鄂尔多斯盆地上三叠统延长组震积岩识别标志研究
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摘要
震积岩主要通过地震驱动形成的软沉积物变形构造来识别。鄂尔多斯盆地南部中生界延长组长6-长8中发育大量软沉积物变形构造,包括微同沉积断裂、震裂缝、液化砂岩脉、沙侵蘑菇、振动液化卷曲变形构造、负荷构造及枕状层、地震角砾岩、震塌岩等。这些变形构造常沿限定的岩层发育,上、下均为未变形的岩层,显示事件变形特征。同时在塔17井中发现完整的震积岩垂向序列,序列自下而上分为下伏未震层、微断裂层、微褶皱层、碎块层及液化均一层、上覆未震层。该震积岩的发现,表明晚三叠世随着秦岭、南祁连海槽的封闭,南北向逆冲带发生强烈活动;并且为盆地西南部延长组长6-长8发育的大规模浊积岩的外界触发机制是由地震活动引起的提供了有力证据。
Seismites are identified mainly by soft-sediment deformation structures.Many earthquake-related seismites have been discovered in the Chang 6-Chang 8 of the Upper Triassic Yanchang Formation in the south of Ordos Basin.Having surveyed the cores of wells,many typical deformation structures are discovered,such as syn-sedimentary micro factures,stone veins,vibrational liquefaction,deformation structure,earthquake breccia and load-casts and balls-and pillows-types,etc.They develop in const-rained horizons bounded by undeformed strata,suggesting that they are syndepositional.The complete vertical sequence of seismite of Well Ta 17,includes a shattered rock bed,ladder-shaped faulted bed,vibrational liquefaction deformation structure bed,liquefied sandstone vein bed, rubble bed and homogenized bed.The discovery of seismite can be used to interpret the tectonic evolution of the basin.In Late Triassic,with the closing of Qinling and the sea slot of the southern Qilian,strong activities occurred in the south-north thrust belt.They are the direct inducing factors of the seismo-deposition in the Yanchang Formation and provide the evidence for the turbidite of Chang 6-Chang 8 of the Yanchang Formation in the southwest of Ordos Basin,that is,the outside trigger mechanism of the turbidite is earthquake activity.
Seismites are identified mainly by soft-sediment deformation structures.Many earthquake-related seismites have been discovered in the Chang 6-Chang 8 of the Upper Triassic Yanchang Formation in the south of Ordos Basin.Having surveyed the cores of wells,many typical deformation structures are discovered,such as syn-sedimentary micro factures,stone veins,vibrational liquefaction,deformation structure,earthquake breccia and load-casts and balls-and pillows-types,etc.They develop in const-rained horizons bounded by undeformed strata,suggesting that they are syndepositional.The complete vertical sequence of seismite of Well Ta 17,includes a shattered rock bed,ladder-shaped faulted bed,vibrational liquefaction deformation structure bed,liquefied sandstone vein bed, rubble bed and homogenized bed.The discovery of seismite can be used to interpret the tectonic evolution of the basin.In Late Triassic,with the closing of Qinling and the sea slot of the southern Qilian,strong activities occurred in the south-north thrust belt.They are the direct inducing factors of the seismo-deposition in the Yanchang Formation and provide the evidence for the turbidite of Chang 6-Chang 8 of the Yanchang Formation in the southwest of Ordos Basin,that is,the outside trigger mechanism of the turbidite is earthquake activity.
引文
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[14]吴贤涛,尹国勋.四川峨眉晚侏罗世湖泊沉积中震积岩的发现及其意义[J].沉积学报,1992,10(3):19-24.
[15]张琴,朱筱敏,张建军,等.酒西盆地青南凹陷柳沟庄-窟窿山地区下白垩统震积岩的发现及意义[J].地质学报,2003,77(2):158-162.
[16]袁静.山东惠民凹陷古近纪震积岩特征及其地质意义[J].沉积学报,2004,22(1):41-46.
