3.6 Ma,and since 3.6 Ma,the Longmen Mountain thrust belt belong to times of isostatic rebound and erosional unloading with NNEdirected dextral strike-slip.This suggests that crustal isostatic rebound is a primary driver for uplift and topography of the present Longmen Mountain.The Wenchuan(Ms8.0) earthquake,which ruptured a large thrust fault with NNE-directed dextral strikeslip along the range front,is an active manifestation of this crustal isostatic rebound process with dextral strike-slipping and shortening.This process may be the cause for the Wenchuan Earthquake and the apparent paradox of high relief,little shortening,the relative dearth of historical seismicity in the region.     

The impact of meso-scale eddies on the Subtropical Mode Water in the western North Pacific

Based on the temperature and salinity from the Argo profiling floats and altimeter-derived geostrophic velocity anomaly (GVA) data in the western North Pacific during 2002–2011, the North Pacific Subtropical Mode Water (NPSTMW) distribution is investigated and cyclonic and anti-cyclonic eddies (CEs and AEs) are constructed to study the influence of their vertical structures on maintaining NPSTMW. Combining eddies identified by the GVA data and Argo profiling float data, it is found that the average NPSTMW thickness of AEs is about 60 dbar, which is thicker than that of CEs. The NPSTMW thicker than 150 dbar in AEs accounts for 18%, whereas that in CEs accounts for only 1%. About 3377 (3517) profiles, which located within one diameter of the nearest CEs (AEs) are used to construct the CE (AE). The composite AE traps low-PV water in the center and with a convex shape in the vertical section. The ‘trapped depth’ of the composite CE (AE) is 300 m (550 m) where the rotational velocity exceeds the transitional velocity. The present study suggests that the anticyclonic eddies are not only likely to form larger amounts of NPSTMW, but also trap more NPSTMW than cyclonic eddies.     

Water quality evaluation in Tidal River reaches of Liaohe River Estuary, China using a revised QUAL2K model

Rivers in the Liaohe River Estuary area have been seriously polluted by discharges of wastewater containing petroleum pollutants and nutrients. In this paper, The Enhanced Stream Water Quality Model (QUAL2K) and its revised model as well as One-dimensional Tide Mean Model (1D model) were applied to predict and assess the water quality of the tidal river reach of the Liaohe River Estuary. Dissolved oxygen (DO), biochemical oxygen demand (BOD₅), ammonia nitrogen (NH₃-N) and total phosphorus (TP) were chosen as water quality indices in the two model simulations. The modelled results show that the major reasons for degraded rivers remain petroleum and non-point source pollution. Tidal water also has a critical effect on the variation of water quality. The sensitivity analysis identifies that flow rate, point load and diffuse load are the most sensitive parameters for the four water quality indices in the revised QUAL2K simulation. Uncertainty analysis based on a Monte Carlo simulation gives the probability distribution of the four water quality indices at two locations (6.50 km and 44.84 km from the river mouth). The statistical outcomes indicate that the observed data fall within the 90% confidence intervals at all sites measured, and show that the revised QUAL2K gives better results in simulating the water quality of a tidal river.     

Determining topographic shielding from digital elevation models for cosmogenic nuclide analysis: a GIS approach and field validation

Topographic shielding of cosmic radiation flux is a key parameter in using cosmogenic nuclides to determine surface exposure ages or erosion rates. Traditionally, this parameter is measured in the field and uncertainty and/or inconsistency may exist among different investigators. This paper provides an ArcGIS python code to determine topographic shielding factors using digital elevation models (DEMs). This code can be imported into ArcGIS as a geoprocessing tool with a user-friendly graphical interface. The DEM-derived parameters using this method were validated with field measurements in central Tian Shan. Results indicate that DEM-derived shielding factors are consistent with field-measured values. It provides a valuable tool to save fieldwork efforts and has the potential to provide consistent results for different regions in the world to facilitate the comparison of cosmogenic nuclide results.     

