Stratigraphy, depositional environments and level reconstruction of the last interglacial Lake Samra in the Dead Sea basin

In this paper we describe the stratigraphy and sediments deposited in Lake Samra that occupied the Dead Sea basin between ∼ 135 and 75 ka. This information is combined with U/Th dating of primary aragonites in order to estimate a relative lake-level curve that serves as a regional paleohydrological monitor. The lake stood at an elevation of ∼ 340 m below mean sea level (MSL) during most of the last interglacial. This level is relatively higher than the average Holocene Dead Sea (∼ 400 ± 30 m below MSL). At ∼ 120 and ∼ 85 ka, Lake Samra rose to ∼ 320 m below MSL while it dropped to levels lower than ∼ 380 m below MSL at ∼ 135 and ∼ 75 ka, reflecting arid conditions in the drainage area. Lowstands are correlated with warm intervals in the Northern Hemisphere, while minor lake rises are probably related to cold episodes during MIS 5b and MIS 5d. Similar climate relationships are documented for the last glacial highstand Lake Lisan and the lowstand Holocene Dead Sea. Yet, the dominance of detrital calcites and precipitation of travertines in the Dead Sea basin during the last interglacial interval suggest intense pluvial conditions and possible contribution of southern sources of wetness to the region.     

Structural controls on fractured coal reservoirs in the southern Appalachian Black Warrior foreland basin

Coal is a nearly impermeable rock type for which the production of fluids requires the presence of open fractures. Basin-wide controls on the fractured coal reservoirs of the Black Warrior foreland basin are demonstrated by the variability of maximum production rates from coalbed methane wells. Reservoir behavior depends on distance from the thrust front. Far from the thrust front, normal faults are barriers to fluid migration and compartmentalize the reservoirs. Close to the thrust front, rates are enhanced along some normal faults, and a new trend is developed. The two trends have the geometry of conjugate strike-slip faults with the same σ₁ direction as the Appalachian fold-thrust belt and are inferred to be the result of late pure-shear deformation of the foreland. Face cleat causes significant permeability anisotropy in some shallow coal seams but does not produce a map-scale production trend.     

Magnetic anomalies across Bastar craton and Pranhita-Godavari basin in south of central India

Aeromagnetic anomalies over Bastar craton and Pranhita-Godavari (P-G) basin in the south of central India could be attributed to NW-SE striking mafic intrusives in both the areas at variable depths. Such intrusions can be explained considering the collision of the Bastar and Dharwar cratons by the end of the Archaean and the development of tensile regimes that followed in the Paleoproterozoic, facilitating intrusions of mafic dykes into the continental crust. The P-G basin area, being a zone of crustal weakness along the contact of the Bastar and Dharwar cratons, also experienced extensional tectonics. The inferred remanent magnetization of these dykes dips upwards and it is such that the dykes are oriented towards the east of the magnetic north at the time of their formation compared to their present NW-SE strike. Assuming that there was no imprint of magnetization of a later date, it is concluded that the Indian plate was located in the southern hemisphere, either independently or as part of a supercontinent, for some span of time during Paleoproterozoic and was involved in complex path of movement and rotation subsequently. The paper presents a case study of the utility of aeromagnetic anomalies in qualitatively deducing the palaeopositions of the landmasses from the interpreted remanent magnetism of buried intrusive bodies.     

关于敦化盆地下白垩统的讨论

前人根据敦化盆地的地层的地层,认为该盆地下白垩统为河流—湖泊相碎屑岩。通过对新钻的敦参1井岩屑录井资料的分析、对16条二维地震资料的层位标定与追踪,以及对敦化盆地早白垩世盆地演化阶段的分析,得到了以下主要结论:1)敦化盆地下白垩统可能有两种分布形态,在盆地的主体部位,以浅变质岩形态存在,而在其他部位则以正常沉积岩形态零星存在;2)敦化盆地白垩系的分布规模不大,夹持于一个北北东向的狭窄长槽内;3)敦化盆地早白垩世处于裂谷盆地发展的初始张裂阶段;4)敦化盆地下白垩统不宜作为勘探目的层。     

大型凹陷向斜区油气倒灌式成藏——以松辽盆地三肇凹陷扶杨油层为例

三肇凹陷扶杨油层为典型大型凹陷向斜区油气倒灌式成藏,利用300条地震剖面、825口井曲线、11口井岩芯和探评井试油资料对扶杨油层断层特征及运动期次、油气下排深度、储层沉积特征等油气成藏主控因素综合研究表明：T2断层受控于基底断层、下部火山口、斜向拉张和伸展量差异四种因素具有平面密集成带、剖面“似花状”组合特征,且油气成藏期活动的油源断层多数为断层密集带边界断层;理论计算超压驱动油气下排深度和实际油底包络面统计扶杨油层含油厚度约为200m;重矿物分析扶杨油层主要受北部拜泉—青冈和西南保康物源影响,两物源在徐家围子地区交汇后向东流出;沉积微相揭示扶杨油层发育向上逐渐退积的河控浅水三角洲沉积体系,顶部为三角洲前缘亚相,中—下部为三角洲分流平原亚相,其中扶Ⅰ7—扶Ⅱ1小层为水退最大期,是油气富集主要层位。明水组末期青山口组源岩达到生油高峰,油气在超压作用下沿开启的断层密集带边界断层幕式下排后沿两侧上升盘河道砂体做短距离侧向运移,即断层密集带两侧地垒或断阶块为油气富集区,而断层密集带内多为地堑式组合,不利于油气聚集,在成藏模式指导下刻画出47个油气富集目标区,为松辽盆地北部扶杨油层下一步的勘探与开发指明了方向。     

