内蒙古东乌珠穆沁旗沙麦地区中-新生代伸展构造特征研究

介绍了伸展构造概念与研究现状，沙麦地区中—新生代伸展构造基本特征与形成机制。认为区内中—新生代盆地是地壳呈北西西—南东东向伸展的结果，地壳的伸展演化并不连续，呈现幕式伸展的特点。     

三角洲平原上网结河的发育与聚煤作用

龙潭组上段（２４＃煤顶板到１２＃煤）是盘县地区含煤最好的层段，对该区西北部本段地层的研究表明其中发育有网结河体系。河道沉积由多层叠置的鞋带状砂体组成，湿地沉积主要由菱铁质泥质岩夹薄层板状细砂岩（决口扇沉积）和煤组成。河流的发育和聚煤作用都显示幕式性，可能主要受海平面变化的控制。网结状河道被认为是海侵期对低位下切河谷充填过程中经侧向冲裂水道并相互连通形成的；稳定、连续的厚煤层发育于河道大范围废弃后的海侵晚期，其次是高水位早期。     

Assessment of episodic acidification in Sierra Nevada,California

Monte-Carlo simulations were used to assess the extent of shortterm alkalinity depressions occuring in Sierra Nevada lakes due to acidic deposition events. The Episodic Event Model (EEM) was used to simulate spring snowmelt events. Snow course data, precipitation data and lake acidification surveys were used to derive values for the EEM parameters. Spring snowmelt events were shown to have great impacts on the water quality of Sierran lakes. Lakes are likely to be most affected by the early-spring snowmelt event because the epilimnion depth is at a minimum, which indicates minimum dilution. Under annual average loading conditions, no Sierran lake has been reported as acidic although 29% of the lakes have alkalinities less than 40 µeq/L indicating a sensitivity to acidification. In simulations of early-spring snowmelt events, using present-day acidic loading conditions, it was estimated 79% ± 9% of the lakes would experience shortterm lake alkalinity depressions to levels less than 40 µeq/L. The results provided by the model simulations are valuable in establishing upper and lower limits on the extent of possible episodic acidification to lake-resources-at-risk. The most critical parameters controlling the magnitude of lake alkalinity depressions during snowmelt episodic events are a) the lake area to watershed area ratio — a measure of input loading, and b) the epilimnion volume — a measure of dilution and mixing.     

超压盆地中泥岩的流体压裂与幕式排烃作用

流体压裂是在异常高流体压力体系的低渗泥岩中流体活动的主要输导通道。流体压裂不仅导致低渗泥岩的幕式压实作用,而且为油气运移,储集的研究提供了新的理论模式。超压盆地泥岩的压实演化可划分为两个阶段,即连续压实和幕式压实阶段,其中幕式压实阶段又可根据导致流体压裂的主控因素进一步划分为两个亚阶段,即水力压裂和生烃压裂,前者主要由于泥岩欠压实和新生流体源的增压所致,后者则主要由于泥岩中有机质生烃及烃类裂解后增     

洞庭盆地中更新世洞庭湖组砾石特征及其意义

对位于洞庭盆地安乡凹陷东南部的两护村ZKC1孔中更新世洞庭湖组砾石层进行了粒度和砾态的统计分析。结果表明,砾石的粒度变化反映出2个较大尺度的由大→小的旋回,早旋回由洞庭湖组下段砂砾层组成,晚旋回由洞庭湖组中段上部的砂砾层组成,反映出中更新世早-中期安乡凹陷的两次由慢→快的幕式沉降过程。在上述2个大的粒度旋回之上,叠加有多个更小尺度的砾石粗、细变化,主要与气候干湿的频繁波动有关。洞庭湖组中段顶部砾石的磨圆度明显偏低,反映其沉积时期盆地沉降和周缘隆起区抬升活动的增强。     

阵发性洪水条件下辫状河型冲积扇构型研究:以准噶尔盆地西北缘现代白杨河冲积扇为例*

白杨河冲积扇是由阵发性洪水期的碎屑流沉积物与间洪期辫状河沉积物组成的复合型冲积扇,其构型与碎屑流扇的构型和河流型扇的构型有很大的不同。本研究选取准噶尔盆地西北缘干旱气候下发育的现代白杨河冲积扇作为解剖实例,对103个天然剖面和9个人工大型探槽进行了详细测量,在沉积微相及不同级别的沉积构型的观测和分析的基础上,分析了阵发性洪水条件下间歇性辫状河型冲积扇体的地貌单元的演化过程和沉积构型特征,研究不同流态的阵发性洪水条件下各种建造和改造机制,明确受阵发性洪水控制的间歇性辫状河型冲积扇的沉积特征,建立了其沉积构型模式。认为: 在洪水期,阵发性洪流(碎屑流)形成席状化的片流(或片洪)沉积,在洪退期,随着洪水强度的减弱,又转变为辫流沉积,而在间洪期,仍有持续的辫状流体(牵引流)在限制性的水道中流动,并对洪水期的碎屑流沉积物进行改造,形成了限制性的(条带状的)辫状河道沉积,2个时期的沉积物在时空上频繁叠置,形成了一种更加复杂的沉积构型。该模式对油田地下冲积扇砂砾储集层的成因识别、预测及对比具有一定的参考价值。     

