乌兰布和沙漠的形成与环境变化

在对乌兰布和沙漠进行野外考察的基础上,通过地貌学、沉积学和年代学的研究,为恢复该地区全新世以来沙漠的形成与演化找到了新的证据。乌兰布和沙漠西南部的吉兰泰盐湖周围及沙漠南部丘间低地湖相地层下部风成砂的系统OSL测年结果表明,乌兰布和沙漠的形成年代约在7 ka BP前后。此外,该沙漠腹地众多的干盐湖,大量含有蓝蚬的湖岸堤,以及丘间低地中的湖相地层和植物根系等的存在,证明了沙漠腹地大古湖的存在。乌兰布和沙漠的形成,可以归因于吉兰泰古湖面积的不断缩小和干涸,湖泊周围松散沉积物的风蚀、搬运及选择性堆积过程。     

吉兰泰盐湖地区沙漠环境变化的遥感研究

吉兰泰盐湖地区沙漠分布广泛。ＴＭ遥感影像显示该地区沙漠的分布主要受两条沙带的控制，一条沙带位于吉兰泰盐湖以西巴音乌拉山的西北部地区，该沙带向西与腾格里沙漠相连，移动速度很快；另一条沙带分布在吉兰泰盐湖的北部和东部，面积很大，沙体连成一片构成乌兰布和沙漠。吉兰泰盐厂于１９８８～１９９７年９年间，相继开展了“湖区补水、治沙一体化工程”等项目，对沙漠的治理工作已取得一定的效果。     

吉兰泰盐湖沙漠化及其治理的遥感监测研究

利用陆地卫星TM标准假彩色合成影像图 ,研究了吉兰泰盐湖地区沙漠的分布、形成和运移规律 ;探讨了进行吉兰泰盐湖治沙、防沙的重点地段。遥感监测了吉兰泰盐场 1988— 1997年 9年间对吉兰泰盐湖治理沙漠的效果     

乌兰布和沙漠东海子湖全新世湖相沉积结构分析及其环境意义

根据乌兰布和沙漠北部东海子湖沉积纪录,对146 cm的连续沉积进行146个样品的沉积结构分析,并运用沉积结构直方图对比、平均粒径值(M_z值)、沉积物标准离差(σ₁值)、风力降尘作用指标(Kd值)等方法对沉积物代表的环境进行分析研究。依据东海子湖沉积剖面的沉积结构特征,可以将乌兰布和沙漠北部地区中全新世以来划分为4个环境变化阶段:①中全新世湖泊(河流湖泊)沉积阶段,沉积纪录年龄为6 550~2 550 aBP,是环境普遍温暖、湿润的阶段。②晚全新世风力作用渐强阶段,沉积纪录年龄为2 550~1 211 aBP,是一个风力作用不断加强的环境变化时期。③晚全新世强风力作用阶段,沉积纪录年龄为1 211~275 aBP,也是乌兰布和沙漠风成沙堆积最旺盛的阶段。④近代强风力作用阶段,沉积纪录年龄为275 aBP以来。这样的环境变化过程表明,乌兰布和沙漠的形成、演化与中国北方环境演变的总体规律是相一致的。     

吉兰泰盐湖的形成及指示的环境意义

选择位于季风边缘区的吉兰泰盐湖为研究对象,利用OSL和14C测年手段重建湖面波动历史,探讨盐湖形成年代与环境变化过程。通过大范围的野外调查发现,在该湖泊南部地区发育高于现代干盐滩9 m的湖滨砂沉积,上覆风成砂沉积,其中湖滨沉积物的OSL年代为6.7 ka BP前后,表明当时该湖泊处于浅水状态,此后湖水经历了快速的下降过程。对于盐湖中心剖面点盐层之下粘土层的14C测年显示,在5 500 aBP以来,集聚大量的石膏、芒硝和石盐等蒸发盐类,该湖泊进入成盐期。通过区域对比发现,吉兰泰湖面快速下降阶段与季风边缘区中全新世干旱事件发生时间相对应。研究认为,吉兰泰盐类矿物的开始沉积,反映了中全新世阿拉善高原区域环境的突然变化,可能指示着5.5 Cal ka BP前后干旱事件的发生。     

沙漠化及其防治

】勺42 .73,TP甲53 2003010158阿拉善东南部自然环境演变与地面流沙路径的分析=Thephysi司envirD~ent evolution and trajectoriesof击ift Sandinsoutheastern川xa of China汪心源,王飞跃…//地理研究一2002,21(4)一479一486 阿拉善东南部包括腾格里和吉兰泰两区.腾格里和吉兰泰两区在晚更新世均是一个湖域广阔的淡水大湖.之后,吉兰泰大湖和腾格里大湖在封闭状态下,一方面因气候转为干早、蒸发致使湖域减小直至完全干涸,露出的湖底在风的吹蚀作用下形成沙漠;另一方面在“狭管效应”作用下,由吉兰泰西部来自雅玛雷克沙漠和在腾格里西部来…     

