A chronology for North Sea Lobe advance and recession on the Lincolnshire and Norfolk coasts during MIS 2 and 6     

《Proceedings of the Geologists' Association. Geologists' Association》2019,130(5):523-540

During the last (MIS 2) and older glaciations of the North Sea, a North Sea Lobe (NSL) of the British-Irish Ice Sheet flowed onshore and terminated on the lowlands of eastern England, constructing inset sequences of either substantial ice-marginal deposits and tills or only a thin till veneer, indicative of complex and highly dynamic glaciological behaviour. The glaciation limit represented by the Marsh Tills and the Stickney and Horkstow Moraines in Lincolnshire is regarded as the maximum margin of the NSL during MIS 2 and was attained at ∼19.5 ka as determined by OSL dating of overridden lake sediments at Welton le Wold. A later ice marginal position is recorded by the Hogsthorpe-Killingholme Moraine belt, within which ice-walled lake plains indicate large scale ice stagnation rapidly followed ice advance at ∼18.4 ka based on dates from supraglacial lake deposits. The NSL advanced onshore in North Norfolk slightly earlier constructing a moraine ridge at Garrett Hill at ∼21.5ka. In addition to the large ice-dammed lakes in the Humber and Wash lowlands, we propose that an extensive Glacial Lake Lymn was dammed in the southern Lincolnshire Wolds by the NSL ice margin at the Stickney Moraine. Previous proposals that older glacier limits might be recorded in the region, lying between MIS 2 and MIS 12 deposits, are verified by our OSL dates on the Stiffkey moraine, which lies immediately outside the Garrett Hill moraine and appears to be of MIS 6 age.  相似文献   

2001年雅江6.0级地震序列震源机制解与应力场分析   总被引：2，自引：0，他引：2  

朱航  陈天长  刘杰  范军 《地震地磁观测与研究》2004,25(4):48-55

叙述了利用P波初动和短周期体波振幅联合测定震源机制解和利用震源机制解求取区域主应力张量的方法,采用成都遥测数字地震台网在2001年2月雅江Ms 5.0、Ms 6.0地震前后的3.0级以上的26个地震,共14个台站的垂直分向速度波形记录进行计算。使用主事件定位法,确定了这些地震较准确的震中位置,并在此后的计算中采用该数据。震源机制解结果表明:5.0和6.0级地震与另外3次地震为走滑型,呈北东向分布;而外围的其他21次地震全部是倾滑型。分析认为,雅江震区位于鲜水河断裂带南端西侧的以贡嘎山为中心的地壳隆起区内,地壳的抬升运动导致震源体的形成,两种破裂方式与之有关。前震与余震时段的最大主压应力σ1轴的方向大致相同,5.0和6.0级地震期间,σ1轴的方向偏转了约100°。  相似文献   

Wood-mediated geomorphic effects of a jökulhlaup in the Wind River Mountains, Wyoming     

Elizabeth B. Oswald  Ellen Wohl   《Geomorphology》2008,100(3-4):549-562

A jökulhlaup burst from the head of Grasshopper Glacier in Wyoming's Wind River Mountains during early September 2003. Five reaches with distinct sedimentation patterns were delineated along the Dinwoody Creek drainage. This paper focuses on a portion of the jökulhlaup route where erosion of the forested banks created 16 large logjams spaced at longitudinal intervals of tens to hundreds of meters. Aggradation within the main channel upstream from each logjam created local sediment wedges, and the jams facilitated overbank deposition during the jökulhlaup. Field surveys during 2004 and 2006 documented logjam characteristics and associated erosional and depositional features, as well as initial modification of the logjams and flood deposits within the normal seasonal high-flow channel. Overbank deposits have not been altered by flows occurring since 2003. Field measurements supported three hypotheses that (i) logjams present along the forested portions of the jökulhlaup route are larger and more closely spaced than those along adjacent, otherwise comparable stream channels that have not recently experienced a jökulhlaup; (ii) logjams are not randomly located along the jökulhlaup route, but instead reflect specific conditions of channel and valley geometry and flood hydraulics; and (iii) the presence of logjams facilitated significant erosional and depositional effects. This paper documents a sequence of events in which outburst floodwaters enhance bank erosion and recruitment of wood into the channel, and thus the formation of large logjams. These logjams sufficiently deflect flow to create substantial overbank deposition in areas of the valley bottom not commonly accessed by normal snowmelt peak discharges, and through this process promote valley-bottom aggradation and sediment storage. Changes in the occurrence of glacier outburst floods thus have the potential to alter the rate and magnitude of valley-bottom dynamics in these environments, which is particularly relevant given predictions of worldwide global warming and glacial retreat. Processes observed at this field site likely occur in other forested catchments with headwater glaciers.  相似文献   

