Flow Cross K-function: a bivariate flow analytical method

Spatial flow data represent meaningful interaction activities between pairs of corresponding locations, such as daily commuting, animal migration, and merchandise shipping. Despite recent advances in flow data analytics, there is a lack of literature on detecting bivariate or multivariate spatial flow patterns. In this paper we introduce a new spatial statistical method called Flow Cross K-function, which combines the Cross K-function that detects marked point patterns and the Flow K-function that detects univariate flow clustering patterns. Flow Cross K-function specifically assesses spatial dependence of two types of flow events, in other words, whether one type of flows is spatially associated with the other, and if so, whether this is according to a clustering or dispersion trend. Both a global version and a local version of Flow Cross K-function are developed. The former measures the overall bivariate flow patterns in the study area, while the latter can identify anomalies at local scales that may not follow the global trend. We test our method with carefully designed synthetic data that simulate the extreme situations. We exemplify the usefulness of this method with an empirical study that examines the distributions of taxi trip flows in New York City.     

气候变化背景下尼雅河流域生态基流研究

流域生态基流是河流生态系统健康稳定的关键,以新疆尼雅河流域为研究区域,根据民丰县气象站1958—2018年的气象数据与尼雅河4个水文监测断面1978—2018年的水文数据,运用趋势拟合、Tennant法、相关性分析和回归模型等分析流域气候变化、确定生态基流并探究其时空分异与保证率变化,揭示生态基流对气候变化的响应。结果表明：61 a来流域气温以0.22 ℃·(10a)^-1的速度增加,年降水量以3.8 mm·(10a)^-1的速度增加;尼雅水库、八一八渠首、尼雅水文站和尼雅渠首的年生态基流推荐值分别为：1.989 m³·s^-1、2.188 m³·s^-1、1.755 m³·s^-1、1.702 m³·s^-1;生态基流年际最大值出现在2010年,最小值在1980年,年内最大值在7月,最小值在1月或12月;空间上表现为上游高下游低,以八一八渠首处最高,尼雅渠首处最低;各站多年平均生态基流保证率分别为：50%、45%、50%、45%,且表现出汛期明显高于非汛期;逐年、逐月生态基流与气温、降水量均在0.01水平上显著相关,但在春夏季对气温敏感,秋冬季对降水量敏感,各水文监测断面的回归模型耦合效果相似,流域整体回归方程R²=0.365,且生态基流对气候变化响应具有整体性和衰减性。研究结果可为尼雅河流域生态调水和水生态修复提供参考。     

Subsurface fluid flow in the deep‐water Kwanza Basin,offshore Angola

Integrated analysis of high‐quality three‐dimensional (3D) seismic, seabed geochemistry, and satellite‐based surface slick data from the deep‐water Kwanza Basin documents the widespread occurrence of past and present fluid flow associated with dewatering processes and hydrocarbon migration. Seismic scale fluid flow phenomena are defined by seep‐related seafloor features including pockmarks, mud or asphalt volcanoes, gas hydrate pingoes, as well as shallow subsurface features such as palaeo‐pockmarks, direct hydrocarbon indicators (DHIs), pipes and bottom‐simulating reflections (BSRs). BSR‐derived shallow geothermal gradients show elevated temperatures attributed to fluid advection along inclined stratigraphic carrier beds around salt structures in addition to elevated shallow thermal anomalies above highly conductive salt bodies. Seabed evidences of migrated thermogenic hydrocarbons and surface slicks are used to differentiate thermogenic hydrocarbon migration from fluid flow processes such as dewatering and biogenic gas migration. The analysis constrains the fluid plumbing system defined by the three‐dimensional distribution of stratigraphic carriers and seal bypass systems through time. Detailed integration and iterative interpretation have confirmed the presence of mature source rock and effective migration pathways with significant implications for petroleum prospectivity in the post‐salt interval. Integration of seismic, seabed geochemistry and satellite data represents a robust method to document and interpret fluid flow phenomena along continental margins, and highlights the importance of integrated fluid flow studies with regard to petroleum exploration, submarine geohazards, marine ecosystems and climate change.     

