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本文首次报道了在山东鲁山南坡山谷发现混合岩表面的颤痕.颤痕是冰川底部携带的岩石碎块在下伏基岩表面刮凿而形成的一系列弧形裂隙,颤痕的弧形突出方向与冰川运动方向一致,而裂隙也是向下游方向深入基岩内部,其中突出的中间部位裂隙最深,向两端逐渐变浅直至消失.作者探讨了颤痕的形成机理,认为:颤痕相当于主剪切面上的伴生构造——R剪切面,在剖面上看就是一系列雁列式排列的R面,它不仅是冰川在基岩上运动留下的重要证据,而且还能指示冰体的运动方向.除了颤痕之外,在鲁山山麓还分布着大量的冰碛地貌:巨漂砾、冰碛堤等,在鲁山山脊上还见有典型的壶穴、冲刷槽等冰川融水侵蚀标志.这些标志与颤痕一起构成了强大的证据群,揭示了中国东部曾经发育过第四纪冰川的历史.中国东部是否发育过第四纪冰川?地学界已经争论了80多年,而颤痕的发现为进一步肯定中国东部存在第四纪冰川活动提供了最直接的证据. 相似文献
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颤痕是冰川作用地区由冰川携带岩屑做周期性或间歇性运动在冰床基岩和冰碛石表面形成的新月形或弧形破裂形态,特征尺度一般不大于1 m。其主要形成机制类似Riedel构造模式中的（R）剪切破裂和（T）拉张破裂,且遵循脆性破裂原理。根据国内外文献报道和野外考察,从术语学角度将冰川颤痕分为狭义和广义两种。广义冰川颤痕,包括曲锥形擦口（狭义颤痕）、半月形裂口、新月形凿口、新月形裂纹和新月形断口5种。测量统计结果显示,23组新月形断口的排列间距,KS和JB检验均符合正态和伽玛分布（置信度95%）,与岩石节理（破裂）的间距特征一致;25组新月形凿口和35组新月形裂纹的排列间距,KS检验符合正态分布和伽玛分布,JB检验不符合正态分布（置信度95%）。证明颤痕在空间分布上大体保持相等的破裂间距,基本符合饱和模式理论。颤痕的定向性、成组特征具有明确的环境意义,与擦痕、擦面的地貌组合是重要的冰川遗迹判别标志。缺少冰蚀地貌组合的孤立“颤痕”,不具有指示冰川作用的价值。近年报道的山东鲁山没有“颤痕”等冰川遗迹。 相似文献
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针对施雅风院士新提出的壶穴之"负球状风化"说,笔者特撰文与施老商榷。笔者认为:壶穴的形成并不受花岗岩中节理的控制,也与风化作用无关,不能用"负球状风化"来解释。壶穴是高速旋转水流侵蚀的结果,在中国东部花岗岩山脊上发现的壶穴是第四纪冰川融水侵蚀的标志。近年来观察到的格陵兰冰上湖泊的突然排泄为壶穴的冰川融水成因说提供了重要的证据。壶穴成因争论的本质是中国东部是否曾经发育过第四纪冰川,建议第四纪学界关注中国东部第四纪冰川的其他地貌标志。韩同林研究员的"冰臼论"促进了中国东部第四纪冰川地貌的再研究,应当给予积极评价。 相似文献
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山西宁武吕梁山北段第四纪冰川遗迹的发现及意义 总被引：4，自引：0，他引：4
山西宁武吕梁山北段,平均海拔约2000米,相对高差数百米至千米左右,属中山区。第四纪冰川遗迹十分发育,类型多种多样,特征明显。冰川遗迹有:U形谷、刃脊、角峰、冰斗、冰窖及分布于U形谷中的大量冰川漂砾、冰碛、冰水堆积、冰臼、变形砾石、条痕石等。该区古冰川遗迹的大量发现,不仅证明了我国东部中低山区有大量第四纪冰川运动存在,而且冰川规模之大完全出乎人们意料之外。为研究该区古气候、古环境演化提供重要依据,为我国第四纪冰期划分和对比提供重要资料和证据。 相似文献
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中国东部(含庐山)第四纪冰期之争,表现在地貌、沉积与冰川发生条件三个方面。笔者认为:庐山冰川仅发生在早更新世,并建立了金锭山冰期。中晚更新世没有冰川发生,前人提及的某些冰川作用证据需要重新认识。庐山晚新生代地层分为18个层组,含11级阶地,只有一个可靠的冰碛层,其他为非冰碛层或似冰碛层。 相似文献
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蒙山“冰川遗迹”辨识中的逻辑谬误分析——以“山东蒙山冰川遗迹的类型、特征和年代”一文为例 总被引：1，自引：0，他引：1
第四纪冰川研究主要根据观察到的地貌学、沉积学特征和年代学结果,通过缜密的逻辑推理判断其成因、时代和环境意义。蒙山"冰川遗迹"的辨识是建立在不适当或错误的证据上,雪线重建和冰期划分是不能成立的;所谓第四纪冰川遗迹,完全可以用非冰川成因予以解释。通过对蒙山堆积和侵蚀地貌的调查,笔者等得知:①拦马墙砾石堆积堤不连续、不对称分布于兰溪下游凹岸,具有立石和叠石景观,砾石组构、叠瓦构造、底泥层和不规则擦痕等表明,拦马墙天然堤为泥石流堆积;②兰溪是典型的V形谷,其基岩谷壁没有擦面和颤痕,非冰蚀擦痕是砾石沿河谷滚动、拖拽摩擦和撞击的结果,主要是泥石流成因;③已报道的蒙山"颤痕",不符合颤痕的定义和形成机制,是无效的冰川遗迹证据。本文初步提出了微观尺度新月形冰蚀地貌的分类方案,并统一称为颤痕。"山东蒙山冰川遗迹的类型、特征和年代"一文存在多处逻辑错误,我们以之为例,主要讨论了该文6个方面的逻辑缪误及其产生的非理性因素。 相似文献
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山东蒙山第四纪冰川组合遗迹的发现及初步研究 总被引：1，自引：0，他引：1
本文介绍了山东蒙山地区南坡保存的丰富而清晰的第四纪冰川遗迹,重点展示了兰溪山谷的冰石河、侧碛堤组合,并对相伴产出的擦痕、磨光面、颤痕等冰川遗迹进行了调查与测量。同时对冰石河、侧碛堤的分布、规模、物质组成、岩石特征进行了介绍。根据侧碛堤的排列位置及砾石的风化程度,初步确定为末次冰期的冰碛遗迹;对山谷两侧磨光面上的擦痕进行了测量统计,显示谷壁磨光面上擦痕的长宽比具有10:1左右的比例规律;根据侧碛最大高度法(MELM),结合对于蒙山侧碛的调查,对蒙山雪线的高度进行了估算,初步估算蒙山南坡末次冰期时的雪线高度约为700 m左右。蒙山地区这些组合冰川遗迹的发现,为中国东部第四纪冰川的研究提供了直接的证据。 相似文献
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神农架是中国第四纪地质环境演变的热点地区之一。本文通过对第四纪冰川地貌、冰碛残迹及二者关系研究,提供了本区第四纪古冰川发育的多方面证据。神农架地区在第四纪时期曾发生三期冰期和两期冰缘期,即松柏冰期、木鱼坪冰期、龙潭冰期、松香坪冰缘期、神农架冰缘期。本文首次系统地建立了本区第四纪气候地层系列. 相似文献
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渐趋完善的第四纪冰川研究范式——记第四届中国第四纪冰川与环境变化研讨会 总被引：4，自引：1，他引：3
