基于DEM的湘桂交界处夷平面的地貌特征研究

湘桂交界处南岭西段山地上广泛发育了夷平面,而对其地貌特征进行定量分析有助于加深对该区地貌演化的认识.本文基于30 m的DEM数据,在ArcGIS 10.3中,通过均值变点法和最小误差分析法分别限定夷平面的高程和坡度,并结合面积指标,提取了该区的夷平面.结果显示,该区夷平面的坡度介于0～13°,海拔介于1 416～1 780 m,且主要分布在南山、鸡公山和越城岭上,面积分别为165.41、154.41和83.75 km²;夷平面主要切割印支期、加里东期和燕山期花岗岩;结合坡向分析显示,3座山脉的夷平面分布高程大体一致,且接近水平,这表明这些夷平面为一个区域性夷平面的残余面,且该区地形曾经历了漫长的侵蚀夷平阶段,其后期构造抬升以水平抬升为主;夷平面的广泛存在表明该区地形演化还处于地貌侵蚀循环的青壮年期,也是南山牧场形成的地质背景.     

对嵩山夷平面的再认识

夷平面是当代地貌学研究的一个重要课题之一,对于重建一个地区的地貌演化历史具有重要的意义．本文在形态分析、构造分析和相关沉积分析的基础上,确定了嵩山山顶古平坦面是早第三纪晚期形成的夷平面,它可与华北以及全球陆地同期的地形面进行对比。     

金沙江攀枝花至凹嘎段水系河道纵剖面形态特征及其对河谷发育的指示

基于数字高程模型,利用ArcGIS和MATLAB中的河流纵剖面工具对金沙江攀枝花-凹嘎段水系的河道纵剖面进行了分析,结果显示,该区大多数支流的河道纵剖面呈上凸型,发育一个或多个裂点,将河道分割成若干河段.其中,大部分裂点聚集分布在海拔2 000～2 300, 1 600～1 800和1 400～1 500 m,可以与该区广泛发育的三级夷平面相对应,共同指示了该区地势上的不整合.根据对裂点之上古河道纵剖面的重建,获得了河谷累积的下切量,结合区域侵蚀速率研究,推算这3次强烈的构造事件分别发生在3.47、2.19和1.45 Ma,说明目前的金沙江河谷是从晚上新世以来河流自夷平面上下切而形成的新蚀河谷.     

川西北若尔盖高原第四纪环境演变概要

若尔盖高原夷平面的塑造过程经历了 个相当长的时期 研究表明:1 新第三纪是主要塑造期 第四纪是高原边缘夷平面的破坏解体期 又是高原腹地继续夷平 熟的时期 高原腹地夷平面的构造解体为侵蚀—堆积所补偿2 第四纪高原湖泊历经兴衰.目前则处于衰亡时期3 气侯经过四次旋回波动 目前气温可能处于颤动下隆的晚期阶段.4 生态环境从多方面显示了它脆弱性     

纪念台维斯侵蚀循环,准平原学说诞生一百周年

台维斯的侵蚀循准平原的理论是１００年来影响地貌学最深刻的一种学说。中国地地文期研究直接来源于台维斯的理论,虽然至今有全新面貌,仍然有许多工作要做,特别是夷平面研究对青藏高原隆升等有重大的理论和实际意义,本文以华北唐县期夷平面为例说明夷平面不同构造单元表现不同,同一夷平面是多成因的,原始高度是彼此接近的。可以用来研究新构造运动的幅度与类型。夷平面研究中核心问题之一是形成年代的确定。     

云台山世界地质公园及周边地区夷平面的形成时代

夷平面是控制"云台地貌"形成与演化的主导因素之一。云台山及周边地区数字高程模型(DEM图)显示区域上有三期比较明显的夷平面分布,通过区内地形、地貌、地质剖面、出露高程、区域分布、地貌组合特征等综合研究,开展了野外调查、测年样品采集、样品数据分析等工作,结合前人研究成果,对各期夷平面进行了详细研究,确立了各期夷平面的形成时代,为云台山世界地质公园科普旅游提供了科学依据。     

论夷平面的成因、年龄与变形

本文探讨了夷平面的若干理论问题,并且阐述了研究夷平面的意义。作者认为夷平面的生成是由于陆块在构造相对宁静时期、在有利的气候条件下(炎热的或温暖的并且是干湿更替的),由于剥蚀作用和夷平作用长期削切地质构造面的结果。作者分析了夷平面生成的外力作用,认为主要是大陆剥蚀,尤以其中的流水作用为主导营力。此外还比较了海蚀夷平面、“准平原”、山足剥蚀平原在成因上的差异。文章讨论了夷平面的年龄及其确定方法,认为夷平面是否具有众多性问题只有对具体地区进行具体分析后才能下结论。作者提出可以应用邻接地层法与相关沉积法来确定夷平面的年龄。本文划分最常见的夷平面变形为四类:断裂、拗曲、拗曲与断裂伴生、掀斜与断裂伴生;对于每一种变形类型并且用若干中国区域夷平面资料作为例子加以说明。     

