Drowned shelf-edge deltas, barrier islands and related features along the outer continental shelf north of the head of De Soto Canyon, NE Gulf of Mexico     

J.V. Gardner  B.R. Calder  J.E. Hughes Clarke  L.A. Mayer  G. Elston  Y. Rzhanov   《Geomorphology》2007,89(3-4):370-390

Four drowned shelf-edge delta complexes, two drowned shelf deltas, three drowned barrier islands, large areas of “hardground”, and fields of bedforms on the mid and outer continental shelf and uppermost slope north of the head of De Soto Canyon, NE Gulf of Mexico were mapped with high-resolution multibeam echosounder. Deltas formed not during the last eustatic low stand, but during one or more interstadials when eustatic sea levels were only 60 to 80 m below present sea level. The barrier islands and deltas must have been cemented prior to rapid falls of eustatic sea level that occurred during global glaciations. Cementation is necessary to have preserved the barrier islands from erosion and subsequent destruction by the rapid sea-level rise during the last deglaciation. The preservation of the relict bathymetry is so good that features that superficially resemble trough blowouts are found in association with one of the relict barrier islands. Asymmetric bedforms on the midshelf in water depths of 50 to 60 m indicate transport directions to the SW but asymmetric bedforms in water depths of the upper slope between 100 and 120 m on the S and SE flanks of the drowned shelf-edge deltas indicate a different current direction, a separate flow that is a continuation of a SW-flowing current that was previously found on the upper slope off NW Florida.  相似文献   

某露天铁矿冰碛土台阶边坡可靠性分析   总被引：1，自引：0，他引：1  

徐鼎平 《岩土工程技术》2007,21(1):11-14

以某露天矿边坡台阶为研究对象,提出一种新的可靠度求取方法———简化统计矩法。采用该法对原设计的台阶边坡和本研究所推荐的台阶边坡进行了可靠性分析。分析结果表明,台阶边坡破坏概率较高,主要是由冰碛土强度的固有不确定性、抗风化能力以及水理性质决定的,而边坡结构因素对其影响不显著。建议采取平台宽度3 m、3 m和16 m的三台阶组方案,同时采用截洪和护坡等有效措施来提高台阶边坡的稳定。  相似文献   

来自东南极西福尔丘陵附近冰碛物中沉积岩砾石的碎屑锆石LA-ICP-MS U-Pb年龄及其意义     

刘健 《地质学报》2011,85(10):1585-1612

东南极西福尔丘陵东南侧分布着长约20 km带状冰碛物,这些冰碛物成分复杂,其中含有少量与该地区高级片麻岩的基岩显著不同的沉积岩砾石.根据冰川流动方向可以推测它们来自西福尔丘陵的东南侧的冰盖之下.对其中8个具有代表性的沉积岩砾石样品进行碎屑锆石LA-ICP-MS U-Pb年龄测试,其U-Pb表面年龄主要集中在2410～2...  相似文献   

南渡河放流罗氏沼虾的增殖试验     

钟进  梁立清 《广东海洋大学学报》1994,(1)

１９９０年７月至１９９２年７月，连续三年投罗氏沼虾苗７０万尾放入南渡增殖，回捕率达２４．０５％，最大个体５８８ｇ，抱卵雌虾占捕获量１０％；每年可捕到一定数量体长７～１１ｃｍ、体重１０～３５ｇ的罗氏沼虾。  相似文献   

Glaciotectonics of the ltterbeck - Uelsen push moraines,Germany     

Sjoerd J. Kluiving 《第四纪科学杂志》1994,9(3):235-244

The two Saalian push moraines of ltterbeck - Uelsen, formed during the Older Saalian glaciation, consist of Tertiary and Quaternary deposits. Locally, glaciofluvial deposits are prominent as a result of reworking of older deposits by meltwater. The push moraines are built up from a number of imbricated and folded structural units, which have moved laterally and, in part, frontally from two glacial basins. Dominant structures are large, shallow and flat-lying glaciotectonic nappes that have been displaced over distances of at lest 1 km in the direction of tectonic transport. Overprinting relations of two deformation phases give a relative age difference between the two push morianes.  相似文献   