冰川是气候变化敏感的指示器,第四纪冰川研究在地球科学中占有重要的地位。2017年8月,第四届中国第四纪冰川与环境变化研讨会在兰州成功举办。与会专家认为,地貌学与沉积地层学的结合以及测年技术的发展,使中国第四纪冰期划分研究取得长足进展,不仅建立了80万年以来可与MIS进行比对的中国第四纪冰期与间冰期演化序列,还推动了中国第四纪环境变化研究的深入。通过研讨和交流,绝大多数专家认为中国东部中低山地某些疑似的第四纪冰川遗迹完全可以用非冰川成因予以解释,在今后的研究工作中应加强岩石地貌、气候地貌和外动力地貌过程的综合研究,尤其需要加强诸如颤痕等微观冰蚀地貌的分类、形成机制和环境意义研究。适时指出泛冰川论的缺陷和不足是本领域科学家的历史责任和使命担当,进一步开展具备科学事实、科学理论和科学观念的研究,从而完善中国第四纪冰川理论。建议国家级学会组织编制第四纪冰川遗迹调查与评价技术规范,加强全国高校自然地理学等相关专业的教师培训工作,同时加大冰川学、地貌学的科学普及力度。 相似文献
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We report the first direct ages for late Quaternary glaciation on the North Island of New Zealand. Mt Ruapehu, the volcanic massif in the North Island's centre, is currently glaciated and probably sustained glaciers throughout the late Quaternary, yet no numeric ages have been reported for glacial advances anywhere on the North Island. Here, we describe cosmogenic 10Be ages of the surface layers of a glacially transported boulder and glacially polished bedrock from the Tararua Range, part of the axial ranges of the North Island. Results indicate that a limited valley glaciation occurred, culminating in recession at the end of the last glacial coldest period (LGCP, ca. 18 ka). This provides an initial age for deglaciation on the North Island during the last glacial–interglacial transition (LGIT). It appears that glaciation occurred in response to an equilibrium‐line altitude (ELA) lowering of ～1400 m below the present‐day mean summer freezing level. Ages for glaciation in the Tararua Range correspond closely to exposure ages for the last glacial maximum (LGM) from the lateral moraines of Cascade Valley in the South Island, and in Cobb Valley, in northern South Island. The corollary is that glaciation in the Tararua Range coincided with the phase of maximum cooling during MIS 2, prior to the Antarctic Cold Reversal (ACR), during the LGCP. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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中国第四纪亚冰期划分之商讨 总被引：6，自引：2，他引：6
本文举例概述中国第四纪冰川流行之证据,包括漂砾、冰溜面及冰川刮痕、表皮构造、冰碛和冰水堆积、冰期时期冰川条痕砾和冰蚀地形等以及动植物遗迹。关于亚冰期之划分及其依据,有的地区亚冰期划分次数最多者可有五、六次。主要依据是:冰碛、冰水沉积特征与其所在地层层位以及新、老冰川地貌的叠加与其干扰现象。 相似文献
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Alastair G. Dawson 《第四纪科学杂志》1994,9(4):349-356
The islands of Tiree and Coll in the Scottish Inner Hebrides are dominated by staircases of glaciated rock-platform surfaces in Lewisian gneiss that are interpreted here as areas of strandflat. The rock platform surfaces exhibit differential glacio-isostatic uplift from east to west and are considered to indicate at least four separate periods of strandflat formation during prolonged intervals of Quaternary cold climate. It is suggested that many of the well-known areas of high rock platform located farther east in the Scottish Inner Hebrides represent eroded remnants of the strandflat surfaces described here. The existence of the Tiree and Coll strandflat surfaces in conjunction with their formation during periods of Quaternary glaciation implies that they