Loch Lomond Stadial and Flandrian shorelines in the inner Moray Firth area,Scotland

Morphological mapping and stratigraphical investigations have identified surface and buried relict marine features in the inner Moray Firth area. The features consist of a buried gravel layer formed during the Loch Lomond Stadial, a buried beach of early Flandrian age, and surface beaches and estuarine flats of mid-late Flandrian age. Analysis of the altitudes of morphological features has identified two buried and five (possibly six) surface glacio-isostatically tilted raised shorelines. The steepest shoreline is associated with the buried gravel layer and slopes down towards N20°E at a gradient of 0.20m/km. Younger shorelines have lower gradients between 0.16–0.03m/km. The shoreline sequence combined with published data defines relative sea-level movements in the area during the last 11000 years. The inner Moray Firth shorelines are correlated with similar features in other areas of Scotland which include the Main Lateglacial, Main Buried and Main Postglacial Shorelines.     

Late Devensian raised shorelines in Angus and Kincardineshire, Scotland

Marine, fluvial and fluvioglacial terraces, and other landforms and deposits associated with them, have been mapped over an area that extends from Dundee to Stonehaven along the coast, and inland in places as far as the Highland edge. All well-defined terraces have been levelled at approximately 50 mintervals along their length. Analysis of the altitude data permits the recognition of eight glacio-isostatically tilted raised shorelines of Late Devensian age, sloping down towards E5S, the lowest at 0.2 m/km and the others at gradients of 0.50-0.85 m/km. Successively lower and less steeply inclined shorelines were formed in close association with a westward-receding ice margin, and there are indications that crustal response to unloading may have been immediate and rapid. Five of the shorelines are correlated with five of the six Late Devensian shorelines recognized by the authors (1966) in eastern Fife, allowing contemporaneous positions of the wasting ice-sheet margin in the two areas to be postulated.     

Late Devensian raised shorelines and ice limits in the inner Moray Firth area, northern Scotland

Marine, fluvial and fluvioglacial landforms and the deposits associated with them, have been mapped in the inner Moray Firth area. The landforms identified indicate a close association between the decay of the Late Devensian Scottish ice sheet and the formation of raised marine features. Analysis of the altitudes of the marine terraces has identified ten glacio-isostatically tilted raised shorelines of Late Devensian age, sloping down towards N25°E, at progressively lower gradients between 0.57 and 0.15 m/km. The shorelines were formed in close association with a westward- and southward-receding ice margin and the shoreline sequence suggests that rates of ice margin retreat were most rapid where the ice terminated in the sea.     

Late Weichselian and Holocene shoreline displacement in the Trondheimsfjord area, central Norway

Shoreline displacement data from the Trondheimsfjord area have been collected and a synthesis of the Late Weichselian and Holocene relative uplift is presented. The isobase direction is N 30–35°E during the whole period. The gradients of the shorelines are 1.7? m/km at 11,800 years B.P., 1.3 m/km at 10,000 years B.P., gradually decreasing towards the present with a value of 0.2 m/km at 5,000 years B.P. Some irregularities in the shoreline gradient curve in the Late Weichselian and Preboreal chronozones may be ascribed to crustal readjustments by faults. An interpolation of the 9,500 years B.P. shoreline to the Ångermanland and Baltic area shows a relative uplift at 11,800 years B.P. of 400–450 m in the central area of glaciation. The island of Hitra was probably deglaciated at about 12,000 years B.P. and Ørlandet/Bjugn somewhat later. The Younger Dryas ice marginal deposits at Tautra have been deposited early in this chronozone, and deposits proximal to this at Hoklingen and Levanger were probably deposited in the late part of the same chronozone.     

