Comparative phylogeography of African rain forest trees: A review of genetic signatures of vegetation history in the Guineo-Congolian region     

Olivier J. Hardy  Céline Born  Katarina Budde  Kasso Daïnou  Gilles Dauby  Jérôme Duminil  Eben-Ezer B.K. Ewédjé  Céline Gomez  Myriam Heuertz  Guillaume K. Koffi  Andrew J. Lowe  Claire Micheneau  Dyana Ndiade-Bourobou  Rosalía Piñeiro  Valérie Poncet 《Comptes Rendus Geoscience》2013,345(7-8):284-296

The biogeographic history of the African rain forests has been contentious. Phylogeography, the study of the geographic distribution of genetic lineages within species, can highlight the signatures of historical events affecting the demography and distribution of species (i.e. population fragmentation or size changes, range expansion/contraction) and, thereby, the ecosystems they belong to. The accumulation of recent data for African rain forests now enables a first biogeographic synthesis for the region. In this review, we explain which phylogeographic patterns are expected under different scenarios of past demographic change, and we give an overview of the patterns detected in African rain forest trees to discuss whether they support alternative hypotheses regarding the history of the African rain forest cover. The major genetic discontinuities in the region support the role of refugia during climatic oscillations, though not necessarily following the classically proposed scenarios. We identify in particular a genetic split between the North and the South of the Lower Guinean region. Finally we provide some perspectives for future study.  相似文献   

西藏泽当蛇绿岩玄武岩SHRIMP锆石U-Pb年龄 及其地质意义   总被引：1，自引：0，他引：1  

刘维亮  夏斌  刘鸿飞  黄炜  周国庆  韦栋梁  钟云  陈玉琴 《地质通报》2013,32(9):1356-1361

雅鲁藏布江缝合带中各蛇绿岩体的准确定年对待提斯洋演化和青藏高原隆升的研究具有重要意义.泽当蛇绿岩是雅鲁藏布江缝合带东段最大的蛇绿岩块体,关于其形成年龄目前仍存在不同的认识.通过SHRIMP锆石U-Pb测年得到蛇绿岩中玄武岩的形成年龄为154.9Ma±2.0Ma(95％置信度,MSWD=0.98).蛇绿岩中的玄武岩是洋脊扩张的产物,其形成年龄代表了扩张事件的时间,也代表了蛇绿岩的形成时代.结合已有的雅鲁藏布江缝合带蛇绿岩的形成年龄,该年龄进一步反映出雅鲁藏布江缝合带蛇绿岩形成时间具有东早西晚的特点.泽当蛇绿岩与含有埃达克质英云闪长岩的泽当岛弧火成岩基本为同期形成的.地球化学特征显示定年的玄武岩形成于俯冲带之上,且具有指示洋内俯冲环境的地球化学特征.因此,泽当SSZ型蛇绿岩可能形成于洋内俯冲机制.  相似文献   

Coupes équilibrées à travers le massif subalpin de la Chartreuse     

Jean-Louis Mugnier  Réjane Arpin  François Thouvenot 《Geodinamica Acta》2013,26(2):125-137

Résumé

Pour étudier la tectonique des chaînes subalpines du Nord, et proposer un modèle cinématique régional, nous avons utilisé les résultats d’une expérience géophysique réalisée en 1985, et les observations géologiques de surface publiées à ce jour. Ces données ont été analysées de manière à préciser le style tectonique, le positionnement des failles par rapport aux horizons stratigraphiques et le schéma de branchement des failles. La construction simultanée d’une coupe interprétative, d’une coupe restaurée et d’une carte de branchement des failles a permis d’estimer l’amplitude du raccourcissement par la méthode des coupes équilibrées. Au niveau du Nord de la Chartreuse, la valeur minimale du raccourcissement global est de 14 km, 4 km étant associés au système chevauchant du Jura et 10 km à celui du massif des Bornes et des Bauges. Compte tenu des imprécisions existant sur les données utilisées, trois modèles cinématiques, qui correspondent à une plage de raccourcissement comprise entre 14 et 25 km, sont proposés.  相似文献   

