Glacial potholes, meltwater channels, salt weathering tafoni and exfoliation on the granite surface in Zhaomiao, Chifeng, Inner Mongolia
-
摘要:
在内蒙古赤峰市巴林左旗林东镇以南约20 km的召庙, 出露一片面积约20 km2的花岗岩, 称为召庙花岗岩体。该岩体被至少2组垂直节理及与地面起伏一致的剥离面理切割成大小不等的弧形岩块, 构成高于周围地表300~400 m的花岗岩山区。在多条花岗岩山脊上保存有大小不等的壶穴, 山脊两侧则发育从上到下紧密排列的泄水槽, 而泄水槽则被剥离面理横向切割, 沿剥离面理的露头线发育大小不等的风化穴。通过详细的野外调查, 认为花岗岩山脊上的壶穴不是风蚀和风化所致, 而是晚更新世冰盖上的冰川融水下泄冲刷形成的; 山脊两侧的泄水槽也是冰川融水下泄冲刷的结果; 剥离面理是第四纪冰川发育导致地表之下岩石温度变化的热变应力所致, 可用于恢复第四纪冰川作用时期的基岩古地貌; 盐风化穴是第四纪冰川退缩后本区重要的物理风化类型, 优先沿着剥离面理发育。本区3种微型地貌景观和大型的剥离面理共生组合记录了更新世以来召庙花岗岩山区的地貌演化史。
Abstract:A granite hill, about 20 km2 in area, is situated 20 km to the south of Lindong Town in the Bairin Left Banner, Chifeng, Inner Mongolia, China.The Yanshannian coarse granite is mainly composed of K-feldspar and quartz.The granite intrusive body has been cut by two sets of vertical joints and a set of exfoliation joints that undulate with topographic relief.The granite hill is about 300~400 m higher than the surrounding area.We investigated the following three mini-landforms, potholes, meltwater channels and salt weathering tafoni and analyzed their formation mechanisms.We also examined the exfoliation and its origin.Potholes on the granite ridge in this area had been reported as wind-erosion evidence by some researchers 20 years ago, or interpreted as a result of chemical weathering lately.However, they were not formed by wind or weathering, but by the fast erosion of melt water from the surface of ice sheet above.According to our explanation, there was a vast icesheet over the Greater Khingan Mountains and the vicinity area in the northeast of Asia in the Late Pleistocene.The thick icesheet tended to create fractures over the granite ridges because of its gravity and drained the melt water through these fractures and thus eroded the bedrock to form potholes on the ridges.Apart from forming potholes on the granite ridges, melt water mainly formed meltwater channels on the surface of the hillside.Meltwater channels are rows of closely spaced erosional notches or grooves on the hillside surface, extending from hilltop to the piedmont, scoured by high-pressure melt water between granite surface and the overlying icesheet.There are abundant tafoni, large and small, along the gently undulating exfoliation joints in this area.These tafoni had been treated as a result of wind erosion and called "wind-eroded habitacles" in the past decades.However, these concave structures are not wind-erosion landforms but typical salt weathering tafoni.Salt weathering is the granular fragmentation of rocks affected by the salt crystallization near/on the rock surface.Salt weathering pits are first initiated along the exfoliation joints and enlarged gradually year by year to form large tafoni.Exfoliation is a common mega-structure in Zhaomiao granite hills.The exfoliation joints are almost parallel to the ground surface, splitting the granite into curved plates.The origin of exfoliation has not been clear until recent years.The sheet joints can be treated as isothermal surfaces underground because of temperature changes induced by Quaternary glaciation.Thus the exfoliation joints reveal the history of Quaternary continental glaciation in the north of Chifeng and the adjacent area.In research area, the Zhaomiao granite hills, potholes and meltwater channels were formed during the later LGM (Last Glacial Maximum) more than 10 thousand years ago, and the landform framework had already been formed by the end of Pleistocene glaciation in the eastern China.Since then, salt weathering has been the major agent to shape the mini-landforms on the flanks of the granite hills.Wind erosion and rain scouring can also be some minor factors but negligible compared to salt weathering.
-
Key words:
- granite intrusive body /
- pothole /
- meltwater channel /
- salt weathering /
- tafoni /
- exfoliation /
- Pleistocene icesheet /
- Inner Mongolia
-
-
[1] 吕洪波, 任晓辉, 杨超. 赤峰等地第四纪大陆冰川的地貌证据[J]. 地质论评, 2006, 52(3): 379-385. doi: 10.3321/j.issn:0371-5736.2006.03.020
[2] 吕洪波, 任晓辉, 许民, 等. 壶穴差异风化或风蚀作用成因质疑[J]. 地质论评, 2008, 54(2): 192-198. doi: 10.3321/j.issn:0371-5736.2008.02.006
[3] 吕洪波, 任晓辉, 许民, 等. 再论山脊壶穴的冰川融水成因——兼与施雅风院士商榷[J]. 地质论评, 2010, 56(5): 693-702. https://www.cnki.com.cn/Article/CJFDTOTAL-DZLP201005013.htm
[4] Gary M, McAfee R J, Wolf C L. Glossary of Geology[M]. American Geological Institute, Washington, 1972: 1-805.