Nature and origin of magnetic minerals within the Middle Jurassic shallow-water carbonate rocks of the Paris Basin, France: implications for magnetostratigraphic dating

The Middle and Upper Jurassic Bathonian-Oxfordian shallow-water carbonate rocks from the Paris Basin, France, consist mainly of oolitic and bioclastic limestones that are hydrocarbon reservoirs in the subsurface. Despite a preliminary positive study, these deposits have been considered to be largely remagnetized (Rochette, private communication), and hence not amenable to palaeomagnetic dating. To establish their magnetic mineralogy and test this remagnetization hypothesis, we have used an integrated investigation combining petrographic, geochemical, rock-magnetic and palaeomagnetic measurements on samples extracted from five cores from the Paris Basin and from outcrops in Burgundy. Magnetic minerals in the Bathonian-Oxfordian carbonates include: (1) primary biogenic single-domain magnetite and detrital multi-domain Ti-magnetite and their oxidized form, maghemite; (2) authigenic spheres of magnetite probably related to hydrocarbons; and (3) goethite, either restricted to ferruginous ooid layers or resulting from surficial alteration, notably replacement of pyrite framboids. Rock-magnetic experiments carried out on 68 samples reveal H _cr/ H _c and M _rs/ M _s ratios ranging from 1.88 to 5.58 and 0.017 to 0.314, respectively. These values are clearly distinct from diagnostic values for a chemical remagnetization. Pyrrhotite was not identified within these sediments. Moreover, the average H _cr/ H _c ratio of 3.14 is significantly different from the value of 1.333 for natural pyrrhotite (Dekkers 1988). These results have a direct implication for the preservation of the primary magnetization; consequently, these deposits are selectively amenable for magnetostratigraphic dating and possible regional correlations.     

Terrestrial heat flow and lithospheric thermal structure in the Chagan Depression of the Yingen-Ejinaqi Basin,north central China

The Chagan Depression in the Yingen-Ejinaqi Basin, located at the intersection of the Paleo-Asian Ocean and the Tethys Ocean domains is an important region to gain insights on terrestrial heat flow, lithospheric thermal structure and deep geodynamic processes. Here, we compute terrestrial heat flow values in the Chagan Depression using a large set of system steady-state temperature data from four representative wells and rock thermal conductivity. We also estimate the “thermal” lithospheric thickness, mantle heat flow, ratio of mantle heat flow to surface heat flow and Moho temperature to evaluate the regional tectonic framework and deep dynamics. The results show that the heat flow in the Chagan Depression ranges from 66.5 to 69.8 mW/m², with an average value of 68.3 ± 1.2 mW/m². The Chagan Depression is characterized by a thin “thermal” lithosphere, high mantle heat flow, and high Moho temperature, corresponding to the lithospheric thermal structure of “cold mantle and hot crust” type. We correlate the formation of the Yingen-Ejinaqi Basin to the Early Cretaceous and Cenozoic subduction of the western Pacific Plate and the Cenozoic multiple extrusions. Our results provide new insights into the thermal structure and dynamics of the lithospheric evolution in central China.     

巴黎城市规划布局规律及特点研究

本文在对巴黎城市布局实地考察的基础上,对城市布局规律及特点进行了较为系统和深入的研究。得出巴黎城市布局的主要特点：（1）选择数个（一般为3个）或在高度或在体量上具有一定特点的建筑物作为整个建筑群的主体性建筑统领全区,使该区内其他的建筑物围绕着这些主体标志规则布局。这就使得上述建筑群的布局大多呈现出“三段式”的典型形式。（2）各区内的建筑物多依其地形、道路的走向规则布局。各建筑物间的组合形式既有方形．长方形,也有梯形、三角形以及不规则的四边形等形状。且各组间多呈闭合状态。（3）在建筑群的中心轴线地带内,均为绿化园林区（带）,各建筑群的布局均主题突出、清晰明确。（4）城市的各交通枢纽（交叉路口）均以城市广场作为其基本的布局形式。各交通枢纽间均以宽阔、笔直的林荫大道相连,且每条大街都通向一处纪念性的建筑物。     

Focused fluid flow systems of the Zhongjiannan Basin and Guangle Uplift,South China Sea

