| Citation: |
XU Hehongxin, GUO Jinjing, LIU Chongqing, ZHAO Haitao, DU Zhirui. The gravel characteristics of Pliocene conglomerates in Zhangxian area on the northern margin of the West Qinling and its geological significance[J]. Geological Bulletin of China, 2020, 39(10): 1561-1572.
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The gravel characteristics of Pliocene conglomerates in Zhangxian area on the northern margin of the West Qinling and its geological significance
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Abstract
There are two sets of Cenozoic sedimentary stratigraphic units separated by angular unconformity in Zhangxian area on the northern margin of the West Qinling, namely, the Lower Oligocene-Miocene salt-bearing sedimentary sequence and Pliocene coarse conglomerates.Based on the observation and statistical analysis for sedimentary cycle, gravel size, roundness, arrangement, composition and its vertical changes of Pliocene coarse conglomerates in this area, the authors have summarized the main characteristics of this set of conglomerates and its gravels as follows:①This set of conglomerates is mainly composed of thick, coarse conglomerates with a thickness of 480m, which covers unconformably the underlying Oligocene-Miocene salt-bearing sedimentary sequence and, from the bottom to the top, it can be divided into five lithologic beds, i.e., alluvial, fluvial, alluvial-fluvial, fluvial, alluvial-fluvial conglomerate beds; ②the gravels of the conglomerates are characterized by poor sorting with wide grain size distribution range in which the maximum size is 120-240 mm with the major size being 10-80 mm, gritty cementation, matrix supported texture with a little grain supported texture, being mainly sub-angular and sub-roundness with a little roundness; ③the gravels of the conglomerates mainly are grayish green feldspar sandstones, feldspar quartz sandstone, gray or grayish red limestone and porphyry granite, granodiorite or diorite porphyrite.In addition, the gravel compositions in different lithologic beds are obviously different.Generally, gravels in the alluvial conglomerate section mainly are various granitic rocks and sandstones, while those in fluvial conglomerate section are dominated by limestone gravel with some roundness; ④the gravel southward imbrication orientation indicates the paleocurrent direction from south to north.Based upon the above mentioned conglomerates' and gravels' characteristics, the spatial distribution controlled by south dip F2 thrust faulting, and consistency of the gravel compositions with the rock composition of the West Qinling orogenic belt, it is suggested that the Pliocene conglomerates should be the rapid accumulation, near-source, alluvial fan deposits in front of the mountain with the boundary of the fault on the north margin of the West Qinling with the nature of regenerated foreland coarse molasse basin.Furthermore, a series of conglomerates are similar to the Pliocene Hanjiagou conglomerates in lithic characteristics, age and tectonic setting, such as Ganjia conglomerates in Xunhua basin and Jishishan conglomerates in Linxia Basin on the northeastern margin of the Tibetan Plateau, and hence it is proposed that the development of Pliocene conglomerates in Zhangxian area on the northern margin of the West Qinling was related to the northward growth and expanding of the Tibetan Plateau to the northern margin of the West Qinling Mountain under the India-Europe collision dynamic background.This northward growth and expanding not only triggered the rapid uplift of the Qinling orogenic belt but also led to the reactivation of the northern margin fault and strong northward thrusting, which resulted in the formation of the regeneration foreland molasse basin.