广西钦州湾海域海床稳定性特征的研究   总被引：1，自引：0，他引：1  

白玉川  廖世智 《海洋通报》2005,24(2):26-32

综合钦州湾龙门站与近海区钓鱼台站长年历史观测资料和2003年7月的6个站点全潮观测资料,阐述了钦州湾的表层沉积物分布和钦州外湾典型位置沉积物组成状况,并结合钦州电厂建设规划,通过海床稳定性的概念和稳定性指标的计算方法,研究钦州电厂取排水工程附近海域及钦州外湾在潮流和波浪作用下的海床稳定情况,计算结果表明所提出的稳定性理论能够反映实际,是可靠的,可以进一步作为钦州电厂相关模拟研究的基础。  相似文献   

CHRONOSTRATIGRAPHY,SEDIMENTATION AND EVOLUTION OF THE XIGAZE FOREARC BASIN: IMPLICATIONS FOR DYNAMIC EVOLUTION OF THE YARLUNG ZANGBO SUTURE ZONE     

Wang Chengshan  Liu Zhifei    Li Xianghui WT  ”BX 《地学前缘》2000,(Z1)

CHRONOSTRATIGRAPHY,SEDIMENTATION AND EVOLUTION OF THE XIGAZE FOREARC BASIN: IMPLICATIONS FOR DYNAMIC EVOLUTION OF THE YARLUNG ZANGBO SUTURE ZONE1　All埁ｇｒｅＣＪ,CourtillotV ,TapponnierP ,etal.StructureandevolutionoftheHimalaya Tibetorogenicbelt[J] .Nature,1984 ,30 7:17～ 2 2 . 2　CoulonC ,MaluskiH ,BollingerC ,etal.MesozoicandCenozoicvolcanicrocksfromcentralandsouthernTibet:3 9Ar 40 Ardating ,petrotogicalcharacteristicsandgeodyn…  相似文献   

α-1,4-葡聚糖裂解酶的动力学性质研究   总被引：1，自引：0，他引：1  

Sun Xue 《中国海洋大学学报(自然科学版)》2000,30(Z1):230-236

红藻中的α-1,4-葡聚糖裂解酶是红藻淀粉的降解酶,除了 红藻淀粉外,它还可以作用于多种底物。文中分别以PNPG和可溶性淀粉作底物,以龙须菜的 几个品系作为材料,研究了该酶促反应的动力学方面的性质。以 PNPG作为底物,该酶在60m in内酶促反应速度与保温时间成线性关系;在野生型龙须菜品系中该酶的最适反应温度是50 ℃,在两种突变型品系中是40℃;最适pH范围在4.4～5.5;底物浓度是4mmol/L时达到最大反 应速度;葡萄糖对该酶促反应有明显的抑制作用。以可溶性淀粉作为底物,在反应60 min内 酶反应速度与保温时间成线性关系;最适反应温度为50℃;最适pH范围在5.0～5.8;底物浓 度是8mg/mL时达到最大反应速度;葡萄糖对可溶性淀粉的抑制作用比对PNPG的弱。  相似文献   

Chevron Ridges and Runup Deposits in the Bahamas from Storms Late in Oxygen-Isotope Substage 5e     

Paul J. Hearty  A.Conrad Neumann  Darrell S. Kaufman 《Quaternary Research》1998,50(3):309-322

