Influence of river channel geometry in stream flow modelling and guidelines for field investigation

Fully physics‐based, process‐level, distributed fluid flow and reactive transport hydrological models are rarely used in practice until recent years. These models are useful tools to help understand the fundamental physical, chemical, and biological processes that take place in nature. In this study, sensitivity analyses based on a mountain area river basin modelling study are performed to investigate the effect of river channel geometric characteristics on downstream water flow. Numerical experiments show that reduction in the river channel geometric measurement interval may not significantly affect the downstream water stage simulation as long as measurement accuracy at special nodes is guaranteed. The special upstream nodes include but are not limited to 1) nodes located close to the observation station, 2) nodes near the borders of different land covers with considerable riverbed roughness changes, 3) nodes at entering points of tributaries causing discharge jump and 4) nodes with a narrow cross‐section width that may control the flow conditions. This information provides guidelines for field investigation to efficiently obtain necessary geometric data for physics‐based hydrological modelling. It is especially useful in alpine areas such as the Tibetan Plateau where field investigation capability is limited under severe topography and climate condition. Copyright © 2013 John Wiley & Sons, Ltd.     

A detailed post‐IR IRSL dating study of the Niuyangzigou loess site in northeastern China

In this study, we report standard quartz SAR OSL and post‐IR infrared (IR) stimulated luminescence (post‐IR IRSL; pIRIR₂₉₀) measurements made on sand‐sized quartz and K‐feldspar extracts from the loess‐palaeosol sequence at Niuyangzigou in northeastern China. The quartz OSL characteristics are satisfactory. Extensive pIRIR_50,290 dose recovery tests were performed by adding doses on top of the natural dose. We found that dose recovery ratios improve significantly when the test dose ranges between ~15 and ~80% of the total dose, and good dose recovery (within ±5% of unity) can be obtained up to ～800 Gy. Otherwise, the dose recovery ratio deviates from unity. The D_e values also depend on the test dose size and so we conclude that the effect of test dose size should be routinely considered in pIRIR dating. First IR stimulation plateau pIRIR₂₉₀ results are compared with multiple elevated temperature ‐pIRIR (MET‐pIRIR) data. It appears that the low temperature MET‐pIRIR data are strongly affected by poor dose recovery, but this is not the case for the pIRIR₂₉₀ results. Natural signal measurements at the highest (first IR) stimulation temperature on a sample expected to be in field saturation suggest that ~10% signal loss occurs in pIRIR signals. Long‐term laboratory bleaching experiments (>80 days) show that a constant (or very difficult to bleach) residual pIRIR₂₉₀ signal is reached after ~300 h, corresponding to a dose of 6.2±0.7 Gy. Quartz OSL and feldspar pIRIR_50,290 ages are in good agreement at least back to c. 70 ka. Beyond this the quartz ages begin to underestimate but the feldspar ages are in agreement with the expected Last Interglacial age palaeosol.     

鄂尔多斯盆地长7段页岩生烃活化能分布及其对页岩原位转化的启发

鄂尔多斯盆地三叠系延长组7段(长7段)中—低熟(R_o<1.0%)页岩面积占该段页岩总面积的90%左右,中—低熟页岩油/油页岩资源丰富,原位转化作为实现其工业开采的有效途径日益受到各方的关注。生烃转化率和活化能是影响页岩原位转化和开采潜力的关键因素,前人研究表明研究区长7段页岩生烃活化能分布特征存在较大的差别,但其分布规律及其控制因素尚不清楚,尤其是有机质丰度、成熟度等对页岩生烃特征和动力学过程的控制作用及其成因机制尚不明确,这必将制约研究区页岩原位转化条件和资源潜力的评价。本次研究选取了长7段成熟度相近、不同有机质丰度的5块页岩样品以及有机质丰度相近、不同成熟度的5块页岩样品,通过开放热模拟实验确定了样品的生烃动力学参数,讨论了有机质丰度和成熟度对长7段页岩动力学特征的影响。根据烃源岩生烃过程的时间-温度补偿原理,将实验室条件下获得的动力学参数外推至页岩原位转化条件下,分析了有机质丰度和成熟度对长7段页岩原位转化温度区间的影响。结果表明,在成熟度相近的情况下,受有机质中藻类体等腐泥组的富集程度影响,烃源岩的生烃活化能随有机质丰度的增大而增大;在有机质丰度相近...     

塔河油田奥陶系走滑断裂体系特征及成因机制

塔河油田奥陶系“断溶体”油藏是塔里木盆地油气勘探开发的重要对象。本文对塔河油田10区西、于奇西、于奇8井三块三维地震资料开展了精细的走滑断裂构造解析,并在此基础上对塔河油田走滑断裂体系的形成演化过程与成因机制有新认识。研究结果表明：(1)除了在塔河油田南部10区西、托普台等区块发育典型的“X”型共轭走滑断裂体系外,首次发现塔河油田北部于奇地区发育非对称式共轭走滑断裂体系,据此划分出塔河油田南、北两大走滑断裂体系,但两者在形成时间、最大主应力方向、动力学来源等方面均存在明显差异;(2)两大走滑断裂体系的形成及演化过程大致分为3个阶段：加里东期中期I幕形成南部NNE、NNW两组走向的“X”型共轭走滑断裂体系,最大主压应力方向为N3°E,主要受到西昆仑洋俯冲消减作用产生的由S向N的挤压应力;加里东期晚期—海西期早期形成北部以近NE走向为主、少量SN走向组成的非对称式共轭走滑断裂体系,最大主压应力方向为N23°E,主要受到南天山洋俯冲消减作用产生的由N向S的挤压应力,海西期晚期继承性活动,主应力方向保持不变;印支期—燕山期两大走滑断裂体系继承性活动,最大主压应力方向为N37°E,主要受到南部古...     

