Geomorphological effects of plate movemen during Quaternary in China＇s tropics

The eastern and western fronts of plate movement in Taiwan Island and Tibetan Plateau respectively are the two major sources of tectonic force for the morphogensis during Quaternary in China’s tropics. Seven examples of geomorphological effects of plate movement are enumerated to discuss the differentiation of tectonic landforms in space and time during Quaternary. The tectonic movement tends to be more active since middle Pleistocene. Some phenomena such as the arc-shape mountain systems, volcanism and crustal deformation imply that the juncture zone of eastern and western tectonic forces is located at about 110°E.     

Geomorphological effects of plate movement during Quaternary in China'' s tropics

China'stropicsliesintheregionsouthofabout24oN,occupyinganareaofabout51.85×104km2(5.4%ofChina).InChina,thistropicalregionisquiteclosetotheeasternandwesternconvergentboundariesbetweentwoplatessothatthegeomorphologicaleffectsofplatetectonicsaremoreobviousthanthoseinnorthernChina.Thisstudywillpresentsevenexamplesofappearanceofplatemovementingeomorphology.1ThesourceoftectonicforceTheregionofChina'stropicsundergoesconvergingattackfromeasternandwestern"fronts"ofplatemovement.Thewesternfrontofther…     

中国热带第四纪板块运动的地貌效应

The eastern and western fronts of plate movement in Taiwan Island and Tibetan Plateau respectively are the two major sources of tectonic force for the morphogensis during Quaternary in China′s tropics. Seven examples of geomorphological effects of plate movement are enumerated to discuss the differentiation of tectonic landforms in space and time during Quaternary. The tectonic movement tends to be more active since middle Pleistocene. Some phenomena such as the arc-shape mountain systems, volcanism and crustal deformation imply that the juncture zone of eastern and western tectonic forces is located at about 1 1O°E.     

气候和地貌对晚第四纪冰川发育差异性的影响

中国第四纪冰川作用极大地推动了高亚洲乃至全球冰川形成机制的探讨。青藏高原以及喜马拉雅山地冰川作用的时限和规模研究得到了广泛关注,为西风带与西南季风带对晚第四纪冰川作用差异性问题的解决提供了有利条件。然而,对于中亚西风环流与东亚季风环流影响下的冰川演化差异性关系不甚明确,两大气候系统控制下的山地第四纪冰川的冰进时序、冰期历史和冰川规模显示出不同特点,其差异性主要体现在:西部山地的冰期启动时间早,冰川规模随时间而逐渐缩小,冰川历史较为完整,绝对年代证据显示冰川作用的启动时间是450 ka 左右的中梁赣冰期(MIS12);东部山地的冰期历史较短,仅保留末次冰期(~75 ka)的冰川遗迹,冰川作用的阶段性明显;冰川演化时间与空间的差异性表明,影响冰川发育的因素不仅仅是区域气候,构造因素也起着相当重要的作用。     

云南千湖山第四纪冰川发育特点与环境变化

千湖山(4249 m) 是横断山脉中段保存确切第四纪冰川遗迹的山地,受西南季风影响强烈。对于研究青藏高原边缘山地冰川发育与气候和构造之间的耦合关系具有十分重要的科学意义。在千湖山海拔3500 m以上保存着古冰川侵蚀与堆积地貌,冰川发育依托海拔4000~4200 m的夷平面及其支谷地形。冰川形态类型为小型的冰帽以及由冰帽边缘溢流进入山谷的山谷冰川。应用相对地貌法,光释光(OSL) 年代测试,本文确定千湖山地区的冰进系列:末次冰盛期(LGM,22.2±1.9 ka BP)、末次冰期中期(MIS3b,37.3±3.7 ka BP、45.6±4.3 ka BP45.6±4.3 ka BP)、末次冰期早期(MIS4)。千湖山冰川前进规模是MIS3b 阶段大于末次冰盛期,主要原因是末次冰期中期(MIS3b) 时本区气候相对湿润,而在末次冰盛期(MIS2) 时气候条件比较干燥。在总体相似的气候背景下,与横断山其它存在多期次冰川作用的山地相比,千湖山只发育末次冰期的冰川作用,其差异性说明该地区冰川发育主要受山体构造抬升控制。     

Deformed Messinian markers in the Cyprus Arc: tectonic and/or Messinian Salinity Crisis indicators?

