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: 2232970
• 负责人: William Sager
• 金额: $ 38.87万
• 依托单位: University of Houston
• 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=2232970&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（英语：Walvis Ridge）是位于南大西洋的一个火山海岭，是非洲板块漂移经过一个热点时喷发的，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如何准确地跟踪记录板块运动。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°到目前的位置。这种变化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，它应该会导致一致的全球转移：太平洋的南向热点运动将与大西洋的北向热点运动配对。该项目将研究在国际海洋发现计划第391次考察（2021年12月至2022年2月）期间从沃尔维斯海岭取芯的火山岩和沉积物，以记录古纬度，并与夏威夷-皇帝古纬度进行比较。该项目将分析和发表IODP 391号考察队的沉积物和玄武岩岩芯古地磁数据研究，目的是为沃尔维斯海岭热点火山建立晚白垩世和新生代早期的古纬度记录。IODP第391号考察队钻探了四个地点，三个在白垩纪瓦尔迪维亚银行高原，一个在古新世盖奥特。以往对太平洋Emperor和Louisville海山的研究在热点地球动力学研究中具有重要影响。在深海钻探计划/大洋钻探计划（DSDP/ODP）对皇帝海山进行钻探之前，热点被认为是固定的地幔标志，通过海山年龄的进展来定义板块运动。DSDP/ODP岩心显示，北方皇帝盖奥特形成于比现在的夏威夷热点偏北约15°的地方。IODP Expedition 330取芯的同时代路易斯维尔盖奥特，发现不显著的纬向运动，得出结论，热点运动是热点间运动的首选解释。因此，热点纬度变化的其他解释目前并不受欢迎。其中一种现象是真极移（TPW），即整个地幔相对于自旋轴的相干移动。TPW在过去的~100 Ma被认为是微不足道的，即使它现在正在发生，而且它在过去发生得更深。夏威夷和路易斯维尔的古纬度数据显示了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跖的沃尔维斯海岭应该显示出相反的古纬度变化。该项目将利用391个考察岩心（利用DSDP第72和74航段的数据）得出沃尔维斯海岭的古纬度数据。一个主要目的是检验晚白垩世-早新生代TPW假说。该项目假设观测到的古纬度变化是TPW和地幔流的组合。该项目解决了重要的地球动力学问题，最终反映地幔结构和对流。该项目支持三个早期职业调查员。此外，该项目的两个学院将从代表性不足的群体中招募本科生工作者进行实习，以帮助他们在STEM教育中取得进步。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值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.