南海海盆海底扩张年代之探讨
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摘要
根据海底地形地貌特征和区域构造走向,可将南海海盆分为三个次海盆:西北次海盆、西南次海盆和中央次海盆。通过地磁异常资料之分析对比,在中央次海盆中鉴别出5d-11号磁异常条带,推测其海底扩张年代为晚渐新世-早中新世(32-17 MaBP);在西南次海盆中鉴别出18-13号磁异常条带,推测其海底扩张年代为晚始新世-早渐新世(42-35 MaBP)。通过对穿过中央次海盆与西南次海盆的地震反射剖面之分析,发现西南次海盆比中央次海盆多一套新生代沉积(T_6-T_g),证明西南次海盆的形成年代早于中央次海盆。用大洋基底的深度资料计算洋壳的年龄,发现西南次海盆洋壳的年龄也老于中央次海盆。由此可见,后两类资料证明了由磁异常条带所推测洋壳年龄的正确性。因此,我们认为,南海海盆存在三条扩张脊,至少经历过两次海底扩张。多扩张中心和多次海底扩张是南海海盆构造演化史的重要特征。
Based on the geomorphology and the regional tectonic trends, the South China Sea Basin is subdivided into three subbasins: i.e.NW Subbasin, SW Subbasin and Central Sub- basin. Analysing the magnetic anomalies in the Central Subbasin, 5d 11 magnetic anomaliy lineations are recognized there and might be infer that its sea floor spreading age was late Oligocene to early Miocene (32 - 17 MaB.P. ). Correspondingly, In the SW Subbasin, 13 - 18 magnetic anomaly lineations are recognized and infered that its spreading age of sea floor was late Eocene to early Oligocene (42 - 35 Ma B. P.) . Whereas interpretes the seismic profile crossing the Central Subbasin and SW Subbasin, the author finds out that there has one more layer (T_6-T_g) in the SW Subbasin than the Cen- tral Subbasin, it shows that the former is older than the later. After calculating the the depth data of the basement of the oceanic crust, the author finds that the the SW Subbasin is older than the Central Subbasin.Therefore, all the sedimentary sequences and the depth of the o- ceanic crust basement data prove the ages of the sea floor infered from magnetic anomaly lin- eations are correct. So we believe that there exist three spreading ridges and two-times of seafloor spreadings at least in the South China Sea Basin.The multi-spreading ridges and multi- times of sea floor spreding are the important characteristics in the tectonic evolution of the South China Sea Basin.
Based on the geomorphology and the regional tectonic trends, the South China Sea Basin is subdivided into three subbasins: i.e.NW Subbasin, SW Subbasin and Central Sub- basin. Analysing the magnetic anomalies in the Central Subbasin, 5d 11 magnetic anomaliy lineations are recognized there and might be infer that its sea floor spreading age was late Oligocene to early Miocene (32 - 17 MaB.P. ). Correspondingly, In the SW Subbasin, 13 - 18 magnetic anomaly lineations are recognized and infered that its spreading age of sea floor was late Eocene to early Oligocene (42 - 35 Ma B. P.) . Whereas interpretes the seismic profile crossing the Central Subbasin and SW Subbasin, the author finds out that there has one more layer (T_6-T_g) in the SW Subbasin than the Cen- tral Subbasin, it shows that the former is older than the later. After calculating the the depth data of the basement of the oceanic crust, the author finds that the the SW Subbasin is older than the Central Subbasin.Therefore, all the sedimentary sequences and the depth of the o- ceanic crust basement data prove the ages of the sea floor infered from magnetic anomaly lin- eations are correct. So we believe that there exist three spreading ridges and two-times of seafloor spreadings at least in the South China Sea Basin.The multi-spreading ridges and multi- times of sea floor spreding are the important characteristics in the tectonic evolution of the South China Sea Basin.
引文
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[2] Taylor B. and Hayes D.E.1 980; Origin and history of the South China Sea Basin; In: D.E.Hayes (ed.) The tectonic and geologic evolution of southeast Asian seas and islands, part I ; American Geophysical Monography, 27: 23-56．
[3] Taylor B. and Hayes D.E. Origin and history of the South China Sea; In D.E. Hayes (ed.) The tectonic and geologic evolution of southeast Asian seas and islands, Part Ⅱ ; American Geophysical Monography, 27: 23-56．
[4] 陈圣源,1987,南海磁力异常图;南海地质地球物理图集;广州:广东地图出版社.
[5] 何廉声,1987,南海大地构造图;南海地质地球物理图集;广州:广东地图出版社.
