江苏扬州西部岗地晚第四纪沉积物的细颗粒(4—11μm)石英光释光测年及其气候地层意义
|
摘要
江苏省扬州地区西部的岗地地貌受控于区域内的NW向走滑并正断的无锡-宿迁断裂的长期活动,同时该断层的活动性也是一个关系到长三角地区地壳稳定性的重要地质问题,而研究该问题的一个关键是对该断层两侧晚第四纪地层的划分及绝对年代的确定。本文对17个采自岗地的样品使用光释光(OSL)测年法中的细颗粒(4—11μm)石英测试技术,采用SMAR法和TT-OSL法进行De值的测试及年龄对比,较系统地对江苏扬州西部岗地晚第四纪沉积物年代和地层层序进行了探讨。结果表明:SMAR法较适用于De <300 Gy的样品;TT-OSL法对于较"低"剂量的样品效果差,而对De>200 Gy的样品测试更适宜,误差相对SMAR法结果更小,与地层的沉积层序符合的更好。17个样品的OSL年龄结果表明:本区岗地主要为晚更新世沉积物,沉积速率约0.1 mm?a-1;在水系及湖岸的附近有少量全新世沉积发育。根据所有样品的宏观岩性和年龄分布,本文初步认为晚更新世沉积物主要形成于MIS5—MIS4阶段、MIS2阶段,沉积物主要为风成,对应区域上的下蜀土,堆积期间本区地壳相对稳定,无锡-宿迁断裂无明显活动。在冰后期—全新世随着气候的变暖,海平面上升,河湖泛滥,水系边缘发育少量湖沼相沉积。总体而言,本区的晚更新世—全新世沉积形成主要受到气候变化影响,构造影响不明显。
Background, aim, and scope The formation of hill geomorphology in western Yangzhou, Jiangsu Province is related to the long-term activity of NW strike-slip and continuous Wuxi-Suqian fault in the region. The division of the formation age of the Late Pleistocene — Holocene strata on the hill and the lack of systematic absolute age data restriction on the stratigraphic sequence are helpful for discussing the formation of sediments in the region since the Late Quaternary. The relationship between tectonic activity or climate change is unfavorable. In this paper, the sedimentary age of the Late Quaternary sediments in the western hilly area of Yangzhou, Jiangsu Province, has been measured by optically stimulated luminescence(OSL) dating. Based on the age results and the characteristics of sediments, the possible tectonic-climatic origin is discussed. Materials and methods In this paper, the shallow Late Quaternary sediments near Gongdao Town in western Yangzhou City were studied. The fine quartz(4 — 11 μm) extracted from the sediments were measured by SMAR method and TT-OSL method in OSL dating, and the age of De was obtained. Results The test results show that SMAR method is suitable for samples with De value less than 300 Gy, TT-OSL method is less effective for samples with "low" dose, but more suitable for samples with De value greater than 200 Gy. The error is smaller than that of SMAR method, and it is better in accordance with the sedimentary sequence of formation. Discussion OSL age shows that the sediments in the study area developed from Late Pleistocene to Holocene. The outcropped Late Quaternary depositional epoch is concentrated in the middle-late Late Pleistocene, and the Holocene depositional development is very limited. The dating of borehole samples shows that the sedimentation rate since the Late Pleistocene is about 0.1 mm ? a-1,which is very low. For the area with altitude >20 m, it is in denudation for a long time, while for the area with altitude of 10 — 20 m, there may be a process of denudation before sedimentation. The time of acceptance of sedimentation may be 30 ka from now on. For the area with altitude less than 10 m, near the lake system and so on, there are deposits formed in Holocene, and the provenances come from it. Deposits in the Yugang area are transported and then accumulated at the edge of the river system. According to the age distribution of 17 samples, the hill deposits were mainly formed in MIS5 — MIS4, MIS2 and Holocene, and the Late Pleistocene deposits were mainly dust deposits in dry and cold climate, corresponding to Xiashu soil. Holocene is a small amount of lake and marsh deposits on the edge of river and lake system, which is related to the rise of sea level and flooding of rivers and lakes. In the dry and cold accumulation stage of aeolian dust, the tectonic activity in this area should be in a very weak state, which is conducive to the stable development and retention of aeolian soil. The Late Pleistocene sediments in the Gangdi are not obviously related to tectonic activities, but are