Soft-sediment deformation structures in NW Germany caused by Late Pleistocene seismicity

New data on seismically triggered soft-sediment deformation structures in Pleniglacial to Late Glacial alluvial fan and aeolian sand-sheet deposits of the upper Senne area link this soft-sediment deformation directly to earthquakes generated along the Osning Thrust, which is one of the major fault systems in Central Europe. Soft-sediment deformation structures include a complex fault and fold pattern, clastic dikes, sand volcanoes, sills, irregular intrusive sedimentary bodies, flame structures, and ball-and-pillow structures. The style of soft-sediment deformation will be discussed with respect to brittle failure, liquefaction and fluidization processes, and was controlled by (1) the magnitude of the earthquake and (2) the permeability, tensile strength and flexural resistance of the alluvial and aeolian sediments. It is the first time in northern Germany that fluidization and liquefaction features can be directly related to a fault. The occurrence of seismicity in the Late Pleistocene and in the seventeenth century indicates ongoing crustal movements along the Osning Thrust and sheds new light on the seismic activity of northern Germany. The Late Pleistocene earthquake probably occurred between 15.9 ± 1.6 and 13.1 ± 1.5 ka; the association of soft-sediment deformation structures implies that it had a magnitude of at least 5.5.     

Morphology and post-Chaudian (Late Pleistocene) evolution of the submarine Danube fan complex

The Danube deep sea fan in the northwestem Black Sea has a lateral dimension of over 150 km and stretches from several hundred metres water depth down to the abyssal plain. Eight seismic sequences have been recognized in the fan complex. Each sequence consists of channel, levee and overbank deposits, as well as mass transport units. The Danube and the Ukrainian rivers have aggraded two surficial channel-levee systems which diverge and decrease in volume downfan. The channels of these systems have a low sinuosity, implying young age, steep gradients and/or limited sediment supply. Significant channel migration occurred in the course of fan development, which could be largely controlled by relative sea-level changes. The six youngest sequences mapped have been correlated to sea-level fluctuations from the post-Chaudian regression to the present day.     

Holocene aeolian dynamics in the European sand‐belt as indicated by geochronological data

Aeolian sands are widespread in the European sand‐belt. While there is a consensus about the timing of increased aeolian activity and, in contrast, of surface stabilization during the Lateglacial, knowledge about Holocene aeolian dynamics is still very sparse. It is generally assumed that aeolian processes have been closely connected to human activities since at least the Neolithic period. A compilation of 189 luminescence dates from aeolian sands of Holocene age and 301 ¹⁴C‐dates from palaeo‐surfaces, comprising palaeosols, buried peats and archaeological features from the whole sand‐belt, is plotted as histograms and kernel density plots and divided into sub‐phases by cluster analysis. This is also done separately for the dates from the areas west and east of the river Elbe. Our results show that aeolian activity did not cease with the end of the Younger Dryas but continued in the whole European sand‐belt until the Mid‐Atlantic (c. 6500 a BP), presenting evidence of vegetation‐free areas at least at the local scale. During the subsequent time period evidence of aeolian sedimentation is sparse, and surface stabilization is indicated by a cluster of palaeo‐surfaces ascribed to the early Subboreal (c. 5000 cal. a BP). The agglomeration of luminescence ages around 4000 years is probably connected with intensified land use during the Late Neolithic. Younger phases of aeolian sedimentation are indicated by clusters of luminescence ages around 1800 years, a group of luminescence ages from the Netherlands and NW Germany around 900 years, and a group of ages around 680 years in Germany. Among the dates from palaeo‐surfaces, clusters were identified around 2700, 1300 and 900 cal. a BP as well as around 690 cal. a BP in the western part and 610 cal. a BP in the eastern part of the sand‐belt. The clusters within the luminescence ages and the ¹⁴C‐dates coincide with phases where increased human impact can be deduced from archaeological and historical sources as well as from environmental history.     

