Oceanic circulation as an element in palaeogeographical reconstructions: the Arenig (early Ordovician) as an example

A new conceptual palaeo-oceanographical model is outlined in this paper. The model differs from previous models by using shifts in Hadley circulation caused by orbital variations, and the rotation rate of the Earth, to locate the position of the planetary oceanic low-and high-pressure systems, around which the planetary ocean surface currents flow. Adapting the model to the Arenig (early Ordovician) the temperate low pressure zones were found to be located at 50° latitude and the subtropical high pressure zones at 25° latitude.
Traditionally, most Palaeozoic palaeogeographical recon-structions are reconstructed using palaeomagnetic data supplemented with data from climate-sensitive lithofacies and palaeo-biogeographical distributions. However, as a new approach in palaeogeographical reconstructions, the con-ceptual palaeo-oceanographical model is combined with palaeobiogeographical data for the Arenig series, comple-menting the palaeomagnetic data, and resulting in a new, refined palaeogeographical reconstruction.     

古喀斯特岩岸的地质意义：以黔中贵阳乌当志留纪岩岸为例

本文记述黔中乌当地区志留纪的喀斯特岩岸，是我国前第四纪岩岸实例的首次报道。志留纪海水始于Ｌｌａｎｄｏｖｅｒｙ世Ａｅｒｏｎｉａｎ晚期浸漫本区并逐级超覆在奥陶纪不同时代的地层之上，形成了一个穿时性喀斯特不整合面，这是宜昌运动和其后长期风化剥蚀，产生强烈地形高差的结果。根据地层发育及不整合面上的沉积和生物特征，肯定喀斯特岩岸在本区的存在，推断岩岸的生物生存环境，海平面升降变化以及宜昌运动牟对贵州中，南部     

陆海统筹地形地貌综合编图方法研究

由于陆海地形数据在调查程度和精度上存在较大差距,地形图件陆海联编较为困难。系统梳理了海岸带地形地貌陆海统筹的复杂程度,总结了陆海联编地形图的基本原则,探讨不同情况下陆海地形数据的无缝拼接方法和图件编制的主要要素。以南通陆海统筹地形地貌综合图为例,按照成果类型综合归类,进行地形、地貌、坡度、冲淤变化等信息的综合集成,绘制陆海统筹的地形地貌综合成果图,通过1张图即可查询。陆海统筹地形地貌综合成果新的展现形式,有利于成果的查询和实际应用,供后期开展相应的陆海图件联编参考。     

神农架地区中元古界混合沉积特征及其发育模式

神农架地区中元古界主要发育碳酸盐岩沉积,局部夹少量陆源碎屑岩。乱石沟组、大窝坑组、矿石山组及台子组位于中元古界中部,混合沉积较为发育,其混合沉积类型及其主控因素尚缺乏系统研究,对陆源碎屑来源及台子组石英砂岩形成环境仍存在较大争议。根据岩石类型和沉积构造组合对神农架地区乱石沟组—台子组沉积相进行分析,并结合岩石薄片及阴极发光分析结果对混合沉积类型、陆源组分特征及来源进行研究,以明确中元古代神农架地区沉积背景及其沉积演化历史。岩石薄片及阴极发光分析表明,神农架地区乱石沟组—台子组陆源碎屑主要来自由大量花岗岩、少量变质岩和沉积岩构成的古陆。乱石沟组—台子组岩石组合特征及混积岩类型存在较大差异,沉积环境、海平面变化及构造活动是控制混积岩分布及混合沉积类型的主要因素。乱石沟组及大窝坑组沉积早—中期,神农架地区毗邻古陆,扬子北缘构造活动相对稳定,地形平缓且水深较浅,以广泛发育“相混合”式混合沉积为特征;大窝坑组沉积晚期及矿石山组沉积早期,扬子北缘开始进入强烈拉张时期并导致相对海平面上升,神农架地区与古陆拉分形成相对独立的碳酸盐台地,以发育缺乏陆源碎屑砂的清水碳酸盐沉积为特征;矿石山组沉积晚期及台子组沉积时期,扬子北缘的持续拉张导致神农架地区进入较深水环境,早期滨岸沉积物崩塌形成重力流搬运至神农顶一带,形成“间断式”混合沉积。乱石沟组—台子组沉积时期处于中元古代重要的构造演化阶段,台子组沉积之后,神农架地区彻底与古陆分隔,不再发育“相混合”式混合沉积,乱石沟组—台子组沉积时期为扬子台地北缘由窄大洋向开阔洋盆演化的重要时期。     