Pattern and chronology of glacial Lake Peace shorelines and implications for isostacy and ice‐sheet configuration in northeastern British Columbia,Canada

Recognition of positions of glacial lakes along the margin of continental ice sheets is critical in reconstructing ice configuration during deglaciation. Advances in remote sensing technology (e.g. LiDAR) have enabled the generation of accurate digital‐elevation models (DEMs) that reveal unprecedented geomorphic detail. Combined with geographical information systems, these tools have considerably advanced the mapping and correlation of geomorphic features such as relict shorelines. Shorelines of glacial Lake Peace (GLP) developed between the Laurentide and Cordilleran ice sheets in northeastern British Columbia and northwestern Alberta. Shoreline mapping from high resolution DEMs produced more than 55 500 elevation data points from 3231 shorelines, enabling the identification of four major phases of GLP: Phase I (altitude 960–990 m a.s.l.); Phase II (890–915 m a.s.l.); Phase III (810–865 m a.s.l.); and Phase IV (724–733 m a.s.l.). The timing of Phase II of GLP is estimated by two optical ages of <16.0±2.5 and 14.2±0.5 ka BP. Extensive mapping of the shorelines allows for measuring of glacial isostatic adjustment as ice retreated. Shorelines currently dip to the northeast at around 0.4–0.5 m km^?1. This slope reflects the asynchronous retreat of the Cordilleran (CIS) and Laurentide (LIS) ice sheets. The relative uplift in the southwest of the study area within the Rocky Mountains and foothills suggests that the Late Wisconsinan (MIS 2) CIS persisted in the foothill after the LIS lost mass and retreated, or that the Late Wisconsinan CIS was very thick and caused deep crustal loading, which resulted in more uplift in the southwest before reaching equilibrium during, or shortly after deglaciation.     

Anomalously high uplift rates along the Ventura—Santa Barbara Coast, California—tectonic implications

The NW—SE trending segments of the California coastline from Point Arena to Point Conception (500 km) and from Los Angeles to San Diego (200 km) generally parallel major right-lateral strike-slip fault systems. Minor vertical crustal movements associated with the dominant horizontal displacements along these fault systems are recorded in local sedimentary basins and slightly deformed marine terraces. Typical maximum uplift rates during Late Quaternary time are about 0.3 m/ka, based on U-series ages of corals and amino-acid age estimates of fossil mollusks from the lowest emergent terraces.In contrast, the E–W-trending segments of the California coastline between Point Conception and Los Angeles (200 km) parallel predominantly northward-dipping thrust and high-angle reverse faults of the western Transverse Ranges. Along this coast, marine terraces display significantly greater vertical deformation. Amino-acid age estimates of mollusks from elevated marine terraces along the Ventura—Santa Barbara coast imply anomalously high uplift rates of between 1 and 6 m/ka over the past 40 to 100 ka. The deduced rate of terrace uplift decreases from Ventura to Los Angeles, conforming with a similar trend observed by others in contemporary geodetic data.The more rapid rates of terrace uplift in the western Transverse Ranges reflect N—S crustal shortening that is probably a local accommodation of the dominant right-lateral shear strain along coastal California.     

Recent crustal uplift of Precambrian cratons: Key patterns and possible mechanisms

Precambrian cratons cover about 70% of the total continental area. According to a large volume of geomorphological, geological, paleontological, and other data for the Pliocene and Pleistocene, these cratons have experienced a crustal uplift from 100-200 m to 1000-1500 m, commonly called the recent or Neotectonic uplift. Shortening of the Precambrian crust terminated half a billion years ago or earlier, and its uplift could not have been produced by this mechanism. According to the main models of dynamic topography in the mantle, the distribution of displacements at the surface is quite different from that of the Neotectonic movements. According to seismic data, there is no magmatic underplating beneath most of the Precambrian cratons. In most of cratonic areas, the mantle lithosphere is very thick, which makes its recent delamination unlikely. Asthenospheric replacement of the lower part of the mantle lithosphere beneath the Precambrian cratons might have produced only a minor part of their Neotectonic uplifts. Since the above mechanisms cannot explain this phenomenon, the rock expansion in the crustal layer is supposed to be the main cause of the recent uplift of Precambrian cratons. This is supported by the strong lateral nonuniformity of the uplift, which indicates that expansion of rocks took place at a shallow depth. Expansion might have occurred in crustal rocks that emerged from the lower crust into the middle crust with lower pressure and temperature after the denudation of a thick layer of surface rocks. In the dry state, these rocks can remain metastable for a long time. However, rapid metamorphism accompanied by expansion of rocks can be caused by infiltration of hydrous fluids from the mantle. Analysis of phase diagrams for common crustal rocks demonstrates that this mechanism can explain the recent crustal uplift of Precambrian cratons.     