辽南晚更新世风成沉积序列与古气候意义

作为中国东部重要的第四纪风成堆积地层,辽南风成沉积反映的气候振荡记录对于揭示区域古气候变化、东亚季风变迁等有着不言而喻的重要性。本研究利用辽南老虎村5.44 m厚的风成沉积剖面作为研究对象,采用光释光（OSL）测年技术建立了研究区沉积地层的年代框架,通过岩石学和代用指标重建了晚更新世期间的风成沉积历史。结果表明：风成活动发生在71.7~61.7 ka,49.4~42.4 ka和约23.0 ka,分别对应深海氧同位素阶段（MIS）5a~4、3b和2,寒冷干燥的气候条件与增强的东亚冬季风促使风成活动加剧;而MIS 3a和MIS 3c的沉积中断可能受到了暖湿气候的影响。研究区的粒度数据表明在MIS5/4转变时期有一个短暂的冬季风波动,同时,中值粒径增大可能与海因里希事件（H6、H5、H2）有关,未来仍需更多的区域气候纪录来支持这一观点。

     

Facies characteristics of Middle Pleistocene (Saalian) ice-margin subaqueous fan and delta deposits,glacial Lake Leine,NW Germany

The blocking of major river valleys in the Leinebergland area by the Early Saalian Scandinavian ice sheet led to the formation of a large glacial lake, referred to as “glacial Lake Leine”, where most of the sediment was deposited by meltwater. At the initial stage, the level of glacial Lake Leine was approx. 110 m a.s.l. The lake level then rose by as much as 100 m to a highstand of approx. 200 m a.s.l.Two genetically distinct ice-margin depositional systems are described that formed on the northern margin of glacial Lake Leine in front of the retreating Scandinavian ice sheet. The Bornhausen delta is up to 15 m thick and characterized by a large-scale tangential geometry with dip angles from 10°–28°, reflecting high-angle foreset deposition on a steep delta slope. Foreset beds consist of massive clast-supported gravel and pebbly sand, alternating with planar-parallel stratified pebbly sand, deposited from cohesionless debris flows, sandy debris flows and high-density turbidity flows. The finer-grained sandy material moved further downslope where it was deposited from low-density turbidity currents to form massive or ripple-cross-laminated sand in the toeset area.The Freden ice-margin depositional system shows a more complex architecture, characterized by two laterally stacked sediment bodies. The lower part of the section records deposition on a subaqueous ice-contact fan. The upper part of the Freden section is interpreted to represent delta-slope deposits. Beds display low- to high-angle bedding (3°–30°) and consist of planar and trough cross-stratified pebbly sand and climbing-ripple cross-laminated sand. The supply of meltwater-transported sediment to the delta slope was from steady seasonal flows. During higher energy conditions, 2-D and 3-D dunes formed, migrating downslope and passing into ripples. During lower-energy flow conditions thick climbing-ripple cross-laminated sand beds accumulated also on higher parts of the delta slope.     

Modelling controls on aeolian dune‐field pattern evolution

A second‐generation, source‐to‐sink cellular automaton‐based model presented here captures and quantifies many of the factors controlling the evolution of aeolian dune‐field patterns by varying only a small number of parameters. The role of sediment supply, sediment availability and transport capacity (together defined as sediment state) in the development and evolution of an aeolian dune‐field pattern over long time scales is quantified from model simulations. Seven dune‐field patterns can be classified from simulation results varying the sediment supply and transport capacity that control the type and frequency of dune interactions, the sediment availability of the system and, ultimately, the development of dune‐field patterns. This model allows predictions to be made about the range of sediment supply and wind strengths required to produce the dune‐field patterns seen in the real world. A new clustered dune‐field pattern is identified from model results and used to propose an alternative mechanism for the formation of superimposed dunes. Bedforms are hypothesized to cluster together, simultaneously forming two spatial scales of bedforms without first developing a large basal dune with small superimposed dunes. Manipulation of boundary conditions produces evolving dune fields with different spatial configurations of sediment supply. Trends of spacing and crest length increase with decreasing variability as the dune field matures. This simple model is a valuable tool which can be used to elucidate the dominant control of aeolian sediment state on the construction and evolution of aeolian dune‐field patterns.     