班戈错盐湖古湖岸堤石英光释光年代学及其古环境指示意义研究

古湖岸堤是湖泊湖面变化的地貌学证据,通过古湖岸堤沉积年代学研究可重建地质时期湖泊演化历史。青藏高原内陆湖泊众多,保存了大量的第四纪时期古湖岸堤,是研究过去湖泊演化和气候变化信息的重要载体。对青藏高原班戈错盐湖北岸和东岸的低位连续古湖岸堤开展了地貌调查和光释光年代学研究。结果表明班戈错自末次冰消期(13. 5±1. 2 ka BP)以来,湖面整体呈波动下降过程,期间出现了4期湖面稳定阶段,分别在末次冰消期(13. 5±1. 2～11. 2±1. 0 ka BP)、全新世早中期(10. 1±0. 8～6. 5±0. 5 ka BP)、全新世后期(4. 2±0. 4～3. 1±0. 2 ka BP)以及全新世晚期(1. 7±0. 1～1. 2±0. 1 ka BP)。全新世晚期约1. 7 ka BP以后湖面迅速退缩,湖泊蒸发浓缩进入盐湖阶段。在末次冰消期班戈错高湖面形成主要与北半球太阳辐射强度增加引起气温升高,导致区域冰雪融水量增加相关,而在全新世湖面变化主要受印度季风强度变化控制。     

塔克拉玛干沙漠的形成时代及发展过程

对塔克拉玛干沙漠腹地的近期研究表明，塔里木盆地虽早在白垩纪晚期已出现明显的干旱环境，但具有现代干旱特征的环境始于第三纪末，形成于第四纪初。盆地内部沙漠环境形成中更新世或其晚期。沙漠在晚更新世晚期和全新世中晚期大模型向西、西南地区和东部发展。     

运城盐湖沉积环境演化

运城盐湖位于山西地堑系运城断陷盆地内的次一级深断陷内。本文通过分析运城盆地新构造运动和运城盐湖区的地层,认为新构造运动对湖盆的形成和湖水、盐份和沉积物的补给起着很重要的作用;盐类矿物的沉积与气候变干有密切的关系;运城盐湖是特殊的构造和气候条件下的产物,是更新世早期古湖的残余。     

近22 ka以来吉兰泰盐湖的环境变化及成盐过程

 根据研究区及毗邻地区第四纪地层沉积特征资料,运用层序地层学的基本方法,对吉兰泰盐湖22 ka BP以来的环境变化和成盐过程进行初步分析。同时,将其划分为6个阶段:冷干期（22.0~14.0 ka BP）,淡水湖演化阶段;冷湿期（14.0~10.0 ka BP）,仙女木期气候颤动期,湖水开始咸水化;暖湿期（10.0~7.0 ka BP）,咸水湖阶段;暖湿转干期（7.0~6.0 ka BP）,咸水湖阶段,亦是湖泊“成盐事件”的预备阶段;冷干期（6.0~4.7 ka BP）,盐湖阶段气候干湿交替,也是盐湖的成盐发展期;凉干期（4.7 ka BP至今）,是盐湖的成盐旺期,盐湖湖水不断缩减,加之周围沙漠的不断吞噬,盐湖开始由干盐湖向沙下湖发展。吉兰泰地区距今22 ka以来的古环境变化及气候转型,不仅是对全球古气候变化的响应,而且对盐湖矿产资源的成盐事件及区域可持续发展具有重要意义。     

Domains of spit evolution in the Goro area, Po Delta, Italy

Goro lagoon was formed during the 19th century in the southern part of the Po Delta. Its origin is related to the growth of a spit system, which progressively occluded the southernmost interdistributary bay from the sea. The development of the spits is due to the morphological prominence of the Po Delta which causes a divergent littoral drift, enhanced by wave refraction over the delta front. During the last century the spit was abandoned, destroyed, and re-constructed several times because of the development of newer spits seawards. Using historical maps and aerial photographs, three different periods are recognised, featuring distinctive spit growth styles: parallel, fan-shaped and branched. The different domains of spit evolution are related to several factors, mainly to the mutual influence of sediment discharge, sand mining along the Po river, wave action over the delta front, human-induced subsidence and direct human interventions along the spits and for flood-control.     