High stands of Holocene sea levels in the Northwest Pacific

Evidence of Holocene sea levels higher than the present level have often been reported from the Northwest Pacific. Eustatic interpretations have been propounded, but age and level of the maximum transgression vary with each new analysis. In this investigation, after an inventory of approximately 250 items of data, some of which are new, a tentative synthesis transcending local scale is advanced. The highest levels are reported from Taiwan, where they often reach several tens of meters in altitude. In the Ryûkyûs and in the main islands of the Japanese Archipelago, evidence of recent emergence is found along most of the coasts. Elevation increases towards the oceanic trenches, but former sea levels at above 6 m and even higher may also be recognized along the coasts of the Sea of Japan. In a few areas, such as in the Niigata Plain, marks of Holocene sea levels higher than at present are lacking. On the other hand, in other basins regarded as subsiding, such as those in the Nôbi and the Kantô plains, evidence of recent emergence is quite frequent. In many places, marks of several sea levels indicate that a step-by-step uplift has occurred. All the investigated insular arcs, therefore, seem to be situated in epeirogenic areas formed by several more or less large blocks affected by relative movements. The blocks are larger in the Outer Zone of Southwestern Japan; in the Inner Zone, an intricate network of fault lines marks the boundaries of many smaller independent blocks. During great earthquakes, relative movements of uplift, subsidence, tilting, or undulation occur in one or several blocks, depending on the position of the epicentres. Subsidence, however, must often be simply of a temporary nature, because a long-term uplift trend seems to prevail in most regions, even if it occurs at different rates. This interpretation may explain the cause of the great variety of ages and elevations of the former sea levels (with the oldest ages corresponding to the highest elevations) and the great number of indicators of step-by-step sea-level change. The inference, drawn by several authors, that the Holocene sea level in the Northwest Pacific was higher than at present, is, therefore, reasonable on a local scale, but does not define an eustatic sea level.     

Allerød- Younger Dryas sea level changes in southwestern Sweden and their relation to the Baltic Ice Lake development

Mt. Kroppefjall is situated just south of the Middle Swedish (Younger Dryas) ice-marginal zone. Its abundance of lake basins makes it very suitable for detailed shore displacement studies close to the Younger Dryas ice margin. Altogether 12 lakes at altitudes between 157 and 78 m were studied and all but one situated above the marine limit contained marine sediments. The dating of their isolation from the sea resulted in a shore displacement curve from c. 11,200 to c. 98M)BP. The relative uplift almost ceased between 10,900 and 10,300 BP, which is mainly related to an ice readvance in the Lake Vanern basin. This period of balance between uplift and sea level rise was preceded by a relative uplift rate of 5 m/lW yr and followed by as high rates as 7–8 m/100 yr, possibly caused by a delayed uplift effect and perhaps also a local fall in sea level caused by the rapidly receding ice margin. The time difference between the formation of two delta surfaces at Odskolts Moar is estimated at 60&800 years. Shoreline diagrams along the Swedish west and east coasts, mainly based on a number of shore displacement curves, reveal large anomalies that are believed to have been caused by dammings and drainages of the Baltic basin. The southwards extrapolated shorelines indicate that the bedrock threshold in the Oresund Strait, between Denmark and Sweden, functioned as the outlet threshold for the Baltic Ice Lake during its dammed stages, while the erosion of the Store Balt and Darss Sill straits began at the culmination of the Ancylus transgression and continued during the rapid IS20 m Ancylus regression.     

Late-Holocene shore displacement of the Finnish south coast: diatom, litho- and chemostratigraphic evidence from three isolation basins

Lake isolation studies provide the most reliable method for reconstructing the shore displacement history of the areas affected by postglacial isostatic land uplift. Due to the slow uplift rate and the presence of numerous lakes, the Finnish south coast is one of the key areas for investigating the Litorina transgression and subsequent shore displacement history of the Baltic. To reconstruct the relative sea-level dynamics during the late Holocene, three small lakes from the critical altitudes were analysed concerning their diatom, sulphate-sulphur, and sodium stratigraphies and loss-on-ignition values. Comparisons of the records indicate that the availability of nutrients significantly influenced the diatom-floristic patterns during the lake isolation. In particular, the mass occurrence of Fragilaria spp. seems to be associated with high values of sulphate-sulphur and sodium during and after isolation. On the basis of the new and old data, a shore displacement curve for the 30 m Litorina isobase is compiled. This indicates that since the clear Litorina transgression at 7500-6500 ¹⁴C BP, no transgressions have taken place but that the shore displacement in the area has been a stable process. The occurrence of a number of raised shore formations between the altitude of the major Litorina shore and the present sea level in south Finland can be attributed to the erosion of soft soil layers by the high-energy wave action on the exposed shore sections.     