This paper focuses on Messinian Salinity Crisis (MSC) evaporites in the Cyprus Arc (eastern Mediterranean) using high‐resolution reflection seismic and multi‐beam data. The results shed new light on the Miocene to Present tectonic evolution of this area and contribute to our general knowledge of the MSC in a deep basin setting. The evaporites and overlying formations show a complex deformation pattern due to a combination of thick‐skinned plate‐tectonic convergence and thin‐skinned disharmonic deformation related to the mobile evaporite‐bearing unit. Several MSC markers are identified and precisely mapped: the base of the MSC unit is a ‘decollement’ level, whereas the top is clearly identified as a toplap surface. Intra‐MSC markers and two MSC subunits are identified and mapped over the entire study area. The geometry of MSC markers shows that the lower MSC subunit was deposited in a relatively quiet tectonic setting. The nature of the anisopachous upper unit indicates a syn‐depositional phase of large‐scale plate‐tectonic activity. A thin‐skinned phase of compressional deformation during the Late Miocene affected the entire MSC unit, overlain by undeformed Pliocene–Quaternary layers. A second thin‐skinned phase, well expressed in the bathymetry, occurred from the Pliocene to Recent, resulting in extensional gravity‐gliding within the evaporites and the Pliocene–Quaternary sequence. We show that the MSC had a dramatic impact on the regional structure. For instance, the erosive nature of the top of the MSC unit is linked to the desiccation episode rather than to the cessation of tectonic activity. This particularly strong and short‐lived erosion may have been enhanced by the regional effects of the MSC, owing to differential uplift/subsidence caused by the drawdown. The evaporites are essential markers for constraining the tectonic framework, provided that active deformation can be distinguished from passive gliding associated with extensional/contractional deformation.     

贺兰山水系流域数值地貌特征及其构造指示意义

基于Arcgis9.3与ASTER GDEM数据,提取了贺兰山两侧主要水系及其流域边界,根据河流及流域指标提取河流纵剖面、流域的Strahler曲线,并计算其面积高度积分值（Hypsometric Intergral）、河流纵剖面的凹度值（Concavity）。通过HI值、凹度值同河流落差、河流长度、流域面积之间相关性分析发现,后3种地貌参数与HI值、凹度值间的相关性较差。对比分析贺兰山两侧河流HI值及凹度值发现：贺兰山东侧北段活动性大于南段,西侧构造活动性分布规律不明显。结合9条河流所处流域的Strahler曲线、河流纵剖面形态和HI值、凹度值分析发现：汝箕沟及其以北贺兰山地区处于地形演化的老年期,汝箕沟以南贺兰山段处于均衡调整的壮年期。     

Geomorphic appraisals of active tectonics associated with uplift of the Gohpur–Ganga section in Itanagar, Arunachal Pradesh, India

The Gohpur–Ganga section is located southwest of Itanagar, India. The study area and its adjacent regions lie between the Main Boundary Thrust (MBT) and the Himalayan Front Fault (HFF) within the Sub-Himalaya of the Eastern Himalaya. The Senkhi stream, draining from the north, passes through the MBT and exhibits local meandering as it approaches the study area. Here, five levels of terraces are observed on the eastern part, whereas only four levels of terraces are observed on the western part. The Senkhi and Dokhoso streams show unpaired terraces consisting of very poorly sorted riverbed materials lacking stratification, indicating tectonic activity during deposition. Crude imbrications are also observed on the terrace deposits. A wind gap from an earlier active channel is observed at latitude 27°04′42.4″ N and longitude 93°35′22.4″ E at the height of about 35 m from the present active channel of Senkhi stream. Linear arrangements of ponds trending northeast–southwest on the western side of the study section may represent the paleochannel of Dokhoso stream meeting the Senkhi stream abruptly through this gap earlier. Major lineament trends are observed along NNE–SSW, NE–SW and ENE–WSW direction. The Gohpur–Ganga section is on Quaternary deposits, resting over the Siwaliks with angular contact. Climatic changes of Pleistocene–Holocene times seem to have affected the sedimentation pattern of this part of the Sub-Himalaya, in association with proximal tectonism associated with active tectonic activities, which uplifted the Quaternary deposits. Older and younger terrace deposits seem to mark the Pleistocene–Holocene boundary in the study area with the older terraces showing a well-oxidized and semi-consolidated nature compared to the unoxidized nature of the younger terraces.     