genetically related to climate. Conclusions SMAR protocol can be used for photoluminescence dating of fine-grained quartz in shallow hilly sediments in this area. However, this method is subjectively considered to be suitable for samples with De value less than 200 Gy, and TT-OSL protocol is more suitable for samples with De value greater than 200 Gy. The outcropped sediments in this area are mainly the Late Pleistocene Qizui Formation(Q3 q) and a small amount of Holocene Dadun Formation(Q4 d). Generally speaking, the sedimentary rate in this area is very slow, and the Late Quaternary of the Yangzhou section of Wuxi-Suqian fault is mainly weak activity. Recommendations and perspectives OSL dating is a powerful tool for the study of sediment chronological framework in this area. In this paper, the applicability of SMAR method for measuring De value is tested systematically. Meanwhile, TT-OSL method is used for testing De value. The test results are used to discuss the activity of Tanlu fault zone and Wuxi-Suqian fault zone and the relationship between sediment formation and tectono-climate in this area since the Late Pleistocene, and new results are obtained. Understanding and thinking can provide a good reference for future research in the region.
Background, aim, and scope The formation of hill geomorphology in western Yangzhou, Jiangsu Province is related to the long-term activity of NW strike-slip and continuous Wuxi-Suqian fault in the region. The division of the formation age of the Late Pleistocene — Holocene strata on the hill and the lack of systematic absolute age data restriction on the stratigraphic sequence are helpful for discussing the formation of sediments in the region since the Late Quaternary. The relationship between tectonic activity or climate change is unfavorable. In this paper, the sedimentary age of the Late Quaternary sediments in the western hilly area of Yangzhou, Jiangsu Province, has been measured by optically stimulated luminescence(OSL) dating. Based on the age results and the characteristics of sediments, the possible tectonic-climatic origin is discussed. Materials and methods In this paper, the shallow Late Quaternary sediments near Gongdao Town in western Yangzhou City were studied. The fine quartz(4 — 11 μm) extracted from the sediments were measured by SMAR method and TT-OSL method in OSL dating, and the age of De was obtained. Results The test results show that SMAR method is suitable for samples with De value less than 300 Gy, TT-OSL method is less effective for samples with "low" dose, but more suitable for samples with De value greater than 200 Gy. The error is smaller than that of SMAR method, and it is better in accordance with the sedimentary sequence of formation. Discussion OSL age shows that the sediments in the study area developed from Late Pleistocene to Holocene. The outcropped Late Quaternary depositional epoch is concentrated in the middle-late Late Pleistocene, and the Holocene depositional development is very limited. The dating of borehole samples shows that the sedimentation rate since the Late Pleistocene is about 0.1 mm ? a-1,which is very low. For the area with altitude >20 m, it is in denudation for a long time, while for the area with altitude of 10 — 20 m, there may be a process of denudation before sedimentation. The time of acceptance of sedimentation may be 30 ka from now on. For the area with altitude less than 10 m, near the lake system and so on, there are deposits formed in Holocene, and the provenances come from it. Deposits in the Yugang area are transported and then accumulated at the edge of the river system. According to the age distribution of 17 samples, the hill