Triple mass-transport deposits （MTDs） with areas of 625, 494 and 902 km^2, respectively, have been identified on the north slope of the Xisha Trough, northern South China Sea margin. Based on high-resolution seismic...Triple mass-transport deposits （MTDs） with areas of 625, 494 and 902 km^2, respectively, have been identified on the north slope of the Xisha Trough, northern South China Sea margin. Based on high-resolution seismic reflection data and multi-beam bathymetric data, the Quaternary MTDs are characterized by typical geometric shapes and internal structures. Results of slope analysis showed that they are developed in a steep slope ranging from 5° to 35°. The head wall scarps of the MTDs arrived to 50 km in length （from headwall to termination）. Their inner structures include well developed basal shear surface, growth faults, stepping lateral scarps, erosion grooves, and frontal thrust deformation. From seismic images, the central deepwater channel system of the Xisha Trough has been filled by interbedded channel-levee deposits and thick MTDs. Therefore, we inferred that the MTDs in the deepwater channel system could be dominated by far-travelled slope failure deposits even though there are local collapses of the trough walls. And then, we drew the two-dimensional process model and three- dimensional structure model diagram af the MTDs. Combined with the regional geological setting and previous studies, we discussed the trigger mechanisms of the triple MTDs.展开更多
针对鄂尔多斯盆地西南缘奥陶系平凉组重力流沉积类型及特征进行了研究。通过露头、薄片及粒度分析等资料分析可知:1)研究区岩石类型丰富,发育砾屑灰岩、泥晶灰岩、砂屑灰岩、砾岩、砂岩及泥岩等。沉积构造丰富,块状层理、粒序层理、交...针对鄂尔多斯盆地西南缘奥陶系平凉组重力流沉积类型及特征进行了研究。通过露头、薄片及粒度分析等资料分析可知:1)研究区岩石类型丰富,发育砾屑灰岩、泥晶灰岩、砂屑灰岩、砾岩、砂岩及泥岩等。沉积构造丰富,块状层理、粒序层理、交错层理、平行层理及槽模等发育。2)东部为碳酸盐岩沉积区,中部为碎屑岩沉积区,西部为碳酸盐沉积区。3)重力流沉积可分为块状搬运复合体(mass transport deposits,MTD)、碎屑流沉积及浊流沉积。MTD以砾屑灰岩及泥晶灰岩为主,变形构造发育,规模大小不一。碎屑流沉积以砾屑灰岩、砾岩为主,块状层理发育,少见粒序层理,呈层状及透镜状,为海底扇内扇-中扇及水道沉积。浊流沉积以砂岩及砂屑灰岩为主,交错层理、平行层理及槽模等极为发育,构成不完整的鲍玛序列,多呈层状及透镜状。4)东部以MTD及深水水道沉积体系为主,中部发育海底扇,包括大型水道及朵叶,西部朵叶沉积较为发育,沉积物分选及磨圆较好。展开更多
基金The National Natural Science Foundation of China under contract Nos 41306057 and 40906028the Open Fund of the Key Laboratory of Submarine Geosciences,State Oceanic Administration under contract No.KLSG1406
文摘Triple mass-transport deposits （MTDs） with areas of 625, 494 and 902 km^2, respectively, have been identified on the north slope of the Xisha Trough, northern South China Sea margin. Based on high-resolution seismic reflection data and multi-beam bathymetric data, the Quaternary MTDs are characterized by typical geometric shapes and internal structures. Results of slope analysis showed that they are developed in a steep slope ranging from 5° to 35°. The head wall scarps of the MTDs arrived to 50 km in length （from headwall to termination）. Their inner structures include well developed basal shear surface, growth faults, stepping lateral scarps, erosion grooves, and frontal thrust deformation. From seismic images, the central deepwater channel system of the Xisha Trough has been filled by interbedded channel-levee deposits and thick MTDs. Therefore, we inferred that the MTDs in the deepwater channel system could be dominated by far-travelled slope failure deposits even though there are local collapses of the trough walls. And then, we drew the two-dimensional process model and three- dimensional structure model diagram af the MTDs. Combined with the regional geological setting and previous studies, we discussed the trigger mechanisms of the triple MTDs.
文摘针对鄂尔多斯盆地西南缘奥陶系平凉组重力流沉积类型及特征进行了研究。通过露头、薄片及粒度分析等资料分析可知:1)研究区岩石类型丰富,发育砾屑灰岩、泥晶灰岩、砂屑灰岩、砾岩、砂岩及泥岩等。沉积构造丰富,块状层理、粒序层理、交错层理、平行层理及槽模等发育。2)东部为碳酸盐岩沉积区,中部为碎屑岩沉积区,西部为碳酸盐沉积区。3)重力流沉积可分为块状搬运复合体(mass transport deposits,MTD)、碎屑流沉积及浊流沉积。MTD以砾屑灰岩及泥晶灰岩为主,变形构造发育,规模大小不一。碎屑流沉积以砾屑灰岩、砾岩为主,块状层理发育,少见粒序层理,呈层状及透镜状,为海底扇内扇-中扇及水道沉积。浊流沉积以砂岩及砂屑灰岩为主,交错层理、平行层理及槽模等极为发育,构成不完整的鲍玛序列,多呈层状及透镜状。4)东部以MTD及深水水道沉积体系为主,中部发育海底扇,包括大型水道及朵叶,西部朵叶沉积较为发育,沉积物分选及磨圆较好。