Landward-pointing V-shaped sand ridges several kilometers long are common along the windward margin of the Bahama Islands. Their axes share a northeast–southwest trend. Internally, the ridges contain low-angle oolitic beds with few erosional truncations. Commonly interbedded are tabular, fenestrae-rich beds such as those formed by the sheet flow of water over dry sand. Defined here as “chevron ridges,” these landforms appear to have originated in the rapid remobilization of bank margin ooid bodies by the action of long-period waves from a northeasterly source. Deposits along adjacent coastlines also preserve evidence of the impact of large waves. Reworked eolian sand bodies preserve beach fenestrae and hydraulic scour traces up to +40 m on older ridges. On cliffed coasts, 1000-ton boulders have been thrown well inland, recording the impact of large waves. Amino acid ratios confirm a correlation of the ridges across the archipelago, while stratigraphy, spacing, and cross-cutting relationships indicate emplacement as sea level fell rapidly from the substage 5e maximum at or above +6 m.  相似文献   

Deep‐water foreland basin deposits of the Cerro Toro Formation,Magallanes basin,Chile: architectural elements of a sinuous basin axial channel belt     

STEPHEN M. HUBBARD  BRIAN W. ROMANS  STEPHAN A. GRAHAM 《Sedimentology》2008,55(5):1333-1359

Coarse‐grained deep‐water strata of the Cerro Toro Formation in the Cordillera Manuel Señoret, southern Chile, represent the deposits of a major channel belt (4 to 8 km wide by >100 km long) that occupied the foredeep of the Magallanes basin during the Late Cretaceous. Channel belt deposits comprise a ca 400 m thick conglomeratic interval (informally named the ‘Lago Sofia Member’) encased in bathyal fine‐grained units. Facies of the Lago Sofia Member include sandy matrix conglomerate (that show evidence of traction‐dominated deposition and sedimentation from turbulent gravity flows), muddy matrix conglomerate (graded units interpreted as coarse‐grained slurry‐flow deposits) and massive sandstone beds (high‐density turbidity current deposits). Interbedded sandstone and mudstone intervals are present locally, interpreted as inner levée deposits. The channel belt was characterized by a low sinuousity planform architecture, as inferred from outcrop mapping and extensive palaeocurrent measurements. Laterally adjacent to the Lago Sofia Member are interbedded mudstone and sandstone facies derived from gravity flows that spilled over the channel belt margin. A levée interpretation for these fine‐grained units is based on several observations, which include: (i) palaeocurrent measurements that indicate flows diverged (50° to 100°) once they spilled over the confining channel margin; (ii) sandstone beds progressively thin, away from the channel belt margin; (iii) evidence that the eroded channel base was not very well indurated, including a stepped margin and injection of coarse‐grained channel material into surrounding fine‐grained units; and (iv) the presence of sedimentary features common to levées, including slumped units inferring depositional slopes dipping away from the channel margin, lenticular sandstone beds thinning distally from the channel margin, soft sediment deformation and climbing ripples. The tectonic setting and foredeep architecture influenced deposition in the axial channel belt. A significant downstream constriction of the channel belt is reflected by a transition from more tabular units to an internal architecture dominated by lenticular beds associated with a substantially increased degree of scour. Differential propagation of the fold‐thrust belt from the west is speculated to have had a major control on basin, and subsequently channel, width. The confining influence of the basin slopes that paralleled the channel belt, as well as the likelihood that numerous conduits fed into the basin along the length of the active fold‐thrust belt to the west, suggest that proximal–distal relationships observed from large channels in passive margin settings are not necessarily applicable to axial channels in elongate basins.  相似文献   

脆性断层运动学研究新进展   总被引：1，自引：0，他引：1  

吴树仁 《地质科技情报》1992,11(1):21-28

本文概述了80年代以来脆性断层运动研究方面的某些成果。介绍了脆性断层带中的一些小构造和显微构造的几何特征以及它们的运动学意义。重点论述了从露头尺度到薄片尺度确定脆性断层运动方向的三种构造判据,既从属裂隙、岩桥构造和方解石e双晶判据。  相似文献   

How warm was Britain during the Last Interglacial? A critical review of Ipswichian (MIS 5e) palaeotemperature reconstructions   总被引：1，自引：0，他引：1       下载免费PDF全文

Ian Candy  Tom S. White  Scott Elias 《第四纪科学杂志》2016,31(8):857-868

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