Paleomagnetic and biostratigraphic properties and datums of ODP Leg 173 and Leg 149 sites@en

We have conducted an integrated paleomagnetic and biostratigraphic study on the Cenozoic sedimentary sequences of the southern Iberia Abyssal Plain margin, focusing on Ocean Drilling Program (ODP) Sites 897, 898, 900, 1067, 1068, and 1069. Reliable magnetostratigraphy from these six sites is presented in this paper. Sedimentary sections from Holes 897C, 898A, 900A, 1067A, 1068A, and 1069A have recorded a pattern of magnetic polarity reversals that correlates well with the known magnetic polarity timescale for the past 56 m.y. The polarity patterns from the Pliocene-Pleistocene turbidite sequence at the Leg 149 sites show that a reliable magnetostratigraphy can be established from the early Pliocene to Holocene, including the Gilbert/Gauss boundary (3.58 m.y.) through the Matuyama/Brunhes boundary (0.78 m.y.). On the basis of distinct intervals of magnetic reversal zones and biostratigraphic datums, five magnetozones (C21n-C25n) can be recognized at the three Leg 173 sites that range from middle Eocene to late Paleocene in age. The magnetostratigraphy of the Iberia sections allows the determination of sedimentation rates and better constraints on the timing of deformation. Combining the age and average inclination information available from the magnetostratigraphy, we also present paleolatitudes vs. time for the Iberia drill sites.本研究针对伊比利亚深海平原南部陆缘的新生代沉积序列开展了综合古地磁与生物地层学研究，重点聚焦大洋钻探计划（Ocean Drilling Program, ODP）的897、898、900、1067、1068及1069站位。本文报道了上述6个站位的可靠磁地层学结果。897C、898A、900A、1067A、1068A及1069A钻孔的沉积剖面记录了磁极性反转模式，该模式与过去56百万年的已知磁极性年表高度吻合。149航次站位的上新世-更新世浊积岩序列的极性模式表明，可建立从早上新世至全新世的可靠磁地层序列，涵盖吉尔伯特/高斯界限（3.58百万年）至松山/布容界限（0.78百万年）的全部区间。基于清晰的磁反转带区间与生物地层基准面，在3个173航次站位中可识别出5个磁极性带（C21n-C25n），其形成时代介于始新世中期至古新世晚期之间。伊比利亚海域钻孔剖面的磁地层学结果可用于确定沉积速率，并更好地限定构造变形的发生时间。结合磁地层学获取的年代与平均倾角数据，本文还给出了伊比利亚钻探站位的古纬度随时间变化曲线。