喀斯特高原山区IRS-P6影像最佳融合方法选择研究——以贵州平塘县四寨镇为例     

刘梦琦  周忠发  李波 《中国岩溶》2009,28(4):419-425

贵州处于中国西南喀斯特的腹心地带,属岩溶高原山区,生态环境背景复杂,地表切割剧烈,海拔落差大,坡度较陡,同时地处季风气候区还伴有常年多云多雨现象,因此卫星遥感数据质量常受到严重影响。文章以贵州南部平塘县四寨镇为例,主要针对IRS-P6卫星遥感影像的多光谱4,3,2波段与其全色PAN波段之间的融合,运用比值变换、主成分分析法（PCA）、乘法变换和IHS变换四种常见融合方法进行对比分析,并对融合后的影像进行主观定性评价和客观定量评价。研究表明IHS融合法效果相对最好,在保持原多光谱影像光谱信息的同时,大大提高了影像的空间分辨率,改善了图像的目视效果,清晰度和纹理细节表现力也得到了较大的提高,是一种适宜于亚热带喀斯特高原地区的融合方法,对解决喀斯特高原山区受雨云天气条件限制难以获取高质量影像的问题有重要意义。   相似文献   

Mechanisms controlling the air–sea flux in the North Sea     

A.E.F. Prowe  Helmuth Thomas  Johannes Ptsch  Wilfried Kühn  Yann Bozec  Laure-Sophie Schiettecatte  Alberto V. Borges  Hein J.W. de Baar 《Continental Shelf Research》2009,29(15):1801-1808

The mechanisms driving the air–sea exchange of carbon dioxide (CO₂) in the North Sea are investigated using the three-dimensional coupled physical–biogeochemical model ECOHAM (ECOlogical-model, HAMburg). We validate our simulations using field data for the years 2001–2002 and identify the controls of the air–sea CO₂ flux for two locations representative for the North Sea's biogeochemical provinces. In the seasonally stratified northern region, net CO₂ uptake is high () due to high net community production (NCP) in the surface water. Overflow production releasing semi-labile dissolved organic carbon needs to be considered for a realistic simulation of the low dissolved inorganic carbon (DIC) concentrations observed during summer. This biologically driven carbon drawdown outcompetes the temperature-driven rise in CO₂ partial pressure (pCO₂) during the productive season. In contrast, the permanently mixed southern region is a weak net CO₂ source (). NCP is generally low except for the spring bloom because remineralization parallels primary production. Here, the pCO₂ appears to be controlled by temperature.  相似文献   

顺义、应县、凉城、浑源震群与张北6.2级地震关系研究   总被引：1，自引：1，他引：0  

张晁军  赵蒙生  王彬  秦莉 《地震研究》2000,23(1):76-82

在晋、冀、蒙三省交界地区,１９９６年１２月出现了顺义震群、１９９７年１１月出现了应县、凉城震群、１９９７年１２月出现了浑源震群;这种现象可能预示着张北地震的到来,另外,这几次震群除应县震群体,ｂ值均较低,可能是张北６．２级地震在孕育过程中应力集中的反映。再,在三省交界区,１９９７年ＭＬ３．０以上地震活动水平较１９９６年明显增强,ｂ值出现了明显下降,可能是张北６．２级地震应力集中造成微破裂加剧的结  相似文献   

