Gene flow and demographic history of the mangrove crab Neosarmatium meinerti: A case study from the western Indian Ocean     

Lapo Ragionieri  Stefano Cannicci  Christoph D. Schubart  Sara Fratini 《Estuarine, Coastal and Shelf Science》2010

Most marine organisms are characterized by at least one planktonic phase during their life history, potentially allowing interconnection of populations separated by several hundred kilometers. For many years, the idea that marine species are genetically homogenous throughout their range of distribution, due to passive larval transport, has been a paradigm. Nowadays, a growing number of studies underline the existence of boundaries in the marine realm and highlight how larval dispersal is a complex process depending on biotic as well as abiotic factors. Marine fragmented habitats, such as atolls, mangroves and estuaries, are optimal systems for investigating the marine dispersion process under a metapopulation approach, since populations can be geographically defined a priori as opposed to those occupying open marine environments. Within this frame, the present paper investigates the population genetic structure and the demographic history of the mangrove crab Neosarmatium meinerti within the western Indian Ocean by partial sequences of the mitochondrial DNA cytochrome oxidase subunit I. A total of 167 specimens were sampled from six mangrove sites distributed along the East African coast, from Kenya to South Africa, also including a mangrove forest located on Mahé Island, Seychelles. A sharp genetic break between the mainland and the Seychelles is recorded, revealing the existence of two historically distinct groups that can be defined as independent evolutionary units. Gene flow along the East African coast appears to be high enough to form a single metapopulation, probably by means of stepping stone populations. Otherwise, this mainland metapopulation is currently under expansion through a gradual moving front from the subtropical toward the equatorial populations.  相似文献   

A field test of a linear stability model for crescentic bars     

M.C.H. Tiessen  S.M. van Leeuwen  D. Calvete  N. Dodd 《Coastal Engineering》2010

A morphodynamical linear stability analysis is used to predict the natural development of crescentic bed patterns and rip channels. The purpose is to investigate whether this technique, which is useful for understanding the physics of emerging bed-forms, can be used to make quantitative predictions in the field, which may then be of use for coastal engineers.  相似文献   

南天山西段南缘断裂构造特征及对乌什凹陷发育的控制   总被引：10，自引：7，他引：3  

郑民  雷刚林  黄少英  吴超  罗慎超  李日俊 《地质科学》2007,42(4):639-655

乌什凹陷位于南天山西段以南,新生代受南天山崛起的陆内造山作用制约,与库车坳陷有相同的成盆动力学背景。因乌什凹陷南有温宿凸起阻挡了挤压应力的传播,东与库车坳陷间有北西向的构造变换带(西秋里塔格构造带)所隔,新生代变形与库车地区有不同的特征。以吉迪克组的泥岩层为滑脱面,乌什凹陷的中-新生界可分为上、下两个构造层,总体看上构造层以背冲构造为特征,下构造层则发育基底卷入的对冲构造。乌什凹陷的这一变形特征还与新生代挤压应力场自东向西迁移和走滑作用吸收了部分冲断变形有关,反映了南天山新生代构造对海西-印支期碰撞构造的继承性。文章简述了南天山造山带的构造演化,介绍了乌什凹陷周缘的主要断裂的特征,恢复了乌什凹陷中-新生代的演化并与库车坳陷进行了对比。在此基础上探讨了乌什凹陷的成盆动力学机制,分析了乌什凹陷与南天山造山带的耦合演化,指出该区的油气勘探应以三叠系为主要目的层。  相似文献   

The Quaternary Lancaster Sound trough‐mouth fan,NW Baffin Bay     

Gang Li  David J.W. Piper  D. Calvin Campbell 《第四纪科学杂志》2011,26(5):511-522

The development of the Lancaster Sound Trough Mouth Fan (TMF) and glacial history in Arctic Canada were studied using a high‐resolution seismic profile across the entire fan and two piston cores. Stacked tills separated by erosion surfaces on the shelf pass seaward through till deltas into thick transparent glacigenic debris flow (GDF) deposits on the slope, separated by thin, well‐stratified glaciomarine layers. An age model was built by ties to the Ocean Drilling Program Site 645. The deepest GDF on the seismic profile was indicative of the onset of shelf‐crossing glaciation in the Early Pleistocene. The transition of the growth of Lancaster Sound TMF from an aggradational sequence (unit M) to an aggradational–progradational sequence (unit F) occurred at the Middle Pleistocene transition in glacial cyclicity. In the most recent glacial cycle, GDF sheets were deposited during Heinrich events 4 and 2 according to the correlation of the main detrital carbonate beds in two piston cores. The outmost till wedge reflects the maximum advance of the grounding glacier, far seaward of previously proposed Last Glacial Maximum ice extent. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Inferring soil water movement and streamflow response in Canadian Prairie riparian areas using hydrologic state variables          下载免费PDF全文

