[M-GI28] 地球掘削科学

[MGI28-P03] Preliminary Reports of International Ocean Discovery Program Expedition 390 and 393: South Atlantic Transect

*桑野 太輔¹、相澤 正隆²、高田 真子³、土井 信寛¹、Coggon Rosalind M. ⁴、Sylvan Jason B.⁵、Teagle Damon A.H.⁴、Reece Julia⁵、Christeson Gail L.^6,7、Estes Emily R.⁵、Williams Trevor J.⁵、the South Atlantic Transect IODP Expedition 390 & 393 Scientists (1.千葉大学、2.琉球大学、3.東京大学、4.Univ. Southampton、5.Texas A&M Univ.、6.National Science Foundation、7.University of Texas Institute for Geophysics)

キーワード：IODP、South Atlantic Transect、Expedition 390、Expedition 393

The South Atlantic Transect (SAT) consists of four International Ocean Discovery Program (IODP) expeditions (Exp. 390C, 395E, 390, and 393). Engineering Exp. 390C (October to December 2020) and 395E (April to June 2021) were conducted without a scientific party during the COVID-19 pandemic. Subsequently, IODP Exp. 390 and 393 occurred in 2022 from April to June and June to August, respectively. The SAT expeditions primarily aim to investigate the evolutionary processes of aging oceanic crust, microbial community variation with substrate composition and age, and reconstruct past climate and oceanic changes throughout the Cenozoic. These expeditions almost completely recovered Paleocene to Recent sedimentary successions and the upper oceanic crust from seven sites (U1556–U1561 and U1583) along the western flank of the Mid-Atlantic Ridge at approximately 31°S. The crustal ages encountered at these sites are 7, 15, 31, 49, and 61 Ma. The sediments across all sites, a total of ~2000 m in length, were mainly composed of calcareous nannofossil ooze and clay. In all holes, age models were constructed based on magnetostratigraphy, planktic foraminiferal biostratigraphy, and calcareous nannofossil biostratigraphy. The sediment/basement interface and the uppermost oceanic crust were successfully recovered at most sites, and approximately 500 m basalt cores were collected during these expeditions. Additionally, geophysical wireline logs were obtained at four sites: U1556, U1557, U1560, and U1583. Since the completion of the expeditions, a wealth of multi-disciplinary and collaborative post-expedition studies are being developed to further investigate the scientific objectives of the South Atlantic Transect.

*the Expedition 390 Scientists; Chiara Borelli, Joshua D. Bridges, Elliot J. Carter, Jaume Dinarès-Turell, Justin D. Estep, William P. Gilhooly III, Lewis Grant, Michael R. Kaplan, Pamela D. Kempton, Walter Kurz, Christopher M. Lowery, Andrew McIntyre, Muthusamy Prakasam, Claire M. Routledge, Angela L. Slagle, Leonardo Tamborrino, Liyan Tian, Yi Wang, Kiho Yang, and Tiantian Yu
*the Expedition 393 Scientists; Elmar Albers, Chiara Amadori, Thomas M. Belgrano, Chiara Borrelli, Timothy D’Angelo, Aled Evans, Gilles M. Guerin, Michelle Harris, Victoria M. Hojnacki, Gilbert Hong, Xiaobo Jin, Mallika Jonnalagadda, Jessica M. Labonte, Adriane R. Lam, Marcin Latas, Wanyi Lu, Paul Moal-Darrigade, Stephen F. Pekar, Claudio Robustelli Test, Jeffrey G. Ryan, Danielle Santiago Ramos, Alina Shchepetkina, Alexandra Villa, Shu Ying Wee, Sarah J. Widlansky, and Guo Liang Zhang