A molecular stratigraphic approach to palaeoenvironmental assessment and the recognition of changes in source inputs in marls of the Mulhouse Basin (Alsace, France)

Principal components analysis (PCA) has been used to investigate changes in concentrations of the components of the hydrocarbon fractions extracted from 71 marl samples, selected to cover two total organic carbon (TOC) maxima in the lower part of the Salt IV formation, a Lower Oligocene evaporitic sequence from the Mulhouse Basin, France. The analysis indicates that the fractions can be ascribed as lying between two end member distributions. The changes in these distributions are gradual, suggesting that they resulted from fairly gradual changes in the depositional palaeoenvironment. These changes are related to increased algal productivity associated with the evolution of a restricted lacustrine environment through to one with a greater marine influence. Systematic variations in the concentrations of selected components relative to the TOC profile point to a repeated sequential evolution in the biological assemblage during deposition of the sequence.     

Sedimentary Characteristics of the Cretaceous in the Songliao Basin

The rupture of the lithosphere in Late Jurassic brought about the eruption of basaltic magma in the Songliao Basin. The evolution of the basin in Cretaceous progressed through six stages: pre-rift doming, extensional fracturing, fault subsidence, fault downwarping, downwarping and shringkage, resulting in the deposition of terrstrial facies nearly 10,000 m thick. There are different depositional sequences in these stages: the depositional period of the Early Cretaceous Shahezi and Yincheng Formations is the development stage of the down-faulted basin, forming a volcanic rock-alluvial fan-fan delta-lacustrine (intercalated with episodic turbidites)-swamp facies sequences; the period of the Early Cretaceous Dengluku Formation is the transformation stage of fault subsidence into fault downwarping of the basin, forming a sequence mainly of alluvial plain-lacustrine facies; the depositional period of the Early Cretaceous Quantou Formation-Late Cretaceous Nenjiang Formation is the downwarping stage of the basin, forming an alluvial plain-delta-lacustrine facies sequence; the period of the Late Cretaceous Sifangtai Formation-Mingshui Formation is the shringkage stage of the basin, forming again a sequence mainly of alluvial plain-alluvial fan and small relict lacustrine facies. These vertical depositional sequences fully display the sedimentary characteristics of a failed continental rift basin. Many facts indicate that the two large-scale lake invasions, synchronous with the global rise of sea level, which took place in the downwarping stage of the basin development, led to the connection between the lake and sea.     

基于ETAS模型对青海地区余震预测效能评估的研究

为系统评估青海地区余震短期发生率的预测效能,以及构建适合地震活动特点的余震早期预测策略和预测指标体系,利用国际上当前较为前沿的时间序列ETAS模型和"瘦化算法"对青海地区2009年以来的8个地震的早期余震序列参数进行拟合,并利用N-test检验方法对预测结果进行回溯性的效能评估。研究表明:ETAS模型和"瘦化算法"对青海地区的余震发生率具有很好的预测能力,建议采用3天的预测时间窗,且对序列早期阶段进行应用,或可取得"最佳"的预测效果。     

大同地震序列的尾波Q值变化特征研究

要：利用大同台网1990～2000年的地震记录资料,系统地分析了大同地震序列尾波Q值随时间的变化,着重分析了尾波Q值在中强地震前的短期变化特征。结果表明,分频率的尾波Q值在几次中强地震前都不同程度出现了低值,并与大同震情“窗口”出现同步的异常。     

Sequence stratigraphy of Jurassic-Cretaceous boundary strata in Luanping,Northern Hebei,China

Division and correlation of terrestrial J-K bound are a knotty-argued problem. The key to solving the problem is to find a deposition-continuous section. Owing to stratigraphic hiatus and organism-phylogeny break, we have been discussing the problem without any unitary criterion for several decades. Tectonic ac-tivities occurring strongly in the J-K transitional pe-riod caused commonly sedimentary omissions and frequently volcanic eruptions in northern Hebei Prov-ince, western Liaoning Prov…     

地球动力学与盆地层序及油气系统分析

油气盆地、沉积层序与油气系统的研究属于不同层次的油气资源评价的基础研究。各类原型盆地的形成与地球动力学环境有关,并可简化为裂谷盆地、前陆盆地、走滑盆地和克拉通盆地等。沉积层序驱动机制由地球动力学的不同环境所决定,沉积层序可分类为裂谷盆地层序、前陆盆地层序和走滑盆地层序。油气系统在不同地球动力学环境下形成裂谷油气系统、台地油气系统和造山油气系统。中国许多大型盆地属于大型叠合盆地,并构成复合油气系统。     