贵州铝土矿含矿岩系中锂的分布特征及富集机理

锂是我国关键矿产和高新产业发展的战略性资源之一。贵州铝土矿资源丰富,含铝岩系分布广,勘查发现铝土矿(岩)中伴生大量的锂资源。研究认为,全省含铝岩系中Li含量高,变化范围大(0.55×10^-6～2725.03×10^-6),平面上Li含量总体呈北东(务正道成矿区)、南西(修文-清镇成矿区)高,中间(播州-瓮安成矿区)低的分布态势;剖面上Li主要富集在矿系上部的致密状铝土岩(矿)中,Li含量一般>500×10^-6,矿系中土状铝土矿(岩)Li含量一般<30×10^-6;气候温湿、风化及淋滤作用强的陆相湖泊沉积环境,有利于高岭石为主的黏土矿物形成及Li⁺与Al³⁺、Mg²⁺、Fe³⁺、Fe²⁺发生类质同象,或被吸附进入黏土矿物层间构造同迁移同富集,Li与Al₂O₃含量呈正相关关系;成岩成矿后的次生改造阶段,古地磁测量及CIA显示为炎热潮湿的氧化环境...     

青藏高原第四纪冰川作用及其气候响应的讨论

关于青藏高原和周边山地第四纪冰川作用及其气候响应存在不同观点.一些学者认为老冰期主要发生在氧同位素奇数阶段;MIS 3和早全新世存在规模较大的冰川前进;南亚季风对青藏高原冰川作用起主导作用(水汽驱动).另一些学者则认为青藏高原冰川作用主要对应于氧同位素偶数阶段;冰川发育是构造隆升-冰期气候耦合的产物(低温驱动).本文基于现有的陆地生成宇宙核素(TCN)和光释光(OSL)等年代结果总结了不同时间尺度和不同类型冰川波动与气候变化历史的对比,并对几个关键的争议问题做了讨论.结果表明,在不同类型冰川区和不同时间尺度下,冰川作用在湿润期和低温期都有可能发生,但总体上主要与低温相对应.青藏高原冰川对气温的响应似乎更为敏感.MIS 3冰进规模较大可能是降水较多结合冷期(或冷事件)降温所致,显示了印度季风降水和气温波动对高原冰川的共同作用.早全新世冰进也与印度季风和北半球冷事件关系密切.目前的测年数据还没有推翻“冰期发生在氧同位素偶数阶段”这种传统认识.当前急需更多精确的数字定年工作,以不断更新对青藏高原冰期时代及其气候响应机制的了解.     

湘西碳酸岩山区页岩气地震勘探采集技术研究

湖南湘西碳酸盐岩山区不同时期灰岩出露,岩性变化较大,且受风化、淋滤、剥蚀作用,溶洞、裂缝十分发育,导致地震波能量衰减严重,且地震波传播路径和地震波场的复杂,地震原始资料信噪比较低。针对上述问题,采用单/双井微测井相结合的精细浅表层结构调查方法,结合药柱长度和爆炸理论计算出的爆炸半径,动态设计井深激发方式。通过室内模拟计算,研究低频检波器多串、线性等组合接收方式在区内压制面波、折射波、多次折射及侧面波等多波干扰的效果,最终选择2串24个检波器等灵敏度组合及小道距、高覆盖观测等关键采集技术。实践表明,该区选择的观测系统较好的克服了南方岩溶地区地震勘探信噪比低的问题,具有极强的推广价值。     

Relative humidity history on the Batang–Litang Plateau of western China since 1755 reconstructed from tree-ring δ18O and δD

We measured the annual variation in the stable isotopes of oxygen (δ¹⁸O) and hydrogen (δD) in tree rings of Abies georgei on the Batang–Litang Plateau of western China. Although correlations between tree-ring δ¹⁸O and δD are relatively weak in semi-arid regions, we found a strong correlation between the δ¹⁸O and δD time series from 1755 to 2009 under the wetter environment. Tree-ring δ¹⁸O and δD time series are both significantly and negatively correlated with moisture conditions from June to August, including relative humidity and total precipitation, respectively, from 1960 to 2009. Considering the difference in low-frequency domain between the two isotopes, the relative humidity histories from June to August, reconstructed separately from the tree-ring δ¹⁸O and δD data with instrumental climate data, reveal a persistent drying trend since 1850s, especially since the early 1970s. There is an obvious offset of reconstructed relative humidity from tree-ring δ¹⁸O and δD in the period 1755–1820, despite the strong similarity in their 21-year moving averages. The decreased relative humidity since the 1850s may be associated with the thermal contrast between the sea surface temperature of the Indian Ocean and the Qinghai-Tibetan Plateau, which determines the strength of moisture transfer via the Indian summer monsoon.