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第58航次在四国盆地钻了3个孔(442、443、444),在大东海岭一海盆区钻了2个孔(445、446)。在四国盆地,钻井穿透了半深海粘土以及下伏的枕状拉斑玄武岩和岩床。玄武岩岩床侵入了沉积物和枕状玄武岩。442孔位的最老沉积物为18～21百万年,而在443和444孔位上,最老沉积物年龄为14～15百万年。在443孔位上,用钾-氩法测得最年轻的枕状玄武年龄为17.2±3.2百万年。442孔位上最老沉积物的年龄与该处6A磁异常的年龄相符,但443和444孔位上最老沉积物的年龄与该两处的3A号磁异常年龄不一致。枕状玄武岩的钾-氩法年龄与一种磁异常解释不符,但却与另一种解释吻合。四国盆地的断裂作用为对称的或不对称的。盆地中海岭以外的火山作用干扰了对基底年代的解释。大东海岭-海盆区孔位(445、446)上的岩石由上、下两部分组成,上部为深海段,下部为火山碎屑浊流沉积物以及碎屑流砂岩和砾岩(446号孔位上有26处岩床侵入)。磁倾角资料表明大东海岭- 海盆区在过去53百万年中从赤道向北漂移了2000公里。所发现的最老沉积物年龄为52—53百万年,这说明该地区形成于西菲律宾海盆裂谷作用的最早期。
In the 58th voyage, three holes (442,443,444) were drilled in the Siguo Basin and two holes (445,446) were drilled in the Dadonghai-Ihai basin. In the Shikoku basin, drilling penetrated semi-deep-sea clays and underlying pillow-like rockblankts and bedrock. Basaltic bed invaded sediments and pillow basalt. The oldest sediment at hole 442 is 18-21 million years old, while the oldest sediment at ages 443 and 444 is 14-15 million years old. At hole 443, the youngest pillow-shaped basalt age measured by the potassium-argon method was 17.2 ± 3.2 million years. The age of the oldest sediment at location 442 coincides with the age of the 6A magnetic anomaly at that site, but the age of the oldest sediments at locations 443 and 444 is not consistent with the age at 3A of the two locations. Potassium-argon dating of pillow-shaped basalts is not consistent with a magnetic anomaly interpretation, but is consistent with another explanation. The fracture of the Shikoku basin is symmetrical or asymmetrical. Volcanism outside the basin Ridge interferes with the interpretation of the basal age. The rocks on the Dadonghai-Hai Basin (445,446) are composed of upper and lower parts, with the upper part being the deep sea section and the lower part being volcanic debris turbidite sediments and debris flow sandstone and conglomerate (Hole 446 There are 26 beds intrusion). Magnetoclinic data indicate that the Dadonghai-Hai Basin drifted 2,000 km northward from the equator in the past 53 million years. The oldest sediment found is 52-53 million years old, indicating the earliest period of rifting in the western Philippine basin.