塔里木盆地西北缘露头区中-下奥陶统碳酸盐岩层序结构、沉积演化及海平面变化
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摘要
柯坪和巴楚地区出露了较完整的中-下奥陶统碳酸盐岩沉积地层,牙形石古生物地层对比表明柯坪水泥厂露头鹰山组与下伏蓬莱坝组呈不整合接触,缺失5.9 Ma地层,与上覆一间房组呈整合接触,两者共沉积约14.4 Ma地层。综合露头、前人地化指标及盆内塔中隆起区井震资料对比分析,将鹰山组至一间房组碳酸盐岩划分出2套以主要不整合面为边界的复合(二级)层序(CS1和CS2),内部包含5套以次一级暴露面、岩相突变面为边界的三级层序(Sq1—Sq5),可进行区域对比。通过对手标本和镜下薄片分析,归纳出11种和6种灰岩、白云岩沉积微相类型,它们以特定的相序组合成台缘礁滩复合体、潮坪内碎屑滩、台内浅滩-滩后、生屑滩、滩间海、云坪等7种微相组合,指示了研究区由CS1时期干旱-半干旱局限台地潟湖、云坪沉积向CS2时期开阔台地内碎屑滩、生屑滩和台地边缘礁滩复合体转变及中奥陶世末期台地被淹没的过程。利用Fischer图解重建了露头剖面相对海平面变化趋势,其与岩相旋回和地化指标所反应的古水深演化具有高度一致性,并与Haq海平面变化曲线整体上可进行对比。海平面变化对层序结构和沉积演化起主导作用,局部受构造和海平面变化双重因素制约,其中,四级海平面变化对相序组合具有明显的控制作用。
Carbonate deposits of the Middle and Lower Ordovician develops well on Kalpin and Bachu outcrops,north-western margin of Tarim Basin.Conodont biostratigraphy shows that the unconformable contact exists between the Ying-shan Formation and its underlying Penglaiba Formation with a 5.9 Ma hiatus,while the Yingshan Formation and its overlying Yijianfang Formation are conformable with a total of 14.4 Ma deposition.Comprehensive analysis of outcrops,existing geochemical indicators,and 3-D seismic and well logging data in Tazhong uplift,indicates that the carbonate rocks of the Yingshan and Yijianfang Formations can be divided into two composite(second-order) sequences(CS1 and CS2) along the major unconformity.From within,five third-order sequences(Sq1-Sq5) are identified along sub-level exposed unconformities or lithofacies mutation boundaries,which may be used for regional correlation.Eleven and six microfacies types are recognized for limestones and dolomites respectively through observation of hand specimens and thin section,which have in turn combined into seven micro-facies associations according to specific facies sequence,namely the reef-shoal complexes at platform margin,clastic shoals within tidal flat,intra-platform shallows and back shoals,bioclast shoals,inter-shoal sea and dolomite flats,indicating a transition from the arid-to-semi-arid restricted platform lagoon and dolomite flat sedimentation of the CS1 to the open intra-platform clastic shoal,bioclast shoal and reef-shoal complex at platform margin of the CS2,as well as the platform drowning in the late of Middle Ordovician.In addition,the fluctuation of relative sea level was reconstructed for the outcrop areas by means of Fischer plot.It's highly consistent with the paleo-water depth evolution demonstrated by facies cycle and geochemical indicators,and can also be correlated with Haq eustatic curve.The eustatic variation dominates the evolution of sequence architectures and deposits,despite that local architectures and deposits are restricted by both eustatic variation and tectonic movement.And the fourth-order eustatic variation starkly controls the facies sequence association.
