巴马盘阳河流域季节性移民社区类型与形成机理

季节性移民聚居现象受到西方学术界的极大关注,而我国鲜有研究。采用观察法和访谈法,对巴马盘阳河流域"一地多类"的季节性移民社区的形成过程、类型特征与作用机理进行归纳与揭示。研究表明：①季节性移民社区演变历经萌芽、快速参与和转型发展三个阶段,社区人口结构、聚居空间、经济业态、景观设施及人文氛围在不同时期呈现出不同的特征;②季节性移民社区形态存在差异,可以归类为交融性社区、优势性社区,共享性社区,纯粹性社区。③季节性移民社区是差异化的"美好生活"需求、独特的长寿资源及乡村生活环境、外来商业资本、地方政府调控和利益共生等"五力驱动"的结果,不同发展阶段其主导动力和作用方式存在差异。     

Evaluating Intensity in the Processing of Guanaco (Lama Guanicoe) at the Lower Basin of the Colorado River (Argentina): Fragmentation Levels and Fracture Patterns Analysis

This article explores the levels of fragmentation and fracture patterns in archaeofaunal assemblages from the lower basin of the Colorado River (Argentina) following Outram's methodology. Remains of ungulates (guanaco) have suffered, in these assemblages, a high degree of fragmentation probably caused during the processing of the carcasses. The presence of helical debris and shaft fragments indicates that fragmentation would respond to processing tasks for the consumption of marrow and possibly bone grease. The results of the application of this methodology that were obtained from the analysis of three late Holocene sites (La Primavera, Loma Ruiz 1 and El Tigre) are presented. These results provide new evidence not only for patterns of marrow and bone grease consumption but also for dealing with the subsistence model proposed for the study area. In this sense, the intensification processes already proposed during the final late Holocene (1000–250 bp ) are discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

Thermal convection in faulted extensional sedimentary basins: theoretical results from finite-element modeling

Thermal convection has the potential to be a significant and widespread mechanism of fluid flow, mass transport, and heat transport in rift and other extensional basins. Based on numerical simulation results, large‐scale convection can occur on the scale of the basin thickness, depending on the Rayleigh number for the basin. Our analysis indicates that for syn‐rift and early post‐rift settings with a basin thickness of 5 km, thermal convection can occur for basal heat flows ranging from 80 to 150 mW m^?2, when the vertical hydraulic conductivity is on the order of 1.5 m year^?1 and lower. The convection cells have characteristic wavelengths and flow patterns depending on the thermal and hydraulic boundary conditions. Steeply dipping extensional faults can provide pathways for vertical fluid flow across large thicknesses of basin sediments and can modify the dynamics of thermal convection. The presence of faults perturbs the thermal convective flow pattern and can constrain the size and locations of convection cells. Depending on the spacing of the faults and the hydraulic properties of the faults and basin sediments, the convection cells can be spatially organized to align with adjacent faults. A fault‐bounded cell occurs when one convection cell is constrained to occupy a fault block so that the up‐flow zone converges into one fault zone and the down‐flow zone is centred on the adjacent fault. A fault‐bounded cell pair occurs when two convection cells occupy a fault block with the up‐flow zone located between the faults and the down‐flow zones centred on the adjacent faults or with the reverse pattern of flow. Fault‐bounded cells and cell pairs can be referred to collectively as fault‐bounded convective flow. The flow paths in fault‐bounded convective flow can be lengthened significantly with respect to those of convection cells unperturbed by the presence of faults. The cell pattern and sense of circulation depend on the fault spacing, sediment and fault permeabilities, lithologic heterogeneity, and the basal heat flow. The presence of fault zones also extends the range of conditions for which thermal convection can occur to basin settings with Rayleigh numbers below the critical value for large‐scale convection to occur in a basin without faults. The widespread potential for the occurrence of thermal convection suggests that it may play a role in controlling geological processes in rift basins including the acquisition and deposition of metals by basin fluids, the distribution of diagenetic processes, the temperature field and heat flow, petroleum generation and migration, and the geochemical evolution of basin fluids. Fault‐bounded cells and cell pairs can focus mass and heat transport from longer flow paths into fault zones, and their discharge zones are a particularly favourable setting for the formation of sediment‐hosted ore deposits near the sea floor.     

