合肥盆地中、新生代沉积相初步研究

合肥盆地是与大别山造山带有密切关系的山前前陆盆地，盆地中、新生界沉积物主要来自南面大别山区以及盆地东部、北部剥蚀区。通过野外实际踏勘、室内岩石薄片显微分析，认为合肥盆地中、新生界发育的沉积相主要有冲积扇相、河流相和湖泊相，其中以河流相最为发育。该盆地中、新生界油气源条件比较丰富，储盖条件良好，生储盖组合形式多样，存在多种油气圈闭类型，是一个油气勘探潜力较大的陆相沉积盆地。     

吉林延边开山屯地区蓝片岩相变质作用——来自硬绿泥石＋纤锰柱石＋多硅白云母组合的证据

吉林延边开山屯低级变质作用发育于兴凯地块西南晚古生代活动大陆边缘，这里产出二叠纪末的消减增生杂岩。低级变质作用矿物除冻蓝闪石、阳起石、玉髓、黝帘石、多硅白云母、绿泥石、钠长石外，还在灰黑色变泥质岩中发现硬绿泥石 纤锰柱石 多硅白云母组合。这是国内首次报道的以泥质岩为原岩并具有硬绿泥石 纤锰柱石标志矿物组合的蓝片岩相岩石。研究表明，该组合的形成温度290．14(或370．8)℃，具明显的低温特征。     

冲积-河流相层序地层模式--以济阳坳陷新近系为例

从层序边界分析人手，对层序类型体系域类型等进行了研究，认为冲积-河流相地层体系域划分具4分性，即发育有低位体系域、扩张体系域、高位体系域，当基准面缓慢下降时，还可发育收缩体系域．同时，根据济阳坳陷新近系沉积特征，指出各体系域对应的沉积体系及相类型，认为低位体系域以侵蚀下切、冲积扇．辫状河沉积为主；扩张体系域由辫状河向曲流河过渡；高位体系域时期以曲流河为主．其次，根据构造演化、古气候变化、古地形等研究认为，尽管新近纪济阳坳陷进入坳陷发育时期，断裂活动明显减弱，但是构造运动对层序发育仍有一定影响；根据古气候分析认为，新近纪经历了北亚热带温湿气候，中亚热带温湿气候，北亚热带干旱气候等阶段．这种气候变化导致了馆陶组沉积早、中期河流纵横交错，辫状河道发育，馆陶组沉积后期逐渐向曲流河过渡；明化镇组沉积期河道相对不发育．由古地形及物源供给分析，认为古地形差异的变化与物源供给对济阳坳陷新近系层序发育、层序样式等有一定程度影响．     

平原河网区域来水组成原理

对于一般树状分布河网，上一级河道总是汇入至下一级河道，位于河道下游断面的流量总是由其上游汇集而至。但对于平原河网地区，特别是人工控制建筑物众多，又受潮汐影响的地区(如太湖流域)，河网错综复杂，水流方向不定，要跟踪某个断面的水流去向，或某个河段的水体、断面流量是从哪里汇集而来的，非常困难。但这样的问题在生产实践中往往对其很感兴趣。例如从常熟枢纽引长江水流进入望虞河后，流向何处?河网各断面流量中或各河段水体中常熟枢纽引江水量占多少比重?对这些问题的研究可以估计常熟枢纽引江的效果和影响范围。因此，平原河网区域来水组成方法在生产实践中具有重要意义。重点介绍了平原河网区域来水组成原理及其在太湖流域的应用。     

处理DEM中闭合洼地和平坦区域的一种新方法

数字高程模型(DEM)中的闭合洼地和平坦区域影响着流域排水网络的自动提取.目前已提出很多方法来处理这两种地形,但均针对已经形成的DEM单元网格进行处理,结果往往生成伪河道及平行河道.在回顾分析了这些方法存在的问题后,提出了一种新的处理方法,该法认为DEM中的闭合洼地和平坦区域是由于低质量的资料输入、生成DEM时的内插误差等引起的.通过增加输入地形高程信息,避免了DEM中平坦区域和闭合洼地的生成,从而使由DEM生成的河网与实际河网能够精确拟合.实例分析表明,该方法效果明显.     

东南极格罗夫山泛非期麻粒岩相变质作用

东南极格罗夫山主要由麻粒岩相高级变质岩和花岗岩类组成，其中变质岩以浅色和暗色含斜方辉石长英质片麻岩占主导地位，夹有少量镁铁质麻粒岩、变沉积岩和含方柱石钙硅酸盐岩。这些岩石一般都展示了平衡的矿物共生结构，但在镁铁质麻粒岩的单斜辉石中普遍发育斜方辉石(易变辉石)的出溶片晶。根据出溶辉石的重组分析获得麻粒岩相变质作用的峰期温度约为850℃，而浅色片麻岩中的石榴子石—斜方辉石—斜长石—石英组合给出的变质压力为0．61～0．67GPa。镁铁质麻粒岩中火成亚钙质普通辉石斑晶的保存表明格罗夫山地区可能只发育单一的泛非期高温麻粒岩相变质事件，岩石在高温变质之后经历了缓慢冷却过程，这主要归因于花岗质岩浆的板底垫托作用。     

Investigation of spatially distributed braided river flows using a two‐dimensional hydraulic model

