罗布泊东阿奇克谷地雅丹地貌与库姆塔格沙漠形成的关系

阿奇克谷地位于罗布泊洼地之东, 93°E以西, 东西长约150km, 南北宽20~30km。为新生代北山与阿尔金山之间的地堑凹地的一部分, 与东面河西走廊的地堑凹地相通。根据出露的雅丹地层河湖相沉积样品所作的ESR测年(2272~10094kaBP)和本区的地质地貌特征可将阿奇克谷地演化与库姆塔格沙漠的发育史归纳为4个时期。①早更新世至中更新世罗布泊古湖扩大时期, 东部湖湾宽约50~60km, 向东延伸至93°15′E或更东; ②中更新世晚期山地上升与古湖湾退缩消失时期, 距今30万年前左右, 青藏高原强烈隆升, 阻挡了海洋水汽的进入, 亚洲内陆加速变干, 由于阿尔金山的左旋向东滑动, 在北面古湖区地层发生了与阿尔山斜交的羽毛状断裂谷群, 并因东北向的断裂上升与东西向的河西地堑谷地斜交, 阻断了疏勒河水不再向西流入罗布泊, 使东部湖湾向西退缩并逐步消失; ③中更新世晚期至晚更新世初, 暴雨径流与强烈的风蚀作用时期, 阿奇克谷地北部的洪积湖相沉积台地支沟口形成雅丹土丘群, 谷地南面库姆塔格沙漠北面羽毛状断裂谷群形成雅丹垄脊和风蚀谷, 谷地中央呈现出季节性的盐碱沼泽和零星雅丹土丘; ④晚更新世末至全新世库姆塔格沙漠扩大, 向北埋没了羽毛状断裂谷(风蚀谷)和雅丹垄脊, 形成了世界上独特的羽毛状沙丘。     

罗布泊地区雅丹形态特征及演化过程

雅丹地貌因其多样形态类型长期以来吸引人们的关注,对其形态特征描述也成为研究热点。作为雅丹地貌形态最早命名地,罗布泊地区雅丹因其形态的独特性和复杂性闻名,然而对该地区雅丹形态特征和发育演化过程的深入研究较为缺乏。本文结合野外实测数据和UAV（小型无人机）所摄地景影像,采用地形数字化方法提取地貌原始数据,选定形态参数后识别测量得到雅丹形态参数数据,基于以上数据和前人研究成果尝试描述罗布泊地区雅丹形态特征并对该地区雅丹演化过程进行讨论。主要结论有：① 罗布泊地区雅丹长度集中分布在20 m以下,少有长度> 160 m,宽度集中分布在8 m以下,高度多2 m以下,表明区内雅丹个体规模总体较小,低矮雅丹在数量上占绝对优势;雅丹长宽比值呈现连续增加的变化过程,伴随高度的增加长宽比值迅速增大,由2∶1逐步增大到4∶1,并持续升至10∶1以上,走向分布集中于22.5°~67.5°,与主风向相类似,雅丹个体平面形态呈现连续变化过程;雅丹的相邻雅丹数值集中分布在3~4个,平均顶间距分布在< 20 m和40~80 m区间,显示罗布泊地区雅丹空间特征的多样性。在个体雅丹形态以外,初成雅丹和雅丹共基座现象是罗布泊地区主要存在的2种复杂化雅丹形态表现。② 罗布泊地区雅丹理想演化模式经历初成期、青年期、成熟期和衰亡期4个阶段,由于存在地层岩性、风力剥蚀、流水作用等控制因素影响,造就了类型复杂、变化多样的罗布泊地区雅丹形态现状。③ 罗布泊地区雅丹发育具有多期性,第四纪以来主要存在晚更新世、早全新世、晚全新世和小冰期等4个发育期,结合形态特征和环境演化情况推测龙城和白龙堆雅丹形成于晚更新世,楼兰北部高大雅丹形成于早全新世,楼兰中北部雅丹多数形成于晚全新世,而楼兰地区的低矮雅丹形成于小冰期;依据地层年代和雅丹高度数据,计算得到0.5 ka B.P.后楼兰遗址附近平均风蚀速率为6.2 mm a^-1。精确描述罗布泊地区雅丹形态特征并探讨其演化过程,对于了解雅丹形态控制因素影响程度,深入分析区域风蚀过程具有重要意义。     