In this article, we document a large number of focused fluid escape structures using high quality 2D seismic reflection data and multibeam bathymetry data from a poorly known area at the intersection of the northern South China Sea (SCS) and the western SCS. Three types of focused fluid escape systems are identified and described: mud volcanoes, pipes and associated pockmarks. The mud volcanoes occur singly or as clustered groups. The overpressure driving the mud volcanism is argued herein to be related to the generation of thermogenic hydrocarbons. The clustered distributions are related to localized tectonic uplift in the basin. Pipes mainly occur within the Guangle Uplift or accompany the mud volcano clusters. The pipes located within the Guangle Uplift are attributed to carbonate dissolution caused by hydrothermal fluids. Fluids ascended through these structures and were expelled at the palaeo‐seabed or present seabed forming palaeo‐pockmarks and present‐day pockmarks. Some ‘mega‐pockmarks’ show evidence of enlargement due to bottom currents. The marginal basins of the SCS are petroliferous, with attention gradually shifting to the deep‐water area. Our results show that fluid migration must be taken into account when assessing seabed stability. This analysis also improves our understanding the petroleum geology in the study area, and is also useful for predicating where chemosynthetic ecosystems may be located.     

基于标准化流量指数(SDI)的石羊河流域水文干旱特征

利用石羊河流域8个水文站1961－2017年逐月实测流量数据和4个气象站点的气象观测资料,采用标准化流量指数（SDI）、游程理论来获得干旱事件的特征指标,分析了石羊河流域水文干旱演变特征,并采用与降水量、最高气温、最低气温、平均气温、蒸发量的相关性来分析石羊河流域SDI的影响因素。结果表明：1961—2017年石羊河流域干旱历时、干旱烈度和干旱强度的变化不是很一致,流域水文干旱历时20世纪70年代最长,80年代最短;干旱烈度全流域90年代最强,烈度最弱出现在80年代;干旱强度全流域60年代最强,80年代强度最弱;石羊河流域及流域中、西部年SDI变化总体上表现为在波动中呈增加趋势,西部增加幅度最大,中部增加幅度很小,流域东部年SDI在波动中呈减小趋势;石羊河全流域及流域东、中和西部年及四季干旱发生频次总体都是中旱和重旱频次最多,四季水文干旱发生频率最高的是春季,冬季干旱发生频率最低;从流域不同地段看,水文干旱发生的频率流域东部最高;构建的SDI 临界值识别出的主要水文干旱事件和实际干旱事件基本一致,干旱等级也较一致,说明使用SDI能够较好地监测到石羊河流域干旱年份及干旱等级;石羊河流域年SDI值与最高气温、平均气温和蒸发量呈负相关,与降水量和平均气温呈正相关。     

Contribution of a three-dimensional regional scale basin model to the study of the past fluid flow evolution and the present hydrology of the Paris basin, France

A basin model was built to simulate in three dimensions the 248 Myr geological history of the Paris basin, France, i.e. sedimentation, erosion, compaction heat and fluid flow. This multidisciplinary study was based on a detailed stratigraphic database of more than 1100 well logs together with a hydrodynamic database of 1000 data (heads and permeabilities). The region covers a maximum surface area of 700 000 km². The NEWBAS code of the Ecole des Mines de Paris was used in order to simulate compaction and heat and fluid flow. Three examples of the use of this model are given to illustrate different features of the geological functioning of the basin. (i) By modelling processes such as sedimentation, compaction, fluid and heat flow, the model provides estimates of the hydraulic conductivity fields within one order of magnitude from observations at the regional scale. This permeability field can reproduce the present‐day observed pressures and fluxes in the basin. (ii) Observed excess pressures in the main aquitards are considered as possible consequences of the geological history of the basin. The calculated excess pressures are small and stay within the range of the measured values, between 0 and 2.75 MPa, close to the pressures in the aquifers. However, the weak excess pressures measured in the Callovo–Oxfordian sequence in the eastern part of the basin are not reproduced by the model. Mechanisms other than compaction disequilibrium must be invoked. (iii) This model also calculates regional‐scale palaeofluid flow whose value is currently arbitrarily assumed by geochemists when studying diagenetic processes. Hence, it provides a hydrologic background for diagenetic models. The cementation in the western Keuper reservoirs was investigated. Topographically driven flow during tectonic inversion periods, e.g. the Lower Cretaceous and Early Tertiary, is shown to be a plausible cause of brine migrations. This brine displacement would then explain the high salinities recorded in the fluid inclusions trapped in the Keuper cements. The conditions for the migration would have been most favourable at the time of the maximum burial, i.e. the Early Tertiary and not the Early Cretaceous as previously suggested.     