Evidence of quaternary transtensional tectonics in the Nekor basin (NE Morocco)

The geodynamic processes in the western Mediterranean are driven by both deep (mantle) processes such as slab‐rollback or delamination, oblique plate convergence and inherited structures. The present‐day deformation of the Alboran Sea and in particular the Nekor basin area is linked to these coeval effects. The seismically active Nekor basin is an extensional basin formed in a convergent setting at the eastern part of the Rif Chain whose boundaries extend both onshore and offshore Morocco. We propose a new structural model of the Nekor basin based on high‐resolution offshore data compiled from recent seismic reflection profiles, swath bathymetry acquisitions and industrial seismic reflection profiles. The new data set shows that the northern limit of the basin is oriented N49° with right‐stepping faults from the Bousekkour–Aghbal fault to the sinistral Bokkoya fault zone. This pattern indicates the presence of an inherited left‐lateral basement fault parallel to the major inherited Nekor fault. This fault has been interpreted as a Quaternary active left‐lateral transfer fault localized on weak structural discontinuities inherited from the orogenic period. Onshore and offshore active faults enclose a rhombohedral tectonic Nekor Basin. Normal faults oriented N155° offset the most recent Quaternary deposits in the Nekor basin, and indicate the transtensional behaviour of this basin. The geometry of these faults suggests a likely rollover structure and the presence at depth of a crustal detachment. Inactive Plio‐Quaternary normal faults to the east of the Ras Tarf promontory and geometries of depocentres seem to indicate the migration of deformation from east to west. The local orientations of horizontal stress directions deduced from normal fault orientations are compatible with the extrusion of the Rifian units and coherent with the westward rollback of the Tethyan slab and the localization of the present‐day slab detachment or delamination.     

Late Quaternary geomorphic evolution of the lower Narmada valley, Western India: implications for neotectonic activity along the Narmada–Son Fault

Geomorphic data combined with stratigraphic studies provide significant information to constrain timing and amount of fault movement. The lower Narmada valley lies astride the Narmada–Son Fault (NSF), an important ENE–WSW-trending tectonic element responsible for the current intraplate seismicity being experienced in the central part of the Indian plate. Varying nature and degree of tectonic movements along the NSF during Late Pleistocene and Holocene have produced four geomorphic surfaces in the lower Narmada valley: the alluvial plain (S₁), ravine surface (S₂), a gravelly fan surface (S₃) and the valley fill terrace surface (S₄). Two major phases of tectonic movements in a compressive stress regime are recorded along the NSF: slow synsedimentary subsidence of the basin during Late Pleistocene due to differential movement, followed by inversion of the basin during the Holocene marked by differential uplift along the NSF. The study suggests that the inversion of the basin is in response to the significant increase in the intensity of compressive stresses in the Indian plate mainly during the Early Holocene. The present incisive drainage and recent seismic activity indicate that the compressive stresses continue to accumulate along the NSF due to continued northward movement of the Indian plate.     