黄土丘陵地貌形成模式与地貌演变

通过对陕西北部典型黄土丘陵区地貌调查,提出了黄土丘陵地貌形成模式,并对地貌演变进行了探讨。黄土高原原生黄土丘陵分布广泛,主要在下伏古丘陵基础上由黄土加积而成;次生黄土丘陵是黄土塬、黄土台塬等经沟谷侵蚀、改造而成。黄土丘陵区河流阶地和沟谷层状地貌反映了河流、沟谷的形成与演变。黄河一级支流形成于早更新世末;早中更新世末、晚中更新世初黄河一级支流和较大的二级支流形成了较完整的水系;中更新世末如韭园沟等较大的沟谷形成;晚更新世末河网、沟谷格局与现在已基本一致;尚未切入基岩的冲沟多形成于全新世;长度百米至数十米的切沟多是历史时期或近几十年来形成的。     

晚更新世以来的季风变化对晋陕蒙接壤区现代侵蚀的影响

黄土高原晚更新世末次冰期时期,冬季风强盛,马兰黄土堆积;全新世以来的间冰期时期,夏季风强盛,降水较丰,侵蚀强烈。晚更新世以来的中国东部海岸线40°N 一带变化最大,同纬度晋陕蒙接壤区是黄土高原季风气候变化最剧烈的地区,致使该区成为黄土高原沙黄土区中现代降水最多的地区。沙黄土和较多降水的组合,使晋陕蒙接壤区成为黄土高原现代侵蚀最剧烈的地区。     

柴达木盆地雅丹形态特征及成因

雅丹是沟槽和垄脊相间排列的典型风蚀地貌,雅丹研究是风沙地貌学科的薄弱环节。结合遥感影像和气象数据,对柴达木盆地雅丹地貌的分布、形态特征和发育环境进行了研究。结果表明:柴达木盆地雅丹体形态参数长(l)与宽(w)之间具有良好的正相关关系,即l=3.8685w+7.7109;雅丹地貌的形态受地形、地层性质、气候条件和外力等因素影响;柴达木盆地主风向为WNW和NW,与该区域雅丹的长轴走向吻合,说明研究区雅丹的形成主要靠风蚀作用。     

晚更新世以来黄渤海海侵与黄土高原地貌区域分异

晚更新世以来, 黄渤海盆地沉降速率较大, 发生了三次大规模的海侵, 黄渤海的出现加强了东亚夏季风和黑潮暖流对黄土高原东部地区气候的影响; 东部地区晚更新世温湿期的气候较早中更新世为湿润, 降水特别是汛期降水较多, 侵蚀强烈。和黄渤海三次大规模海侵相对应, 东部地区晚更新世以来有三次强侵蚀期, 中更新世末的统一黄土高原被侵蚀分异为梁峁区和塬区。东部地区的东北部陕北北部、晋西北一带, 由于黄土粒度粗, 抗蚀性差, 侵蚀暴雨多, 侵蚀最为强烈, 形成了现今的梁峁地貌; 南、西、西北部, 由于黄土粒度细, 抗蚀性较好, 或侵蚀暴雨少, 侵蚀相对微弱, 形成现今的塬、残塬地貌。     

中国雅丹地貌申报世界自然遗产的可行性研究

中国干旱区分布的大面积典型雅丹地貌具备申报世界自然遗产的条件,但是中国雅丹地貌的“申遗”工作长期以来被忽视。依据《世界遗产公约操作指南》中的相关标准,分析了中国雅丹地貌的世界自然遗产价值,论证了中国雅丹地貌申报世界自然遗产的条件,讨论了中国雅丹地貌申报世界自然遗产的重要意义,并建议有关部门尽快开展中国雅丹地貌“申遗”工作,使中国雅丹地貌尽早被世界遗产委员会列入《世界遗产名录》。     

