鄂尔多斯盆地长8油层组古地理环境与沉积特征
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摘要
通过对地震、钻井资料的综合分析,认为延长组下部长8沉积时期鄂尔多斯湖盆可能不具有明显的"南陡北缓"的古地貌特征,也可能不存在大面积分布的半深湖—深湖环境。长8期湖盆古地形较为平坦,坡降不足0.1°或2m/km,气候较为干旱,湖泊水体为微咸水,水深小于10 m。具有如下特征的浅水湖泊三角洲为此时盆地的主体沉积类型:1)砂岩以中—细粒岩屑长石砂岩和长石岩屑砂岩为主;2)三角洲前缘延伸范围大(80～100 km),并频繁暴露;3)砂体主要为水下分支河道沉积成因;4)河口坝和重力流沉积不发育;5)吉尔伯特型三角洲具有的顶积、前积和底积三元结构在长8不发育。盆地南北古地形之间的显著差异出现在长8之后的长7早期,受印支运动及与盆地西南边缘毗邻的西秦岭强烈造山活动的影响,鄂尔多斯盆地的基底不对称挠曲变形,从而形成"南陡北缓"的盆地古地貌格局。从长7开始至晚三叠世末,盆内坡折带普遍发育,具有顶积、前积和底积三元结构的吉尔伯特型三角洲也就成为盆地内部最主要的沉积类型之一。
Data of seismic and bore hole show that the palaeotopography of the Triassic Chang 8,in the lower part of the Yanchang Formation,Ordos basin,was possibly not "steep to the south while gentle to the north" style as the previous studies suggested,and large areas of bathyal or abyssal areas were also impossible in this age.The bed form of the lake was very gentle on the basin scale with the slope angle no more than 0.1°,or 2 m/km.The climate was possibly a little dry and the mildly brackish water with depth no more than 10m was the dominant media of the sediments.Vertical or high angel burrows and root systems,coal seams or coaly mudstones and plant fossils of Neocalamites are commonly inclusions either at the edge or in the center of the basin.Shallow lacustrine delta with the following characters were well developed in this basin at that time: 1) detrital components mostly medium-fine graded lithic arkose and feldspathic litharenite,2)wide delta front with 80~100 km in length and uncovered frequently to the air,3) sandstones mainly the subaqueous distributary channel deposits,4) mouthbar and the gravity flow deposits being infrequent,5) topsets,foresets and bottomsets of the Gilbert Delta not developed. Obvious difference of the slopes of the southern part and the northern part of the basin emerged in the early Chang 7,tightly following the Chang 8 in age.Triggered by the early Indosinian movement and the uplift of the west Qinling Mountains at the southwestern margin of the Ordos basin,the base of this basin was bended over unsymmetrically and the palaeotopography of the "steep to the south while gentle to the north" was generated.And from this time(Chang 7) to the end of the late Triassic slope-breaks and deltas with three elements of topsets,foresets and bottomsets were well developed in the basin.
Data of seismic and bore hole show that the palaeotopography of the Triassic Chang 8,in the lower part of the Yanchang Formation,Ordos basin,was possibly not "steep to the south while gentle to the north" style as the previous studies suggested,and large areas of bathyal or abyssal areas were also impossible in this age.The bed form of the lake was very gentle on the basin scale with the slope angle no more than 0.1°,or 2 m/km.The climate was possibly a little dry and the mildly brackish water with depth no more than 10m was the dominant media of the sediments.Vertical or high angel burrows and root systems,coal seams or coaly mudstones and plant fossils of Neocalamites are commonly inclusions either at the edge or in the center of the basin.Shallow lacustrine delta with the following characters were well developed in this basin at that time: 1) detrital components mostly medium-fine graded lithic arkose and feldspathic litharenite,2)wide delta front with 80~100 km in length and uncovered frequently to the air,3) sandstones mainly the subaqueous distributary channel deposits,4) mouthbar and the gravity flow deposits being infrequent,5) topsets,foresets and bottomsets of the Gilbert Delta not developed. Obvious difference of the slopes of the southern part and the northern part of the basin emerged in the early Chang 7,tightly following the Chang 8 in age.Triggered by the early Indosinian movement and the uplift of the west Qinling Mountains at the southwestern margin of the Ordos basin,the base of this basin was bended over unsymmetrically and the palaeotopography of the "steep to the south while gentle to the north" was generated.And from this time(Chang 7) to the end of the late Triassic slope-breaks and deltas with three elements of topsets,foresets and bottomsets were well developed in the basin.