[5] 《英汉综合地质学词汇》编写组. 英汉综合地质学词汇[M]. 北京: 科学出版社, 1970: 1-608.
[6] 武汉地质学院外语教研室. 英汉常用地质学词汇[M]. 北京: 科学出版社, 1984: 1-340.
[7] 《地理学词典》编写组. 地理学词典[M]. 上海: 上海辞书出版社, 1983: 1-804.
[8] 周成虎(主编). 地貌学辞典[M]. 北京: 中国水利水电出版社, 2006: 1-303.
[9] 韩同林, 郭克毅. 河北及内蒙古中低山区罕见的冰臼群[J]. 中国地质, 1998, 25 (6): 42-45. https://www.cnki.com.cn/Article/CJFDTOTAL-DIZI199806013.htm
[10] 崔之久, 李洪江, 南凌, 等. 内蒙、河北巨型壶穴与赤峰风道的发现[J]. 科学通报, 1999, 44(13): 1429-1434。 doi: 10.3321/j.issn:0023-074X.1999.13.016
[11] 李洪江, 崔之久, 赵亮. 内蒙、河北山区壶穴的成因探讨——兼论壶穴的成因分类[J]. 地理学报, 2001, 56(2): 223-231. doi: 10.3321/j.issn:0375-5444.2001.02.011
[12] 周尚哲. 锅穴一定是第四纪冰川的标志吗?[J]. 第四纪研究, 2006, 26(1): 117-125. doi: 10.3321/j.issn:1001-7410.2006.01.015
[13] 孙洪艳, 田明中, 武法东. 克什克腾世界地质公园青山花岗岩臼的特征及成因研究[J]. 地质论评, 2007, 53(4): 486-490. doi: 10.3321/j.issn:0371-5736.2007.04.007
[14] 周旭, 田明中, 王璐琳. 内蒙古巴林左旗岩臼型花岗岩景观形成演化分析[J]. 干旱区资源与环境, 2014, 28(12): 166-171. https://www.cnki.com.cn/Article/CJFDTOTAL-GHZH201412029.htm
[15] 吕洪波, 章雨旭. 壶穴、锅穴、冰臼、岩臼等术语的辨析与使用建议[J]. 地质通报, 2008, 27(6): 917-922. doi: 10.3969/j.issn.1671-2552.2008.06.022 http://dzhtb.cgs.cn/gbc/ch/reader/view_abstract.aspx?file_no=20080622&flag=1
[16] 吕洪波, 苏德辰, 章雨旭, 等. 中国不同气候带盐风化作用的地貌特征[J]. 地质论评, 2017, 63(4): 911-926. https://www.cnki.com.cn/Article/CJFDTOTAL-DZLP201704006.htm
[17] Lu H B. An outline of Earth Sciences (second edition)[M]. Dongying: China University of Petroleum Press, 2006: 1-506.
[18] 舒良树. 普通地质学(第三版)[M]. 北京: 地质出版社, 2010: 1-292.
[19] 韩同林. 发现冰臼[M]. 北京: 华夏出版社, 2004: 1-190.
[20] 赵国龙, 朱洪森, 李泊洋, 等. 论内蒙古第四纪冰川和冰臼群成因[J]. 中国区域地质, 2001, 20(2): 200-205. doi: 10.3969/j.issn.1671-2552.2001.02.014
[21] 章雨旭. "冰臼"成因争鸣——以克什克腾旗青山岩臼群为例[J]. 地质论评, 2005, 51(6): 680, 712. https://www.cnki.com.cn/Article/CJFDTOTAL-DZLP200506012.htm
[22] 施雅风, 崔之久, 李吉均. 中国东部第四纪冰川与环境问题[M]. 北京: 科学出版社, 1989: 1-462.
[23] 施雅风. 中国冰川与环境——现在、过去和未来[M]. 北京: 科学出版社, 2000: 1-410.
[24] 施雅风. 韩同林的"冰臼论"是对花岗岩类岩石"负球状风化"的误解[J]. 地质论评, 2010, 56(3): 349-354. https://www.cnki.com.cn/Article/CJFDTOTAL-DZLP201003007.htm
[25] 章雨旭, 刘恋. 山脊壶穴不能作为中国东部第四纪冰川的证据[J]. 科技导报, 2011, 29(33): 62-68. doi: 10.3981/j.issn.1000-7857.2011.33.009
[26] 吕洪波. 大兴安岭冰盖的证据和影响[EB/OL]. [2019-07-12](2021-05-04). http://blog.sciencenet.cn/home.php?mod=space&uid=39040&do=blog&id=1189267.2019.