Elemental analysis and characterization of ochre sources from Southern Arizona

Iron oxides and other associated minerals (ochre) were widely used in ancient times, however, the use and procurement of these materials is not well understood and there has been little research on the elemental characterization of the material compared to other artifact classes. To assess the possibility of identifying ochre differences between locations, the original potential geological sources should be thoroughly characterized. This paper describes the collection of potential geologic sources of ochre in the Tucson basin of Arizona, sampling of those sources, instrumental neutron activation analysis (INAA), and subsequent multivariate analysis of the data. This paper has several goals, including characterizing geochemical trends within and between ochre sources, identifying the important elements in geochemical characterization of ochre, and establishing a database for further investigations. This preliminary study indicates that the inter- and intra-source variations in geological sources of ochre in the Tucson basin region can be differentiated. Future analysis of iron oxide artifacts will be performed to examine correlations between artifacts and sources and provide a basis for further deductions concerning ancient ochre procurement.     

Equations of state for basin geofluids: algorithm review and intercomparison for brines

Physical properties of formation waters in sedimentary basins can vary by more than 25% for density and by one order of magnitude for viscosity. Density differences may enhance or retard flow driven by other mechanisms and can initiate buoyancy‐driven flow. For a given driving force, the flow rate and injectivity depend on viscosity and permeability. Thus, variations in the density and viscosity of formation waters may have or had a significant effect on the flow pattern in a sedimentary basin, with consequences for various basin processes. Therefore, it is critical to correctly estimate water properties at formation conditions for proper representation and interpretation of present flow systems, and for numerical simulations of basin evolution, hydrocarbon migration, ore genesis, and fate of injected fluids in sedimentary basins. Algorithms published over the years to calculate water density and viscosity as a function of temperature, pressure and salinity are based on empirical fitting of laboratory‐measured properties of predominantly NaCl solutions, but also field brines. A review and comparison of various algorithms are presented here, both in terms of applicability range and estimates of density and viscosity. The paucity of measured formation‐water properties at in situ conditions hinders a definitive conclusion regarding the validity of any of these algorithms. However, the comparison indicates the versatility of the various algorithms in various ranges of conditions found in sedimentary basins. The applicability of these algorithms to the density of formation waters in the Alberta Basin is also examined using a high‐quality database of 4854 water analyses. Consideration is also given to the percentage of cations that are heavier than Na in the waters.     

Exploring the potential linkages between oil‐field brine reinjection,crystalline basement permeability,and triggered seismicity for the Dagger Draw Oil field,southeastern New Mexico,USA, using hydrologic modeling

We used hydrologic models to explore the potential linkages between oil‐field brine reinjection and increases in earthquake frequency (up to M_d 3.26) in southeastern New Mexico and to assess different injection management scenarios aimed at reducing the risk of triggered seismicity. Our analysis focuses on saline water reinjection into the basal Ellenburger Group beneath the Dagger Draw Oil field, Permian Basin. Increased seismic frequency (>M_d 2) began in 2001, 5 years after peak injection, at an average depth of 11 km within the basement 15 km to the west of the reinjection wells. We considered several scenarios including assigning an effective or bulk permeability value to the crystalline basement, including a conductive fault zone surrounded by tighter crystalline basement rocks, and allowing permeability to decay with depth. We initially adopted a 7 m (0.07 MPa) head increase as the threshold for triggered seismicity. Only two scenarios produced excess heads of 7m five years after peak injection. In the first, a hydraulic diffusivity of 0.1 m² s^?1 was assigned to the crystalline basement. In the second, a hydraulic diffusivity of 0.3 m² s^?1 was assigned to a conductive fault zone. If we had considered a wider range of threshold excess heads to be between 1 and 60 m, then the range of acceptable hydraulic diffusivities would have increased (between 0.1–0.01 m² s^?1 and 1–0.1 m² s^?1 for the bulk and fault zone scenarios, respectively). A permeability–depth decay model would have also satisfied the 5‐year time lag criterion. We also tested several injection management scenarios including redistributing injection volumes between various wells and lowering the total volume of injected fluids. Scenarios that reduced computed excess heads by over 50% within the crystalline basement resulted from reducing the total volume of reinjected fluids by a factor of 2 or more.     