Carbonate deposits of the Middle and Lower Ordovician develops well on Kalpin and Bachu outcrops,north-western margin of Tarim Basin.Conodont biostratigraphy shows that the unconformable contact exists between the Ying-shan Formation and its underlying Penglaiba Formation with a 5.9 Ma hiatus,while the Yingshan Formation and its overlying Yijianfang Formation are conformable with a total of 14.4 Ma deposition.Comprehensive analysis of outcrops,existing geochemical indicators,and 3-D seismic and well logging data in Tazhong uplift,indicates that the carbonate rocks of the Yingshan and Yijianfang Formations can be divided into two composite(second-order) sequences(CS1 and CS2) along the major unconformity.From within,five third-order sequences(Sq1-Sq5) are identified along sub-level exposed unconformities or lithofacies mutation boundaries,which may be used for regional correlation.Eleven and six microfacies types are recognized for limestones and dolomites respectively through observation of hand specimens and thin section,which have in turn combined into seven micro-facies associations according to specific facies sequence,namely the reef-shoal complexes at platform margin,clastic shoals within tidal flat,intra-platform shallows and back shoals,bioclast shoals,inter-shoal sea and dolomite flats,indicating a transition from the arid-to-semi-arid restricted platform lagoon and dolomite flat sedimentation of the CS1 to the open intra-platform clastic shoal,bioclast shoal and reef-shoal complex at platform margin of the CS2,as well as the platform drowning in the late of Middle Ordovician.In addition,the fluctuation of relative sea level was reconstructed for the outcrop areas by means of Fischer plot.It's highly consistent with the paleo-water depth evolution demonstrated by facies cycle and geochemical indicators,and can also be correlated with Haq eustatic curve.The eustatic variation dominates the evolution of sequence architectures and deposits,despite that local architectures and deposits are restricted by both eustatic variation and tectonic movement.And the fourth-order eustatic variation starkly controls the facies sequence association.
引文
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[19] 赵宗举,赵治信,黄智斌,等.塔里木盆地奥陶系牙形石带及沉积层序[J].地层学杂志,2006,30(3):193-203.Zhao Zongju,Zhao Zhixin,Huang Zhibin,et al.Ordovician conodont zones and sedimentary sequences of the Tarim Basin,Xin Jiang,N W China[J].Journal of Stratigraphy,2006,30(3):193-203.
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[21] 王清龙,林畅松,李浩,等.塔里木盆地西北缘中下奥陶统碳酸盐岩沉积微相特征及演化[J].天然气地球科学,2018,29(9):1274-1288.Wang Qinglong,Lin Changsong,Li Hao,et al.Carbonate sedimentary microfacies characteristic and evolution of the middle and lower Ordovician in northwestern of Tarim basin[J].Natural Gas Geoscience,2018,29(9):1274-1288.
[22] Fischer A G.The lofter cyclothems of the alpine Triassic [J].Kansas Geological Survey Bulletin,1964,169:107-149.
[23] 鲍志东,朱井泉,江茂生,等.海平面升降中的元素地球化学响应-以塔中地区奥陶纪为例[J].沉积学报,1998,16(4):32-36Bao Zhidong,Zhu Jingquan,Jiang Maosheng,et al.Isotope and trace element evolution:Responding to sea-level fluctuation-an example of Ordovician in middle Tarim basin[J].Acta Sedimentologica Sinica,1998,16(4):32-36.
[24] 胡明毅.塔北柯坪奥陶系碳酸盐岩地球化学特征及环境意义[J].石油与天然气地质,1994,15(2):158-163.Hu Mingyi.Geochemical characters and envoironmental significance of Ordovician carbonate rocks in Keping area,Tarim basin[J].Oil & Gas Geology,1994,15(2):158-163.
[25] Haq B U,Stephen R S.A chronology of Paleozoic sea-level changes[J].Science,2008,322(5898):64-68.
[2] Clyde H,Moore.Carbonate reservoirs:porosity evolution and diagenesis in a sequence stratigraphic framework[M].Holland:Elsevier BV,2001:349-352.
[3] Erik Flugel.Microfacies of carbonate rocks:analysis,interpretation and application(2nd edition)[M].Berlin:Springer-Verlag,2004:1-6.