Military geology of Antietam battlefield, Maryland, USA—geology, terrain, and casualties

The geology of a battlefield, or that which underlies the area in which a military campaign occurs, rarely truly affects the outcome of battle. Confederate General Robert E. Lee's Maryland campaign and the Battle of Antietam fought against Union General George B. McClellan in 1862 during the American Civil War, are however, major exceptions to this rule. Lee used the geology and structure of the area in choosing the invasion route, in a major delaying tactic prior to the battle, and in the battle itself. In this article, we show the affects of geology on the battle by using standard morphometric measures to quantify terrain variables and relate these data to the numbers of killed and wounded during the battle. We also include a field guide to various locations on the battlefield where the relations between geology, terrain, and casualties can easily be seen.     

Northern Gondwanan affinity of the East Moesian Terrane based on chitinozoans

Identification of palaeocontinental affinities is important to place Moesia in the global context of palaeogeographical reconstructions. In the absence of palaeomagnetic data and relevant macrofauna, palynological data and especially chitinozoans represent an important tool, recently used to unravel palaeogeographical affinities. Chitinozoans from three main boreholes (Călăraşi 2881, Zăvoaia 2581 and Ţăndărei 1052) located in East Moesia have been studied. They indicate a predominant palaeogeographical affinity with northern Gondwana.     

基于GIS的岩溶区土地利用的地形梯度分布研究——以酉阳县板溪乡为例

基于 RS 和 GIS 技术,采用地形位指数、分布指数和土地利用程度综合指数,探讨了2002、2011两年重庆市酉阳县板溪乡不同地形梯度土地利用结构的变化特征和定量分析了土地利用程度。结果显示：建设用地、耕地和水域对地形条件的选择性较强;建设用地主要聚集在海拔〈850 m、坡度〈15°176;的区域,耕地主要聚集在海拔〈1050 m 和坡度〈25°176;的区域,5和7级地形位为制约水域分布的地形条件;2011年,灌木林地在海拔650-1250 m、坡度〉15°176;的区域集中增加。总体上,该研究区的土地利用程度较高,但仍然存在耕地分布不合理的现象。     

Holocene transgression of the Rhine river mouth area,The Netherlands/Southern North Sea: palaeogeography and sequence stratigraphy

This study presents a detailed reconstruction of the palaeogeography of the Rhine valley (western Netherlands) during the Holocene transgression with systems tracts placed in a precise sea‐level context. This approach permits comparison of actual versus conceptual boundaries of the lowstand, transgressive and highstand systems tracts. The inland position of the highstand Rhine river mouth on a wide, low‐gradient continental shelf meant that base‐level changes were the dominant control on sedimentation for a relatively short period of the last glacial cycle. Systems in such inland positions predominantly record changes in the balance between river discharge and sediment load, and preserve excellent records of climatic changes or other catchment‐induced forcing. It is shown here that the transgressive systems tract‐part of the coastal prism formed in three stages: (i) the millennium before 8·45 ka bp , when the area was dominated by fluvial environments with extensive wetlands; (ii) the millennium after 8·45 ka, characterized by strong erosion, increasing tidal amplitudes and bay‐head delta development; and (iii) the period between 7·5 and 6·3 ka bp when the Rhine avulsed multiple times and the maximum flooding surface formed. The diachroneity of the transgressive surface is strongly suppressed because of a pulse of accelerated sea‐level rise at 8·45 ka bp . That event not only had a strong effect on preservation, but has circum‐oceanic stratigraphical relevance as it divides the early and middle Holocene parts of coastal successions worldwide. The palaeogeographical reconstruction offers a unique full spatial–temporal view on the coastal and fluvial dynamics of a major river mouth under brief rapid forced transgression. This reconstruction is of relevance for Holocene and ancient transgressive systems worldwide, and for next‐century natural coasts that are predicted to experience a 1 m sea‐level rise.     