近35 年青藏高原雨量和雨日的变化特征

利用青藏高原1971-2005 年49 个气象台站逐日雨量和雨日资料, 分析了青藏高原年、 季雨量和雨日变化趋势。结果表明, 近35 年西藏大部分地区年雨量、雨日呈现显著增加趋 势, 而青海省大部分地区雨量、雨日却呈减少趋势。夏半年, 高原上雨日减少, 雨量增加, 说明降水越来越集中, 降水强度在增加。冬半年, 高原上雨日、雨量均在增加。高原夏半年小雨(0.1~4.9 mm) 雨日减少, 雨量增加; 小雨(5.0~9.9 mm) 和中雨的雨日和雨量均呈增加趋 势, 大雨以上的雨日和雨量均减少。冬半年, 青藏高原小雪、中雪、大雪不同量级日数和雪 日的平均雪量均呈增加趋势; 暴雪日和雪量变化均不明显。     

雷州半岛灯楼角沙岬的形成

沙岬(沙嘴)是一种海岸动力地貌类型。通过区域地貌背景、海底地貌-浅地层、海洋动力条件、相关的海岸沙坝和现代海滩的分析,认为灯楼角沙岬是来自琼州海峡的东向波浪和来自北部湾的西向波浪两种相向波浪动力平衡、灯楼角东沿岸存在逆时针环流和灯楼角西沿岸存在顺时针环流两者于此辐合,并把带来的砂子沉积下来的结果。     

山东莱州浅滩的沉积动态与地貌演变

在野外观测和历史地貌调查的基础上，利用地理信息系统和遥感技术，研究了现代莱州浅滩的地貌演变规律和人类活动对浅滩地貌冲淤动态的影响。结果表明，受其特有的沉积动力过程控制，莱州浅滩不断淤高并向东北迁移、西北延伸。1958年以来由于修建水库、码头和海底采沙等人类活动导致泥沙亏损，浅滩在继续向东北迁移、西北延伸的同时，总体上处于侵蚀、解体状态，在中部和近岸部分之间、近岸部分和刁龙嘴海岸之间先后形成了贯通的潮流槽，不同地貌部位冲淤状态存在差异。     

Total sediment budget of a transgressive barrier-spit,Skallingen, SW Denmark: A review

Average sea-level rise in the northern part of the Danish Wadden Sea has been 1.3 mm a^?1 during the last 100 years but during the last 25 years a rise of 4.2 mm a^?1 was observed. Concurrent with the recent sea-level rise the Skallingen barrier spit has migrated landward by 3–5 m a^?1. Long term sediment budgets for each of the morphological units involved in the migration are reviewed (e.g. onshore in the shore face +90.000 m³ a^?1, longshore -641.000 m³ a^?1, foredunes +65,000 m³ a^?1, overwash fan including shorenormal dunes +11,000 m³ a^?1, spit terminus -96,000 m³ a^?1, tidal flat + 10,000 m³ a^?1 and backbarrier salt marsh +33,000 m³ a^?1) and used to establish the relative importance of sediment transport processes involved in barrier migration. Strong interannual variations exist in the long term budget making evaluation of barrier behaviour based on short term measurements doubtful. In a cross shore sense the barrier spit is accreting in spite of the sea level rise. This is specially pronounced at an active overwash fan. However, due to substantial sediment losses to longshore transport the barrier, gets narrower and shorter during its transgressive behaviour. This may indicate that preservation of barriers in the geological record during rapid sea level rise is promoted when sediment loss to longshore transport is insignificant.     

小浪底工程修建对黄河河口淤积影响

本文在整理、分析黄河小浪底工程建成后 ,坝下游来水来沙条件变化的基础上 ,利用若干经验关系式 ,就小浪底工程修建后对黄河河口区清水沟流路的淤积特征和变化趋势进行了研究 ,得到了 :在小浪底水库初期蓄水拦沙运用阶段 ,淤积减少、河口砂嘴发展速度变缓 ;在后期正常调水调沙运用阶段 ,淤积又有所恢复 ,河口砂嘴发展加快的认识。     