柴达木盆地西部湖相地层风力侵蚀对黄土高原物源贡献的研究进展

柴达木盆地是我国西北地区最干旱的盆地之一,常年盛行强劲的西北风,尤其在冬春季更甚。柴达木盆地西部地区自新生代以来沉积了巨厚的河湖相沉积。自上新世晚期以来,随着气候的逐步干化和盆地内部构造变形的加剧,该地区风力侵蚀地貌开始出现。早更新世出现的古盐壳和古雅丹地貌说明当时侵蚀已经相当剧烈。晚更新世以来,气候的极端干旱化和冰期的出现,更加促进了风蚀地貌的发育,在强劲的低空风力的雕刻下,形成了盆地西部几万平方千米的"百万雅丹"地貌,十分壮观。柴达木盆地不同地区地层的厚度和风蚀速率都不同,最大分别可达3 000 m和1.1 mm/yr,如此巨量的物质搬运必然为下风向的地区(都兰、青海湖地区、西宁盆地、黄土高原)的粉尘堆积提供可观的物源物质。研究表明,柴达木盆地西部被侵蚀的古湖相地层是上述地区,尤其是黄土高原重要的物源物质。随着研究的深入,其盆地内侵蚀物质输送到黄土高原的机制,已得到学界越来越清晰的认识。     

新疆罗布泊地区白龙堆雅丹地貌形态特征及成因研究

雅丹地貌是风沙地貌研究的薄弱环节,目前从形态描述到定量研究还未出现较大突破,亟待结合新的技术手段开展创新性研究.新疆罗布泊地区极端干旱,风蚀作用强烈,广泛分布着不同时期发育的雅丹,是研究雅丹地貌形态的理想区域.在Google Earth上沿着新疆罗布泊地区盛行风向测量并分析了白龙堆雅丹4个子区域共1000个雅丹个体的长...     

罗布泊雅丹地貌旅游资源评价与开发研究

本文对罗布泊雅丹地貌旅游进行资源评价与开发研究,分析了罗布泊雅丹地貌旅游资源的特征,并对区内各雅丹地貌景观异同进行了对比,通过SWOT分析定性评价了罗布泊雅丹地貌的旅游开发条件,认为罗布泊雅丹地貌已经具备一定的旅游规模,有很大的开发潜力。从旅游资源价值、旅游区位条件、旅游市场条件3方面定量评价了罗布泊各雅丹地貌分区的旅游资源,认为三垄沙和龙城属于1级景区,宜重点开发;白龙堆和楼兰雅丹属于2级景区,宜特色开发;阿奇克谷地属于3级景区,是辅助资源。运用面状容量法测算了雅丹地貌区的旅游环境容量并分析了罗布泊雅丹旅游生命周期变化过程。最后,提出了罗布泊雅丹地貌旅游开发策略。     

雅丹共基座现象对雅丹形态测量的影响

雅丹形态特征吸引人们的长期关注,对其形态的定量描述至今仍讨论热烈且众说纷纭。通过对罗布泊地区风蚀地貌的野外调查和无人机测量,发现普遍存在雅丹共基座现象。分布在同一个基座体上的风蚀残丘称之为共基座雅丹,属于雅丹与基座体的复合。对共基座雅丹和基座体开展雅丹形态参数的测量及分析,结果表明：共基座雅丹长宽比比值集中分布于3∶1~5∶1区间,与鲸背状等流线型雅丹形态表现相似,显示单一风向侵蚀残留特征;雅丹共基座现象是风蚀切穿深一层抗风蚀相对较强的地层形成的风蚀垄岗现象,厚度不等的不同抗风蚀强度地层在垂向上交替出现和受单一风向的风蚀作用是形成该现象的重要因素;通过对雅丹共基座现象的阐释和定量分析,对完善雅丹形态测量、深化雅丹形态变化的理解以及认识差异性风蚀过程具有重要意义。     

达来诺尔的变迁

达来诺尔是在汗克拉源水头两个新生代断陷盆地、古地貌、新构造运动的影响下,几经变迁发育而成.中更新世中期该湖出现在好鲁厍一带,末期湖面扩大;晚更新世中期湖水占据现代分水岭两侧宽广地带,末期湖水越过分水岭超复全区;全新世地壳上升,湖水退缩在区内景低位置.     