Soil-stratigraphic techniques in the study of soil and landform evolution across the Southern Alps, New Zealand

The Southern Alps lie along the convergent Pacific-Indian plate boundary. Geomorphically distinct eastern, axial and western regions reflect the east-west gradient in tectonic uplift (1 to 10 mm a⁻¹) and precipitation (600 to 10,000 mm a⁻¹). The eastern region is divided into front-ange and basin-and-range subregions. Soil-sequence studies on terraces established temporal contrasts in pedogenesis within and between eastern and western regions encompassing Entisols, Inceptisols and Spodosols. On Late Pleistocene and early Holocene terraces Dystrochrepts are persistent soils in the eastern region and Aquods in the western region. These soil sequences are used in the interpretation of relative soil age, stratigraphy and erosion history in hill and mountain drainage basins of the eastern and western regions. In the subhumid to humid eastern front-range subregion, simple soil forms occur as catenary sequences, and there is little evidence of erosion following the destruction of forests in the last millenium. Mollisols are dominant in the subhumid, and Dystrochrepts in humid areas, respectively. Soil-debris mantle regoliths date from the early Holocene and are still developing on slopes. The soil pattern on mountain slopes in the humid, eastern basin-and-range subregion is a complex array of simple, eroded, composite and compound soils. This pattern has resulted from erosion following forest destruction within the last millenium. The oldest surface or buried forest soils are Dystrochrepts dating from the Late Pleistocene to early Holocene. Wind erosion of these low-fertility soils contributes to the loessial sediments in which younger soils have formed. In the western region, soil patterns and soil stratigraphy indicate continous instability with a complex pattern of highly leached, shallow Orthents and bedrock outcrops on slopes. The soils are eroded from slopes within 2 ka. These contrasts in soil development and erosion periodicity in the eastern and western regions of the Southern Alps parallel the east-west contrasts in erosion rates of ca. 1–10 mm a⁻¹.     

第四纪江汉-洞庭盆地东部中段构造-沉积地貌类型划分及特征

以第四纪构造活动、沉积作用以及现今地势高低和地貌形态特征为主要依据,对江汉-洞庭盆地东部中段及其东缘(1:25万岳阳市幅)进行构造-沉积地貌类型的划分与编图。研究区共厘定出9种构造-沉积地貌类型,各地貌类型的地表高程、第四纪地壳升降特征、风化剥蚀和沉积作用等各具特征。构造-沉积地貌类型的划分及其地貌图的编制,既反映出地表地理环境暨地貌特征,又提供直观表达不同地区第四纪地层、构造特征及其反映的地质与环境演化过程的有效途径,有助于促进和深化江汉-洞庭盆地第四纪地质与环境研究。     

Between plate and salt tectonics—New stratigraphic constraints on the architecture and timing of the Dead Sea basin during the Late Quaternary

The Dead Sea is an extensional basin developing along a transform fault plate boundary. It is also a terminal salt basin. Without knowledge of precise stratigraphy, it is difficult to differentiate between the role of plate and salt tectonics on sedimentary accumulation and deformation patterns. While the environmental conditions responsible for sediment supply are reasonably constrained by previous studies on the lake margins, the current study focuses on deciphering the detailed stratigraphy across the entire northern Dead Sea basin as well as syn and post-depositional processes. The sedimentary architecture of the late Quaternary lacustrine succession was examined by integrating 851 km of seismic reflection data from three surveys with gamma ray and velocity logs and the stratigraphic division from an ICDP borehole cored in 2010. This allowed seismic interpretation to be anchored in time across the entire basin. Key surfaces were mapped based on borehole lithology and a newly constructed synthetic seismogram. Average interval velocities were used to calculate isopach maps and spatial and temporal sedimentation rates. Results show that the Amora Formation was deposited in a pre-existing graben bounded by two N-S trending longitudinal faults. Both faults remained active during deposition of the late Pleistocene Samra and Lisan Formations—the eastern fault continued to bound the basin while the western fault remained blind. On-going plate motion introduced a third longitudinal fault, increasing accommodation space westwards from the onset of deposition of the Samra Formation. During accumulation of these two formations, sedimentation rates were uniform over the lake and similar. High lake levels caused an increase in hydrostatic pressure. This led to salt withdrawal, which flowed to the south and southwest causing increased uplift of the Lisan and En Gedi diapirs and the formation of localized salt rim synclines. This induced local seismicity and slumping, resulting in an increased thickness of the Lisan succession within the lake relative to its margins. Sedimentation rates of the Holocene Ze'elim Fm were 4–5 times higher than before. The analysis presented here resolves central questions of spatial extent and timing of lithology, deposition rates and their variability across the basin, timing of faulting at and below the lake floor, and timing and extent of salt and plate tectonic phases and their effect on syn and post-depositional processes. Plate tectonics dictated the structure of the basin, while salt tectonics and sediment accumulation were primarily responsible for its fill architecture during the timeframe examined here.     

