Paleomagnetic characterization and age of several ODP Leg 198 sites, Shatsky Rise

Shatsky Rise, a medium-sized large igneous province in the west Central Pacific Ocean, has three main topographic highs that preserve a thick sedimentary record from Cretaceous through Cenozoic. During Ocean Drilling Program (ODP) Leg 198 to Shatsky Rise, a total of ~768 m of late Miocene-Holocene sediments was recovered from six sites. Sites 1207 and 1208 were drilled on the Northern and Central Highs, respectively, and yielded expanded late Miocene-Holocene sequences. Sites 1209, 1210, 1211, and 1212 were drilled on the Southern High and yielded shorter sequences of similar age. Clearly interpretable magnetic stratigraphies were obtained from all sites using the shipboard pass-through magnetometer. These results were augmented using discrete sample cubes (7 cm**3) collected shipboard and measured postcruise. Miocene age sediments are separated by a hiatus from Oligocene, Eocene, and Cretaceous age sediments beneath. An astrochronological age model was developed for the six sites based on cycles observed in reflectance data, measured shipboard. This age model is in good agreement with published astrochronological polarity chron ages in the 1 to 6 Ma interval.

沙茨基海隆（Shatsky Rise）是中西太平洋海域的中型大火成岩省（large igneous province），拥有三处主要地形高地，保存了自白垩纪至新生代的厚层沉积记录。在大洋钻探计划（Ocean Drilling Program, ODP）第198航次赴沙茨基海隆开展钻探期间，科研人员从6个站位共获取了约768米的晚中新世-全新世沉积物。其中，站位1207与1208分别钻探于北部高地与中部高地，获得了连续完整的晚中新世-全新世沉积序列；站位1209、1210、1211及1212钻探于南部高地，获取了时代相近但厚度较薄的同期沉积序列。所有站位均通过船上贯通式磁力仪获得了清晰可解译的磁地层序列，后续又通过采集船上获取的7立方厘米（7 cm³）离散样品块并在航次结束后开展测量，对上述结果进行了补充完善。中新世沉积与下伏的渐新世、始新世及白垩纪沉积之间存在沉积间断。基于船上实测的反射率数据中的旋回特征，科研人员为这6个站位建立了天文年代标尺模型，该模型与1~6 Ma区间内已发表的天文极性年表年龄结果吻合度良好。