基于PPAR模型视二维地震时间序列预测的初步研究

PP投影寻踪是一种长于分析非正态、非线性的高维数据的新统计方法,它通过投影降维,客观地寻找反映高维数据结构特征的投影方向,从而解决“维数祸根”和高维数据间的非正态、非线性问题。将PP理论和时间序列分析中的自回归(AR(K))模型结合起来,建立投影寻踪自回归预测模型(PPAR)。尝试实现地震震级和时间的视二维预测,即在固定研究区里。实现震级和时间二要素的预测,进而建立视二维地震时间序列的投影寻踪自回归模型。研究中首先选取北天山地区作为实验区,模型的回归拟合和外符检验效果较理想,可实现视二维预测目标。考虑到实际预测意义。即中强地震的预测,又以天山地区为研究区。令其震级序列的震级阈值分别为5．0和5．5,分别以未删除余震和删除余震的序列建立模型。对比分析表明,后所建立的模型要优于前的模型。特别是对时间间隔序列的预测。两外符检验的合格率均较高,故认为对于震级和时间二要素的预测是有一定实效的。     

后续地震发生时间估计及序列性质判定--以海城7.4级、巴楚-伽师6.8级地震序列为例

在前人研究的基础上,给出利用参数k判定序列性质及利用前期地震预测后续地震发生时间的方法.理论分析表明,参数k以0为界,不同的取值表征了不同的地震活动状态,这与地震趋势估计及后续地震预测密切相关.k<0表明地震间时间间隔逐渐增长,呈现一种类似余震序列逐渐衰减的活动特征;k=0意味着地震间时间间隔不变,地震活动表现为以T为周期的准周期性活动;k>0表明地震间时间间隔逐渐缩短,呈现一种类似前震序列或地震累积频次指数增长的异常活动特征.如果k值在正、负区间随机分布,则该组地震之间无相关性可言.利用1975年2月4日海城7.4级地震前、余震序列及2003年2月24日巴楚-伽师6.8级地震序列对上述方法进行了检验并对有关问题进行了初步讨论.     

FMAT-251质谱仪三相电源的智能保护装置

介绍FMAT-251质谱仪专用的智能三相保护电源装置。解决了FMAT-251质谱仪在改造后实际工作中由于外部三相供电电源错相导致机械泵反转,造成真空系统严重污染等事故的相序错相问题;同时针对三相电动机安全运行的缺相、过压、欠压、漏电保护等问题,进一步完善三相电动机供电电源的电压、电流和漏电的自动保护功能。     

Unravelling the microfacies signatures of parasequences using computer-optimized similarity matrices

The microfacies of a Lower Cretaceous carbonate drillcore from Oman are characterized using optimizing matrices of Jaccard's similarity coefficients of community. Other than systems tract boundaries, there is no obvious evidence of individual parasequences in the core. However, diagnostic patterns in microfossil distribution identify environmental gradients recording changes in water depth. These gradients are used to define individual parasequences, parasequence sets, stacking patterns and key surfaces. The patterns suggest that deposition was controlled by successive fourth‐ to fifth‐order (high‐frequency) relative sea‐level cycles superimposed on an underlying third‐order relative sea‐level rise. Although the correlation of these depositional subunits to systematic changes in water depth and the rate of carbonate accumulation alone is not incontrovertible proof of such a sea‐level control, concurrent multiorder relative sea‐level cyclicity provides by far the most likely explanation. A microfacies deposited when the water depth was shallowing is characterized by a relay of microfossils with affinities that shallow upwards. Conversely, a microfacies that records a gradual increase in water depth has a relay of microfossils with affinities that deepen upwards. Microfacies characterized by an assemblage of microfossils with similar affinities record deposition when the benthic environmental conditions remained stable, either because of an equilibrium between shallow water carbonate deposition and rising sea level, or in deeper water where sediment composition was relatively insensitive to changes of water depth. Microfacies characterized by mixed affinity assemblages record syndepositional reworking. During periods of embedded multiorder sea‐level changes, individual parasequences within systems tracts are shown to record more complex environmental gradients than simply the repetition of successive shallowing‐up units as traditionally represented in carbonate sequence stratigraphic models. The microfacies of an individual parasequence may shallow up, or may record both deepening‐up and shallowing‐up depositional phases, as well as periods of sedimentation when benthic environments remained stable. Individual parasequence boundaries may be submarine or subaerial unconformities, or be conformable, as part of a predictable stratigraphic pattern related to the temporal position of an individual parasequence within the underlying third‐order cycle of relative sea‐level change. The hitherto ubiquitous use of assemblages to describe carbonate microfacies, coupled with the widespread use of the metre‐scale shallowing‐up template to identify parasequences, may have led to such complexities previously being overlooked.