An evolutionary model for sabkha development on the north coast of the UAE

The north coast of the United Arab Emirates (UAE) provides a typical example of coastal sabkha (supratidal flat) formation. Various stages of sabkha development can be recognized along this coast. This paper combines previous studies of sabkha environment with the results of field investigation of sabkha geomorphology, sedimentology, and stratigraphy on the north coast of UAE, to formulate a model of sabkha evolution.The model has six stages in the evolution of coastal sabkhas following the early Holocene sea-level rise. These are: Stage 1: sea-level rise results in the formation of an embayment. Stage 2: involves subsequent spit development and progradation across the bay as a result of sediment availability. Stage 3: coincident with spit evolution is the development of a khor (tidal inlet) with or without mangrove. Channel depth of Khors varies from 4 to 6 m. Stage 4: sediment accumulates in the khor reducing the khor depth, turning it into a lagoon. There are three sub-stages of the lagoon stage. (a) With lagoon depths of 1–2 m, (b) with lagoon depths 0.5 m or less, (c) when the lagoon floor is exposed at low tide. Stage 5: is sabkha formation; development occurs in two sub-stages. In the first the sabkha is immature and flooded during rain storms and spring tides (0.1 m above present sea-level). Later the sabkha is only flooded after rainstorms, when it reaches an elevation of about 1 m or more above present sea-level. Stage 6: in sabkha development is the coastal plain, which results when large sabkhas are linked together.     

Sequence morphodynamics at an emergent barrier island, middle Atlantic coast of North America

The southern Delmarva Peninsula is located along the middle Atlantic Coastal Plain of the United States. The axial highland of the peninsula formed in four stages of Pleistocene spit progradation. The landward shoreline of the peninsula is on the Chesapeake Bay. The seaside shoreline of the peninsula is on the Atlantic Ocean. The coast of the peninsula is composed of five landscape sections described as a headland, a left-hand spit, a right-hand spit, a wave-dominated barrier island, and tide-dominated barrier islands.Fisherman Island is a barrier island located at the southern end of the southern Delmarva Peninsula. The landscape features on Fisherman Island do not illustrate a direct linkage to (1) the sediment dispersion from the Delaware headland or (2) the influence of local antecedent topography. The island has a bipolar progradational history that is normal to the axis of the southerly sediment dispersion pattern from the Delmarva headlands.During the late Holocene, sea-level rise flooded the low-elevation land at the distal end of the southern Delmarva Peninsula. The submerged area formed a shallow platform in the entrance to the Chesapeake Bay. Two sediment dispersion tracts affected the development of this area. On the ocean side of the peninsula, sediment moved southward along the lower shoreface to the Chesapeake Bay entrance. On the west side of the peninsula, southerly moving bay currents also dispersed sediment to the entrance of the bay. The two tracts converged on the northern side of the bay entrance forming a broad sand shoal. Wave diffraction and refraction around the margins of the shoal “swept” sediment into linear sand bars that migrated back toward the peninsula.By the middle of the 19th century, the fusion of sand bars on the shoal surface produced a permanent nucleus for island development. Wave refraction caused wave crests to “wrap around” the island core producing separate easterly and westerly components of shore aggradation. The westerly aggradational history is recorded in closely spaced sets of beach ridges. The easterly aggradational history is recorded in broadly spaced hammocks.     

Protecting an eroding shoreline: the evolution of management response

Sandy Hook. New Jersey, was used by the US Army until 1970 for coastal defence installations at the entrance to New York harbour and as an ordnance proving ground. Since 1970, Sandy Hook has been managed by the US National Park Service as a part of Gateway National Recreation Area. An important problem which managers of both institutions have had to face is the instability of the narrow neck of the spit. The high rates of erosion which have predominated at the neck have jeopardized the overland access route to the facilities at the northern end of the spit, and both Army and Park Service managers have taken steps to alleviate the problem. A breach in the neck in 1896 led the Army engineers to construct a seawall to close the breach and to protect the access road. Over the next 30 years, several projects were undertaken to extend the length of the seawall and to reinforce the structure. The Park Service managers are currently facing the same problem, although the focus of erosion has been transferred northward. The National Park Service has chosen a more dynamic solution to the problem in accordance with their objectives for this eroding area. This study demonstrates that the protection approaches selected for use by the managers of both institutions were a function of differing objectives. In addition, the study provides an example of how management decisions made in the past influence present management actions.     

黄河口海岸线演变时空特征及其与黄河来水来沙关系

黄河是世界上含沙量最高的河流 ,每年向河口三角洲及附近海域输送数亿吨泥沙 ,使得黄河口地区成为世界上海岸线变迁最快的地区。本文以 1976年黄河改道清水沟流路以来 2 0景多时相遥感影像为主要数据源 ,经过几何精校正与配准 ,形成相对完整时间序列的遥感影像集。在此基础上 ,对影像进行监督分类处理后自动提取海岸线 ,通过GIS叠加分析 ,剖析了现行黄河河口地区海岸线演变的时空动态特征。最后 ,结合利津水文站水文统计资料 ,探讨了黄河口海岸线演变与黄河来水来沙条件之间的关系 ,并就黄河口未来水沙条件初步预测了其演变趋势