The lateglacial lakes of Glens Roy,Spean and vicinity (Lochaber district,Scottish Highlands)

This paper summarises the evidence for glacial ice advance into lower Glen Spean during the Loch Lomond Stadial which involved the blockage of westward-flowing drainage to form a series of ice-dammed lakes, the former surfaces of which are marked by prominent shorelines. Detailed mapping of glacigenic landforms and instrumental levelling of the shorelines reveals a dynamic interplay between the glacier margins and lake formation. Subsequent deglaciation led to lowering of the lake levels, at times by catastrophic drainage beneath the ice (jökulhlaup). The abandoned shorelines have been warped and dislocated in numerous places as a result of glacio-isostatic deformation, faulting and landslip activity. The pattern of retreat of the ice can be deduced from the mapped distributions of retreat moraines and the levelled altitudes of numerous kame and fluvial terrace fragments. The sequence of events outlined in this paper provides important context for understanding the evolution of the landscape of the Glen Roy area during the Loch Lomond Stadial, and a prelude to more recent studies reported in other contributions to this thematic issue.     

津冀海岸线现状、变化特征及保护建议

根据覆盖全区的3期遥感影像和实地调查,以及对滨海新区和滦河口2个典型区更深入的案例研究(包括回溯至1870年、1950年的基准岸线及逐年遥感信息),对津冀沿海海岸线现状进行解译和分类,并分析岸线变化特征及成因。津冀沿海现状岸线总长度894km,可以划分为自然岸线、半开发岸线和人工岸线3类,长度分别为90km、329km和475km。1950年以前为自然因素主导的岸线变化,1950年以后变为人类活动主导的岸线向海推进,逐渐加强的人类活动至2010年达到顶峰。在全球海面上升和区域地面下沉的大背景下,海岸线的自然演化趋势应该是向陆蚀退,但是人类活动主导的岸线变化却表现为违反自然趋势的向海推进。今后,向海推进最前沿的围海造陆区将受到来自海洋越来越强烈的影响,亟需加强监测和防护。兼顾环境保护与开发两方面的长远需求,建议赋予海岸线新的定义与内涵,划定岸线保护红线,恢复部分岸线的自然属性。     

基于重磁场的延边微板块地壳结构特征研究

延边地区位于多个微板块的结合部位,区内发育长白山活动火山群,地震活动频繁。本文通过重磁小波多尺度分解与莫霍面、居里面深度反演分析,研究延边地区的微板块地壳结构特征。其中敦化-密山断裂以东的胶辽地块地壳厚度最大,约38~40km,兴凯地块则最小,约34~36km,敦化-密山断裂以西的松嫩地块地壳厚度变化平缓,约36~37km;NE向敦化-密山断裂为延边地区的一级断裂,切穿莫霍面,为松嫩地块的东侧边界;NW向展布的富尔河-红旗河断裂、秋梨沟老头沟断裂与汪清-敬信断裂则属于胶辽地块与兴凯地块之间的缝合带,控制居里面分区及形态,而居里面隆起区及其边缘则多分布火山口,表明居里面的局部隆起与岩浆活动关系密切。     

Differential tectonic movements in the confluence area of the Huang Shui and Huang He rivers (Yellow River), NE Tibetan Plateau,as inferred from fluvial terrace positions

