Collaborative Research: Late Cretaceous - early Cenozoic paleolatitude of the Walvis Ridge hotspot: Implications for true polar wander and hotspot geodynamics

合作研究：白垩纪晚期 - 新生代早期沃尔维斯海岭热点的古纬度：对真正的极地漂移和热点地球动力学的影响

• 批准号: 2232971
• 负责人: Sonia Tikoo-Schantz
• 金额: $ 19.5万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-02-01 至 2025-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2232971&HistoricalAwards=false
• 关键词: Collaborative; Research; Late; Cretaceous; early

The Walvis Ridge is a volcanic ridge in the South Atlantic Ocean that was erupted on the African plate as it drifted over a hotspot, similar to the Hawaiian-Emperor seamount chain in the Pacific Ocean. Scientists are debating how accurately such hotspot tracks record plate motion. During the formation of the Emperor chain paleomagnetic data show that the hotspot moved southward by ~10-15°to its current location. This shift might be caused by movement of the hotspot. An alternate cause could be the shift of the Earth’s spin axis, or true polar wander (TPW). If TPW occurred, it should cause a consistent global shift: southward hotspot motion in the Pacific would be paired with northward hotspot motion in the Atlantic. This project will study volcanic rocks and sediments cored from Walvis Ridge during International Ocean Discovery Program Expedition 391 (December 2021-February 2022) to produce a record of paleolatitudes for comparison with Hawaii-Emperor paleolatitudes. The project supports several early career researchers.This project will analyze and publish studies of sediment and basalt core paleomagnetic data from IODP Expedition 391, with the object of developing a paleolatitude record for Walvis Ridge hotspot volcanoes for Late Cretaceous and early Cenozoic. IODP Expedition 391 drilled four sites, three on the Cretaceous Valdivia Bank plateau and one on a Paleocene guyot. Previous studies from Emperor and Louisville seamounts in the Pacific Ocean have been influential in studies of hotspot geodynamics. Prior to Deep Sea Drilling Project/Ocean Drilling Program (DSDP/ODP) drilling of Emperor seamounts, hotspots were considered fixed mantle markers, defining plate motions by seamount age progressions. DSDP/ODP cores showed that northern Emperor guyots were formed ~15° farther north than the current Hawaiian hotspot. IODP Expedition 330 cored coeval Louisville guyots, finding insignificant latitudinal motion, concluding that hotspot motion is the preferred explanation for inter-hotspot motion. Consequently, other explanations for hotspot latitude changes are not currently favored. One such phenomenon is true polar wander (TPW), the coherent shift of the entire mantle relative to the spin axis. TPW has been deemed insignificant for the past ~100 Ma, even though it is occurring at present and it has occurred deeper in the past. Hawaii and Louisville paleolatitude data show a small amount of mutual southward motion. If this results from TPW, the Walvis Ridge, almost antipodal to Hawaii and Louisville, should show the opposite paleolatitude change. This project will produce paleolatitude data for the Walvis Ridge using Expedition 391 cores (with data from DSDP Legs 72 and 74). A major objective is to test the hypothesis of Late Cretaceous-early Cenozoic TPW. This project hypothesizes that observed paleolatitude shifts are a combination of TPW and mantle flow. The project addresses important geodynamical problems that ultimately reflect mantle structure and convection. This project supports three early career investigators. In addition, the two faculty on this project will recruit undergraduate student workers from under-represented groups for internships that will help them advance in STEM education.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

沃尔维斯海岭是南大西洋的一条火山脊，在非洲板块漂流过热点时喷发，类似于太平洋的夏威夷-皇帝海山链。科学家们正在争论这样的热点跟踪记录板块运动的准确性。在皇帝链形成期间，古地磁数据显示热点向南移动了约 10-15° 至当前位置。这种转变可能是由热点的移动引起的。另一个原因可能是地球自转轴的移动，或真极漂移（TPW）。如果TPW发生，它应该会引起一致的全球变化：太平洋向南的热点运动将与大西洋向北的热点运动配对。该项目将研究国际海洋发现计划第 391 次探险（2021 年 12 月至 2022 年 2 月）期间从鲸湾港取芯的火山岩和沉积物，以生成古纬度记录，以便与夏威夷-皇帝古纬度进行比较。该项目为几位早期职业研究人员提供支持。该项目将分析并发布 IODP 391 号探险队的沉积物和玄武岩核心古地磁数据的研究成果，目的是开发鲸湾岭热点火山晚白垩世和早新生代的古纬度记录。 IODP 391 探险队钻探了四个地点，其中三个位于白垩纪瓦尔迪维亚浅滩高原，一个位于古新世盖奥特。先前对太平洋皇帝海山和路易斯维尔海山的研究对热点地球动力学研究产生了影响。在深海钻探项目/海洋钻探计划 (DSDP/ODP) 钻探皇帝海山之前，热点被认为是固定的地幔标记，通过海山年龄进程来定义板块运动。 DSDP/ODP 核心显示，北部皇帝古奥特形成的位置比当前夏威夷热点向北约 15°。 IODP Expedition 330 岩心同时代的路易斯维尔居奥特发现了微不足道的纬向运动，得出结论认为热点运动是热点间运动的首选解释。因此，目前不赞成对热点纬度变化的其他解释。其中一种现象是真极漂移（TPW），即整个地幔相对于自转轴的相干移动。 TPW 在过去约 100 Ma 内被认为是微不足道的，尽管它现在正在发生，并且在过去更深处发生过。夏威夷和路易斯维尔的古纬度数据显示有少量的相互向南运动。如果这是 TPW 的结果，那么几乎与夏威夷和路易斯维尔对映的沃尔维斯海岭应该显示出相反的古纬度变化。该项目将使用 Expedition 391 核心（数据来自 DSDP 第 72 和 74 段）生成鲸湾海岭的古纬度数据。一个主要目标是检验晚白垩世-早新生代 TPW 的假设。该项目假设观测到的古纬度变化是 TPW 和地幔流的结合。该项目解决了最终反映地幔结构和对流的重要地球动力学问题。该项目支持三名早期职业调查员。此外，该项目的两名教师将从代表性不足的群体中招募本科生工人进行实习，这将有助于他们在 STEM 教育方面取得进步。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Preliminary Characterization of Submarine Basalt Magnetic Mineralogy Using Amplitude‐Dependence of Magnetic Susceptibility

利用振幅对磁化率的依赖性对海底玄武岩磁性矿物学进行初步表征

• DOI: 10.1029/2023gc011222
• 发表时间: 2024
• 期刊: Geosystems
• 作者: Yang, H.;Tikoo, S. M.;Carvallo, C.;Bilardello, D.;Solheid, P.;Gaastra, K. M.;Sager, W. W.;Thoram, S.;Hoernle, K.;Höfig, T. W.
• 通讯作者: Höfig, T. W.

Nature and Origin of Magnetic Lineations Within Valdivia Bank: Ocean Plateau Formation by Complex Seafloor Spreading

• DOI: 10.1029/2023gl103415
• 发表时间: 2023-07
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: S. Thoram;W. W. Sager-W.;K. Gaastra;S. Tikoo;C. Carvallo;A. Avery;A. V. Del Gaudio;Y. Huang;K. Hoernle;T. W. Höfig;R. Bhutani;D. M. Buchs;C. Class;Y. Dai;G. Dalla Valle;S. Fielding;S. Han;D. Heaton;S. Homrighausen;Y. Kubota;C.-F. Li;W. R. Nelson;E. Petrou;K. E. Potter;S. Pujatti;J. Scholpp;J. Shervais;M. Tshiningayamwe;X. J. Wang;M. Widdowson