引文
1郑希民,宋广寿,王多云,等.陕甘宁盆地陇东地区长8油组厚层非均质砂体的沉积学解剖[J].沉积学报,2003,21(2):273-276[Zheng Ximin,Song Guangshou,Wang Duoyun,et al.Sedimentary a-natomy of thick anisotropic sandstones for Chang 8 oil-bearing intervalin Longdong area,Shaan-Gan-Ning Basin[J].Acta SedimentologicaSinica,2003,21(2):273-276]
2王志坤,王多云,郑希民,等.陕甘宁盆地陇东地区三叠系延长统长6—长8储层沉积特征及物性分析[J].天然气地球科学,2003,14(5):380-385[Wang Zhikun,Wang Duoyun,Zheng Ximin,et al.Depositional characteristics and physical behavior analysis of theChang 6-8 reservoir of Triassic Yanchang Formation in Longdong area,Shaan-Gan-Ning basin[J].Natural Gas Geoscience,2003,14(5):380-385]
3武福礼,李文厚,李玉宏,等.鄂尔多斯盆地上三叠统延长组三角洲沉积与演化[J].古地理学报,2004,6(3):307-315[Wu Fuli,Li Wenhou,Li Yuhong.Delta sediments and evolution of the YanchangFormation of Upper Triassic in Ordos Basin[J].Journal of Palaeogra-phy,2004,6(3):307-315]
4杨友运.鄂尔多斯盆地南部延长组沉积体系与层序特征[J].地质通报,2005,24(4):369-272[Yang Youyun.Characteristics of thedepositional systems and sequence evolution of the Yanchang Formationin the Southern Ordos Basin[J].Geological Bulletin of China,2005,24(4):369-272]
5杨友运,张蓬勃,张忠义.鄂尔多斯盆地西峰油田长8油组辫状河三角洲沉积特征与层序演化[J].地质科技情报[J].2005,24(1):45-48[Yang Youyun,Zhang Pengbo,Zhang Zhongyi.Sedimen-tary features and sequence evolution of braided river delta of Chang 8oil-bearing interval of Xifeng Oilfield in Ordos Basin[J].GeologicalScience and Technology Information,2005,24(1):45-48]
6杨华,付强,付金华.鄂尔多斯晚三叠世盆地沉积层序与油气成藏[M].北京:地质出版社,2007[Yang Hua,Fu Qiang,Fu Jin-hua.Sedimentary Sequence and Petroleum Play of the Late Triassic,Ordos Basin[M].Beijing:Geological Publishing House,2007]
7邓秀芹,蔺昉晓,刘显阳,等.鄂尔多斯盆地三叠系延长组沉积演化及其与早印支运动关系的探讨[J].古地理学报,2008,10(2):159-166[Deng Xiuqin,Lin Fangxiao,Liu Xianyang.Discussion on re-lationship between sedimentary evolution of the Triassic Yanchang For-mation and the Early Indosinian movement in Ordos basin[J].Journalof Palaeography,2008,10(2):159-166]
8李相博,郭彦如,刘化清,等.浅谈小波分析在鄂尔多斯盆地延长组层序地层划分中的应用[J].天然气地球科学,2006,17(6):779-782[Li Xiangbo,Guo Yanru,Liu Huaqing,et al.The applicationof wavelet analysis in sequence stratigraphic subdivision of the Yan-chang Formation,Ordos basin[J].Natural Gas Geosciences,2006,17(6):779-782]
9郭彦如,刘化清,李相博,等.大型坳陷湖盆层序地层格架的研究方法体系———以鄂尔多斯盆地中生界延长组为例[J].沉积学报,2008,26(3):384-390[Guo Yanru,Liu Huaqing,Li Xiangbo,et al.Method system on studying sequence stratigraphic framework of largesagged lacustrine basin:A case study from Mesozoic Yanchang Fm.,Ordos Basin[J].Acta Sedimentologica Sinica,2008,26(3):384-390]