Revealing storage-area relationship of open water in ungauged subalpine wetland — Napahai in Northwest Yunnan, China

Mountains and plateaus in Southwest China contain many subalpine and alpine wetlands, with significant hydroecological functions. But ungauged or poorly gauged conditions limit the study and understanding of hydrological regimes of these wetland types. This study selects an ungauged subalpine wetland-Napahai in Northwest Yunnan, China-as a case for developing a practical approach to revealing its storage-area relationship of open water. A Trimble R8 GNSS (Global Navigation Satellites Systems) RTK (Real-time Kinematic system) and sonar fathometer were used to survey fine-resolution elevation data and generate a digital elevation model of the Napahai Wetland. Forty-four Landsat images from 1987 to 2011 were collected, and the Normalized Difference Water Index was used to classify open water features in the area. The area of open water in Napahai was calculated for each phase. With these data and a developed conceptual model, the storage of open water for each phase was estimated using ArcGIS tools. Both storage and area of open water showed significant intra-annual and inter-annual variations. In the rainy season, the monthly change of average storage of open water in Napahai showed about 1-2 months lag behind mean monthly rainfall. The storage-area relationship of open water was well fit by a power function equation (R 2 ≈0.91, n=44). This study indicates that if detailedelevations are available for similarly ungauged subalpine wetlands in Southwest China, researchers can use this practical approach to estimate multi- temporal areas and storages and reveal the storage-area relationship of open water in the wetlands. The study provided valuable information of this case wetland for optimizing its hydro-ecological managements and a new method to wetland researchers and managers for the hydrological study of similarly ungauged wetland complex.     

Engineering geological assessment for route selection of railway line in geologically active area: A case study in China

The Cheng-Lan railway links Chengdu, a central city in Southwestern China, and Lanzhou, a central city in Northwestern China. The railway passes through the Longmenshan fault zone (Wenchuan earthquake happened there on May 12, 2008), Minjiang fault zone, and Dongkunlun fault zone, which are all active. It runs over the Yangtze River and the Yellow River, and crosses high mountains and deep valleys. There exists, along the railway’s alignment, different kinds of strata of hard granite and soft, weak metamorphic rocks such as carbonaceous slate, schist, and phyllite. It is, therefore, a key issue for such an infrastructure construction to assess the engineering geological conditions and risks, so as to mitigate or avoid possible georisks and to offer optional designs. Geological survey and georisk assessment along the railway corridor are carried out. Special attention is given to active faults, earthquakes and seismic zones. Based on these, discussions about geological aspects for route selection of the railway are conducted and countermeasures for georisk control are proposed accordingly. Main conclusions are achieved as follows: (1) Geohazards such as landslides, rockfalls and debries flows dominate both the route selection of the railway and the engineering structures (e.g., tunnels or bridges) adopted; (2) Tunnel has been proved to be an excellent structure for linear engineering in geologically active area; and (3) In the case where avoiding is impractical, necessary protection measures should be taken to engineering slopes in high earthquake intensity areas, especially the area with earthquake of Ms. 8 or greater.     

Effects of exposure to four endocrine disrupting-chemicals on fertilization and embryonic development of Barbel chub (Squaliobarbus curriculus)

The toxicities of 4 common endocrine-disrupting chemicals (EDCs), 17β-estradiol (E2), p,p′-dichlorodiphenyldichloro-ethylene (DDE), 4-nonylphenol (NP) and tributyltin (TBT), to sperm motility, fertilization rate, hatching rate and embryonic development of Barbel chub (Squaliobarbus curriculus) were investigated in this study. The duration of sperm motility was significantly shortened by exposure to the EDCs at the threshold concentrations of 10 ng L^?1 for E2 and TBT, 1 μg L^?1 for NP and 100 μg L^?1 for DDE, respectively. The fertilization rate was substantially reduced by the EDCs at the lowest observable effect concentrations (LOECs) of 10 ng L^?1 for E2 and TBT and 10 μg L^?1 for DDE and NP, respectively. Of the tested properties of S. curriculus, larval deformity rate was most sensitive to EDC exposure and was significantly increased by DDE at the lowest experimental level of 0.1 μg L^?1. Other EDCs increased the larval deformity rate at the LOECs of 1 ng L^?1 for E2, 10 ng L^?1 for TBT and 1 μg L^?1 for NP, respectively. Despite their decreases with the increasing EDC concentrations, the hatching rate and larval survival rate of S. curriculus were not significantly affected by the exposure to EDCs. The results indicated that all the 4 EDCs affected significantly and negatively the early life stages of the freshwater fish S. curriculus. Overall, E2 and TBT were more toxic than NP and DDE, while DDE might be more toxic to larval deformity rate than to other measured parameters. Thus, the 4 EDCs showed potential negative influences on natural population dynamics of S. curriculus. Our findings provided valuable basic data for the ecological risk assessment of E2, DDE, NP and TBT.