Displacive phase transitions in C-centred clinopyroxenes: spodumene, LiScSi2O6 and ZnSiO3     

T. Arlt  R. J. Angel 《Physics and Chemistry of Minerals》2000,27(10):719-731

The clinopyroxenes spodumene (LiAlSi₂O₆), LiScSi₂O₆ and ZnSiO₃, all with space group C2/c at ambient conditions, were studied under high pressures by single-crystal X-ray diffraction in a diamond-anvil cell. Changes in the evolution of the unit-cell parameters, optical properties and the appearance of h + k odd reflections characteristic of a primitive lattice, indicate that all three pyroxenes undergo phase transitions. The transitions are mostly displacive in character, and are non-quenchable. Transition pressures are 3.19 GPa in spodumene, ∼0.6 GPa in LiScSi₂O₆ and 1.92 GPa in ZnSiO₃. The space group of all three high-pressure phases was determined to be P2₁/c by structure refinement to single-crystal X-ray intensity data collected in the DAC. In the ZnSiO₃ clinopyroxene the intermediate P2₁/c phase further transforms to a second C2/c phase (HP-C2/c) at 4.9 GPa (confirmed by structure refinement). The volume change at this transition is about 2.6%, three times larger than in the first phase transition, and typical of the P2₁/c→ HP-C2/c phase transitions found previously in MgSiO₃, FeSiO₃, etc. These results therefore provide the first direct evidence that the HP-C2/c and the HT-C2/c structures of pyroxenes are distinct polymorphs with the same space group. The phase transition from C2/c to P2₁/c symmetry in spodumene and LiScSi₂O₆ therefore occurs because the polymorphs stable at ambient conditions are isotypic to the high-temperature C2/c phases of clinopyroxenes such as pigeonite and clinoenstatite. Received: 22 December 1999 / Accepted: 7 June 2000  相似文献   

利用Access97和VB6的ADO开发工程勘察数据库   总被引：3，自引：0，他引：3  

朱绍卿 《岩土工程技术》2000,(3):125-129

根据开发工程勘察数据库的经历,介绍了利用YB6的ADO和Access97开发工程勘察数据库的步骤、方法和技巧,以及开发过程中可能遇到的问题和解决办法。  相似文献   

浅水不规则波浪中油轮运动研究   总被引：8，自引：2，他引：6  

杨建民  肖龙飞 《海洋工程》2000,18(3):25-29

本文对一般油轮在浅水不规则波浪中六自由度运动进行了试验分析,并对其碰底情况做了研究。试验时对有流情况下不同波高、不同装载的条件进行了分析比较。模型的六自由度运动是用非接触式六自由度运动测量与分析方法求得。该方法应用位置测量仪（ＰＳＤ）对安置在模型上的红外线发光源（ＬＥＤ）进行测量,然后所编制的软件计算出模型的六个自由度运动情况。  相似文献   

融合蛋白IL6-OmpW的质粒构建及表达纯化     

黄浦江  黄郁葱  简纪常  吴灶和  鲁义善  黄瑜  樊云霞 《广东海洋大学学报》2013,(4)

以重组质粒pMD18-T/IL6和pMD18-T/OmpW为模板,分别扩增红笛鲷IL-6基因和哈维氏弧菌外膜蛋白OmpW基因,运用PCR重叠延伸剪切技术,将IL-6和OmpW基因融合,将融合基因定向克隆到原核表达载体pET-32a(+),转化大肠杆菌BL21(DE3)感受态,经异丙基-β-D-硫代半乳糖苷(IPTG)诱导融合蛋白高效表达,融合蛋白分子质量约为66.6 ku。优化后表达条件为温度37℃,IPTG浓度0.2 mmol·L-1,诱导时间5 h。用HisTrap HP亲和柱纯化重组蛋白,最佳咪唑洗脱浓度为400 mmol·L-1,纯化蛋白的质量浓度为480μg·mL-1。Western-blot分析显示,该融合蛋白可与鼠抗His-tag单克隆抗体发生特异反应,表明目的蛋白得以正确表达。  相似文献