中国华北山地的层状地貌与喜马拉雅构造运动

层状地貌是在较短的距离内 ,从海岸到山顶的坡面上多级分布的阶梯状地貌。一般来说 ,它反映了地壳的构造运动。但并不是所有的层状地貌都是这样。只有地壳活动时期的火山喷发、砾石扇和地壳稳定时期的风化壳、古河道发育的层状地貌才能表明地壳的一次大的构造运动。据此认为 ,中国华北山地的喜马拉雅运动起始于始新世 ,至渐新世结束了第一幕。中新世是喜马拉雅运动的较激烈期 ,至上新世结束了第二幕。自第四纪进入了第三幕的第一亚幕 ,也就是新构造运动。自晚更新世进入了第三幕的第二亚幕 ,即最新构造运动。现在 ,第三幕尚未结束     

Rifting and pre‐rift lithosphere variability in the Orphan Basin,Newfoundland margin,Eastern Canada

The Orphan Basin, lying along the Newfoundland rifted continental margin, formed in Mesozoic time during the opening of the North Atlantic Ocean and the breakup of Iberia/Eurasia from North America. To investigate the evolution of the Orphan Basin and the factors that governed its formation, we (i) analysed the stratigraphic and crustal architecture documented by seismic data (courtesy of TGS), (ii) quantified the tectonic and thermal subsidence along a constructed geological transect, and (iii) used forward numerical modelling to understand the state of the pre‐rift lithosphere and the distribution of deformation during rifting. Our study shows that the pre‐rift lithosphere was 200‐km thick and rheologically strong (150‐km‐thick elastic plate) prior to rifting. It also indicates that extension in the Orphan Basin occurred in three distinct phases during the Jurassic, the Early Cretaceous and the Late Cretaceous. Each rifting phase is characterized by a specific crustal and subcrustal thinning configuration. Crustal deformation initiated in the eastern part of the basin during the Jurassic and migrated to the west during the Cretaceous. It was coupled with a subcrustal thinning which was reduced underneath the eastern domain and very intense in the western domains of the basin. The spatial and temporal distribution of thinning and the evolution of the lithosphere rheology through time controlled the tectonic, stratigraphic and crustal architecture that we observe today in the Orphan Basin.     

金沙江奔子栏-达日河段大型泥石流堆积扇的成因机制

金沙江上游奔子栏-达日河段属横断山区的干热河谷地带,河谷沿岸大型古泥石流堆积扇广泛发育,其成因却一直没有得到很好的研究.对该区瓦卡大型古泥石流堆积物进行了沉积结构、粒度、地球化学和孢粉等分析,揭示了泥石流的沉积环境及其形成过程.通过粗颗粒石英的光释光单片再生法(SAR)测年研究,获得金沙江上游奔子栏-达日河段古泥石流大规模暴发的年代为12 600～4 500 a BP.丰富的风化碎屑物源、陡峻的地形及雨季降水集中是该区古泥石流形成的主要原因.全新世早期青藏高原东南缘受西南季风加强的影响,气候趋于暖湿,季节性暴雨增加.金沙江上游干热河谷区大型泥石流堆积扇的发育年代暗示其是全新世早期西南季风加强作用下的地貌响应.从地质灾害防治的角度,由于现代气候因素导致泥石流灾害的频度和规模较小,预防该区地质灾害的重点应是防止人工砍伐树木和不合理的人工切坡导致对地表环境的破坏加剧.     