Brittle Rock Failure in the Steg Lateral Adit of the Lötschberg Base Tunnel

Summary  During the crossing of brittle rock formations at the L?tschberg base tunnel, failure phenomena have been observed both at the tunnel face and at the walls. A detailed analysis has been undertaken to explain these behaviours, based on the recent developments of Canadian research on brittle failure mechanisms. At the tunnel walls, a very good agreement is found between the calculated and observed damage and between two prediction methods, i.e. a semi-empirical failure criterion and elastic calculations with the “brittle Hoek-Brown parameters.” Near the face, due to the 3D nature of the stress conditions, some limitations of these approaches have been highlighted, and the growth of wall failure has been analysed. This research allowed a better understanding of the brittle rock mass behaviour at the L?tschberg base tunnel and showed that brittle failure processes dominate the behaviour of deep, highly stressed excavations in massive to moderately jointed rock. It also illustrates where improvements to the adopted approaches are required.     

Estimating economic losses of midrise reinforced concrete shear wall buildings in sedimentary basins by combining empirical and simulated seismic hazard characterizations

Studies of recorded ground motions and simulations have shown that deep sedimentary basins can greatly increase the intensity of earthquake ground motions within a period range of approximately 1–4 s, but the economic impacts of basin effects are uncertain. This paper estimates key economic indicators of seismic performance, expressed in terms of earthquake‐induced repair costs, using empirical and simulated seismic hazard characterizations that account for the effects of basins. The methodology used is general, but the estimates are made for a series of eight‐ to 24‐story residential reinforced concrete shear wall archetype buildings in Seattle, WA, whose design neglects basin effects. All buildings are designed to comply with code‐minimum requirements (i.e., reference archetypes), as well as a series of design enhancements, which include (a) increasing design forces, (b) decreasing drift limits, and (c) a combination of these strategies. As an additional reference point, a performance‐based design is also assessed. The performance of the archetype buildings is evaluated for the seismic hazard level in Seattle according to the 2018 National Seismic Hazard Model (2018 NSHM), which explicitly considers basin effects. Inclusion of basin effects results in an average threefold increase in annualized losses for all archetypes. Incorporating physics‐based ground motion simulations to represent the large‐magnitude Cascadia subduction interface earthquake contribution to the hazard results in a further increase of 22% relative to the 2018 NSHM. The most effective of the design strategies considered combines a 25% increase in strength with a reduction in drift limits to 1.5%.     

Mapping mineralogy in evaporite basins through time using multispectral Landsat data: Examples from the Bonneville basin,Utah, USA

The Bonneville basin, located in north-western Utah, is a vast evaporite basin which is home to the world-renowned Bonneville Salt Flats international speedway and is a highly valued landscape undergoing rapid change and anthropogenic influence. Air quality, snowpack, the local hydrological system, and state tourism are all impacted by the nature of the surface sediments exposed in the Bonneville basin. Mapping the Bonneville basin over time with remote sensing methods provides insight into the dynamics and impacts of the changing surface landscape. Utilizing the Landsat-5 Thematic Mapper (TM) and Landsat-8 Operational Land Imager (OLI) sensors, a set of band math indices are empirically established to map the predominant halite, gypsum, and carbonates mineralogical zones of the Bonneville basin. Spectral comparisons of representative samples from the study area and image-derived spectra indicate the halite of the Bonneville basin is wet and that gypsum deposits are slightly mixed with halite. The established indices are assessed in four ways, all of which support the ability of the indices to accentuate the associated mineralogical endmembers. Two study areas within the Bonneville basin are investigated temporally from 1986, 1995, 2005, and 2016 and show changing patterns in mineral distribution that align with surface processes active through these timescales. These indices provide a resource for mapping mineralogy though time in evaporite basins globally with diverse applications for questions about land use and environmental change.     

Role of reservoir regulation and groundwater feedback in a simulated ground-soil-vegetation continuum: A long-term regional scale analysis

The regional terrestrial water cycle is strongly altered by human activities. Among them, reservoir regulation is a way to spatially and temporally allocate water resources in a basin for multi-purposes. However, it is still not sufficiently understood how reservoir regulation modifies the regional terrestrial- and subsequently, the atmospheric water cycle. To address this question, the representation of reservoir regulation into the terrestrial component of fully coupled regional Earth system models is required. In this study, an existing process-based reservoir network module is implemented into NOAH-HMS, that is, the terrestrial component of an atmospheric–hydrologic modelling system, namely, the WRF-HMS. It allows to quantitatively differentiate role of reservoir regulation and of groundwater feedback in a simulated ground-soil-vegetation continuum. Our study focuses on the Poyang Lake basin, where the largest freshwater lake of China and reservoirs of different sizes are located. As compared to streamflow observations, the newly extended NOAH-HMS slightly improves the streamflow and streamflow duration curves simulation for the Poyang Lake basin for the period 1979–1986. The inclusion of reservoir regulation leads to major changes in the simulated groundwater recharges and evaporation from reservoirs at local scale, but has minor effects on the simulated soil moisture and surface runoff at basin scale. The performed groundwater feedback sensitivity analysis shows that the strength of the groundwater feedback is not altered by the consideration of reservoir regulation. Furthermore, both reservoir regulation and groundwater feedback modify the partitioning of the simulated evapotranspiration, thus affecting the atmospheric water cycle in the Poyang Lake region. This finding motivates future research with our extended fully coupled atmospheric–hydrologic modelling system by the community.