Post Mid‐Cretaceous Tectonic and Topographic Evolution of Western Marie Byrd Land, WestAntarctica: Insights from Apatite FissionTrack and (U‐Th‐Sm)/He Data

Abstract

New low-temperature thermochronological data from granitic basement of western Marie Byrd Land (MBL) provide insights into the still poorly constrained tectonic and topographic evolution of West Antarctica during and after continental breakup. Here, we present the first apatite (U-Th-Sm)/He data from the Devonian Ford Granodiorite and the mid-Cretaceous Byrd Coast Granite suites from the Ford Ranges and the Edward VII Peninsula. Thermal history modeling integrating apatite (U-Th-Sm)/He dates of 109-68 Ma with revised apatite fission track data in combination with geologic information indicates a thermal history with diachronous enhanced cooling at~100-60 Ma and subsequent slow cooling until the present day. Enhanced cooling at~100-70 Ma was related to activity of the West Antarctic rift system and to continental breakup, thereby exhuming most samples to shallow crustal levels. Localized cooling at~75-60 Ma is interpreted as resulting from faulting in the eastern Ross Sea region. Slow cooling after~70-60 Ma corresponds with formation of erosion surfaces in western MBL. Comparison of our results from western MBL with data from the literature indicates progressive formation of erosion surfaces from west to east along the MBL-Thurston Island crustal blocks. Late Cenozoic activity of the West Antarctic rift system and MBL dome uplift appear to have caused only minor exhumation of <1.5 km in western MBL.

High geothermal heat flow beneath Thwaites Glacier in West Antarctica inferred from aeromagnetic data

“…The relatively high T e estimates across the continental shelf are likely an effect of the up to 7 km thick sedimentary sequence of inferred early Cretaceous to Cenozoic age 30 . The region of high T e propagates east towards Thurston Island Block, which was part of a vast region along the formerly convergent paleo-Pacific margin stretching as a magmatic arc from the eastern Amundsen Sea sector to and along the western Antarctic Peninsula 31 . Regions of low T e are prone to react more sensitively to changes in crustal loads.…”

Apatite Fission Track Signatures of the Ross Sea Ice Flows During the Last Glacial Maximum

“…Generally, exhumation ages detected on bedrock samples from East Antarctica are older than those from West Antarctica (Figure 3). For example, Fitzgerald (1994) detected AFT ages of 253 – 339 Ma in the Miller Range along the TAM, whereas apatite fission track ages in the Marie Byrd Land are Cretaceous or younger (Adams et al, 1995; Lisker & Olesch, 1998; Spiegel et al, 2016; Zundel et al, 2019). Moreover, published detrital fission track ages from piston cores located in the ERS (therefore sourced certainly from West Antarctica) are all younger than 222 Ma (Perotti et al, 2017).…”

“…Locally Swanson Formation and intrusives rocks are affected by high‐grade metamorphism during Devonian‐Carboniferous and Cretaceous forming the today exposed migmatitic dome of the Fosdik Mountain (Siddoway, Baldwin, et al, 2004; Siddoway, Richard, et al, 2004). The Cretaceous phase of deformation was followed by a rapid exhumation testified by low‐temperature thermochronological data coming from Edward VII Peninsula and Ford Range, showing in general a cluster of mid‐Cretaceous ages for apatite and zircon fission track dating (Adams et al, 1995; Lisker & Olesch, 1998; Zundel et al, 2019). During the Cenozoic, starting from about 35 Ma, the region of Marie Byrd Land was affected by an intense alkaline volcanism and uplift (LeMasurier et al, 2011).…”

Extensive palaeo-surfaces beneath the Evans–Rutford region of the West Antarctic Ice Sheet control modern and past ice flow

“…Erosion surfaces in western Marie Byrd Land, which formed around ca. 70-60 Ma, have also been identified, corresponding to slow cooling following activity in the West Antarctic Rift System (Zundel et al, 2019).…”