Cosmogenic Be and Al exposure ages of tors and erratics, Cairngorm Mountains, Scotland: Timescales for the development of a classic landscape of selective linear glacial erosion     

William M. Phillips  Adrian M. Hall  Ruth Mottram  L. Keith Fifield  David E. Sugden 《Geomorphology》2006,73(3-4):222-245

The occurrence of tors within glaciated regions has been widely cited as evidence for the preservation of relic pre-Quaternary landscapes beneath protective covers of non-erosive dry-based ice. Here, we test for the preservation of pre-Quaternary landscapes with cosmogenic surface exposure dating of tors. Numerous granite tors are present on summit plateaus in the Cairngorm Mountains of Scotland where they were covered by local ice caps many times during the Pleistocene. Cosmogenic ¹⁰Be and ²⁶Al data together with geomorphic relationships reveal that these landforms are more dynamic and younger than previously suspected. Many Cairngorm tors have been bulldozed and toppled along horizontal joints by ice motion, leaving event surfaces on tor remnants and erratics that can be dated with cosmogenic nuclides. As the surfaces have been subject to episodic burial by ice, an exposure model based upon ice and marine sediment core proxies for local glacial cover is necessary to interpret the cosmogenic nuclide data. Exposure ages and weathering characteristics of tors are closely correlated. Glacially modified tors and boulder erratics with slightly weathered surfaces have ¹⁰Be exposure ages of about 15 to 43 ka. Nuclide inheritance is present in many of these surfaces. Correction for inheritance indicates that the eastern Cairngorms were deglaciated at 15.6 ± 0.9 ka. Glacially modified tors with moderate to advanced weathering features have ¹⁰Be exposure ages of 19 to 92 ka. These surfaces were only slightly modified during the last glacial cycle and gained much of their exposure during the interstadial of marine Oxygen Isotope Stage 5 or earlier. Tors lacking evidence of glacial modification and exhibiting advanced weathering have ¹⁰Be exposure ages between 52 and 297 ka. Nuclide concentrations in these surfaces are probably controlled by bedrock erosion rates instead of discrete glacial events. Maximum erosion rates estimated from ¹⁰Be range from 2.8 to 12.0 mm/ka, with an error weighted mean of 4.1 ± 0.2 mm/ka. Three of these surfaces yield model exposure-plus-burial ages of 295_− 71^+ 84, 520_− 141^+ 178, and 626_− 85^+ 102 ka. A vertical cosmogenic nuclide profile across the oldest sampled tor indicates a long-term emergence rate of 31 ± 2 mm/ka. These findings show that dry-based ice caps are capable of substantially eroding tors by entraining blocks previously detached by weathering processes. Bedrock surfaces and erratic boulders in such settings are likely to have nuclide inheritance and may yield erroneous (too old) exposure ages. While many Cairngorm tors have survived multiple glacial cycles, rates of regolith stripping and bedrock erosion are too high to permit the widespread preservation of pre-Quaternary rock surfaces.  相似文献   

浙江省中西部地区丹霞地貌特征及其旅游资源     

吕惠进 《浙江国土资源》2001,17(2):66-73

浙江省丹霞地貌比较发育,具有丰富的旅游资源.本文在考察浙江中西部地区比较典型的丹霞地貌、旅游资源的基础上,分析了丹霞地貌的特征和旅游资源及其开发现状.  相似文献   

龙虎山世界地质公园丹霞地貌成景系统特征及其演化   总被引：1，自引：0，他引：1  

郭福生  姜勇彪  胡中华  刘林清  李虹 《山地学报》2011,29(2)

龙虎山世界地质公园内分布着大量以石寨、石墙、巷谷、峰林、石峰、石柱、石崖、巷谷、一线天、造型石等景观类型,它们形成于晚白垩系龟峰群,是我国典型的丹霞地貌分布区之一.其形成不仅与红层、构造及流水等外营力等构成了丹霞地貌的成景系统因素有关,而且也与它们在信江盆地内的空间位置相关,共同制约着不同位置上丹霞地貌的演化进程及其景观总体特征.  相似文献   

贵州赤水南部地区丹霞地貌类型特征及成因演化分析   总被引：2，自引：0，他引：2  

李霞  何庆成  董颖  曹晓娟  王智勇  段学敏 《地球学报》2013,34(4):501-508

贵州赤水南部地区广泛分布着白垩系嘉定群巨厚红层,受构造活动、流水侵蚀、风化剥蚀和重力崩塌等内外力地质作用影响,形成了类型丰富的丹霞地貌景观。本文将丹霞地貌的类型特征与成因演化相结合,按主导动力对丹霞地貌进行分类,包括丹霞构造地貌、丹霞水蚀地貌、丹霞风化地貌和丹霞重力地貌等类型,并对典型的代表景观特征进行描述。重点分析了赤水南部地区丹霞地貌的成因演化过程,从地质学的角度揭示出丹霞地貌景观的成因演化机理,起到普及地球科学知识,开展地学研究的作用。  相似文献   

资新盆地丹霞地貌景区申报世界地质公园刍议     

谢莉  杨载田 《热带地理》2010,30(1)

运用地理学的资源评价法和区域比较分析法,分析了我国已有风景区中最典型最有代表性的资新盆地丹霞地貌景观特征,并与我国其它著名丹霞地貌景观进行了对比和景观质量评价,指出资新盆地丹霞地貌景区具备申报世界地质公园的诸多有利条件和基础,广西资源县与湖南新宁县应该联合起来协调申报。  相似文献   