Late Pleistocene aeolian and fluvial interactions in the development of the Nizzana dune field, Negev Desert, Israel

The interdunal areas in the Nizzana linear sand dune field contain both sandy and silty sediments. A series of trenches was excavated across the interdunal corridor exposing stacked sequences of silty and sandy units which are locally restricted to palaeodepressions. The silty units contain fining upward sequences and are interpreted as overbank deposits from the Nahal Nizzana. Thermoluminescence dating and identification of buried palaeosols indicates that the silt and clay layers were deposited over a period of several thousands of years in the late Pleistocene. The sands between the silt layers have been fluvially reworked and are not primary aeolian deposits. The stacked sequences of fluvial deposits indicate that the palaeodepressions persisted in the landscape for a significant time attesting to long-term stability of the interdunal areas. It also suggests that the linear dunes themselves have not moved laterally during this time despite climatic changes and devegetation. Since the end of the late Pleistocene the Nahal Nizzana has downcut and overbank deposition no longer occurs within the interdunal corridors. The playa deposits today are positive relief features indicating that topographic inversion has occurred and that the interdunal areas are geomorphically active.     

Autostratigraphic modelling of the growth of alluvial‐shelf systems during steady base‐level cycles: Two‐dimensional tank experiments

Autostratigraphy is the stratigraphy generated by large‐scale autogenesis, developed based on the full recognition of the non‐equilibrium behaviour of depositional systems in response to steady external forcing. The existing autostratigraphic concepts were derived mostly from studies of river deltas growing during a single rise or fall of base level (or relative sea level). The present study challenges to extend the autostratigraphic framework to the alluvial‐shelf system growing through steady base‐level cycles by two‐dimensional tank experiments. During each experimental run, the base level was changed symmetrically, wherein through cycles, the rise and fall had the same constant rate (|R_bl|) and period (T_bl), and thus the same constant amplitude (A_bl), but with no basin tectonism. In total, nine runs with different combinations of |R_bl| and A_bl were performed. The experimental results brought the following implications. (i) The shelf‐transiting active depositional system takes non‐equilibrium responses in earlier base‐level cycles, during each of which the system experiences episodes of degradation with base‐level fall. (ii) After the system has sufficiently grown through cycles, non‐equilibrium responses change into equilibrium responses, whereby the shelf‐transiting alluvial system, whether retrogradational or progradational, is free from degradation and continues to aggrade but with a gradually decreasing rate of aggradation. (iii) The alluvial topset river tentatively but autogenically attains a graded state during the falling limb of an intermediate cycle, which separates the earlier degradation‐inclusive and later aggradation‐sustainable cycles. (iv) The number (or duration) of cycles elapsed prior to this phase‐transition is linearly proportional to the amplitude (or the square of the period) of base‐level cycles, with a coefficient defined by the rates of base‐level change and sediment supply. Such a growth pattern does not necessarily hold when considering long‐term tectonic subsidence or uplift. These notions help to understand the stratigraphic architectures of natural alluvial‐shelf systems evolved through base level cycles.     

Multiphase salt tectonic evolution in NW Germany: seismic interpretation and retro-deformation

The Central European Basin is a classic area of salt tectonics, characterized by heterogeneous structural evolution and complex salt movement history. We studied an area on its SW margin, based on prestack depth-migrated 2D and 3D seismic data. We use seismic interpretation and retro-deformation to obtain a better understanding of salt tectonics, structural control, and sedimentary response in this region. The first phase of salt tectonic evolution started with two main events of NW–SE extension and rafting in the Triassic before the Upper Bunter and before the Upper Muschelkalk. Rafting was accompanied by first salt diapirism and an increased sedimentary thickness adjacent to the salt structure. After salt supply ceased updip to the salt structure, a mini-basin grew in the intra-raft area. This sedimentary differential loading caused salt movement and growth of a pillow structure basinward. The second phase of salt movement was initiated by the formation of a NNW–SSE striking basement graben in the Middle Keuper that triggered reactive diapirism, the breakthrough of the pillow’s roof and salt extrusion. The following downbuilding process was characterized by sedimentary wedges with basal unconformities, onlap structures and salt extrusions that ceased in the Jurassic. The third and latest phase of salt tectonic evolution was activated in the Late Cretaceous to Lower Tertiary by compressional tectonics indicated by salt rise and a small horizontal shortening of the diapir. The interpreted salt tectonic processes and the resulting geometries can now be better tied in with the regional heterogeneous framework of the basin. Unfortunately, the entire article was originally published Online First with errors. The publishers wish to apologize for this mistake. The correct article is shown here. The online version of the original article can be found at     