This paper reports the application of a two‐dimensional hydraulic model to a braided reach of the Avoca River, New Zealand. Field measurements of water surface elevation, depth and velocity obtained at low flow were used to validate the model and to optimize the parameterization of bed friction. The main systematic trends in the measured flow variables are reproduced by the model. However, field data are characterized by greater spatial variability than model output reflecting differences in the scale of processes measured in the field and represented by the model. Additional model runs were conducted to simulate flow patterns within the study reach at five higher discharges. The purpose of these simulations was to evaluate the potential for using two‐dimensional hydraulic models to quantify the reach‐scale hydraulic characteristics of braided rivers and their dependence on discharge. Changes in flow depth and velocity with increasing discharge exhibit trends that are consistent with the results of previous field investigations, although the tendency for the wetted area of the braidplain within particular depth and velocity categories to remain fixed as discharge rises, as has been noted for several braided rivers in New Zealand, was not observed. Modelled shear stress frequency distributions fit gamma functions that incorporate a distribution shape parameter, the value of which follows clear systematic trends with rising discharge. These results illustrate both the problems of, and potential for, using two‐dimensional hydraulic models in braided river applications. This leads to something of a paradox in that while such models provide a means of generating hydraulic information that would be difficult to obtain in the field at an equivalent spatial resolution, they are, due to the problems inherent to data collection, difficult to validate conclusively. Despite this limitation, the application of spatially distributed models to investigate relationships between discharge and reach‐scale form and process variables appears to have considerable potential. Copyright © 2003 John Wiley & Sons, Ltd.     

石羊河流域水质环境遥感监测评价研究

利用遥感技术对流域水质环境的监测评价,可实现全流域水质的同步监测,其监测结果具有可比性。以石羊河流域为实验区,研究了一种基于遥感技术的河流水质环境监测与评价方法,该方法克服了传统监测方法的局限性,完善了表面水质遥感信息获取的基础方法研究体系。     

Geomorphological and sequence stratigraphic variability in wave‐dominated,shoreface‐shelf parasequences

Abstract Physical stratigraphy within shoreface‐shelf parasequences contains a detailed, but virtually unstudied, record of shallow‐marine processes over a range of historical and geological timescales. Using high‐quality outcrop data sets, it is possible to reconstruct ancient shoreface‐shelf morphology from clinoform surfaces, and to track the evolving morphology of the ancient shoreface‐shelf. Our results suggest that shoreface‐shelf morphology varied considerably in response to processes that operate over a range of timescales. (1) Individual clinoform surfaces form as a result of enhanced wave scour and/or sediment starvation, which may be driven by minor fluctuations in relative sea level, sediment supply and/or wave climate over short timescales (10¹?10³ years). These external controls cannot be distinguished in vertical facies successions, but may potentially be differentiated by the resulting clinoform geometries. (2) Clinoform geometry and distribution changes systematically within a single parasequence, reflecting the cycle in sea level and/or sediment supply that produced the parasequence (10²?10⁵ years). These changes record steepening of the shoreface‐shelf profile during early progradation and maintenance of a relatively uniform profile during late progradation. Modern shorefaces are not representative of this stratigraphic variability. (3) Clinoform geometries vary greatly between different parasequences as a result of variations in parasequence stacking pattern and relict shelf morphology during shoreface progradation (10⁵?10⁸ years). These controls determine the external dimensions of the parasequence.     

Strain partitioning and preservation of Ar/Ar ages during Variscan exhumation of a subducted crust (Malpica–Tui complex, NW Spain)

The Malpica–Tui complex (NW Iberian Massif) consists of a Lower Continental Unit of variably deformed and recrystallized granitoids, metasediments and sparse metabasites, overridden by an upper unit with rocks of oceanic affinities. Metamorphic minerals dated by the ⁴⁰Ar/³⁹Ar method record a coherent temporal history of progressive deformation during Variscan metamorphism and exhumation. The earliest stages of deformation (D1) under high-pressure conditions are recorded in phengitic white micas from eclogite-facies rocks at 365–370 Ma. Following this eclogite-facies peak-metamorphism, the continental slab became attached to the overriding plate at deep-crustal levels at ca. 340–350 Ma (D2). Exhumation was accompanied by pervasive deformation (D3) within the continental slab at ca. 330 Ma and major deformation (D4) in the underlying para-autochthon at 315–325 Ma. Final tectonothermal evolution included late folding, localized shearing and granitic intrusions at 280–310 Ma.

Dating of high-pressure rocks by the ⁴⁰Ar/³⁹Ar method yields ages that are synchronous with published Rb–Sr and Sm–Nd ages obtained for both the Malpica–Tui complex and its correlative, the Champtoceaux complex in the French Armorican Massif. The results indicate that phengitic white mica retains its radiogenic argon despite been subjected to relatively high temperatures (500–600 °C) for a period of 20–30 My corresponding to the time-span from the static, eclogite-facies M1 peak-metamorphism through D1-M2 eclogite-facies deformation to amphibolite-facies D2-M3. Our study provides additional evidence that under certain geological conditions (i.e., strain partitioning, fluid deficiency) argon isotope mobility is limited at high temperatures, and that ⁴⁰Ar/³⁹Ar geochronology can be a reliable method for dating high pressure metamorphism.