[17]陈世悦,袁文芳,鄢继华.济阳坳陷早第三纪震积岩的发现及其意义[J].地质科学,2003,38(3):377-386.
[18]张传恒,刘典波,张传林,等.新疆博格达地区早二叠世软沉积物变形构造:弧后碰撞前陆盆地地震记录[J].地学前缘,2006,13(4):255-266.
[19]赵重远,刘池洋.华北克拉通沉积盆地形成与油气赋存[M].西安:西北大学出版社,1990:1-63.
[20]杜远生,韩欣.论震积作用和震积岩[J].地球科学进展,2000,15(4):389-394.
[2]SEILACHER A.Sedi mentary structures tentativelyattributed to seismic events[J].Marine Geology,1984,55(1/2):1-12.
[3]MOHINDRA R,BAGATI T N.Seismically inducedsoft-sedi ment deformation structures(seismites)around Sumdointhe Lower Spitti valley(Tethys Hi-malaya)[J].Sedi mentary Geology,1996,101(1-2):69-83.
[4]PLAZIATJ C,AHMAMOU M.Mechanic processesactive in seismites:their identification and tectonicsignificance in the Pliocene basin of the Sais of Fesand Meknes(Morocco)[J].Geodynamic Acta,1998,11(4):183-203.
[5]VANNESTE K,MEGHRAOUI M,CAMELBEECKT.Late Quaternary earthquake-related soft-sedi mentdeformation along the Belgian portion of the FeldbissFault,Lower Rhine Graben system[J].Tectono-physics,1999,309(1-4):57-79.
[6]SHIKI T,CITA MB,GORSLINE D S.Sedi menta-ry features of seismite,seismo-turbidites and tsu-namiites-an introduction[J].Sedi mentary Geology,2000,135(1-4):7-9.
[7]乔秀夫,宋天锐,高林志,等.碳酸盐岩振动液化地震序列[J].地质学报,1994,68(1):16-34.
[8]乔秀夫,李海兵,高林志.华北地台震旦纪-早古生代地震节律[J].地学前缘,1997,4(3-4):155-160.
[9]乔秀夫,高林志.华北中新元古代及早中生代地震灾变事件及与Rodinia的关系[J].科学通报,1999,44(16):1753-1758.
[10]乔秀夫,高林志,彭阳,等.古郯庐带沧浪铺阶地震事件、层序及构造意义[J].中国科学(D辑),2001,31(11):911-918.
[11]孙晓猛,梁定益,聂泽同.大陆边缘震积岩序列以金沙江中段震积岩为例[J].现代地质,1995,9(3):271-278.
[12]杜远生,张传恒,韩欣.滇西地区中元古代大龙口组震积岩的新发现[J].沉积学报,1999,24(增刊):28-37.
[13]杜远生,张传恒,韩欣.滇西中元古代昆阳群的地震事件沉积及其地质意义[J].中国科学(D辑),2001,31(4):283-289.
[14]吴贤涛,尹国勋.四川峨眉晚侏罗世湖泊沉积中震积岩的发现及其意义[J].沉积学报,1992,10(3):19-24.
[15]张琴,朱筱敏,张建军,等.酒西盆地青南凹陷柳沟庄-窟窿山地区下白垩统震积岩的发现及意义[J].地质学报,2003,77(2):158-162.
[16]袁静.山东惠民凹陷古近纪震积岩特征及其地质意义[J].沉积学报,2004,22(1):41-46.
[17]陈世悦,袁文芳,鄢继华.济阳坳陷早第三纪震积岩的发现及其意义[J].地质科学,2003,38(3):377-386.
[18]张传恒,刘典波,张传林,等.新疆博格达地区早二叠世软沉积物变形构造:弧后碰撞前陆盆地地震记录[J].地学前缘,2006,13(4):255-266.
[19]赵重远,刘池洋.华北克拉通沉积盆地形成与油气赋存[M].西安:西北大学出版社,1990:1-63.
[20]杜远生,韩欣.论震积作用和震积岩[J].地球科学进展,2000,15(4):389-394.
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