Late Pleistocene and Holocene cool‐water carbonates of the Western Mediterranean Sea

Post‐glacial, neritic cool‐water carbonates of the Western Mediterranean Sea were examined by means of hydroacoustic data, sediment surface sampling and vibrocoring to unravel geometries and to reconstruct sedimentary evolution in response to the last sea‐level rise. The analysed areas, located on the Alboran Ridge, in the Bay of Oran, and at the southern shelf of the island of Mallorca, are microtidal and bathed by oligotrophic to weakly mesotrophic waters. Seasonal water temperature varies between 13 °C and 27 °C. Echosounder profiles show that the Bay of Oran and the southern shelf of Mallorca are distally steepened ramps, while the Alboran Ridge forms a steep‐flanked rugged plateau around the Alboran Island. In the three areas, an up to 10 m thick post‐glacial sediment cover overlies an unconformity. In Oran and Mallorca, stacked lowstand wedges occur in water depths of 120 to 130 m. On the Alboran Ridge and in the Bay of Oran, highstand wedges occur at 35 to 40 m. Up to 5 m long cores of upper Pleistocene to Holocene successions were recovered in water depths between 40 and 81 m. Deposits contain more than 80% carbonate, with mixed carbonate‐volcaniclastics in the lower part of some cores in Alboran. The carbonates consist of up to 53% of aragonite and up to 83% of high magnesium calcite. Radiocarbon dating of bivalve shells, coralline algae and serpulid tubes indicates that deposits are as old as 12 400 cal yr bp . The carbonate factories in the three areas are dominated mostly by red algae, but some intervals in the cores are richer in bivalves. A facies rich in the gastropod Turritella, reflecting elevated surface productivity, is restricted to the Mallorca Shelf. Rhodoliths occur at the sediment surface in most areas at water depths shallower than 70 m; they form a 10 to 20 cm thick veneer overlying rhodolith‐poor bioclastic sediments which, nonetheless, contain abundant red algal debris. This rhodolith layer has been developing for the past 800 to 1000 years. Similar layers at different positions in the cores are interpreted as reflecting in situ growth of rhodoliths at times of reduced net sedimentation. Sedimentary successions in the cores record the post‐glacial sea‐level rise and the degree of sediment exposure to bottom currents. Deepening‐upward trends in the successions are either reflected by shallow to deep facies transitions or by a corresponding change of depth‐indicative red algae. There are only weak downcore variations of carbonate mineralogy, which indicate that no dissolution or high magnesium to low magnesium calcite neomorphism occurs in the shallow subsurface. These new data support the approach of using the Recent facies distribution for interpretation of past cool‐water, low‐energy, microtidal carbonate depositional systems. Hydroacoustic data show that previous Pleistocene transgressive and highstand inner ramp deposits and wedges were removed during sea‐level lowstands and accumulated downslope as stacked lowstand wedges; this suggests that, under conditions of high‐amplitude sea‐level fluctuations, the stratigraphic record of similar cool‐water carbonates may be biased.     