敦煌雅丹地貌区晚更新世以来的区域构造运动特征

河流阶地和活动断层是研究区域构造运动的良好证据。分析了敦煌雅丹地貌区的活动断层和河流阶地的特征与性质,并取样测定活动断层形成时间,进而通过区域对比确定研究区晚更新世以来的构造运动特征和性质。研究区晚更新世以来受区域构造运动影响强烈,特别是阿尔金构造系和北山构造系的次级构造对研究区影响明显。距今约10万年以来,研究区共发生过3次明显的间歇性构造抬升活动：Ⅰ期发生于距今约10万年前,强度最弱;Ⅱ期发生于距今约7万年前,最为强烈;Ⅲ期发生在距今4万年前。     

A Tertiary-Quaternary section at Sarsbukta, Spitsbergen, Svalbard, and its foraminifera

Tertiary and Quaternary deposits outcrop in the coastal cliff of Balanusviken at Sarsbukta in Vest-Spitsbergen. The Tertiary deposits appear by their foraminifera to belong to the Middle to Upper Oligocene. The Quaternary deposits consist of an upper part of Late Pleistocene to Holocene age, and a lower part which had previously been considered Middle Weichselian of age. Its foraminiferal assemblages suggest a higher age (Late Saalian, Eemian?). This lower part of the Quaternary deposits is related to a series of raised beaches with an upper limit at SO m above present day sea level. They were probably formed during the Eemian, and have not been distorted by later glaciation. The present study is based on sediment samples collected from the coastal cliff of Balanusviken, and particularly from that of Balanuspynten, Sarsbukta, Spitsbergen, during the summer expedition of Norsk Polarinstitutt in 19Sø.     

Geomorphology and tectonics of uplifted coasts: New chronostratigraphical constraints for the Quaternary evolution of Tyrrhenian North Calabria (southern Italy)

The Tyrrhenian coastal sector of North Calabria, stretching between Torre S. Nicola and the Lao river, belongs to the inner extensional sector of the Neogene Apennines thrust belt. It is characterised by a stair of Quaternary marine and fluvial terraces representing the geomorphic response to the interaction between the Quaternary sea level fluctuations and the regional trend of tectonic uplift experienced by the margins of the Tyrrhenian back-arc basin. Since the last century, several authors studied the North Calabria coasts, where the flight of terraces preserves significant marine and continental successions, and proposed several paleo-geomorphological and tectonic reconstructions. In this paper we present a new stratigraphic and morphostructural setting of the North Calabria coasts based on both chronostratigraphical constraints obtained from marine deposits and detailed geomorphological analysis. A ten order stair of marine terraces, stepping between 240 and 0 m a.s.l., was recognized and time-constrained by the age of the Fornaci S. Nicola marine succession which was ascribed by integrated paleoecological, biostratigraphical and paleomagentic analyses to the early Middle Pleistocene (MIS 19–15). In particular, the 240, 200 and 160 m a.s.l. high strandlines were ascribed to the Early Pleistocene and the ones between 100 and 15 m a.s.l. to the Middle Pleistocene. The total amount of the vertical motion experienced by the studied area was estimated, and evaluation of the average rates of uplift for the Middle and Late Pleistocene times were also given. Considering the elevation a.s.l. of the oldest terraces, a tectonic uplift of at least 240 m was calculated for the North Calabria coasts since the Early Pleistocene times, 100 m of which gained from the beginning of the Middle Pleistocene. On the other hand, the 8-m high Late Pleistocene strandlines display a negligible vertical displacement affecting the area during the last 130 ka. The entire staircase of terraces preserves a record of slowing down in the rate of uplift, which attained an average value of 0.15 mm/year during the Middle Pleistocene.     