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References
[1] Molnar P, Tapponnier P.Cenozoic tectonics of Asia:Effects of a continental collision[J].Science, 1975, 189(4201):419-426. doi: 10.1126/science.189.4201.419 [2] Molnar P, England P, Martinod J.Mantle dynamics, uplift of the Tibetan Plateau, and the Indian monsoon[J].Reviews of Geophysics, 1993, 31(4):357-396. doi: 10.1029/93RG02030 [3] Xiao X C, Li T D.Tectonic evolution and uplift of Qinghai-Tibet Plateau[J].Episode.1995, 18(1/2):31-35. [4] Dewey J F, Cande S, Pitman W C.Tectonic evolution of the India-Eurasian Collision Zone[J].Eclogae Geologicae, 1989, 82(3):717-734. [5] Yin A, Harrison T M.Geologic evolution of the Himalayan-Tibetan orogen[J].Annu.Rev.Earth Planet.Sci.Lett., 2000, 28:211-280 doi: 10.1146/annurev.earth.28.1.211 [6] Tapponnier P, Zhiqin X, Roger F, et al.Oblique stepwise rise and growth of the Tibet Plateau[J].Science, 2001, 294(5547):1671-1677. doi: 10.1126/science.105978 [7] Royden L H, Burchfiel B C, van der Hilst R D.The geological evolution of the Tibetan Plateau[J].Science, 2008, 321:1054-1058. doi: 10.1126/science.1155371 [8] Wang C S, Dai J G, Zhao X X, et al.Outward-growth of the Tibetan Plateau during the Cenozoic:A review[J]. Tectonophysics, 2014, 621:1-43. doi: 10.1016/j.tecto.2014.01.036 [9] 李吉均, 方晓敏, 马海洲, 等.晚新生代黄河上游地貌演化与青藏高原隆起[J].中国科学(D辑), 1996, 26(4):316-322. [10] 潘桂棠, 王立全, 张万平, 等.青藏高原及邻区大地构造图及说明书[M].北京:地质出版社, 2013. [11] 许志琴, 杨经绥, 李海兵, 等.造山的高原——青藏高原的地体拼合、碰撞造山及隆升机制[M].北京:地质出版社, 2007:1-458. [12] 吴珍汉, 吴中海, 胡道功, 等.青藏高原新生代构造演化与隆升过程[M].北京:地质出版社, 2009.1-333. [13] 王成善, 戴紧根, 刘志飞, 等.西藏高原与喜马拉雅的隆升历史和研究方法:回顾与进展[J].地学前缘, 2009, 16(3):1-30. [14] Yuan D Y, Ge W P, Chen Z W, et al.The growth of northeastern Tibet and its relevance to large-scale continental geodynamics:A review of recent studies[J].Tectonics, 2013, 32:1358-1370. doi: 10.1002/tect.20081 [15] 郑德文, 张培震, 万景林, 等.青藏高原东北边缘晚新生代构造变形的时序——临夏盆地碎屑颗粒磷灰石裂变径迹记录[J].中国科学(D辑), 2003, 33(S1):190-198. [16] 郑德文, 张培震, 万景林, 等.构造、气候与砾岩——以积石山和临夏盆地为例[J].第四纪研究, 2006, 26(1):63-69. [17] 张培震, 郑德文, 尹功明, 等.有关青藏高原东北缘晚新生代扩展与隆升的讨论[J].第四纪研究, 2007, 26(1):5-13. [18] 司家亮, 李海兵, Barrier L, 等.青藏高原西北缘晚新生代的隆升特征——来自西昆仑山前盆地的沉积学证据[J].地质通报, 2007, 26(10):1356-1367. [19] 陈杰, Wyrwoll K H, 卢演俦, 等.祁连山北缘玉门砾岩的磁性地层年代与褶皱过程[J].第四纪研究, 2006, 26(1):20-31. [20] 刘栋梁, 宋春晖, 颜茂都, 等.初探玉门砾岩沉积速率时空变化对气候构造相互作用的意义[J].大地构造与成矿学, 2011, 35(1):56-63. [21] 赵志军, 方小敏, 李吉均, 等.酒泉砾石层的古地磁年代与青藏高原隆升[J].科学通报, 2001, 46(14):1208-1212. [22] 宋春晖, 方小敏, 高军平, 等.青藏高原东北部贵德盆地新生代沉积演化与构造隆升[J].沉积学报, 2001, 19(4):493-500. [23] 方小敏, 宋春晖, 戴霜, 等.青藏高原东北部阶段性变形隆升:西宁、贵德盆地高精度磁性地层和盆地演化记录[J].地学前缘, 2007, 14(1):230-242. [24] Fang X M, Yan M D, VanderVoo Rob, et al.Late Cenozoic deformation and uplift of the NE Tibetan Plateau:Evidence from high-resolution magnetostratigraphy of the Guide Basin, Qinghai Province, China[J].Bulletin of the Geological Society of America, 2005, 117(9/10):1208-1225. [25] Zhang P, Molnar P, Downs W.Increased sedimentation rates and grain sizes 2-4 Myr ago due to the influence of climate changes on erosion rates[J].Nature, 2001, 410:891-897 doi: 10.1038/35073504 [26] 郭进京, 韩文峰, 胡晓隆, 等.