Recent geoid computations for the Hellenic area

New geoid computations for the Hellenic area are carried out using (a) gravity anomalies for the land area available from old and new data bases, and gravity data for the sea area derived from altimetry and a recent digitization of sea gravity maps, and (b) a 1km × 1km digital terrain model. The EGM96 geopotential model is used as the reference field. In order to assess the quality of the computed geoid heights in the continental area comparisons were carried out with GPS/leveling heights and the recently available European Gravimetric Geoid EGG97. In the sea area the geoid heights were compared with sea surface heights of the recent and more accurate TOPEX/POSEIDON (T/P) altimetry mission. At the end of this article the improvement of the data bases is discussed and some plans for further development in the methodological schedule are pointed out.     

渤海湾西MIS3阶段海侵边界探讨

渤海湾西天津南部平原区是研究海侵和海平面变化的天然理想场所。基于2个钻孔(ZKQ1孔和ZK1孔)沉积特征、测年(AMS ¹⁴C)及微体古生物和生物壳体等综合研究,推测研究区MIS3阶段第2海侵的最大影响边界在ZK1孔和ZKQ1孔两孔之间,界线西侧表现为河湖相的陆相沉积,界线东侧为滨海湖沼的过渡相沉积,该位置即是现今黑龙港河一带,也曾是古河道故道,推测该期海侵影响范围受到了古河道制约。结合研究区前期3个钻孔(ZKQ4孔、CGZ5孔和CGZ7孔)资料,建立了E→W向(海→陆)联合钻孔对比剖面,进一步对MIS3阶段海侵层位追踪,表明E→W依次由海相(CGZ7孔、CGZ5孔)→过渡相(ZKQ4孔、ZKQ1孔)→陆相(ZK1孔)相变。推测研究区内MIS3阶段海侵边界位于静海区的东尚码头村(CGZ5孔)和高家庄(ZKQ4孔)一带。研究成果对恢复该区域古地理演化、海平面变迁研究以及水工环地质勘查等具有重要意义。     

黔中开阳磷矿沉积区震旦纪陡山沱期定量岩相古地理重建*

磷矿的沉积和成矿与成磷期的古地理环境密切相关。本文首次将“单因素分析多因素综合作图法”运用于开阳地区震旦纪陡山沱期沉积型磷矿床的成矿分析和找矿预测上。通过选取陡山沱组及其各岩性段的地层厚度及磷矿层品位作为单因素,确定开阳地区古地理格局;结合地层岩性组合、沉积特征等多因素综合分析,恢复开阳地区成矿期沉积环境,编制陡山沱早期、中期和晚期岩相古地理图。根据定量岩相古地理重建结果,认为开阳地区陡山沱期整体处于南靠黔中古陆、地势南高北低、局部地形复杂的滨岸海滩沉积环境,其中临滨带为最有利成矿带,局部地形变化也会造成矿层厚度、品位的差异;矿层受到的水流冲蚀、暴露、淋滤及再沉积作用是导致矿石品位显著提升的关键因素。通过定量岩相古地理学精确还原成矿期古地理环境、解析多期次沉积成矿过程,对于确定磷矿控矿因素、构建找矿预测模型和预测矿体空间位置具有重要意义。     

