17 Aug 2023
 | 17 Aug 2023
Status: this preprint is open for discussion.

Uplift and denudation history of the Ellsworth Mountains: insights from low temperature thermochronology

Joaquín Bastías-Silva, David Chew, Fernando Poblete, Paula Castillo, William Guenthner, Anne Grunow, Ian W. D. Dalziel, Airton Dias, Cristóbal Ramírez de Arellano, and Rodrigo Fernanddez

Abstract. While thermochronological studies have constrained the landscape evolution of several of the crustal blocks of West and East Antarctica, the tectono-thermal evolution of the Ellsworth Mountains remains relatively poorly constrained. These mountains are among the crustal blocks that comprise West Antarctica and exhibit an exceptionally well-preserved Palaeozoic sedimentary sequence. Despite the seminal contribution of Fitzgerald and Stump (1991), who suggested an Early Cretaceous uplift event for the Ellsworth Mountains, further thermochronological studies are required to improve the current understanding of the landscape evolution of this mountain chain. We present new zircon (U-Th)/He (ZHe) ages, which provide insights into the landscape evolution of the Ellsworth Mountains. The ZHe ages collected from near the base and the top of the sequence suggest that these rocks underwent burial reheating after deposition. A cooling event is recorded during the Jurassic–Early Cretaceous, which we interpret as representing exhumation in response to rock uplift of the Ellsworth Mountains. Moreover, our results show that, while ZHe ages at the base of the sequence are fully reset, towards the top ZHe are partially reset. Uplift and exhumation of the Ellsworth Mountains during the Jurassic–Early Cretaceous was contemporaneous with the rotation and translation of this crustal block with respect to East Antarctica and possibly the Antarctic Peninsula. Furthermore, this period is characterised by widespread extension associated with the disassembly and breakup of Gondwana, with the Ellsworth Mountains playing a key role in the opening of the far South Atlantic. Based on these results, we suggest that uplift of the Ellsworth Mountains during the disassembly of Gondwana provides additional evidence for major rearrangement of the crustal blocks between the South American, African, Australian and Antarctic plates. Finally, uplift of the Ellsworth Mountains commenced during the Jurassic, which predates the Early Cretaceous uplift of the Transantarctic Mountains. This may indicate that continental scale, rift-related exhumation was diachronous, initiating in the Ellsworth Mountains in the Jurassic and then propagating southwards into the Transantarctic Mountains during the Early Cretaceous.

Joaquín Bastías-Silva et al.

Status: open (until 21 Oct 2023)

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Joaquín Bastías-Silva et al.

Joaquín Bastías-Silva et al.


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Short summary
The Ellsworth Mountains are located in a remote area of Antarctica. They are 350 km long and 50 km wide, and include the highest point of Antarctica. Only a reduced number of researchers have been able to study it, leading to a scarce understanding of its formation. Our study shows that this mountain chain was formed from 180 to 100 million years ago. We obtained these results by analysing apatite minerals. These results help to understand when and how the Antarctic mountains were formed.