[6] 吕文正,1987,南海中央次海盆磁异常特征及构造演化;海洋学报,9(1) ,69-78．
[7] 姚伯初,1991,南海海盆在新生代的构造演化,南海地质研究(3) ;广州:广东科技出版社,3:9-23．
[8] Hayes D.E.1995; Maigins of the Southwest Subbasin of the South China Sea-A frontier exploration target? Energy, 10(3/4) , 373-382．
[9] Hayes D E.1 984; Marginal seas of Southeast Asia-Their geophysical characteristics and structure; Proceedings of the 27th International Geological Congress, 23: 123-154．
[10] Briais A., Patriat P.and Tapponnier P. 1993; Updated interpretation of magnetic anomalies and seafloor spreading stages in the South China Sea: Implications for the Tertiary tectonics of Southeast Asia; J.Geophys.Res., (98) 6299-6328．
[11] Briais A., Hayes D.E., Spangler S., Yao B., Zeng W., 1987; Age and evolution of the South China Sea Southwest Subbasin; EOS Trans. AGU, 68: 1496．
[12] 姚伯初,曾维军,Hayes D.E,Spangler S.et al.1994;中美联合调研南海地质专报;武汉:中国地质大学出版社
[13] 鲍才旺,1987;南海地形图;南海地质地球物理图集;广州:广东地图出版社.
[14] 薛万俊,1987;南海地貌图;南海地质地球物理图集;广州:广东地图出版社.
[15] 姚伯初,王光宇,1983;南海海盆的地壳结构;中国科学,B辑,2:177-186．
[16] YaoBochu, 1995; Tectonic evolution on the southern margin of the South China Sea; CCOP Technical Bulletin, 25: 143-160．
[17] Ludwig W.J., Nafe J.E.and Drake C.L.1970; Seismic refraction in the sea; PartI, 4: 53-84．
[18] Hess H.H.1978; Histoiy of ocean basins, In A.E.J.Engel et al. (eds. ) Petrologic studies; New York,Geol.Soc.America; 599-620．
[19] Vine F.J.1963; Spreading of the ocean floor: Evidence; Science, 154: 1405-1415．
[20] LePichonX., Houtz R.E. et al.; Crustal structure of the mid-ocean ridges, PartI; J.Geophys.Res.70: 319-339．
[21] Parsons B.and Sclater J.G.1977; An analysis of the variation of ocean floor bathymetry and heat flow with age; J.Geophys.Res.83: 803-827．
[2] Taylor B. and Hayes D.E.1 980; Origin and history of the South China Sea Basin; In: D.E.Hayes (ed.) The tectonic and geologic evolution of southeast Asian seas and islands, part I ; American Geophysical Monography, 27: 23-56．
[3] Taylor B. and Hayes D.E. Origin and history of the South China Sea; In D.E. Hayes (ed.) The tectonic and geologic evolution of southeast Asian seas and islands, Part Ⅱ ; American Geophysical Monography, 27: 23-56．
[4] 陈圣源,1987,南海磁力异常图;南海地质地球物理图集;广州:广东地图出版社.
[5] 何廉声,1987,南海大地构造图;南海地质地球物理图集;广州:广东地图出版社.
[6] 吕文正,1987,南海中央次海盆磁异常特征及构造演化;海洋学报,9(1) ,69-78．
[7] 姚伯初,1991,南海海盆在新生代的构造演化,南海地质研究(3) ;广州:广东科技出版社,3:9-23．
[8] Hayes D.E.1995; Maigins of the Southwest Subbasin of the South China Sea-A frontier exploration target? Energy, 10(3/4) , 373-382．
[9] Hayes D E.1 984; Marginal seas of Southeast Asia-Their geophysical characteristics and structure; Proceedings of the 27th International Geological Congress, 23: 123-154．
[10] Briais A., Patriat P.and Tapponnier P. 1993; Updated interpretation of magnetic anomalies and seafloor spreading stages in the South China Sea: Implications for the Tertiary tectonics of Southeast Asia; J.Geophys.Res., (98) 6299-6328．
[11] Briais A., Hayes D.E., Spangler S., Yao B., Zeng W., 1987; Age and evolution of the South China Sea Southwest Subbasin; EOS Trans. AGU, 68: 1496．
[12] 姚伯初,曾维军,Hayes D.E,Spangler S.et al.1994;中美联合调研南海地质专报;武汉:中国地质大学出版社
[13] 鲍才旺,1987;南海地形图;南海地质地球物理图集;广州:广东地图出版社.
[14] 薛万俊,1987;南海地貌图;南海地质地球物理图集;广州:广东地图出版社.
[15] 姚伯初,王光宇,1983;南海海盆的地壳结构;中国科学,B辑,2:177-186．
[16] YaoBochu, 1995; Tectonic evolution on the southern margin of the South China Sea; CCOP Technical Bulletin, 25: 143-160．
[17] Ludwig W.J., Nafe J.E.and Drake C.L.1970; Seismic refraction in the sea; PartI, 4: 53-84．
[18] Hess H.H.1978; Histoiy of ocean basins, In A.E.J.Engel et al. (eds. ) Petrologic studies; New York,Geol.Soc.America; 599-620．
[19] Vine F.J.1963; Spreading of the ocean floor: Evidence; Science, 154: 1405-1415．
[20] LePichonX., Houtz R.E. et al.; Crustal structure of the mid-ocean ridges, PartI; J.Geophys.Res.70: 319-339．
[21] Parsons B.and Sclater J.G.1977; An analysis of the variation of ocean floor bathymetry and heat flow with age; J.Geophys.Res.83: 803-827．
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