黄河中游的地貌与地文期问题

上起积石峡下至三门峡的黄河中游地区在晚新生代期间发育了一级夷平面、一级剥蚀面和七级河流阶地。夷平面形成于２．４Ｍａ以前的晚第三纪，剥蚀面形成于２．４～１．８Ｍａ Ｂ．Ｐ的第四纪初期；黄河的七级阶地分别是开始于１３００、１１００、７８０、５９０、１４０、５０、１０ｋａ Ｂ．Ｐ的河流下切形成的，其原因在于构造的脉动式上升。基于上述研究成果，我们将每一地貌面形成的时期定义为一个地文期，它与其后因构造运动     

1761—1780年极端气候事件影响下的天山北麓移民活动研究

以1761—1780年新疆天山北麓的移民活动为研究对象,讨论移民政策、移民高潮与移民迁出地极端气候事件之间的关系。结果显示:1761—1780年间有3次移民高潮,分别发生在1764—1766年、1772—1773年和1777—1780年。1761—1780年,天山北麓的移民政策没有发生大的改变,但1763—1765年、1771年、1775—1778年移民迁出地——河西走廊发生了3次极端干旱事件,揭示1761—1780年的3次移民高潮受极端干旱事件的驱动,且移民高潮的出现滞后迁出地极端干旱事件1~2年。第3次干旱推动了第3次移民高潮的出现,使得当时的清政府于1780年转变了移民政策。1775—1780年河西走廊极端干旱事件—天山北麓移民高潮—政府移民政策转变之间形成了一个完成的气候变化-社会响应链条。     

旺苍地区岩溶地貌形态特征及成因机理研究

旺苍地区发育有典型的南方亚热带岩溶地貌,主要以峰丛-溶蚀洼地、大-中型岩溶漏斗、溶蚀峡谷以及地下溶洞和洞内化次生化学沉积物最具特色。通过对研究区存在的夷平面进行探讨,认为本区存在两级夷平面和一级剥蚀面,形成了米仓山期、元山坪期岩溶夷平面和盆地期剥蚀面。米仓山期仅存保留于2 000 m左右的峰顶平坦面,主要以丘峰-岩溶洼地组合为主;元山坪期以峰丛-峡谷、大型溶洞组合为主,海拔高程在1 200~1 500 m;盆地期剥蚀面以溶蚀漏斗、落水洞、中-小型溶洞及地下河流组合为主要特征,海拔高程在500~900 m。在大量野外调查的基础上,对旺苍地区岩溶发育成因机理进行系统分析,认为岩性、水的侵蚀、地质构造等为旺苍地区岩溶发育的主控因素并且还受到地形地貌、气候等的综合影响。     

Comments on the planation surface once more

The authors reviewed the research of planation surface in recent years and commented on the development of method and theory about the planation surface. Some aspects of research, such as the restrictive planation surface, the karst planation surface, the fossil planation surface, the dating of weathering crust, the research of weathering crust and environmental evolution, extremely enriched the method and theory of the planation surface. Besides, the authors pointed out that we must take further steps to study the following issues: the deformation of planation surface, the original height of planation surface, the recognition and contrast of the planation surface. The weathering crust and planation surface should be regarded as a whole, and it will still be a principal aspect in the future.     

The reconstruction of fossil planation surface in China

On the basis of results of relative subjects, the fossil planation surface has been discussed by the authors from the point of geomorphologic view. The discussion contents included the characteristic information, research methods, paleotopography (gradient and altitude) and other problems about fossil planation surface. The recognition and reconstruction of fossil planation surface mainly rely on the following characteristic information: ( i ) the character of erosion unconformity surface; (ii) the paleo-weathering crust and residual deposits; (iii) the paleo-karst and filled deposit in the paleo-karst under the unconformity surface,and (iv) the character and environment of sediment above the unconformity surface. According to the above-mentioned characteristic information, the authors recognized and reconstructed two stages of fossil planation surface on Paleo-land of North China and Yangtze Paleo-land. These two fossil planation surfaces formed from Middle Ordovician to Lower Carboniferous and from Lower Permian to Upper Permian respectively. The paleo-gradient of fossil planation surface changed within 0.31‰-1.32‰, mostly less than 1.0‰. According to the developing depth of paleo-karst, the authors considered that in Suqiao buried-hill region of Paleo-land of North China, the paleo-altitude is 300 m or so above paleo-sea-level. The authors hope that the research is in favor of discussion about rising scale and process of the Tibetan Plateau. Besides, the research of fossil planation surface can provide a theoretical base for relative research,such as the reconstruction of paleoenvironment, the evolution and drift of paleo-continent, the formation and distribution of weathering ore deposits, the reservior and prospection of oil and gas, etc.     