Response of the Rhine–Meuse fluvial system to Saalian ice-sheet dynamics

A new reconstruction of the interaction between the Saalian Drente glaciation ice margin and the Rhine–Meuse fluvial system is presented based on a sedimentary analysis of continuous core material, archived data and a section in an ice-pushed ridge. Optically Stimulated Luminescence (OSL) was applied to obtain independent age control on these sediments and to establish a first absolute chronology for palaeogeographical events prior to and during the glaciation. We identified several Rhine and Meuse river courses that were active before the Drente glaciation (MIS 11-7). The Drente glaciation ice advance into The Netherlands (OSL-dated to fall within MIS 6) led to major re-arrangement of this drainage network. The invading ice sheet overrode existing fluvial morphology and forced the Rhine–Meuse system into a proglacial position. During deglaciation, the Rhine shifted into a basin in the formerly glaciated area, while the Meuse remained south of the former ice limit, a configuration that persisted throughout most of the Eemian and Weichselian periods. An enigmatic high position of proglacial fluvial units and their subsequent dissection during deglaciation by the Meuse may partially be explained by glacio-isostatic rebound of the area, but primarily reflects a phase of high base level related to a temporary proglacial lake in the southern North Sea area, with lake levels approximating modern sea levels. Our reconstruction indicates that full 'opening' of the Dover Strait and lowering of the Southern Bight, enabling interglacial marine exchange between the English Channel and the North Sea, is to be attributed to events during the end of MIS 6.     

连云港新石器时代人类聚居遗址分布 与海岸线变迁关系的剖析*

对连云港新石器遗址地貌、洪门钻孔的沉积环境以及古遗址时空分布的研究表明,新石器文化始于7000年前全新世气候变暖和海平面上升时期。早期青莲岗文化时期(6800~5900aB.P.)的遗址有8处,主要分布在锦屏山、南云台山和大伊山的丘陵山地边缘的洪积扇阶地上和西北部未遭受海侵影响的丘陵岗地上,洪门钻孔相应地层显示该时期为湖沼陆相环境,海岸线向海推进,该时期海岸线分布在南云台山以东地区;全新世中期最高海面时,约相当于大汶口文化时期(5900~4400aB.P.)的遗址仅发现两处,遗址退缩至锦屏山以西的丘陵岗地上。洪门钻孔的有孔虫组合显示了浅海环境,海岸线在洪门和锦屏山以东;至龙山文化期(4400~3800aB.P.),连云港的古文化发展至新石器时代的顶峰,遗址约15处,其中藤花落遗址处于南云台山与北云台山之间谷地的冲积平原,表明此时期的海岸线退至中云台山以东;龙山文化晚期(3800aB.P.左右)又一次海侵导致盛极一时的龙山文化遗址退缩到锦屏山以西地区,使得连云港地区行将跨入文明门槛的原始文化突然衰落。古环境变化对史前文化的兴衰影响巨大。     

辽东半岛长兴岛八岔沟古泻湖型泥炭的形成及全新世最高海平面

通过对辽东半岛西部的长兴岛八岔沟古泻湖平原进行钻孔调查取样,对由海向陆4个不同地点的100余个钻孔样品,进行粘土混浊水导电率测定,区分了八岔沟古泻湖平原的海陆相沉积层,查明了该古泻湖平原的海相层上限的高度.结果表明:该平原各孔的海相层上限高度具有明显的一致性,大约为海拔4.0～4.2 m,此高度代表了该古泻湖平原全新世最高海平面期间海水所达到的平均高潮线的高度.通过测定和讨论覆盖在海相层上的泥炭底部14C年代,明确了该区略早于5 800 cal.aB.P.达到全新世最高海平面.全新世最高海面期的平均海平面高度约为海拔3.4～3.6 m.将此高度与辽东半岛东部大孤山一带的全新世高海平面期(6 000～5 500 cal.aB.P.)的平均海平面的高度值约2 m相对比,显示出在全新世期间辽东半岛西部八岔沟一带较东部的大洋河平原有相对上升的趋势.深达9 m的B3孔的导电率有两个高峰值,反映该平原全新世曾发生过两次海侵,较晚一次海侵的最大范围达到距现代海岸线约1.2 km处.     