国内外红层与丹霞地貌研究述评   总被引：8，自引：0，他引：8  

彭华  潘志新  闫罗彬  Scott SIMONSON 《地理学报》2013,68(9):1170-1181

在中国丹霞地貌走向世界,开始一个新的发展阶段的时候,回顾并评述国内外红层和丹霞地貌的研究进展十分必要。国内在该领域的研究长期集中在红层特性、工程地质、丹霞地貌特征及发育的基本问题等方面,但对红层的地质和地貌融合研究不足,对不同红层的岩性差异及其在外动力条件下的地貌表现和地貌发育过程缺乏深度研究;国外还没有红层地貌和丹霞地貌的专门研究,学者们主要关注红层形成的地质背景,有关红层地貌的研究多分散在砂岩地貌中,但其在微观、定量、实验研究方面值得借鉴。本文认为当前有关红层和丹霞地貌的研究大多为单因子研究,缺乏系统的思想方法,各学科研究存在多张皮的问题。提出应明确红层和丹霞地貌的学科归属,深化基础研究,加强各学科之间的融合,并推动国际交流和对比研究。  相似文献   

Elementary forms for land surface segmentation: The theoretical basis of terrain analysis and geomorphological mapping   总被引：10，自引：0，他引：10  

Jozef Minr  Ian S. Evans 《Geomorphology》2008,95(3-4):236-259

Land surface morphology is fundamental to geomorphological mapping and many GIS applications. Review and comparison of various approaches to segmentation of the land surface reveals common features, and permits development of a broad theoretical basis for segmentation and for characterization of segments and their boundaries. Within the context of defining landform units that maximise internal homogeneity and external differences, this paper introduces the concept of elementary forms (segments, units) defined by constant values of fundamental morphometric properties and limited by discontinuities of the properties. The basic system of form-defining properties represents altitude and its derivatives, constant values of which provide elementary forms with various types of homogeneity. Every geometric type of elementary form can be characterized by a defining function, which is a specific case of the general polynomial fitted function. Various types of boundary discontinuity and their connections and transformations into other types of morphological unit boundaries are analysed.The wealth of types of elementary forms and their boundaries is potentially unbounded and thus is sufficient to cover the real variety of landforms. Elementary forms in the basic set proposed here have clear potential for genetic and dynamic interpretation. A brief worked example documents the possibility of analytical computation of various models of ideal elementary forms for particular segments of landform. Ideal elementary forms can be considered as attractors, to which the affinity of surface segments can be measured by multivariate statistical methods. The use of the concept of elementary forms in landscape segmentation is promising and it could be adapted for elementary segmentation of various other spatial fields.  相似文献   

泰宁创建世界级旅游目的地的几个问题   总被引：1，自引：0，他引：1  

曾启鸿  袁书琪 《云南地理环境研究》2008,20(4):99-102

近几年来,泰宁旅游业取得了惊人的发展速度和骄人的发展成就。作为新兴旅游区,泰宁已拥有世界地质公园品牌,应创建世界级旅游目的地,二者之间存在相互促进相互制约的关系。从战略上看,泰宁应建成世界亚热带丹霞山水旅游带的生态博物馆,世界环台湾海峡旅游圈的丹霞湖泊接待地。泰宁应采取编制高水平发展战略及规划,开发具有世界吸引向性的旅游产品,构建整体合理的土地利用格局、建设高档次旅游中心城镇、形成高素质旅游行业队伍等措施。  相似文献   

丹霞山顺层洞穴风化特征的试验研究   总被引：1，自引：1，他引：0  

彭 华邱卓炜  潘志新 《地理科学》2014,34(4):454-463

以丹霞盆地丹霞组2段顺层洞穴为研究对象,探讨不同岩性红层抗风化能力的差异,重点关注软岩夹层的风化特征及其对顺层洞穴发育的影响。在野外考察的基础上,选择3个典型顺层洞穴为案例,采集了洞穴剖面不同岩性红层的岩样及夹层水样品,进行一系列的岩矿理化测试和水样分析实验。结果表明：洞穴剖面岩性的不均一性及软岩夹层的风化凹进是形成丹霞山顺层洞穴的主要原因。顺层洞穴发育的软岩夹层一般是粉砂质泥岩,粘土矿物含量高,以泥质胶结为主,吸水性较强,开型空隙率较大,抗压强度小,易于风化破碎;上下岩层主要是砂岩和砂砾岩,以钙质和铁质胶结为主,吸水性较弱,开型孔隙率较小,抗压强度较大,风化速度较慢。在洞穴岩层风化过程中,粘土矿物的胀缩、钙质胶结物的溶解, 及铁质胶结物的水化作用等是导致岩体结构破坏的重要因素,但促使不同岩性红层风化的主导因素有所差别。粉砂质泥岩的风化以粘土矿物的胀缩作用为主,砂岩和砂砾岩的风化则以钙质胶结物的溶解作用为主。此外,酸性雨水渗入岩体后与各种矿物进行的一系列离子交换作用也促进了顺层洞穴岩层的风化。  相似文献   

丹霞地貌危岩景观分类及可持续开发对策——以龙虎山景区为例   总被引：2，自引：0，他引：2  

郭福生  姜伏伟  胡中华  吴知勇  姜勇彪  蒋兴波 《山地学报》2012,(1):99-106

从可持续开发的角度,根据稳定程度将丹霞地貌景观分为危岩景观和稳定景观,并依据规模大小、外观形态、失稳模式、旅游价值和灾害性,将危岩景观进行了简要分类。在龙虎山丹霞地貌景观特征和旅游开发现状调查的基础上,对该区危岩景观的类型进行了划分,分析了危岩景观的开发现状、潜在威胁和保护对策。  相似文献