Spillage sedimentation on large river floodplains

Active deposition across the floodplains of large rivers arises through a variety of processes; collectively these are here termed ‘spillage sedimentation’. Three groups of 11 spillage sedimentation styles are identified and their formative processes described. Form presences on large river floodplains show different combinations of active spillage styles. Only some large floodplains have prominent levees; some have coarse splays; many have accessory channel dispersion and reworking, while still‐water sedimentation in lacustrine environments dominates some lower reaches. Infills are also commonly funnelled into prior, and often linear, negative relief forms relating to former migration within the mainstream channel belt. Shuttle Radar Topography Mission (SRTM) and Landsat 8 data are used to map spillage form types and coverage along a 1700 km reach of the Amazon that has an active floodplain width of up to 110 km with a systematic character transformation down‐valley. Spillage forms associated directly with mainstream processes rarely account for more than 5% of the floodplain deposits. There is a marked decrease in floodplain point bar complexes (PBC) over 1700 km downstream (from 34% to 5%), and an increase in the prevalence of large water bodies (2% to 37%) and accompanying internal crevasses and deltas (0% to 5%). Spillage sedimentation is likely within the negative relief associated with these forms, depending on mainstream sediment‐laden floodwater inputs. Spillage style dominance depends on the balance between sediment loadings, hydrological sequencing, and morphological opportunity. Down‐river form sequences are likely to follow gradient change, prior up‐river sediment sequestration and the altered nature of spilled loads, but also crucially, local floodplain relief and incident water levels and velocities at spillage times. Considering style distribution quantitatively, as a spatially distributed set of identifiable forms, emphasizes the global variety to spillage phenomena along and between large rivers. © 2016 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

Estimating the sediment trap efficiency of intermittently dry reservoirs: lessons from the Kruger National Park,South Africa

The assessment of sediment yield from reservoir siltation requires knowledge of the reservoir's sediment trap efficiency (TE). Widely used approaches for the estimation of the long‐term mean TE rely on the ratio of the reservoir's storage capacity (C) to its catchment size (A) or mean annual inflow (I). These approaches have been developed from a limited number of reservoirs (N ≤ 40), most of them located in temperate climate regions. Their general applicability to reservoirs receiving highly variable runoff such as in semi‐arid areas has been questioned. Here, we examine the effect of ephemeral inflow on the TE of 10 small (≤ 280 × 10³ m³), intermittently dry reservoirs located in the Kruger National Park. Fieldwork was conducted to determine the storage capacity of the reservoir basins. The frequency and magnitude of spillage events was simulated with the daily time step Pitman rainfall–runoff model. Different runoff scenarios were established to cope with uncertainties arising from the lack of runoff records and imperfect input data. Scenarios for the relationship between water and sediment discharge were created based on sediment rating curves. Taking into account uncertainties in hydrological modelling, uncertainties of mean TE estimates, calculated from all scenarios (N = 9), are moderate, ranging from ±6 to ±11% at the 95% confidence level. By comparison, estimating TE from the storage capacity to catchment area (C/A) ratio induces high uncertainty (ranges of 35 to 65%), but this uncertainty can be confined (15 to 33%) when the latter approach is combined with hydrological modelling. Established methods relying on the storage capacity to mean annual inflow (C/I) ratio most probably lead to an overestimation of the TE for the investigated reservoirs. The approach presented here may be used instead to estimate the TE of small, intermittently dry reservoirs in semi‐arid climate regions. Copyright © 2017 John Wiley & Sons, Ltd.     

Prediction of episodic acidification in North‐eastern USA: an empirical/mechanistic approach

Observations from the US Environmental Protection Agency's Episodic Response Project (ERP) in the North‐eastern United States are used to develop an empirical/mechanistic scheme for prediction of the minimum values of acid neutralizing capacity (ANC) during episodes. An acidification episode is defined as a hydrological event during which ANC decreases. The pre‐episode ANC is used to index the antecedent condition, and the stream flow increase reflects how much the relative contributions of sources of waters change during the episode. As much as 92% of the total variation in the minimum ANC in individual catchments can be explained (with levels of explanation >70% for nine of the 13 streams) by a multiple linear regression model that includes pre‐episode ANC and change in discharge as independent variables. The predictive scheme is demonstrated to be regionally robust, with the regional variance explained ranging from 77 to 83%. The scheme is not successful for each ERP stream, and reasons are suggested for the individual failures. The potential for applying the predictive scheme to other watersheds is demonstrated by testing the model with data from the Panola Mountain Research Watershed in the South‐eastern United States, where the variance explained by the model was 74%. The model can also be utilized to assess ‘chemically new’ and ‘chemically old’ water sources during acidification episodes. Copyright © 1999 John Wiley & Sons, Ltd.     

Memory in place

Geographers and psychologists both seek to understand people's behaviour and their cognitive and emotional lives so it is somewhat surprising that there has not been more theoretical cross‐fertilisation of the two disciplines. ‘On time, place and happiness’ is a rare but welcome exception, showing how research in social‐cognitive psychology might usefully clarify thinking about temporality, place and well‐being. This commentary examines several additional human memory phenomena that geographers might like to consider in their theorising about these matters.