were produced during periods when mainland Scotland was ice-covered yet when the western margin of the ice sheet was normally located east of these islands. A prominent Late-glacial raised shoreline also occurs on both islands and declines in altitude to the west, from 22 m in northeastern Coll to 9 m in western Tiree. It is believed that this shoreline, whose regional gradient is 0.39 m km?1, may represent part of the Main Wester Ross Shoreline that was formed in the Northwest Highlands of Scotland during a period of glacial advance that interrupted the decay of the last (Late Devensian) ice sheet. The general similarity in altitude between the Late-glacial shoreline features and rock platform surfaces implies that during each period of Quaternary strandflat formation, relative sea-level returned to the same approximate position. This would appear to indicate that the glacio-isostatic and glacio-eustatic components affecting the positions of relative sea level in Scotland have remained in approximate equilibrium throughout the duration of the Quaternary. 相似文献
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庐山东南麓冰川作用表皮构造特征及其意义 总被引：4，自引：1，他引：4
庐山东南麓第六阶地基座上,发现了早更新世冰川作用表皮构造。按其形态与成因可分为巨砾压入基岩、小型倒转构造与不协调褶皱、逆冲-贯入构造、大型片麻岩包裹体等四种类型。早更新世初期之庐山,确实多次发生过山麓冰川作用。 相似文献
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Cosmic ray exposure ages of frost-weathered bedrock from mountain summits in the Outer Hebrides exceed the age of Late Devensian glaciation. Exposure ages of most glacially-abraded bedrock surfaces at low and intermediate elevations are younger than the age of maximum Late Devensian glaciation. These results confirm that previously mapped periglacial trimlines in the Outer Hebrides define the upper limit of bedrock erosion by Late Devensian ice. They are consistent with the interpretation, based on geomorphological evidence, that the trimlines mark the approximate upper limit of a Late Devensian Outer Hebrides Ice Cap. A postglacial exposure age from the summit of Oreval (662 m) suggests that this mountain was overrun during the last glaciation, indicating thicker ice cover and a lower surface gradient west of the ice-cap divide than previously inferred. Although bedrock surfaces below the trimlines are strongly ice-moulded, some show evidence of prior cosmic ray exposure, which we attribute to limited erosion during Late Devensian glaciation. If this interpretation is correct, the youngest apparent ages from these surfaces give the most reliable dates for deglaciation, at ca. 14.5–14 ka. This implies that ice persisted at favourable sites through the warm opening phase of the Windermere Interstade. Comparison with radiocarbon-dated evidence from offshore cores suggests net ice margin retreat of ∼74 km eastwards across the adjacent shelf in > 2.3 ± 1.0 ka. The dating evidence is consistent with relatively rapid retreat of calving margins to the coast, then slower withdrawal of ice margins to high ground. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献