In the Northeastern Tibetan Plateau (NETP), the courses of the Huang Shui and Huang He near their confluence are characterized by alternating gorges and wide depressions, segmenting the fluvial systems. The river valleys have developed terrace staircases, which are used to infer relative tectonic motions between the segments. The terrace staircases are correlated by means of relative height and optically stimulated luminescence (OSL) dating. At least eight terraces are present, two of which have been dated by OSL (the sixth and the third ones; c. 70 and c. 24 ka, respectively). The correlated longitudinal terrace profiles show no distinct relative tectonic movements within the confluence area, demonstrating that this area behaved as one tectonic block. The correlation of the terrace staircase of this block with areas upstream (Xining area) and downstream (eastern Lanzhou area) indicates relative tectonic movements, which therefore represent different tectonic blocks. The fluvial incision rate since c. 70 ka was much higher in the confluence area than in the blocks upstream and downstream, possibly indicating relative uplift. This relatively strong uplift provided more space for differentiation within the terrace staircase as a result of climatic changes, leading to six terraces formed as a response to minor climatic fluctuations (10³–10⁴ year timescale) since the last interglacial. This may indicate that the stronger the tectonic movement the better the climatic imprint as expressed in the form of terrace development. Over a shorter timescale, two accumulation terraces with thick stacked deposits (>18 m) may indicate relative subsidence in the confluence, occurring sometime between 20 and 70 ka. This indicates changes in relative vertical crustal motions at timescales of tens of thousands of years. We speculate that the inferred tectonic motions are related to transpression movements in the NETP as a result of the collision of the Indian and Asian plates.     

Postglacial uplift and relative sea level changes in Finnmark,northern Norway

The outer coast of Finnmark in northern Norway is where the former Fennoscandian and Barents Sea ice sheets coalesced. This key area for isostatic modelling and deglaciation history of the ice sheets has abundant raised shorelines, but only a few existing radiocarbon dates constrain their chronology. Here we present three Holocene sea level curves based on radiocarbon dated deposits from isolation basins at the outermost coast of Finnmark; located at the islands Sørøya and Rolvsøya and at the Nordkinn peninsula. We analysed animal and plant remains in the basin deposits to identify the transitions between marine and lacustrine sediments. Terrestrial plant fragments from these transitions were then radiocarbon dated. Radiocarbon dated mollusk shells and marine macroalgae from the lowermost deposits in several basins suggest that the first land at the outer coast became ice free around 14,600 cal yr BP. We find that the gradients of the shorelines are much lower than elsewhere along the Norwegian coast because of substantial uplift of the Barents Sea. Also, the anomalously high elevation of the marine limit in the region can be attributed to uplift of the adjacent seafloor. After the Younger Dryas the coast emerged 1.6–1.0 cm per year until about 9500–9000 cal yr BP. Between 9000 and 7000 cal yr BP relative sea level rose 2–4 m and several of the studied lakes became submerged. At the outermost locality Rolvsøya, relative sea level was stable at the transgression highstand for more than 3000 years, between ca 8000 and 5000 cal yr BP. Deposits in five of the studied lakes were disturbed by the Storegga tsunami ca 8200–8100 cal yr BP.     

Holocene soil chronoassociation in part of the Middle Gangetic Plain: morphological and micromorphological characteristics

Systematic variations in soil characteristics related to degree of soil profile development in part of the Middle Gangetic Plain suggest a soil chronoassociation similar to the soil chronosequences observed on some river terrace formed by tectonic uplift. This chronoassociation has five members QG1 to QG5, the youngest being QG1 (< 500 yr BP). Variations in degree of horizon differentiation, profile thickness, clay accumulation, plasma separation, argillan thickness, weathering stage and day mineralogy have been used to determine the degree of soil development.
Pedogenic processes active in these soils are decalcification, translocation of clay, sesquioxide and organic matter, plasma separation and weathering of minerals. The amount and variability of clay minerals are significantly related to the type and duration of pedogenesis in different parts of the area. The oldest soils with pedogenic calcite (10 000 yr BP) developed during a dry period. Since 8000 yr BP climatic conditions of higher rainfall and better drainage have prevailed in the area.
Neotectonic movements have tilted the Gandak megafan block and have caused shifting of the Gandak river to the east about 105 km from its original course, leaving behind numerous channels, ponds, lakes and other features of impeded drainage.     

Effect of local variations of vertical and horizontal stresses on the Cenozoic structuring of the mid-Norwegian shelf