Paleoclimatic evolution of central Sudan during the Late Miocene to Pleistocene

In this paper, information derived from X-ray diffraction and heavy and light fractions analyses were discussed with the aim to trace the paleoclimatic changes of central Sudan during the Late Miocene to Pleistocene. Based on lithological and mineralogical characters noted in the Sayal and Umm Ruwaba Formations, four phases of distinct paleoclimatic changes were recognized. The first phase commenced in the Late Miocene during the deposition of the Sayal formation. The area was slightly uplifted and of gentle slope, a feature deduced from the deposition of clayey and fine-grained sandy materials with subordinate gravely component. A hot and humid climate, depicted from the development of kaolinite and iron oxide, is proposed during the deposition of the Sayal formation. The second phase is characterized by development of depressions in which alluvial streams and possibly small lacustrine basins occurred. This is inferred from the presence of sandy and silty materials, a characteristic of the lower and middle parts of the Umm Ruwaba Formation. The climate remained hot and humid during the deposition of the lower part of the Umm Ruwaba Formation in the early Pliocene. A shift to dry conditions with possible periodic humid seasons is, however, thought to be established during the deposition of the middle part of the Umm Ruwaba Formation deduced from the observed increase in salinity and decrease in iron oxide content. During the third phase, throughout the deposition of the upper part of the Umm Ruwaba Formation, the kinetic energy of streams increased as can be inferred from the presence of gravely intercalations. Deposition under arid climate is suggested for the lowermost part due to the increased amount of feldspars and the absence of iron oxide. However, evidence of cool condition is again noted at the topmost part of the formation inferred from the relatively high content of iron oxide in the deposits.     

Nature,origin and evolution of a Late Pleistocene incised valley‐fill,Sunda Shelf,Southeast Asia

Understanding the stratigraphic fill and reconstructing the palaeo‐hydrology of incised valleys can help to constrain those factors that controlled their origin, evolution and regional significance. This condition is addressed through the analysis of a large (up to 18 km wide by 80 m deep) and exceptionally well‐imaged Late Pleistocene incised valley from the Sunda Shelf (South China Sea) based on shallow three‐dimensional seismic data from a large (11 500 km²), ‘merge’ survey, supplemented with site survey data (boreholes and seismic). This approach has enabled the characterization of the planform geometry, cross‐sectional area and internal stratigraphic architecture, which together allow reconstruction of the palaeo‐hydrology. The valley‐fill displays five notable stratigraphic features: (i) it is considerably larger than other seismically resolvable channel forms and can be traced for at least 180 km along its length; (ii) it is located in the axial part of the Malay Basin; (iii) the youngest part of the valley‐fill is dominated by a large (600 m wide and 23 m deep), high‐sinuosity channel, with well‐developed lateral accretion surfaces; (iv) the immediately adjacent interfluves contain much smaller, dendritic channel systems, which resemble tributaries that drained into the larger incised valley system; and (v) a ca 16 m thick, shell‐bearing, Holocene clay caps the valley‐fill. The dimension, basin location and palaeo‐hydrology of this incised valley leads to the conclusion that it represents the trunk river, which flowed along the length of the Malay Basin; it connected the Gulf of Thailand in the north with the South China Sea in the south‐east. The length of the river system (>1200 km long) enables examination of the upstream to downstream controls on the evolution of the incised valley, including sea‐level, climate and tectonics. The valley size, orientation and palaeo‐hydrology suggest close interaction between the regional tectonic framework, low‐angle shelf physiography and a humid‐tropical climatic setting.     

Late Pleistocene loess‐palaeosol sequences in the Vojvodina region,north Serbia

Late Pleistocene loess‐palaeosol sequences are widespread in the Vojvodina region, with thicknesses reaching a maximum of about 20 m. Our investigations include more than 40 of these loess sections. Geochronology of the last glacial loess‐palaeosol sequences, based on luminescence dating and amino acid racemisation, provides correlations between Upper Pleistocene loess‐palaeosol sediments in Vojvodina and comparable deposits at other European localities. Sedimentary logs of magnetic susceptibility, grain‐size measurements and carbonate content, combined with malacological evidence, indicate two main relatively cold and arid phases during the last glacial period, related to intensive accumulation of loess units L1L1 and L1L2, as well as many brief episodes of dry and windy climatic conditions, suggesting a possible relationship with cold events recorded in the North Atlantic region. Generally, late Pleistocene climate in the region was dry and relatively warm, compared with glacial period sites in central Europe, and was characterised by sharp differences between glacial and interglacial modes. New data and interpretations presented in this study emphasise the significance of loess‐palaeosol sequences in Vojvodina for the reconstruction of the temporal and spatial evolution of late Pleistocene palaeoclimate in this part of Europe. Copyright © 2007 John Wiley & Sons, Ltd.     