Origin of the in situ stress field in south-eastern Australia

The in situ stress field of south‐eastern Australia inferred from earthquake focal mechanisms and bore‐hole breakouts is unusual in that it is characterised by large obliquity between the maximum horizontal compressive stress orientation (S_Hmax) and the absolute plate motion azimuth. The evolution of the neotectonic strain field deduced from historical seismicity and both onshore and offshore faulting records is used to address the origin of this unusual stress field. Strain rates derived from estimates of the seismic moment release rate (up to ～10^?16 s^?1) are compatible with Quaternary fault–slip rates. The record of more or less continuous tectonic activity extends back to the terminal Miocene or early Pliocene (10–5 Ma). Terminal Miocene tectonic activity was characterised by regional‐scale tilting and local uplift and erosion, now best preserved by unconformities in offshore basins. Plate‐scale stress modelling suggests the in situ stress field reflects increased coupling of the Australian and Pacific Plate boundary in the late Miocene, associated with the formation of the Southern Alps in New Zealand.     

冀东平原第四纪沉积物地球化学特征及其古地理意义

本文根据第四纪沉积物化学分析资料,研究各种元素在不同沉积时期分布、迁移和累积的规律,探讨冀东平原地球化学环境的形成特征以及与古地理环境的关系。     

The origin of the Sierra de Aracena Hollows in the Sierra Morena, Huelva, Andalucia, Spain

Hollows in the Sierra de Aracena, part of western sector of Sierra Morena region (Huelva, Spain), are geoecologically unusual macroforms. They are underlain by deeply weathered bedrock but have eutrophic soils with distinctive vegetation. Paleosols with very dark colours, a predominance of smectites and large amounts of total and free iron occur on the floors on the hollows. An evolutionary model is proposed for the hollows, involving differential weathering during the Mesozoic on plutonic and amphibolitic rocks, alpine tectonic activity followed by Quaternary erosion and exhumation leading to formation of erosional terraces.     

淡水河口海岸阶地之对比

海阶是海平面变动、地壳变动或两者共同作用之结果．海阶研究不仅可据以推论古气候、往昔海平面变化及地壳变动状况,更可藉以了解各区域间变动的差异,对全盘了解大地构造具有基本的重要性．本文研究区位于欧亚大陆板块与菲律宾海板块的碰撞地带,地壳活动频繁,海阶的分布、规模等,除了受到海平面变动影响之外,尚受到区域性地壳隆升以及近期火山活动的影响．研究结果显示,淡水河两岸的海阶阶序,分别为北岸9阶,由低至高为第Ⅰ阶0～10m、第Ⅱ阶30～50m、第Ⅲ阶55～95m、第Ⅳ阶100～130m、第V阶135～173m、第Ⅵ阶190～275m、第Ⅶ阶285～310m、第Ⅷ阶320～365m、第Ⅸ阶375～405m．南岸有7阶,第Ⅰ阶0～10m、第Ⅱ阶25～50m、第Ⅲ阶65～95m、第Ⅳ阶115～138m、第V阶150～200m、第Ⅵ阶230～275m、第Ⅶ阶285～350m．利用海阶对比基图,得到各段阶地生成年代分别为北岸6kaBP（Ⅰ）、40kaBP（Ⅱ）、57kaBP（Ⅲ）、77．5kaBP（Ⅳ）、88．5kaBP（Ⅴ）、126．5kaBP（Ⅵ）、148．5kaBP（Ⅶ）、183kaBP（Ⅷ）、202kaBP（Ⅸ）．淡水河口南岸分别为6kaBP（Ⅰ）、40kaBP（Ⅱ）、57kaBP（Ⅲ）、79kaBP（Ⅳ）、100kaBP（Ⅴ）、126．5kaBP（Ⅵ）、173．4kaBP（Ⅶ）．淡水河两岸仅一水之隔,区域性地壳变动及海平面变动大致相同,但大屯火山之活动年代较观音火山之年代早,因而大屯山地势较高,经过比对,隆升速率影响地势高低与海阶发育特征,两岸之平均隆升速率分别是北岸的2．2mm／a和南岸的2．15mm/a,北岸略较南岸活跃,阶数多,地势高．