The mid-Norwegian margin has a complex history and has experienced several phases of changing horizontal and vertical stresses on regional and local scale during the Cenozoic time. In addition to regional stresses related to the opening of the North Atlantic (i.e. ridge push), local variations in stress history may be important for development, distribution and reactivation of structures in the Vøring area in Cenozoic time. Presence and stability of flexural hinge zones between areas of relative uplift and subsidence have played an important role for focusing shallow horizontal stresses within the basins. Emplacement of lower crustal bodies during break-up will, whatever the nature of these bodies, have substantial isostatic effects, and modelling show that this could cause many hundred meters of temporal uplift above the lower crustal bodies, locally exceeding 1300 m of surface uplift. Effects of intra plate stress (IPS) are modelled along three 2D transects across the Vøring Basin. Modelling shows that IPS may have given substantial vertical motions in certain areas of the mid-Norwegian shelf, both with extensional IPS at the time of break-up, and later with compressive IPS during Tertiary time. The modelling assumes a strongly reduced effective elastic thickness (EET) due to lithospheric heating at break-up and later increasing EET as the lithosphere cooled towards present time. Our modelling takes into account the tectonic and isostatic effects of loading faulting and lithospheric thinning throughout the geological history, including several phases of extension prior to the Cenozoic compression. This approach emphasizes the importance of the deformation history of the lithosphere compared to other studies that only take into account the effects of Cenozoic processes of compression and loading on the sedimentary units. We do not state that isostatic uplift or intra plate stress are the most important causes for Cenozoic uplift and compressional deformation in this area, but point to the fact that these factors locally may have played an important role in focusing deformation caused by an interplay of different mechanisms.     

喀喇昆仑山-西昆仑山地区湖泊演化

由于地质构造的控制,本区湖泊可分为三个湖泊带。本区湖泊几乎均为封闭湖泊,在湖盆中有众多的古湖岸线遗迹。由古湖岸线的分布推算高湖面时期的古湖泊范围为本区总面积的10.6%,为今日湖泊面积的3.06倍。根据地貌、第四纪沉积和¹⁴C 测年数据分析,最高湖面时期即最高古湖岸线所围限的古湖泊出现的时期为40000—20000aB.P.,大致与末次冰期间冰段相当。本区湖泊退缩十分强烈,喀喇昆仑山以北的湖泊退缩速度大于喀喇昆仑山以南。     

某水准路线所经地区现代升降运动的初步探讨

本文主要是利用水准复测资料来阐述某地区的现代升降运动。文中将复、初测高程进行比较,作出了现代地壳运动幅度图,图中看出东都上升幅度小,速度梯度变化也小;西部上升幅度大,速度梯度变化也大。在整个剖面中更可以看出,在较短距离内出现大幅度的隆起,隆起中又有相对凹陷。由实际资料得出,本区现代地壳运动有继承性,并出现三种类型的上升运动:(1)平稳的上升运动;(2)掀斜的上升运动;(3)强烈隆起。     

Deformations and Manifestations of Degassing in the Sedimentary Cover of the Equatorial Segment of the West Atlantic: Implications for Lithospheric Geodynamics

Manifestations of fluids and deformations in the sedimentary cover, which are both factors of brightening (blanking anomalies) in seismoacoustic records, in the equatorial segment of the Atlantic coincide with the sublatitudinal zones of the activated passive parts of transform faults and with zones of lower gravity anomalies and higher values of remnant magnetization, which form as a result of serpentinization. The cause-and-effect sequence of intraplate phenomena includes: the contrasting geodynamic state → horizontal movements that form macrofractures → water supply to the upper mantle → serpentinization of rocks in the upper mantle → deformations associated with vertical uplift of basement and sedimentary cover blocks, coupled with fluid generation → and fluid accumulation in the sedimentary cover, accompanied by the formation of anomalies in seismoacoustic records. Based on the seismic data, we have identified imbricate-thrust deformations, diapir structures, stamp folds, and positive and negative flower structures, indicating the presence of strike-slip faults in the passive parts of transform faults. The general spatial distribution of deformation structures shows their concentration in cold mantle zones. Correlative comparison of the structural characteristics of deformations shows the direct relationship between the heights of structures and the development of serpentinization processes. As per the age of the basement, deformations range from 27–38 to 43–53 Ma; a quite thick sedimentary cover makes it possible to reveal them based on the characteristic types of seismoacoustic records. The formation of the Antilles arc ca. 10 Ma ago affected the equatorial segment of the Atlantic; it formed kink bands where lithospheric blocks underwent displacements with counterclockwise rotations, deformations related to compression and vertical uplift of crustal fragments, and local extension that favored degassing of endogenous fluids. Sublatitudinally oriented imbricate-thrust deformations with different vergences indicate irregularity and alternating strike-slip directions as blocks between fractures were laterally influenced.