Cretaceous Rapid uplift of the Transantarctic Mountains-not due to rift-flank-uplift
Authors: Huerta Audrey , Blythe Ann , Winberry Paul 
Published: March 2022

&lt;p&gt;The Transantarctic Mountains (TAM) form a sinuous, &gt;3000 km-long boundary between East and West Antarctica with extreme relief reaching from below sea level to &gt;4500 m in elevation. Despite the impressive extent of this mountain range, there is no consensus on the processes responsible for the uplift and/or maintenance of the high topography.&lt;/p&gt;&lt;p&gt;Here we present the results of an extensive low-temperature thermochronology study of the Byrd Glacial Outlet region of the central TAM combined with numerical thermal-kinematic modelling. Results of this study confirm that rift-flank-uplift is not responsible for the development of the high elevation of the TAM in this region, and that the observed Cretaceous rapid crustal cooling was due to incision of a km&amp;#8217;s deep gorge.&lt;/p&gt;&lt;p&gt;Proximity of the TAM to the Cretaceous/Paleogene West Antarctic Rift System (WARS) suggests a genetic relationship between development of the TAM and extension of West Antarctica. However, the details of this relationship remain elusive. Four distinct scenarios have been proposed: (1) Cenozoic rift-flank-uplift along rift faults along the mountain front; (2) subduction related crustal thickening and highland development during the Phanerozoic; (3) Mesozoic burial followed by Mesozoic/Cenozoic uplift; and (4) edge-driven lithospheric foundering and buoyancy-driven uplift.&lt;/p&gt;&lt;p&gt;We focus on the results of apatite fission track (AFT) analysis of &amp;#160;seventeen samples collected along two vertical transects along the walls of the Byrd Glacial Outlet. All seventeen of these samples yield AFT ages of ~80 Ma. Transect A, located 45 km from the mountain front, has nine ~80 my old samples along &gt;1500 m of elevation (580-2140 m asl), and Transect B, located 70 km from the mountain front, has eight ~80 my old samples along 700 m of elevation (450 m to 1150 m asl).&lt;/p&gt;&lt;p&gt;Generally, these ~identical cooling ages would be interpreted to indicate that over 1500 m of the crust moved rapidly through the apatite partial annealing zone (PAZ; 120&amp;#176;C-60&amp;#176;C) at 80 Ma. However, inverse modeling (HeFTy) of these data indicate that the samples cooled slowly, and remained within the PAZ for 30-60 my. Thus, there appears to be an inherent contradiction between the inferred rapid cooling at ~80 Ma and the&amp;#160; very slow cooling indicated by HeFTy models.&amp;#160;&lt;/p&gt;&lt;p&gt;Results of finite-difference thermal-mechanical models confirm that regional erosion alone can not be responsible for the unique cooling history of the region. Rather, successful simulations must include rapid incision of a km&amp;#8217;s deep gorge coeval with regional erosion, followed by 10&amp;#8217;s of millions of years of regional erosion.&amp;#160;&lt;/p&gt;&lt;p&gt;These results reveal the Cretaceous development of high topography far inland from the current mountain front. The great distance (~70 km) from the current mountain front is inconsistent with uplift due to processes associated with rift-flank uplift. Additional AFT ages from samples collected along a horizontal transect at ~ sea level show a temporal pattern of ages consistent with headward erosion of a fluvial system draining a Cretaceous highland. The processes responsible for developing this highland could be either subduction-related crustal thickening, and/or lithospheric foundering.&amp;#160;&lt;/p&gt;