10魏永佩,陈会鑫.沉积盆地碎屑岩原始厚度恢复经验图板———一种快速实用的方法[J].石油与天然气地质,1999,20(1):90-93[Wei Yongpei,Chen Huixin.Recovering plate on initial thickness ofclastic rocks in sedimentary basins:A quick and practical method[J].Oil&Gas Geology,1999,20(1):90-93]
11李元昊,刘池洋,独育国,等.鄂尔多斯盆地西北部上三叠统延长组长8油层组浅水三角洲沉积特征及湖岸线控砂[J].古地理学报,2009,11(3):265-274[Li Yuanhao,Liu Chiyang,Du Yu-guo,et al.Sedimentary characteristics of shallow water delta and lakeshoreline control on sandbodies of Chang 8 oil-bearing interval of theUpper Triassic Yanchang Formation in northwestern Ordos Basin[J].Journal of Palaeogeography,2009,11(3):265-274]
12韩永林,王成玉,王海红,等.姬塬地区长8油层组浅水三角洲沉积特征[J].沉积学报,2009,27(6):1057-1064[Han Yonglin,Wang Chengyu,Wang Haihong,et al.Sedimentary characteristics ofshallow-water deltas in Chang-8 subsection of Yanchang Formation,Jiyuan area[J].Acta Sedimentologica Sinica,2009,27(6):1057-1064]
13陈飞,樊太亮,高志前.鄂尔多斯盆地富县地区上三叠统延长组砂质碎屑流的沉积特征[C]∥第四届全国沉积学大会论文集,2009:480-488[Chen Fei,Fan Tailiang,Gao Zhiqian.SedimentaryCharacteristics of Debris Flow of the Upper Triassic Yanchang Forma-tion,Fuxian District,Ordos Basin[C]∥Symposium of the 4th Na-tional Sedimentary Congress.2009:480-488]
14谢渊,王剑,刘家铎,等.鄂尔多斯盆地东南部延长组湖盆致密砂岩储层层序地层与油气勘探[M].北京:地质出版社,2004[Xie Yuan,Wang Jian,Liu Jiaduo,et al.Reservoir Sequence Stra-tigraphy and Petroleum Exploration of Tight Sandstones of the Yan-chang Formation,Southeastern Ordos Basin[M].Beijing:GeologicalPublishing House,2004]
15罗顺社,银晓.鄂尔多斯盆地姬塬地区延长组长8沉积相的研究[J].石油天然气学报,2008,30(4):4-9[Luo Shunshe,Yin Xi-ao.Study on the sedimentary facies of Chang 8 of the Yanchang For-mation in the Jiyuan area,Ordos basin[J].Journal of Oil and GasTechnology,2008,30(4):4-9]
16全国地层委员会.中国地层指南及中国地层指南说明书(修订版)[M].北京:地质出版社,2001[National Commission on Stra-tigraphy.China Stratigraphic Guide and the Manual of China Strati-graphic Guide(Revised Edition)[M].Beijing:Geological Publish-ing House,2001]
17刘化清,李相博,白云来,等.鄂尔多斯盆地“崆峒山砾岩”成因初步分析[J].天然气地球科学,2006,17(5):668-671[LiuHuaqing,Li Xiangbo,Bai Yunlai,et al.Origin of the“KongtongConglomerate”in Ordos Basin[J].Natural Gas Geoscience,2006,17(5):668-671]
18邓秀芹,李文厚,刘新社,等.鄂尔多斯盆地中三叠统与上三叠统地层界线讨论[J].地质学报,2009,83(8):1089-1096[DengXiuqin,Li Wenhou,Liu Xinshe,et al.Discussion on the stratigraphicboundary between the middle Triassic and Upper Triassic[J].ActaGeologica Sinica,2009,83(8):1089-1096]
19赵俊兴,陈洪德,付锁堂,等.鄂尔多斯盆地南部延长组中几个重要事件沉积及其油气聚集关系[J].矿物岩石,2008,28(3):90-95[Zhao Junxing,Chen Hongde,Fu Suotang,et al.Discussionon some important depositional events and their relationship with hy-drocarbon accumulation of Yanchang Formation in South Ordos Basin[J].Mineral Petrology,2008,28(3):90-95]