澧阳平原晚更新世晚期至全新世早中期环境演变及其对人类活动的影响

通过对澧阳平原野外调查,多剖面地层对比分析及岩板垱（YBD）剖面样品的粒度、地球化学元素分析和年代测定,揭示该区晚更新世晚期至全新世早中期环境演变,并探讨其对人类活动的影响。研究结果表明,30~6 ka B.P.间,澧阳平原由冲沟发育的黄土台地向河湖发育的平原丘岗地貌过渡;气候环境经历了弱暖湿-气候变差-凉湿-波动回暖-暖湿的变化;更新世末至全新世早期稻作农业的出现与该区的环境条件和文化基础密切相关;环境演变也推动了古人类活动范围和聚落特征的变化。     

粤西河流阶地的分布与特征

依据广东西部超过18条河流、39处河流阶地、至少35个14C、热释光的冲积层测龄数据等情况,可知粤西最多有4级河流阶地(不包括湛江组和北海组阶地);多数河流最高阶地靠近现代主河床分布,深切曲流中有河流阶地,反映近数十万年来河床改道不大;西江在封开有广东高度最高(76 m)的河流阶地,而广东高度最高的地下河阶地是111 m,大致显示出地面与地下剥蚀强度的差异;通常山区河流长度越大,河漫滩和河流阶地的高度越大,河流阶地的级数和级别也常增加;在河流上游的下段和中游的上段,河流阶地的高度最大且级数也最多;在晚更新世之前与后,河谷中下游地区的新构造运动趋势由上升变为稳定或沉降;连滩盆地是广东全新世构造沉降最典型的山间盆地。     

Quaternary soil chronosequences on terraces of the Susquehanna river, Pennsylvania

Susquehanna River terraces are used to establish time lines along a 150 km reach of the river, from the Lower Piedmont to the edge of the Appalachian Plateau. This is achieved by generating soil chronosequences at two locations — Marietta, PA, in the Lower Piedmont, and Muncy, PA, near the glacial border on the boundary between the Valley and Ridge province and the Appalachian Plateau. These sites preserve the most complete record of fluvial incision on the Susquehanna River with flights of seven Quaternary terraces ranging in elevation from 3 m to 51 m above the modern river.Soil characteristics used to develop the soil chronosequences include complexity of horizonization, thickness of B horizon, clay content of B horizon, soil color, CBD extractable Fe, Al, and Mn, total extractable Fe, and clay mineralogy. Terrace age constraints are based on soil development, correlation to regional glacial stratigraphy, correlation to dated fluvial and glaciofluvial deposits, and by paleomagnetic analysis of sediments. Terrace ages at the Muncy site range from modern (< 150 ybp) to Middle Middle through Early Middle Pleistocene (∼ 300 ka to ∼ 770 ka). Marietta has terrace ages ranging from modern (< 150 ybp) to Early Pleistocene through Late Pliocene (∼ 770 ka to ∼ 2400 ka).     

Holocene paleoecology of a wild rice (Zizania sp.) lake in Northwestern Ontario, Canada

Whitefish Lake is a large (11-km-long), shallow, basin in Northwestern Ontario, Canada. The presence of extensive stands of wild rice (Zizania sp.) in combination with high archaeological site density suggests that this lake was ecologically important to regional precontact populations. Collection and analysis of sediment from Whitefish Lake was initiated in 2008 in order to reconstruct changes in lake depth, climate, and vegetation throughout the Holocene. In general, the upper 4.5 m of basinal sediment is composed of ~1.5+ m of varves, which is overlain by a 1.5-m-thick unit with ped-like structures, and ~1.5 m of lacustrine sediment. This sequence documents an early proglacial lake phase, followed by a dry interval before 4,300 (4,900 cal) BP when the lake was significantly shallower, and the establishment of the modern lake during the late Holocene. Plant microfossil (phytolith) evidence indicates that wild rice had colonized the basin ~5,300 (6,100 cal) BP as the lake level rose in response to climate change. Beginning ~4,000 (4,500 cal) BP, changes in elemental data suggest a sharp increase in lake productivity and a switch to anaerobic depositional conditions as the rate of organic sedimentation increased. Recent archaeological research confirms that wild rice was locally processed and consumed during the Middle and Late Woodland periods (~300 BC–AD 1700) although it was evidently growing in the lake well before this time.