deposits were mainly formed in MIS5 — MIS4, MIS2 and Holocene, and the Late Pleistocene deposits were mainly dust deposits in dry and cold climate, corresponding to Xiashu soil. Holocene is a small amount of lake and marsh deposits on the edge of river and lake system, which is related to the rise of sea level and flooding of rivers and lakes. In the dry and cold accumulation stage of aeolian dust, the tectonic activity in this area should be in a very weak state, which is conducive to the stable development and retention of aeolian soil. The Late Pleistocene sediments in the Gangdi are not obviously related to tectonic activities, but are genetically related to climate. Conclusions SMAR protocol can be used for photoluminescence dating of fine-grained quartz in shallow hilly sediments in this area. However, this method is subjectively considered to be suitable for samples with De value less than 200 Gy, and TT-OSL protocol is more suitable for samples with De value greater than 200 Gy. The outcropped sediments in this area are mainly the Late Pleistocene Qizui Formation(Q3 q) and a small amount of Holocene Dadun Formation(Q4 d). Generally speaking, the sedimentary rate in this area is very slow, and the Late Quaternary of the Yangzhou section of Wuxi-Suqian fault is mainly weak activity. Recommendations and perspectives OSL dating is a powerful tool for the study of sediment chronological framework in this area. In this paper, the applicability of SMAR method for measuring De value is tested systematically. Meanwhile, TT-OSL method is used for testing De value. The test results are used to discuss the activity of Tanlu fault zone and Wuxi-Suqian fault zone and the relationship between sediment formation and tectono-climate in this area since the Late Pleistocene, and new results are obtained. Understanding and thinking can provide a good reference for future research in the region.
引文
江苏省地质调查研究院.2003.1∶25万南京市幅区域地质调查报告[R].南京:江苏省地质调查研究院.[Geological Survey of Jiangsu Province.2003.Report of regional geological survey of Nanjingshi(1∶250000)[R].Nanjing:Geological Survey of Jiangsu Province.]
王旭龙,卢演俦,李晓妮.2004.红光固体二极管点阵在释光测年中的光照应用[J].海洋地质与第四纪地质,24(1):133-138.[Wang X L,Lu Y C,Li X N.2004.Red led and its application to luminescence lighting[J].Marine Geology&Quaternary Geology,24(1):133-138.]
王旭龙,卢演俦,李晓妮.2005a.黄土细颗粒单测片再生法光释光测年的进展[J].核技术,28(5):383-387.[Wang X L,Lu Y C,Li X N.2005.Progress in luminescence dating of Chinese loess by Single Aliquot Regenerativedose(SAR)protocol[J].Nuclear Techniques,28(5):383-387.]
王旭龙,卢演俦,李晓妮.2005b.细颗粒石英光释光测年:简单多片再生法[J].地震地质,27(4):615-623.[Wang X L,Lu Y C,Li X N.2005.Luminescence dating of fine-grained quartz in Chinese loess:simplified multiple aliquot regenerative-dose(MAR)protocol[J].Seismology and Geology,27(4):615-623.]
王旭龙.2005.中国黄土释光测年研究--新方法和新技术[D].西安:中国科学院地球环境研究所.[Wang X L.2005.Studies on luminescence dating of Chinese Loessnew methods and protocols[D].Xi’an:Institute of Earth Environment,Chinese Academy of Sciences.]
吴中海,周春景,谭成轩,等.2016.长江经济带地区活动构造与区域地壳稳定性基本特征[J].地质力学学报,22(3):379-411.[Wu Z H,Zhou C J,Tan C X,et al.2016.The active tectonics and regional crustal stability features in the area of Yangtze river economic belt[J].Journal of Geomechanics,22(3):379-411.]
Aitken M J.1985.Thermoluminescence dating[M].London:Academic Press.
Aitken M J.1998.An introduction to optical dating[M].London:Oxford University Press.
Durcan J A,King G E,Duller G A T.2015.DRAC:Dose Rate and Age Calculator for trapped charge dating[J].Quaternary Geochronology,28:54-61.
Lu Y C,Wang X L,Wintle A G.2007.A new OSL chronology for dust accumulation in the last 130,000 yr for the Chinese Loess Plateau[J].Quaternary Research,67(1):152-160.