Development features and original altitude of a karst planation surface: Preliminary review

Traditional theories of geographical cycle and pediplain cannot describe correctly the development of planation surfaces in karst regions. Authors, therefore, put forward conception of karst planation and karst planation surface, suggesting that karst planation is another type of planation process characterized by chemical erosion and transformation. To identify the distinction between evolution features of normal landforms and those of karst landforms developed in the South China, authors suggest karst planation surfaces under similar environmental conditions may reach a lower altitude and gradient ratio, in contrast with normal landform areas. This may be applied to researching on Tibetan Plateau uplift.     

Comment on planation surface

Planation surfaces includes peneplain, pediment and etchplain, which differ from each other in formation and distribution. The double leveling surfaces theory offered by Budel can be used to explain the landforms in limestone areas. According to Budel, that the residue is the upper layer of a planation surface is very important in studying the formation environment and weathering crust deposit in planation. In recent years, some researchers have expresses doubt whether it is reliable to use fossils to interpret the rising amount and rate of rise of the Tibet Plateau. It is believed that the primary planation surface can be used as a reliable indicator of land rising.     

夷平面形成的气候因素研究

夷平面是在构造相对稳定条件下经过长期外营力作用形成的一个接近基准面的平坦地形。因为它们都是在构造相对稳定条件形成的,地质构造作用在夷平面的形成因素中就退居次要位置,且又是以截面的形式横切所有在年龄上先于它的地层和构造,岩性也不起决定性作用;而其发育的外营力作用主要是受气候因素支配,所以夷平面形成的气候因素是首当其冲的。本文对前人提出的夷平面类型按气候因素进行了重新划分,得出4种类型：1）温湿夷平面,主要分布在水热条件较好的热带亚热带地区,夷平作用以流水侵蚀为主;2）萨瓦纳夷平面,发育在具有明显干湿季节交替的热带稀树草原（Savanna）地区,主要是通过山麓化作用形成的;3）干旱夷平面,发育在干旱半干旱气候条件下,机械风化为主导营力;4）寒冻夷平面,形成在气候寒冷的冰缘地区,以融冻夷平作用为主进行发育的。     

Geologic relationships and geochronology of the Cenozoic volcanoes and interbedded weathered mantles of Yulinshan in Qiangtang, North Tibet

The Yulinshan accumulations of volcanic rocks and interbedded weathered mantles provide a unique chance for studying the processes and environment of the formation of the planation surface in central Tibetan Plateau. Geochemical,⁴⁰Ar/³⁹Ar and K/Ar geochronologic investigations of the weathered mantles and high-potassium volcanic rocks reveal that the volcano-weathered mantle accumulations formed under arid or semi-arid subtropic environment in 30–24 Ma. The sole planation surface of the Qiangtang region finally formed in about 20 Ma.     

Geomorphologic evolution and environmental changes in the Shaluli Mountain region during the Quaternary

Geologic and geomorphologic evidence from the Shaluli Mountain indicates that the planation surface that formed in the Late Tertiary disintegrated during the Late PUocene-Early Quaternary. At the same time, rift basins appeared on some parts of the planation surface, and began to accumulate fluvial-lacustrine sediment. These are interpreted as being the response of this region to Phase-A of the Qingzang Teetnnic Movement. After this, the Shaluli Mountain eontinued to rise in several pulses. Faulting and incision by some large tributaries of the Jinsha and Yalong Rivers resulted in several rift river valleys and the earliest terraces. Generally. the planation surface in this region had been uplifted to ahout 3500--3700 m a.s.I, no later than 550-600 ka BP. after the Kunlun-Huanghe Tectonic Movement, and coupled with global glacial climate, and resulted in the earliest glaciation recognized so far in the Hengduan Mountains. At the same time, Ioess was deposited in the Ganzi area of the northern Shaluli Mountain. During the last glacial period, the Shaluii Mountain approached its present altitude and developed several large ice caps, such as the Daocheng Ice Cap and Xinlong Ice Cap, as well as several huge valley glaciers. These paleoglaciers produced some of the most Spectacnlar glacial topography on the Tibetan Plateau.     

青藏高原地面抬升证据讨论

当前学术界在青藏高原地面何时达到现代高度问题上存在着许多不同观点,概括起来主要有３种：１４Ｍａ前已达到高于现代的最大高度,８Ｍａ前已达到或超过现代高度,距今３．４Ｍａ来分阶中强烈上升并逐步达到现代高度,之所以出现如此大的意见分歧,除高原面积广阔,研究程度不深和覆盖面不够的原因外,不同研究者所使用研究方法和证据的差异也是重要因素,在分析了各种证据对高原地面上升的记录机理后,我们认为夷平面、河流附地,