[27] Porreca C, Briner J P, Kozlowski A. Laurentide ice sheet meltwater routing along the Iro-Mohawk River, eastern New York, USA[J]. Geomorphology, 2018, 303: 155-161. doi: 10.1016/j.geomorph.2017.12.001
[28] Glasser N F, Hambrey M J. Subglacial meltwater channels at Thurstaston Hill, Wirral and their significance for Late Devensian ice sheet dynamics[J]. Procdddings of the Geologists' Association, 1998, 109: 139-148. doi: 10.1016/S0016-7878(98)80013-8
[29] Leviston D. Subglacial meltwater channels at Lymm Dam, Cheshire[J]. Proceedings of the Geologists' Association, 2001, 112: 147-154. doi: 10.1016/S0016-7878(01)80023-7
[30] 徐叔鹰. 论盐风化过程及其地貌意义[J]. 铁道师院学报(自然科学版), 1992, 9(3): 24-30. https://www.cnki.com.cn/Article/CJFDTOTAL-SZTD1992S3003.htm
[31] 徐叔鹰. 干旱区盐风化过程的初步研究[J]. 干旱区地理, 1993, 16(2): 14-20. https://www.cnki.com.cn/Article/CJFDTOTAL-GHDL199302002.htm
[32] 吕洪波. 红岩怪石——酒泉青稞地[J]. 科学通报, 2014, (1): 38-39.
[33] Gilbert G K. Domes and dome structures of the high Sierra[J]. Geological Society of America Bulletin, 1904, 15(1): 29-36. doi: 10.1130/GSAB-15-29
[34] Bahat D, Grossenbacher K, Karasaki K. Mechanism of exfoliation joint formation in granitc rocks, Yosemite National Park[J]. Journal of Structural Geology, 1999, 21: 85-96. doi: 10.1016/S0191-8141(98)00069-8
[35] Mandl G. Rock joints—The mechanical genesis[M]. Springer-Verlag Berlin Heidelberg, 2005: 1-221.
[36] Twidale C R. On the origin of sheet jointing[J]. Rock Mechanics, 1973, 5: 163-187. doi: 10.1007/BF01238046
[37] Vidal Romani J R, Twidale C R. Sheet fractures, other stress forms and some engineering implications[J]. Geomorphology, 1999, 31: 13-27. doi: 10.1016/S0169-555X(99)00070-7
[38] Vidal Romani J R, Twidale C R. Structural or climatic control in granite landforms? The development of sheet structure, foliation, boudinage, and related features[J]. Cadernos Lab. Xeoloxico de Laxe Coruna, 2010, 35: 189-208.
[39] Bradley W C. Large-scale exfoliation in massive sandstones of the Colorado Plateau[J]. Geological Society of America Bulletin, 1963, 74: 519-528. doi: 10.1130/0016-7606(1963)74[519:LEIMSO]2.0.CO;2
[40] Harland W B. Exfoliation joints and ice action[J]. Journal of Glaciology, 1957, 3: 8-10. doi: 10.1017/S002214300002462X
[41] Huggett R J. Fundamentals of geomorphology (Second edition)[M]. Routledge New York, 2007: 1-458.
[42] Migon P. Evolution of granite landscapes in the Sudetes (Central Europe): some problems of interpretation[J]. Proceedings of the Geologists' Association, 1996, 107: 25-37. doi: 10.1016/S0016-7878(96)80065-4
[43] Migon P. Granite landscapes of the world[M]. New York: Oxford University Press, 2006: 1-384.
[44] Ziegler M, Loew S, andBahat D. Growth of exfoliation joints and near-surface stress orientations inferred from fractographic markings observed in the upper Aar valley (Swiss Alps)[J]. Tectonophysics, 2014, 626: 1-20. doi: 10.1016/j.tecto.2014.03.017
[45] Martel S J. Progress in understanding sheeting joints over the past two centuries[J]. Journal of Structural Geology, 2017, 94: 68-86. doi: 10.1016/j.jsg.2016.11.003
[46] Zak J, Vyhnalek B, Kabele P. Is there a relationship between magmatic fabrics and brittle fractures in plutons? A view based on structural analysis, anisotropy of magnetic susceptibility and thermo-mechanical modelling of the Tanvald pluton (Bohemian Massif)[J]. Physics of the Earth and Planetary Interriors, 2006, 157: 286-310. doi: 10.1016/j.pepi.2006.05.001
[47] Ziegler M, Loew S, Moore J R. Distribution and inferred age of exfoliation joints in the Aar Granite of the central Swiss Alps and relationship to Quaternary landscape evolution[J]. Geomorphology, 2013, 201: 344-362. doi: 10.1016/j.geomorph.2013.07.010
[48] Ziegler M, Loew S, andAmann F. Near-surface rock stress orientations in alpine topography derived from exfoliation fracture markings and 3D numerical modelling[J]. International Journal of Rock Mechanics & Mining Sciences, 2016, 85: 129-151.
[49] 吕洪波, 高于, 浦津, 等. 大兴安岭南段赛罕乌拉石海剖面分析及其与蒙山拦马墙石河结构对比[J]. 地质论评, 2020, 66(6): 1572-1588. https://www.cnki.com.cn/Article/CJFDTOTAL-DZLP202006009.htm
-
下载:
图(8)
计量
- 文章访问数: 2167
- PDF下载数: 85
- 施引文献: 0