Late Pleistocene glaciation of the Kleiner Arbersee area in the Bavarian Forest,south Germany

During Pleistocene mountain glaciation of the Bavarian Forest, south Germany, the Wurmian Kleiner Arbersee glacier left behind glacial landforms and sediments which are described, classified and interpreted using a combination of geomorphological, sedimentological, pedological, surveying and absolute dating methods. The latest Kleiner Arbersee glacier with a maximum length of 2600 m, a minimum width of 800 m and a thickness of 115 m formed an elongated cirque, four lateral moraines, one divided end moraine, one recessional moraine, a proglacial lake and a basin in which lake Kleiner Arbersee was established after deglaciation. Beyond the glacial limit the landscape is denuded by periglacial slope deposits which are differentiated from the glacigenic sediments based upon clast fabrics, clast shapes and sediment consolidation. Within the glacial limit sandy–gravelly to silty–gravelly tills are widely distributed, whereas glaciolacustrine sediments are restricted to a small area north of the lake. Small variations in the sand and silt fraction of the tills are explained by melt-out processes. Quartz, mica and chlorite derived from gneiss bedrock are dominant in the clay mineral spectrum of tills, but also gibbsite as a product of pre-Pleistocene weathering is present giving evidence of glacially entrained saprolites. An IRSL-date of glaciolacustrine sediments (32.4±9.4 ka BP) confirms the Wurmian age for the glaciation and radiocarbon ages of the basal sediments (12.3±0.4 and 12.5±0.2 ka BP uncalibrated) in the lake Kleiner Arbersee prove that the basin was ice-free before the Younger Dryas.     

Late Pleistocene piñon pines in the Chihuahuan Desert

Examination of late Pleistocene packrat middens from the northern and central Chihuahuan Desert disclosed macrofossils of Colorado piñon (Pinus edulis) and Texas piñon (P. remota). Radiocarbon dating indicates that Texas piñon was widespread in Trans-Pecos Texas and northeastern Mexico between 30,000 and 11,000 yr B.P. Today it is found in small refugia east of its former range. In the late Pleistocene Colorado piñon occurred at lower elevations on the northern edge of the Chihuahuan Desert. Both species occurred in the Hueco Mountains, near El Paso, Texas. No clear evidence was found of the presence of Mexican piñon (P. cembroides), though today it is abundant in the Davis and Chisos Mountains. A paleoclimate is postulated that had the following characteristics: increased winter precipitation from Pacific frontal sources, reduced summer temperatures and precipitation, and milder winter temperatures due to a reduced frequency of Arctic airmass incursion. Winter precipitation appears to have decreased from north to south, while winter temperatures, and, possibly, summer precipitation, increased from north to south. During the late Pleistocene, the northern Chihuahuan Desert was dominated by woodlands of piñon pines, junipers, and oaks. The desert-scrub communities that characterize the area today are a Holocene phenomenon.     

Evolution and architecture of a West Mediterranean Upper Pleistocene to Holocene coastal apron‐fan system