20梅志超,林晋炎.湖泊三角洲的地层模式和骨架砂体的特征[J].沉积学报,1991,9(4):1-11[Mei Zhichao,Lin Jinyan.Strati-graphic pattern and character of skeletal sand bodies in lacustrine del-tas[J].Acta Sedimentologica Sinica,1991,9(4):1-11]
2王志坤,王多云,郑希民,等.陕甘宁盆地陇东地区三叠系延长统长6—长8储层沉积特征及物性分析[J].天然气地球科学,2003,14(5):380-385[Wang Zhikun,Wang Duoyun,Zheng Ximin,et al.Depositional characteristics and physical behavior analysis of theChang 6-8 reservoir of Triassic Yanchang Formation in Longdong area,Shaan-Gan-Ning basin[J].Natural Gas Geoscience,2003,14(5):380-385]
3武福礼,李文厚,李玉宏,等.鄂尔多斯盆地上三叠统延长组三角洲沉积与演化[J].古地理学报,2004,6(3):307-315[Wu Fuli,Li Wenhou,Li Yuhong.Delta sediments and evolution of the YanchangFormation of Upper Triassic in Ordos Basin[J].Journal of Palaeogra-phy,2004,6(3):307-315]
4杨友运.鄂尔多斯盆地南部延长组沉积体系与层序特征[J].地质通报,2005,24(4):369-272[Yang Youyun.Characteristics of thedepositional systems and sequence evolution of the Yanchang Formationin the Southern Ordos Basin[J].Geological Bulletin of China,2005,24(4):369-272]
5杨友运,张蓬勃,张忠义.鄂尔多斯盆地西峰油田长8油组辫状河三角洲沉积特征与层序演化[J].地质科技情报[J].2005,24(1):45-48[Yang Youyun,Zhang Pengbo,Zhang Zhongyi.Sedimen-tary features and sequence evolution of braided river delta of Chang 8oil-bearing interval of Xifeng Oilfield in Ordos Basin[J].GeologicalScience and Technology Information,2005,24(1):45-48]
6杨华,付强,付金华.鄂尔多斯晚三叠世盆地沉积层序与油气成藏[M].北京:地质出版社,2007[Yang Hua,Fu Qiang,Fu Jin-hua.Sedimentary Sequence and Petroleum Play of the Late Triassic,Ordos Basin[M].Beijing:Geological Publishing House,2007]
7邓秀芹,蔺昉晓,刘显阳,等.鄂尔多斯盆地三叠系延长组沉积演化及其与早印支运动关系的探讨[J].古地理学报,2008,10(2):159-166[Deng Xiuqin,Lin Fangxiao,Liu Xianyang.Discussion on re-lationship between sedimentary evolution of the Triassic Yanchang For-mation and the Early Indosinian movement in Ordos basin[J].Journalof Palaeography,2008,10(2):159-166]
8李相博,郭彦如,刘化清,等.浅谈小波分析在鄂尔多斯盆地延长组层序地层划分中的应用[J].天然气地球科学,2006,17(6):779-782[Li Xiangbo,Guo Yanru,Liu Huaqing,et al.The applicationof wavelet analysis in sequence stratigraphic subdivision of the Yan-chang Formation,Ordos basin[J].Natural Gas Geosciences,2006,17(6):779-782]
9郭彦如,刘化清,李相博,等.大型坳陷湖盆层序地层格架的研究方法体系———以鄂尔多斯盆地中生界延长组为例[J].沉积学报,2008,26(3):384-390[Guo Yanru,Liu Huaqing,Li Xiangbo,et al.Method system on studying sequence stratigraphic framework of largesagged lacustrine basin:A case study from Mesozoic Yanchang Fm.,Ordos Basin[J].Acta Sedimentologica Sinica,2008,26(3):384-390]
10魏永佩,陈会鑫.沉积盆地碎屑岩原始厚度恢复经验图板———一种快速实用的方法[J].石油与天然气地质,1999,20(1):90-93[Wei Yongpei,Chen Huixin.Recovering plate on initial thickness ofclastic rocks in sedimentary basins:A quick and practical method[J].Oil&Gas Geology,1999,20(1):90-93]