地质内、外力作用形成的堰塞湖     

季泰 《城市地质》2008,3(3):49-50

该文简要介绍了地震堰塞湖、火山堰塞湖、冰碛堰塞湖的形成原因及特点。  相似文献   

辽西阜新夏家沟地区新元古界殷屯组发现的意义     

卢崇海  刘振伟  曹煜昊  李彪  徐耸  关树野  陈历佳  卢思桥 《地质与资源》2021,30(5):521

在对辽西夏家沟地区出露的中元古界长城系、蓟县系岩石地层单位进行考察时,在中元古界长城系串岭沟组之上,发现了新元古界北方南华系下统殷屯组冰碛杂砾岩地体,该地体与中元古界长城系串岭沟组呈角度不整合接触.该项发现填补了辽西地区新元古代时期陆相岩石地层单位沉积的一项空白,对于讨论辽西地区新元古代地壳的演化历史增添了新的内容,具有重要的地质意义.  相似文献   

The Geomorphology of Valley-Floor Troughs Illustrated From Depositional Sequences in the Durance Valley,Southeast France     

《自然地理学》2013,34(6):475-493

Three kinds of valley-floor troughs occur in the Durance catchment of southeast France. Details of widths and spatial variations of 10 different sedimentary forms are presented to show how these relate to the present types of troughs and their margins. Internal controls, such as geology, altitude, and available relief, provide a wide variety of conditions, which have been modified through time by external controls such as past and present climates and their hydrological regimes, as well as by anthropogenic activity over several millennia. The 10 sedimentary forms occupy more than 900 km² or 6.4% of the total catchment area, with the present enlarged floodplain having just over 50% of this area. The present channel occupies less than 10%, which is less than the Würm terrace (17.2%) but somewhat more than the marginal colluvia in the lower valley (8.6%). The other forms include older Pleistocene terraces, moraines from the last three glacial stages, and alluvial fans. It is the type of trough and its relative age that condition what, where, and how much of past and present sedimentary forms can survive.  相似文献   

The morphological characteristics of glacial deposits during the Last Glaciation, taking the Parlung Zangbo River Basin as an example   总被引：1，自引：0，他引：1  

RenRong Chen  ShangZhe Zhou  YingBin Deng 《寒旱区科学》2013,5(6):0698-0708

Moraine morphology is a valuable indicator of climate change. The glacial deposits of ten valleys were selected in the Parlung Zangbo River Basin, southeastern Tibetan Plateau, to study the glacial characteristics of the Last Glaciation and the climate change processes as revealed by these moraines. Investigation revealed that a huge moraine ridge was formed by ancient glacier in the Marine Isotope Stage 2 （MIS2）, and this main moraine ridge indicates the longest sustained and stable climate. There are at least two smaller moraine ridges that are external extensions of or located at the bottom of the main moraine ridge, indicating that the climate of the glacial stage before MIS2 was severer but the duration was relatively shorter. This distribution may reflect the climate of MIS4 or MIS3b. The glacial valleys show multi-channel, small-scale moraine ridges between the contemporary glacial tongue and the main moraine ridge. Some of these multi-channel mo- raine ridges might be recessional moraine, indicating the significant glacial advance during the Younger Dryas or the Heinrich event. The moraine ridges of the Neoglaciation and the Little Ice Age are near the ends of the contemporary glaciers. Using high-precision system dating, we can fairly well reconstruct the pattern of climate change by studying the shape, extent, and scale characteristics of glacial deposits in southeastern Tibet. This is valuable research to understand the relationship between regional and global climate change.  相似文献   

江西德安县地方性氟中毒区生态地球化学研究     

谢振东  钟达洪  衷存堤  张旭 《火山地质与矿产》2012,(1):56-61

江西德安吴山地区地方性氟中毒区域存在高氟的地球化学异常。富氟的岩（矿）石为其原生源,受表生地质作用和人为活动的影响,在土壤、水和生物体中形成了富氟的生态地球化学环境系统。研究发现,该地区氟进入人体主要通过5个途径,其中食物是进人人体最主要途径,食物中的氟元素超标情况严重,其次是通过饮用水进入人体,并根据这些规律提出德安地方性氟中毒病几点防治建议。  相似文献