[4] 林畅松,杨海军,蔡振中,等.塔里木盆地奥陶纪碳酸盐岩台地的层序结构演化及其对盆地过程的响应[J].沉积学报,2013,31(5):907-919.Lin Changsong,Yang Haijun,Cai Zhenzhong,et al.Evolution of depositional architecture of the Ordovician carbonate platform in the Tarim basin and its response to basin processes[J].Acta Sedimentologica Sinica,2013,31(5):907-919.
[5] 郭峰,赖生华,郭岭,等.塔里木盆地大阪塔格奥陶系地层层序及沉积演化[J].地层学杂志,2010,34(2):135-144.Guo Feng,Lai Shenghua,Guo Ling,et al.Ordovician sequence stratigraphy and sedimentology in the Dabantage area,Tarim Basin[J].Journal of Stratigraphy,2010,34(2):135-144.
[6] 赵宗举,潘文庆,张丽娟,等.塔里木盆地奥陶系层序地层格架[J].大地构造与成矿学,2009,33(1):175-188.Zhao Zongju,Pan Wenqing,Zhang Lijuan,et al.Sequence stratigraphy in the Ordovician in the Tarim basin[J].Geotectonica Et Metallogenia,2009,33(1):175-188.
[7] 赵宗举,吴兴宁,潘文庆,等.塔里木盆地奥陶纪层序岩相古地理[J].沉积学报,2009,27(5):939-955.Zhao Zongju,Wu Xingning,Pan Wenqing,et al.Sequence lithofacies paleogeography of Ordovician in Tarim basin[J].Acta Sedimentologica Sinica,2009,27(5):939-955.
[8] 于炳松,陈建强,林畅松,等.塔里木盆地奥陶系层序地层格架及其对碳酸盐岩储集体发育的控制[J].石油与天然气地质,2005,26(3):305-316.Yu Bingsong,Chen Jianqiang,Lin Changsong,et al.Sequence stratigraphic framework and its control on development of Ordovician carbonate reservoir in Tarim basin[J].Oil & Gas Geology,2005,26(3):305-316.
[9] 赵治信,张桂芝,肖继南,等.新疆古生代地层及牙形石[M].北京:石油工业出版社,2002:1-88.Zhao Zhixin,Zhang Guizhi,Xiao Jinan,et al.Paleozoic stratigraphy and conodonts in Xinjiang[M].Beijing:Petroleum Industry Press,2002:1-88.
[10] 高志前,樊太亮,焦志峰,等.塔里木盆地寒武-奥陶系碳酸盐岩台地样式及其沉积响应特征[J].沉积学报,2006,24(1):19-27.Gao Zhiqian,Fan Tailiang,Jiao Zhifeng,et al.The structural types and depositional characteristics of carbonate platform in the Cambrian-Ordovician of Tarim basin[J].Acta Sedimentologica Sinica,2006,24(1):19-27.
[11] 高志前,樊太亮,李岩,等.塔里木盆地寒武-奥陶纪海平面升降变化规律研究[J].吉林大学学报(地球科学版),2006,36(4):550-556.Gao Zhiqian,Fan Tailiang,Li Yan,et al.Study on eustatic sea-level change rule in Cambrian-Ordovician in Tarim basin[J].Journal of Jilin University(Earth Science Edition),2006,36(4):550-556.
[12] Lin Changsong,Yang Haijun,Liu Jingyan,et al.Distribution and erosion of the Paleozoic tectonic unconformities in the Tarim basin,Northwest China:Significance for the evolution of paleo-uplifts and tectonic geography during deformation[J].Journal of Asian Earth Sciences,2012,46:1-19.
[13] 林畅松,杨海军,刘景彦,等.塔里木早古生代原盆地古隆起地貌和古地理格局与地层圈闭发育分布[J].石油与天然气地质,2008,29(2):189-197.Lin Changsong,Yang Haijun,Liu Jingyan,et al.Paleohigh geomorphology and paleogeographic framework and their controls on the formation and distribution of stratigraphic traps in the Tarim basin[J].Oil & Gas Geology,2008,29(2):189-197.
