Postglacial floodplain development and Mesolithic-Neolithic occupation in the Russian forest zone

River valleys have always been attractive places for human occupation. The history of Mesolithic and Neolithic floodplain occupation is linked with archives of fluvial evolution, in particular the intricate relationships between palaeo-hydrological regimes, ecological development and sedimentary environments. This paper describes floodplain evolution in the Russian forest lowland around Moscow since the last deglaciation. Although there is an obvious climatic driving force for the initial fluvial incision at the end of the last glacial, there are many arguments pointing to complex intrinsic evolution involving successive pedogenesis, floodplain accumulation, flooding and fluvial incision from the beginning of the Holocene towards recent times. Increasing wetness during the early and middle Holocene forced people to move from the lowest parts of the valley towards its edges until ultimately, during the most severe flooding episode (at around 2600 years BP), they had to abandon the valley altogether.     

Stochastic Simulation of Patterns Using Distance-Based Pattern Modeling

The advent of multiple-point geostatistics (MPS) gave rise to the integration of complex subsurface geological structures and features into the model by the concept of training images. Initial algorithms generate geologically realistic realizations by using these training images to obtain conditional probabilities needed in a stochastic simulation framework. More recent pattern-based geostatistical algorithms attempt to improve the accuracy of the training image pattern reproduction. In these approaches, the training image is used to construct a pattern database. Consequently, sequential simulation will be carried out by selecting a pattern from the database and pasting it onto the simulation grid. One of the shortcomings of the present algorithms is the lack of a unifying framework for classifying and modeling the patterns from the training image. In this paper, an entirely different approach will be taken toward geostatistical modeling. A novel, principled and unified technique for pattern analysis and generation that ensures computational efficiency and enables a straightforward incorporation of domain knowledge will be presented.     

Discussion: Oil seepage or fossil podzol? An Early Oligocene oil seepage at the southern rim of the North Sea Basin,near Leuven (Belgium). Reply by the Authors

Geologie en Mijnbouw -     

Changing hillslope and fluvial Holocene sediment dynamics in a Belgian loess catchment

Floodplain deposition is an essential part of the Holocene sediment dynamics of many catchments and a thorough dating control of these floodplain deposits is therefore essential to understand the driving forces of these sediment dynamics. In this paper we date floodplain and colluvial deposition in the Belgian Dijle catchment using accelerator mass spectrometric radiocarbon and optical stimulated luminescence dating. Relative mass accumulation curves for the Holocene were constructed for three colluvial sites and 12 alluvial sites. A database was constructed of all available radiocarbon ages of the catchment and this database was analysed using relative sediment mass accumulation rates and cumulative probability functions of ages and site‐specific sedimentation curves. Cumulative probability functions of ages were split into different depositional environments representing stable phases and phases of accelerated clastic deposition. The results indicate that there is an important variation between the different dated sites. After an initial stable early and middle Holocene phase with mainly peat growth in the floodplains, clastic sedimentation rates increased from 4000 BC on. This first phase was more pronounced and started somewhat earlier for colluvial deposits then for alluvial deposits. The main part of the Holocene deposits, both in colluvial and alluvial valleys, was deposited during the last 1 ka. The sedimentation pattern of the individual dated sites and the catchment‐wide pattern indicate that land use changes are responsible for the main variations in the Holocene sediment dynamics of this catchment, while the field data do not provide indications for a climatological influence on the sediment dynamics. Copyright © 2011 John Wiley & Sons, Ltd.     

Paleoenvironment and stratigraphy during the last glacial in the Belgian-Dutch border region

The Weichselian deposits of the flat Dutch-Belgian coversand area are characterized by highly varying facies types. The geomorphological location and the role of water during the deposition and the transportation of the original eolian sediments may fully explain the texture and sedimentary structures of the lithostratigraphic units. Directly deposited eolian loams and sands on the dry interfluves contrast with the same, but reworked, sediments in wet valleys and depressions. The formation of periglacial phenomena is also dependent on the geomorphologic, lithologic, and hydrologic conditions. The occurrence of peaty beds is restricted to wet environments without precise climatic significance. The Pleniglacial sequence is subdivided into early and late Pleniglacial stades, both characterized by (partial) permafrost conditions, interrupted by a middle Pleniglacial interstadial complex with clearly milder conditions.     