The Quaternary deposits of tectonically stable areas are a powerful tool to investigate high‐frequency climate variations (<10 ka) and to distinguish allogenic and autogenic factors controlling deposition. Therefore, an Upper Pleistocene–Holocene coastal apron‐fan system in north–western Sardinia (Porto Palmas, Italy) was studied to investigate the relations between climate changes, sea‐level fluctuations and sediment source‐supply that controlled its development. The sedimentary sequence records the strong influence of local (wet/dry) and worldwide (sea‐level) environmental variations in the sedimentation and preservation of the deposits. A multi‐disciplinary approach allowed subdivision of the succession into four major, unconformity‐bounded stratigraphic units: U1 U2, U3 and U4. Unit U1, tentatively dated to the warm and humid Marine Isotopic Stage (MIS) 5, consists of sandy, gravelly coastal/beach deposits developed during high sea‐level in low‐lying areas. Unit U2 consists of debris‐flow dominated fan‐deposits (ca 74 ka; MIS 4), preserved as partial fills of small valleys and coves. Unit U2 is mainly composed of reddish silty conglomerate to pebbly siltstones sourced from the Palaeozoic metamorphic inland hills (bedrock), superficially disintegrated during the preceding warm, vegetation‐rich MIS 5. The cold and semi‐arid climate strongly reduced vegetation cover along the valley flanks. Therefore, sediment gravity‐flow processes, possibly activated by rainstorms, led to deposition of debris‐flow dominated fans. Unit U3 consists of water‐flow dominated alluvial‐fan deposits (ca 47 to 23 ka; MIS 3), developed on a slightly inclined coastal plain. Unit U3 is composed of sandstone and sandy conglomerate fed from two main sediment sources: metamorphic inland bedrock and Quaternary bioclastic‐rich shelf‐derived sands. During this cold phase, sea‐level dropped sufficiently to expose bioclastic sands accumulated on the shelf. Frequent climate fluctuations favoured inland aeolian transport of sand during dry phases, followed by reworking of the aeolian bodies by flash floods during wet phases. Bedrock‐derived fragments mixed with water‐reworked, wind‐blown sands led to the development of water‐flow dominated fans. The Dansgaard–Oeschger events possibly associated with sand landward deflation and main fan formations are Dansgaard–Oeschger 13 (ca 47 ka), Dansgaard–Oeschger 8 (ca 39 ka) and Dansgaard–Oeschger 2 (ca 23 ka). No record of sedimentation during MIS 2 was observed. Finally, bioclastic‐rich aeolianites (Unit U4, ca 10 to 5 ka; MIS 1), preserved on a coastal slope, were developed during the Holocene transgression (ca 10 to 5 ka; MIS 1). The studied sequence shows strong similarities with those of other Mediterranean sites; it is, however, one of the few where the main MIS 4 and MIS 3 climatic fluctuations are registered in the sedimentary record.     

大凌河河口地区中更新世晚期以来沉积环境演化

大凌河河口地区LZK06孔40m以浅岩心的沉积学、古生物学和年代学等综合研究以及该地区LZK02-04钻孔资料,揭示了研究区中更新世晚期以来经历了两次海侵-海退旋回,依次形成了中更新世晚期湖相/河流相→晚更新世海相-湖相/河流相→全新世海相-河流相地层。全新世早中期由于物源供给很少,研究区处于长达约10ka的饥饿滞留相沉积环境,平均沉积速率仅约0.02～0.05cm/a。全新世晚期约1500a cal BP以来,由于人类活动导致水土流失,河流输砂量增加,研究区开始了快速加积过程,平均沉积速率约0.9～1.2cm/a,下辽河平原被快速充填,开始成陆。与全球海面变化时空分布特征的对比,推断辽东湾的第II海相层发育于MIS 5-MIS 3早期,第I海相层发育于MIS 1阶段高海面时期。晚更新世以来频繁的海面升降是辽东湾泥质海岸带地层和环境演化的主要控制因素。     

西藏阿里孔雀河晚更新世以来的阶地发育特征

一直以来,喜马拉雅山河流阶地发育的控制因素广受讨论。本研究选取了喜马拉雅山北坡的孔雀河作为分析对象,通过详细的野外考察和精确定年,探究了气候变化和构造运动对阶地发育的影响。结果表明孔雀河共发育了5级河流阶地,且均为基座阶地。阶地面砾石的¹⁰Be暴露测年揭示了T5~T1阶地分别形成于88.8±5.8 ka、约18.7~16.8 ka、14.5±1.3 ka、11.9±1.2~11.2±1.1 ka和1.9±0.5 ka;对比青藏高原气候变化资料以及恒河、印度河上游阶地研究成果,表明轨道尺度的气候变化或千年尺度的快速气候变化导致河流堆积下切过程快速转换,形成多级河流阶地。在降水较少的冷期,河道水动力条件减弱,河道堆积;在印度季风增强的暖期,侵蚀能力增强,河道快速下切。研究区晚更新世至末次冰盛期（LGM）期间的河流下切过程稳定,下切速率约为0.5 mm/a;LGM以来,孔雀河下切速率加快,约为1.0~1.8 mm/a。