加大柴达木盆地生态建设和环境保护力度

柴达木盆地脆弱的生态环境是制约经济开发的重要因素之一,实施生态环境保护和绿色发展战略,是地区社会经济可持续发展的必然选择。为此,要以科学发展观为指导,不断加强对公民的生态意识教育,合理利用自然资源,建立资源节约型社会,统筹人与自然的和谐发展,加大资源和环境保护的行政管理和治理力度,使生态建设和环境保护走上法制化的轨道。     

Hunter–gatherer responses to environmental change during the Pleistocene–Holocene transition in the southern North Sea basin: Final Palaeolithic–Final Mesolithic land use in northwest Belgium

Situated along the southern fringe of the North Sea basin, northwest Belgium holds great potential for understanding hunter–gatherer responses to environmental change at the Pleistocene–Holocene transition. Recent intensive fieldwork has yielded valuable data on the palaeoenvironment, chronology, and hunter–gatherer mobility and land use in this region. At the Late Glacial/Early Holocene transition this region was comprised of a landscape of coversand ridges and lakes that flanked the northern part of the Scheldt river basin. This landscape was highly productive for hunter–gatherer populations. As the landscape developed in response to the increasing water table caused by the inundation of the North Sea populations responded by changing their forms of mobility and land use. These changes are indicated by the reduction in the number and density of sites, as well as their geographical settings, from the Late Glacial (Federmesser) and Early Mesolithic to the Middle-Final Mesolithic. Late Glacial/Early Mesolithic sites indicate much higher mobility comprised of rapid displacements of camps and re-occupation of the same coversand ridges over long time-spans. Middle/Late Mesolithic sites indicate a reduction in mobility, increasing focus on prolonged riverside settlement, and a more rigid organization of residential sites.     

ON THE RESOLUTION OF H/V MEASUREMENTS TO DETERMINE SEDIMENT THICKNESS,A CASE STUDY ACROSS A NORMAL FAULT IN THE LOWER RHINE EMBAYMENT,GERMANY

In recent years, H/V measurements have been increasingly used to map the thickness of sediment fill in sedimentary basins in the context of seismic hazard assessment. This parameter is believed to be an important proxy for the site effects in sedimentary basins (e.g. in the Los Angeles basin). Here we present the results of a test using this approach across an active normal fault in a structurally well known situation. Measurements on a 50 km long profile with 1 km station spacing clearly show a change in the frequency of the fundamental peak of H/V ratios with increasing thickness of the sediment layer in the eastern part of the Lower Rhine Embayment. Subsequently, a section of 10 km length across the Erft-Sprung system, a normal fault with ca. 750 m vertical offset, was measured with a station distance of 100 m. Frequencies of the first and second peaks and the first trough in the H/V spectra are used in a simple resonance model to estimate depths of the bedrock. While the frequency of the first peak shows a large scatter for sediment depths larger than ca. 500 m, the frequency of the first trough follows the changing thickness of the sediments across the fault. The lateral resolution is in the range of the station distance of 100 m. A power law for the depth dependence of the S-wave velocity derived from down hole measurements in an earlier study [Budny, 1984] and power laws inverted from dispersion analysis of micro array measurements [Scherbaum et aL, 2002] agree with the results from the H/V ratios of this study.