Modeling Conditional Distributions of Facies from Seismic Using Neural Nets

We present a general, flexible, and fast neural network approach to the modeling of a conditional distribution of a discrete random variable, given a continuous or discrete random vector. Although many more applications of the neural net technique could be envisioned, the aim is to apply the developed methodology to the integration of seismic data into reservoir models. Many geostatistical methods for integrating seismic data rely on a screening assumption of further away seismic events by the colocated seismic datum. Such assumption makes the task of modeling cross-covariances and local conditional distributions much easier. In many cases, however, the seismic data exhibit distinct and locally varying spatial patterns of continuity related to geological events such as channels, shale bodies, or fractures. The previous screening assumption prevents recognizing and hence utilizing these patterns of seismic data. In this paper we propose to relate seismic data to facies or petrophysical properties through a colocated window of seismic information instead of the single colocated seismic datum. The variation of seismic data from one window to another is accounted for. Several examples demonstrate that using such a window improves the predictive power of seismic data.     

Adding Local Accuracy to Direct Sequential Simulation

Geostatistical simulations are globally accurate in the sense that they reproduce global statistics such as variograms and histograms. Kriging is locally accurate in the minimum local error variance sense. Building on the concept of direct sequential simulation, we propose a fast simulation method that can share these opposing objectives. It is shown that the multiple-point entropy of the resulting simulation is related to the univariate entropy of the local conditional distributions used to draw simulated values. Adding local accuracy to conditional simulations does not detract much from variogram reproduction and can be used to increase multiple-point entropy. The methods developed are illustrated using a case study.     

River response to variations of periglacial climate in mid-latitude Europe

The Last Glaciation was characterised by considerable changes in climate. Many European river basins reacted to these changes by initial incision and subsequent pattern change. Earlier research explained this by the time lag of vegetation development after a climatic change, which considerably affected the sediment load. However, since some river basins react differently, or do not react at all, this model needs to be refined. This paper deals with the fluvial evolution of several rivers in northern and central Europe during the Last Glaciation, and two of them, the Weiße Elster river in the Leipzig area and the Spree river in the Niederlausitz (Germany), are discussed in more detail. The vegetation cover on the floodplain, in combination with the presence of frozen ground, which affects the discharge characteristics, largely determines the river type. Nevertheless, when the sequences are compared, not only synchronous changes in fluvial development may be observed, but also distinct differences in fluvial development. By analysing the different rivers in their varying geomorphological settings, it appears that grain size, basin configuration and catchment size are important parameters also, which can determine whether a threshold is exceeded or not.     

最近1 000 ka来东亚冬季风变化的多时间尺度分析

以洛川黄土剖面中〉３０ｕｍ的粗颗粒含量作为东亚冬季风强度代用指标,根据模式并结合绝对年代控制点建立了较精确的独立的时间标尽。对该时间序列进行了小小变换分析和频谱分析。结果表明,这１０２４ｋａ以来东亚冬季风变化在１２８ｋｇ和６４ｋａ时间尺度上最大,更短或更长的时间尺度冬季风变化幅度减小。东亚冬季风变化的１００ｋｇ和２１ｋｇ等周期可能受地球轨道运动驱动的太阳辐射量变化控制,而５７ｋａ和３３ｋａ等周期的     

山西大同、内蒙古鄂尔多斯冰楔、砂楔群的发现及其环境意义

研究了山西大同、内蒙古东胜和乌审旗地区发现的大量冰楔假型、砂楔、寒冻裂隙和南部白城子附近的冰卷泥.根据这些冰缘现象,并参考前人工作成果,划定了晚更新世晚期末次冰期时多年冻土的南界,并根据所获得的年代资料划分了4次冰缘期:33ka BP,30～26ka BP,20～16ka BP和8ka BP左右,当时的温度比今天分别降低8.4℃,12～13℃,10℃和7～10℃.