Lu Y C,Zhang J Z,Xie J.1988.Thermoluminescence dating of loess and paleosols from the Lantian section,Shaanxi Province,China[J].Quaternary Science Reviews,7:245-250.
Murray A S,Wintle A G.2000.Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol[J].Radiation Measurements,32(1):57-73.
Murray A S,Wintle A G.2003.The single aliquot regenerative dose protocol:potential for improvements in reliability[J].Radiation Measurements,37(4/5):377-381.
Wang X L,Lu Y C,Wintle A G.2006b.Recuperated OSLdating of fine-grained quartz in Chinese loess[J].Quaternary Geochronology,1(2):89-100.
Wang X L,Wintle A G,Lu Y C.2006a.Thermally transferred luminescence in fine-grained quartz from Chinese loess:basic observations[J].Radiation Measurements,41(6):649-658.
王旭龙,卢演俦,李晓妮.2004.红光固体二极管点阵在释光测年中的光照应用[J].海洋地质与第四纪地质,24(1):133-138.[Wang X L,Lu Y C,Li X N.2004.Red led and its application to luminescence lighting[J].Marine Geology&Quaternary Geology,24(1):133-138.]
王旭龙,卢演俦,李晓妮.2005a.黄土细颗粒单测片再生法光释光测年的进展[J].核技术,28(5):383-387.[Wang X L,Lu Y C,Li X N.2005.Progress in luminescence dating of Chinese loess by Single Aliquot Regenerativedose(SAR)protocol[J].Nuclear Techniques,28(5):383-387.]
王旭龙,卢演俦,李晓妮.2005b.细颗粒石英光释光测年:简单多片再生法[J].地震地质,27(4):615-623.[Wang X L,Lu Y C,Li X N.2005.Luminescence dating of fine-grained quartz in Chinese loess:simplified multiple aliquot regenerative-dose(MAR)protocol[J].Seismology and Geology,27(4):615-623.]
王旭龙.2005.中国黄土释光测年研究--新方法和新技术[D].西安:中国科学院地球环境研究所.[Wang X L.2005.Studies on luminescence dating of Chinese Loessnew methods and protocols[D].Xi’an:Institute of Earth Environment,Chinese Academy of Sciences.]
吴中海,周春景,谭成轩,等.2016.长江经济带地区活动构造与区域地壳稳定性基本特征[J].地质力学学报,22(3):379-411.[Wu Z H,Zhou C J,Tan C X,et al.2016.The active tectonics and regional crustal stability features in the area of Yangtze river economic belt[J].Journal of Geomechanics,22(3):379-411.]
Aitken M J.1985.Thermoluminescence dating[M].London:Academic Press.
Aitken M J.1998.An introduction to optical dating[M].London:Oxford University Press.
Durcan J A,King G E,Duller G A T.2015.DRAC:Dose Rate and Age Calculator for trapped charge dating[J].Quaternary Geochronology,28:54-61.
Lu Y C,Wang X L,Wintle A G.2007.A new OSL chronology for dust accumulation in the last 130,000 yr for the Chinese Loess Plateau[J].Quaternary Research,67(1):152-160.
Lu Y C,Zhang J Z,Xie J.1988.Thermoluminescence dating of loess and paleosols from the Lantian section,Shaanxi Province,China[J].Quaternary Science Reviews,7:245-250.
Murray A S,Wintle A G.2000.Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol[J].Radiation Measurements,32(1):57-73.
Murray A S,Wintle A G.2003.The single aliquot regenerative dose protocol:potential for improvements in reliability[J].Radiation Measurements,37(4/5):377-381.
Wang X L,Lu Y C,Wintle A G.2006b.Recuperated OSLdating of fine-grained quartz in Chinese loess[J].Quaternary Geochronology,1(2):89-100.
Wang X L,Wintle A G,Lu Y C.2006a.Thermally transferred luminescence in fine-grained quartz from Chinese loess:basic observations[J].Radiation Measurements,41(6):649-658.