西秦岭北缘漳县新生代伸展断陷盆地确定及其地质意义[J].地学前缘, 2017, 24(5):230-244. [27] 郭进京, 韩文峰, 赵海涛, 等.西秦岭北缘漳县地区红层沉积地层格架及其地质意义[J].西北地质, 2016, 49(1):82-91. [28] 郭进京, 吉夏, 赵海涛, 等.西秦岭北缘漳县韩家沟砾岩对青藏高原东北缘地壳隆升的约束[J].地质科学, 2017, 52(4):1011-1025. [29] 方小敏, 李吉均, 朱俊杰, 等.甘肃临夏盆地新生代地层绝对年代测定与划分[J].科学通报, 1997, 42(14):1457-1471. [30] 刘宝珺.沉积岩石学[M].北京:地质出版社, 1980:104-113. [31] 姜在兴.沉积学[M].北京:石油地质出版社, 2003:41-50. [32] 朱晓敏.沉积岩石学(第四版)[M].北京:石油工业出版社, 2008:56-58. [33] 刘少峰, 张国伟.盆山关系研究的基本思路、内容和方法[J].地学前缘, 2005, 12(3):101-111. [34] 王清晨.造山带隆起剥蚀过程与沉积记录[J].地质科学, 2013, 48(1):1-31. [35] Friedman G M, Sanders J E.Principles of Sedimentology[M].New York:John Wiley & Sons, 1978. ① 甘肃省地质调查院.1: 250000(I48C002001C岷县幅)区域地质调查报告.2007. -
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XU Hehongxin, GUO Jinjing, LIU Chongqing, ZHAO Haitao, DU Zhirui. The gravel characteristics of Pliocene conglomerates in Zhangxian area on the northern margin of the West Qinling and its geological significance[J]. Geological Bulletin of China, 2020, 39(10): 1561-1572.
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Figure 1.
Geological sketch map of Zhangxian area on the northern margin of the West Qinling
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Figure 2.
A-B geological section in Zhangxian area of the northern margin of West Qinling
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Figure 3.
Pliocene conglomerate stratigraphic section in Zhangxian area, northern margin of the West Qinling
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Figure 4.
Comprehensive histogram of Pliocene Hanjiagou conglomerate in Zhangxian area, northern margin of the West Qinling
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Figure 图版Ⅰ.
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Figure 5.
Histogram of gravel diameter distribution of Pliocene Hanjiagou conglomerate in Zhangxian area
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Figure 6.
Cumulative curve of gravel diameters of Hanjiagou conglomerate in Zhangxian area
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Figure 7.
Statistics of gravel roundness of Pliocene Hanjiagou conglomerate in Zhangxian area
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Figure 8.
Variation of gravel roundness of Pliocene Hanjiagou conglomerate in Zhangxian area
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Figure 9.
Typical gravel imbrication arrangement in Pliocene Hanjiagou conglomerate in Zhangxian area
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Figure 10.
Statistics of paleocurrents of Pliocene Hanjiagou conglomerate in Zhangxian area
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Figure 11.
Gravel litho-composition of Pliocene Hanjiagou conglomerate in Zhangxian area
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Figure 12.
Variation of gravel litho-composition of Pliocene Hanjiagou Conglomerate in Zhangxian area