MagNetZ With Liang Gao (2023/08/16) - Paleomagnetic constraints on the northern Antarctic Peninsula
Channel: MagNetZ
Date: 2023-08-16

New paleomagnetic constraints on the Cretaceous-Cenozoic tectonic evolution of the northern Antarctic Peninsula and opening process of the Drake Passage

The video is also available for download at: https://earthref.org/ERDA/2720/
and can be referenced with the doi: 10.7288/V4/ERDA/2720

Title: New paleomagnetic constraints on the Cretaceous-Cenozoic tectonic evolution of the northern Antarctic Peninsula and opening process of the Drake Passage
Author: Liang Gao from China University of Geosciences, China

Plate reconstructions provide basic constraints on the tectonic evolution of the Antarctic Peninsula-South Shetland Islands (AP-SSI) but they are limited by a scarcity of paleomagnetic data. Here, using a combination of new and published paleomagnetic data and geological evidence, we present an updated plate reconstruction of the AP-SSI since ~100 Ma. The SSI experienced large-scale counterclockwise rotation during ~100-90 Ma. Similar counterclockwise rotation has been identified from Southern Patagonian Andes (SPA) but is absent in the northern AP, suggesting the affinity between the SSI and SPA. The oroclinal bending of the northern AP (~68°S-63°S) also occurred at ~100-90 Ma, which is attributed to the compression caused by South America's southward drift due to the opening of the northern Atlantic Ocean. The eastward compression generated by the oroclinal bending of the northern AP starting at ~100 Ma can explain the initiation of the ancestral South Sandwich subduction zone. The rectilinear AP-SPA orogen before ~100 Ma is thus supported by both paleomagnetism and geological evidence.
The AP experienced a small-scale clockwise rotation at ~90-62 Ma. Then, the subduction of the Phoenix Plate induced rapid clockwise rotation of the AP at ~62-55 Ma, and followed by a counterclockwise rotation after ~50 Ma. This counterclockwise rotation facilitated lithospheric extension and basin opening in the South Scotia Ridge region, contributing to the opening of the Drake Passage. The late Paleocene separation between the AP and SPA can be explained by the rapid clockwise rotation of the AP at ~62-55 Ma. In addition, differential rotation along the rectilinear AP-SPA orogen at ~100-90 Ma created three different segments and two pivots under extensional conditions, can explain outcrop of limited mixed magma at Anvers Island pivot (54.6-55.7 Ma), as well as the rapid uplift of the subducted metamorphosed oceanic crustal material at Elephant (~110-100 Ma) and Smith (~65-62 Ma) Islands around two pivots, leading to the development of a new model of plate rotation-related magmatism and metamorphism in the forearc zone. In summary, the AP plate rotation fits well with the process observed in the Phoenix Plate subduction, long-term variation of the magmatism and tectonic evolution around the Scotia Sea region, clarifying the relationship between these geological events.


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00:00 - Intro
01:15 - Presentation
30:05 - Questions
38:05 - Announcements