北京清水河流域现代稀性泥石流物质选频释光特性

采用BG2003释光谱仪对北京清水河流域达摩沟、西北山沟的稀性泥石流物质选频释光特性进行研究,并将其与云南蒋家沟流域现代粘性泥石流物质进行比较。研究表明:北京清水河流域泥石流物质样品受热激发后,290nm、310nm、400nm、480nm释光响应最为明显。储能电子主要源自的能级为4.28eV、4.00eV、3.50eV、2.58eV。用532nm绿光激发后,310nm、480nm释光响应最为明显,相应的储能电子主要源自的能级为4.00eV、2.58eV。采用选频释光技术能够区分清水河流域和蒋家沟流域的泥石流物质。该事实对进一步探索采用选频释光技术进行泥石流断代及泥石流物源识别具有基础性意义。     

Temporal and spatial trends of precipitation and river flow in the Yangtze River Basin, 1961–2000

The suspected impact of climate warming on precipitation distribution is examined in the Yangtze River Basin. Daily precipitation data for 147 meteorological stations from 1961–2000 and monthly discharge data for three stations in the basin have been analyzed for temporal and spatial trends. The methods used include the Mann–Kendall test and simple regression analysis. The results show (1) a significant positive trend in summer precipitation at many stations especially for June and July, with the summer precipitation maxima in the middle and lower Yangtze River basin in the 1990s; (2) a positive trend in rainstorm frequency that is the main contributor to increased summer precipitation in the basin; and (3) a significant positive trend in flood discharges in the middle and lower basin related to the spatial patterns and temporal trends of both precipitation and individual rainstorms in the last 40 years. The rainstorms have aggravated floods in the middle and lower Yangtze River Basin in recent decades. The observed trends in precipitation and rainstorms are possibly caused by variations of atmospheric circulation (weakened summer monsoon) under climate warming.     

Crustal‐scale fluid flow during the tectonic evolution of the Bighorn Basin (Wyoming,USA)

Stable isotope measurements (O, C, Sr), microthermometry and salinity measurements of fluid inclusions from different fracture populations in several anticlines of the Sevier‐Laramide Bighorn basin (Wyoming, USA) were used to unravel the palaeohydrological evolution. New data on the microstructural setting were used to complement previous studies and refine the fracture sequence at basin scale. The latter provides the framework and timing of fluid migration events across the basin during the Sevier and Laramide orogenic phases. Since the Sevier tectonic loading of the foreland basin until its later involvement into the Laramide thick‐skinned orogeny, three main fracture sets (out of seven) were found to have efficiently enhanced the hydraulic permeability of the sedimentary cover rocks. These pulses of fluid are attested by calcite crystals precipitated in veins from hydrothermal (T > 120 °C) radiogenic fluids derived from Cretaceous meteoric fluids that interacted with the Precambrian basement rocks. Between these events, vein calcite precipitated from formational fluids at chemical and thermal equilibrium with surrounding environment. At basin scale, the earliest hydrothermal pulse is documented in the western part of the basin during forebulge flexuring and the second one is documented in basement‐cored folds during folding. In addition to this East/West diachronic opening of the cover rocks to hydrothermal pulses probably controlled by the tectonic style, a decrease in ^87/86Sr values from West to East suggests a crustal‐scale partially squeegee‐type eastward fluid migration in both basement and cover rocks since the early phase of the Sevier contraction. The interpretation of palaeofluid system at basin scale also implies that joints developed under an extensional stress regime are better vertical drains than joints developed under strike‐slip regime and enabled migration of basement‐derived hydrothermal fluids.     