Cody A. Ross  Genevieve Ali  David Lobb 《水文研究》2017,31(22):3765-3782

  相似文献   

An empirical approach to estimating population parameters from censored fracture-length distributions   总被引：1，自引：0，他引：1  

Pascal de Caprariis 《Mathematical Geology》1988,20(7):803-814

Most fracture data sets are length-censored because of incomplete exposure at the surface, so estimating values of parameters of the sampled populations is difficult. Unless the form of the distribution function of the population is known, or one which is analytically tractable is assumed, length-censoring presents formidable problems in determining population parameters. Tests conducted on experimental fracture patterns developed in clay samples subjected to simple shear loading are the basis of a distribution-free way to estimate population parameters. Comparison of random samples of censored and uncensored fracture lengths shows that a useful, homogeneous data set consists of those cracks which lie entirely within the sampling area (two-ended cracks). The properties of this data set can be used to estimate the mean and variance of uncensored data. Estimates of the maximum fracture length of uncensored data, using the variance and maximum length of these two-ended cracks, show good agreement with measured values. Knowledge of the mean, variance, and maximum value of fracture-length populations are of interest in engineering and hydraulic studies, as well as in remote sensing studies of the Earth and other planets. Application of these results to data on rock masses are subject to the caveat that different crack-growth mechanisms in clay and rock may affect the accuracy of the calculations.  相似文献   

Late quaternary monsoon patterns on the Loess Plateau of China     

Li Jijun And  Feng Zhaodon  Tang Lingyu 《地球表面变化过程与地形》1988,13(2):125-135

China's Loess Plateau was formed under special conditions. The tectonic movement, topographical characteristics, and monsoon patterns combined to create a favourable environment for the accumulation of thick loessic deposits. The Loess Plateau itself is part of the ‘Monsoon Triangle’ of China, a region very susceptible to climatic changes. Throughout the Upper Pleistocene the palaeoenvironment on the Loess Plateau alternated from steppe, to deciduous forest and coniferous forest, in response to shifts in the atmospheric circulation. Three monsoon patterns appear to be indicated: (1) a full glacial monsoon pattern (18000–15000 yr BP) which induced a cold and dry climate favouring loess accumulation in steppe conditions; (2) an interglacial monsoon pattern (last interglacial and Holocene) in which a warm humid climate prevailed with deciduous forests, leaving palaeosols interbedded within the loess sequence; and (3) a transitional or interstadial monsoon pattern (50 000–23 000 yr BP) in which the climate was cold and humid in the Loess Plateau, encouraging the development of coniferous forest.  相似文献   

Statistical methods for investigating quiescence and other temporal seismicity patterns     

Mark V. Matthews  Paul A. Reasenberg 《Pure and Applied Geophysics》1988,126(2-4):357-372

  相似文献   

A four-parameter,two degree-of-freedom block-spring model: Effect of the driver velocity     

Jose L. Brun  Javier B. Gomez 《Pure and Applied Geophysics》1994,143(4):633-653

We analyze the effect of tectonic plate velocities in the earthquake pattern using a simple mass-spring model of the Burridge and Knopoff type with two blocks and a velocity-weakening friction law. Previous versions of the two-block model assume a steady driver during slip events (limit of zero driver velocity), which, in some cases makes necessary the introduction of artificial parameters to start the numerical integration of the equations of motion at impending slip of any block. Still maintaining the condition of zero driver velocity during slip, we shall introduce a procedure to start the numerical integration without introducing artificial parameters and this will be done by using a linearized version of the equations of motion valid for small velocities and considering nonzero driver velocity. We also introduce a four parameter model in which the driver velocity enters the equations during the whole simulation, and analyze the effect of the new parameter, the driver velocity, in the displacement and time patterns of blocks motion, directly related to earthquake statistics such as coseismic slips and average repeat times.  相似文献   

The Evolutionary History of Ore-forming Processes of Metallic Ore Deposits in Northern Guangxi1     

Chen Yuchuan  Mao Jinwen  Wang Ping'an 《《地质学报》英文版》1995,8(2):155-170

Abstract The northern Guangxi region is an important rare metal, rare earth metal and polymetallic metallogenic province. In the region there exist five metallogenic series and two metallogenic subseries, whose metallogenesis shows features of polycyclic spiral evolution throughout the geological history. As far as various cycles are concerned, mantle-derived ore substances were reduced while crust-derived ore substances increased from early to late times; in the whole geological evolutionary history, mantle-derived substances decreased gradually while crust-derived ones increased. Meanwhile ore element associations became more and more varied. In terms of space, mineralization migrated from the old basement outwards, i.e. from west to east during the Precambrian, and from north to south during the Phanerozoic, and again from east to west during the Yanshanian.  相似文献