黄海西部沿岸流系特征分析及其对物质输运的影响

黄海西部沿岸是我国人类活动和海洋经济开发较为集中的地带,陆地和海洋相互作用较为强烈,其特殊的地形和所处的独特地理位置,使得该海域的环流复杂多变,沿岸海域各水团与陆架锋以及长江口东北部的锋面一起构成了黄海西部特有的环流体系和背景场,对该海域的物质输运和扩散、海水运动以及海洋生物地球化学过程产生影响,并制约着沿岸海域对污染...     

Effect and Prospect of Basic Geological Survey Based on Airborne Gravimetry in China

The airborne gravimetry was an important leap and innovation in the world’s history of geophysical exploration. China's first test of the airborne gravity geological survey in the onshore-offshore transitional area of the western and southern part of the Bohai Sea was successful and effective in geology. Based on the airborne gravity data, and combining previous ground gravity, seismic and drilling data etc., we carried out the geological interpretation by forward and inverse methods. The result shows that the airborne Bouguer gravity anomaly was clear, the fracture interpretation was reliable, and the inversion depth of the main geological interfaces was relatively accurate. This airborne gravity geological survey not only filled the exploring gaps in the onshore-offshore transitional area, and realized the geological and tectonic junction between the sea and the land, but also discovered four local gravity anomalies, 11 fractures and three sags or subsags, and so on. The good geological effect of airborne gravimetry not restricted by terrain condition shows that it can be served as a new geophysical method in the exploration of complex terrain physiognomy area such as mountain, jungle, desert, marsh, onshore-offshore transitional area and so on, and has an extensive application prospect in China in the future.     

Late-Quaternary sea level changes,Umnak Island,Aleutians—Their effects on ancient Aleuts and their causes

Late-Quaternary sea level changes in the eastern Aleutian Islands are of paramount importance in the reconstruction of the migrations and environment of the ancient Aleuts. A radiocarbon-dated ash stratigraphy provides the chronology into which geomorphic events can be fitted. These provide evidence for the sea level changes. Deployment of beach material and coastal configuration intimate that sea level was about 2–3 m above the present level about 8250 radiocarbon yr BP. Beach deposits suggest that sea level remained high until about 3000 radiocarbon y.a. when it gradually dropped to its present position. It is concluded that the ancient Aleuts that settled Anangula about 8400 y.a. used boats; all major passes in the eastern Aleutians were flooded, and did not have winter ice. Those ancient Aleuts did not have available the major year-around food resources of the present strandflats as they were cut during the high sea level stand 8250–3000 yr BP. The ancient Aleuts must have been marine oriented, for land-based food resources would have been limited.The cause of relative sea level changes on Umnak Island is considered indeterminate with present data. Eustatic, glacial isostatic, water isostatic, tectonic, and volcanic causes are considered the main possible controls in combinations such that a basic eustatic sea level curve and likely a glacial-water isostatic curve must be common to any solution. Representative solutions are given to illustrate some of the problems.     

DEM在构造地貌定量分析中的应用与展望

作为一种描述地形起伏特征的数据模型,数字高程模型（Digital Elevation Model,DEM）通过有限的地形高程数据实现对地形曲面的数字化模拟（即地形表面形态的数字化表示）,为研究地表的演化过程提供了数据基础。文章归纳梳理了DEM在基本地形因子、流域地貌特征、古地貌面的重塑、构造地貌发育模式、地貌分类与制图以及地形特征提取算法等领域的应用现状。总的来看,DEM研究对象以陆地为重点,以河流地貌和山地地貌为主要内容;研究过程从早期对地貌形态的定性描述向多种地貌参数的半定量、定量分析转变;研究尺度空间上从某个小流域到整个造山带,时间上从数小时向百万年扩展。构造地貌演化时间序列的不确定性、地貌参数获取的复杂性、地形模型算法的多样化以及DEM生成过程中的误差因素,这些均影响构造地貌定量分析结果的准确度,因此在归纳梳理已有研究成果的同时,对DEM在构造地貌研究领域的应用进行了一些思考。