Effect of the Cretaceous Serra Geral igneous event on the temperatures and heat flow of the Parana Basin, southern Brazil

We investigate the effects of the cooling of intrusive and extrusive igneous bodies on the temperature history and surface heat flow of the Parana Basin. The Serra Geral igneous event (130–135 Ma) covered most of this basin with flood basalts. Associated with this event numerous sills and dykes intruded the sediments and basement, and extensive underplating may have occurred in the lower crust and upper mantle beneath the basin. We develop an analytical model of the conductive cooling of tabular intrusive bodies and use it to calculate temperatures within the sediments as a function of time since emplacement. Depending on the thickness of these igneous bodies and the timing of sequential emplacement, the thermal history of a given locus in the basin can range from a simple extended period of higher temperatures to multiple episodes of peak temperatures separated by cooling intervals. The cooling of surface flood basalts, sills and dykes is capable of maintaining temperatures abovc the normal geothermal gradient temperatures for a few hundred thousand years, while large-scale underplating may influence temperatures for up to 10 million years. We conclude that any residual heat from the cooling of the Serra Geral igneous rocks has long since decayed to insignificant values and that present-day temperatures and heat flow are not affected. However, the burial of the sediments beneath the thick basalt cap caused a permanent temperature increase of up to 50°C in the underlying sediments since the beginning of the Cretaceous.     

Multiethnic Economic Activity Along Three Immigrant Corridors in Paris

Ethnic neighborhoods and ethnic economies do not always involve a single nationality or ethnic group. Quite often several groups operate side by side in the neighborhood and within the establishments themselves. This can give rise to a modification of the ethnic economy concept. We discuss an example of such a multiethnic residential and business district in Paris, the Goutte d’Or, with particular attention to three shopping streets. Although somewhat distinct from one another, each of these streets is multiethnic in regard to the proprietors, employees, and customers, and this multiethnicity extends within the establishments themselves. The primary questions we ask in this article are, first, what the nature of this ethnic economy is and how it fits within the different types of ethnic economy. Beyond this, we demonstrate how the activities taking place here reflect separate circuits of activity at separate spatial scales and what this ethnic business activity suggests for immigrant incorporation in Paris and the nature of cross-ethnic relations. To answer these questions, we rely on observation, interviews with several merchants in defined commercial corridors, and some official statistical and political information gleaned from various government sources. This Parisian neighborhood exemplifies strategies of immigrant incorporation into French society. As such, it provides a possible new model of a multiethnic economy, one that might become a common fixture in increasingly diverse cities in the world.     

Effect of the Cretaceous Serra Geral igneous event on the temperatures and heat flow of the Paraná Basin, southern Brazil

We investigate the effects of the cooling of intrusive and extrusive igneous bodies on the temperature history and surface heat flow of the Paraná Basin. The Serra Geral igneous event (130–135 Ma) covered most of this basin with flood basalts. Associated with this event numerous sills and dykes intruded the sediments and basement, and extensive underplating may have occurred in the lower crust and upper mantle beneath the basin. We develop an analytical model of the conductive cooling of tabular intrusive bodies and use it to calculate temperatures within the sediments as a function of time since emplacement. Depending on the thickness of these igneous bodies and the timing of sequential emplacement, the thermal history of a given locus in the basin can range from a simple extended period of higher temperatures to multiple episodes of peak temperatures separated by cooling intervals. The cooling of surface flood basalts, sills and dykes is capable of maintaining temperatures above the normal geothermal gradient temperatures for a few hundred thousand years, while large-scale underplating may influence temperatures for up to 10 million years. We conclude that any residual heat from the cooling of the Serra Geral igneous rocks has long since decayed to insignificant values and that present-day temperatures and heat flow are not affected. However, the burial of the sediments beneath the thick basalt cap caused a permanent temperature increase of up to 50°C in the underlying sediments since the beginning of the Cretaceous.     

石羊河流域的水资源

石羊河流域分为径流形成区(山区)和散失区(平原区),由河流联接成为统一的水资源系统和完整的生态单元。全流域出山地表水资源15.82亿立方米,平原区纯地下水天然资源1.54亿立方米,合计7.36亿立方米。地表径流主要形成于高山区,面积占30%的高山区(3400米以上),产流量占74%。山区河流有连续丰、枯水年,丰水年持续期为10年,枯水年持续期达20年。本流域山前平原地区的地表水、地下水相互制约,相互转化,水资源主要来自山区,地下水是地表水的渗漏,泉水是出露的地下水。水资源转化为重复利用和提高利用率创造了条件,但不能增加数量。