[14] Lin Changsong,Li Hao,Liu Jingyan,et al.Major unconformities,tectonostratigraphic framework and evolution of the superimposed Tarim basin,Northwest China[J].Journal of Earth Science,2012,23(4):395-407.
[15] 林畅松,李思田,刘景彦,等.塔里木盆地古生代重要演化阶段的古构造格局与古地理演化[J].岩石学报,2011,27(1):210-218.Lin Changsong,Li Sitian,Liu Jingyan,et al.Tectonic framework and paleo-geographic evolution of the Tarim basin during the Paleozoic major evolutionary stages[J].Acta Petrologica Sinica,2011,27(1):210-218.
[16] 丁文龙,林畅松,漆立新,等.塔里木盆地巴楚隆起构造格架及形成演化[J].地学前缘,2008,15(2):242-252.Ding Wenlong,Lin Changsong,Qi Lixin,et al.Structural framework and evolution of Bachu uplift in Tarim basin[J].Earth Science Frontiers,2008,15(2):242-252.
[17] 蔡习尧,钱一雄,陈跃,等.塔中地区中下奥陶统划分与对比[J],新疆石油地质,2007,28(3):292-295.Cai Xiyao,Qian Yixiong,Chen Yue,et al.Division and correlation of middle-lower Ordovician in Tazhong area,Tarim basin[J].Xinjiang Petroleum Geology,2007,28(3):292-295.
[18] 赵治信,谭泽金,唐鹏,等.塔里木盆地覆盖区奥陶纪生物地层[J].新疆石油地质,1999,20(6):493-500.Zhao Zhixin,Tan Zejin,Tang Peng,et al.Biostratigraphy of Ordovician in cover area of Tarim basin [J].Xinjiang Petroleum Geology,1999,20(6):493-500.
[19] 赵宗举,赵治信,黄智斌,等.塔里木盆地奥陶系牙形石带及沉积层序[J].地层学杂志,2006,30(3):193-203.Zhao Zongju,Zhao Zhixin,Huang Zhibin,et al.Ordovician conodont zones and sedimentary sequences of the Tarim Basin,Xin Jiang,N W China[J].Journal of Stratigraphy,2006,30(3):193-203.
[20] 景秀春.塔里木盆地奥陶纪台地相区牙形石及寒武-奥陶系界线[D].北京:中国地质大学(北京),2009.Jing Xiuchun.The Ordovician conodonts and the Cambrian-Ordovician boundary at the platform facies in the Tarim basin,China[D].Beijing:China University of Geosciences(Beijing),2009.
[21] 王清龙,林畅松,李浩,等.塔里木盆地西北缘中下奥陶统碳酸盐岩沉积微相特征及演化[J].天然气地球科学,2018,29(9):1274-1288.Wang Qinglong,Lin Changsong,Li Hao,et al.Carbonate sedimentary microfacies characteristic and evolution of the middle and lower Ordovician in northwestern of Tarim basin[J].Natural Gas Geoscience,2018,29(9):1274-1288.
[22] Fischer A G.The lofter cyclothems of the alpine Triassic [J].Kansas Geological Survey Bulletin,1964,169:107-149.
[23] 鲍志东,朱井泉,江茂生,等.海平面升降中的元素地球化学响应-以塔中地区奥陶纪为例[J].沉积学报,1998,16(4):32-36Bao Zhidong,Zhu Jingquan,Jiang Maosheng,et al.Isotope and trace element evolution:Responding to sea-level fluctuation-an example of Ordovician in middle Tarim basin[J].Acta Sedimentologica Sinica,1998,16(4):32-36.
[24] 胡明毅.塔北柯坪奥陶系碳酸盐岩地球化学特征及环境意义[J].石油与天然气地质,1994,15(2):158-163.Hu Mingyi.Geochemical characters and envoironmental significance of Ordovician carbonate rocks in Keping area,Tarim basin[J].Oil & Gas Geology,1994,15(2):158-163.
[25] Haq B U,Stephen R S.A chronology of Paleozoic sea-level changes[J].Science,2008,322(5898):64-68.