11李元昊,刘池洋,独育国,等.鄂尔多斯盆地西北部上三叠统延长组长8油层组浅水三角洲沉积特征及湖岸线控砂[J].古地理学报,2009,11(3):265-274[Li Yuanhao,Liu Chiyang,Du Yu-guo,et al.Sedimentary characteristics of shallow water delta and lakeshoreline control on sandbodies of Chang 8 oil-bearing interval of theUpper Triassic Yanchang Formation in northwestern Ordos Basin[J].Journal of Palaeogeography,2009,11(3):265-274]
12韩永林,王成玉,王海红,等.姬塬地区长8油层组浅水三角洲沉积特征[J].沉积学报,2009,27(6):1057-1064[Han Yonglin,Wang Chengyu,Wang Haihong,et al.Sedimentary characteristics ofshallow-water deltas in Chang-8 subsection of Yanchang Formation,Jiyuan area[J].Acta Sedimentologica Sinica,2009,27(6):1057-1064]
13陈飞,樊太亮,高志前.鄂尔多斯盆地富县地区上三叠统延长组砂质碎屑流的沉积特征[C]∥第四届全国沉积学大会论文集,2009:480-488[Chen Fei,Fan Tailiang,Gao Zhiqian.SedimentaryCharacteristics of Debris Flow of the Upper Triassic Yanchang Forma-tion,Fuxian District,Ordos Basin[C]∥Symposium of the 4th Na-tional Sedimentary Congress.2009:480-488]
14谢渊,王剑,刘家铎,等.鄂尔多斯盆地东南部延长组湖盆致密砂岩储层层序地层与油气勘探[M].北京:地质出版社,2004[Xie Yuan,Wang Jian,Liu Jiaduo,et al.Reservoir Sequence Stra-tigraphy and Petroleum Exploration of Tight Sandstones of the Yan-chang Formation,Southeastern Ordos Basin[M].Beijing:GeologicalPublishing House,2004]
15罗顺社,银晓.鄂尔多斯盆地姬塬地区延长组长8沉积相的研究[J].石油天然气学报,2008,30(4):4-9[Luo Shunshe,Yin Xi-ao.Study on the sedimentary facies of Chang 8 of the Yanchang For-mation in the Jiyuan area,Ordos basin[J].Journal of Oil and GasTechnology,2008,30(4):4-9]
16全国地层委员会.中国地层指南及中国地层指南说明书(修订版)[M].北京:地质出版社,2001[National Commission on Stra-tigraphy.China Stratigraphic Guide and the Manual of China Strati-graphic Guide(Revised Edition)[M].Beijing:Geological Publish-ing House,2001]
17刘化清,李相博,白云来,等.鄂尔多斯盆地“崆峒山砾岩”成因初步分析[J].天然气地球科学,2006,17(5):668-671[LiuHuaqing,Li Xiangbo,Bai Yunlai,et al.Origin of the“KongtongConglomerate”in Ordos Basin[J].Natural Gas Geoscience,2006,17(5):668-671]
18邓秀芹,李文厚,刘新社,等.鄂尔多斯盆地中三叠统与上三叠统地层界线讨论[J].地质学报,2009,83(8):1089-1096[DengXiuqin,Li Wenhou,Liu Xinshe,et al.Discussion on the stratigraphicboundary between the middle Triassic and Upper Triassic[J].ActaGeologica Sinica,2009,83(8):1089-1096]
19赵俊兴,陈洪德,付锁堂,等.鄂尔多斯盆地南部延长组中几个重要事件沉积及其油气聚集关系[J].矿物岩石,2008,28(3):90-95[Zhao Junxing,Chen Hongde,Fu Suotang,et al.Discussionon some important depositional events and their relationship with hy-drocarbon accumulation of Yanchang Formation in South Ordos Basin[J].Mineral Petrology,2008,28(3):90-95]
20梅志超,林晋炎.湖泊三角洲的地层模式和骨架砂体的特征[J].沉积学报,1991,9(4):1-11[Mei Zhichao,Lin Jinyan.Strati-graphic pattern and character of skeletal sand bodies in lacustrine del-tas[J].Acta Sedimentologica Sinica,1991,9(4):1-11]
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