Mid-Cretaceous oblique rifting of West Antarctica: Emplacement and rapid cooling of the Fosdick Mountains migmatite-cored gneiss dome

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

“…Thermal history modeling of all samples in this study suggest that the currently exposed rocks of western MBL cooled from temperatures >120 °C to near‐surface temperatures during mid‐ to Late Cretaceous and Paleocene times (Figure ). Mostly overlapping AFT and AHe dates of this study and the close correspondence of LT and HT thermochronological data as well as the overlap of cooling ages with U‐Pb zircon crystallization ages of the Byrd Coast Granite suite (e.g., Korhonen et al, ; McFadden et al, ; Siddoway et al, ) point to continuous rapid cooling of western MBL from temperatures >800 °C to <100 °C for the time interval ~105–90 Ma (Figure a). Thus, onset of cooling of the sample's host rocks is inferred directly after granite emplacement, which relates HT cooling predominantly to thermal relaxation associated with magmatic cooling.…”

“…Samples from the Edward VII Peninsula and the Ford Ranges show LT cooling to temperatures <80 °C between ~100 and 88–80 Ma at comparable rates. This timing of LT cooling overlaps with the activity of the WARS as constrained by HT cooling and exhumation of extensional structures in western MBL between 102 and 94 Ma (Figure a; McFadden et al, ; Richard et al, ; Siddoway et al, ). LT cooling may therefore represent a continuation of the HT cooling history (Figure a).…”

“…(a) Compilation of time‐temperature paths showing low‐temperature cooling of the Ford Ranges and Edward VII Peninsula (this study) together with other cooling rate and high‐temperature age constraints from the literature (Adams et al, ; Korhonen et al, ; Kula et al, ; Larter et al, ; McFadden et al, ; Siddoway et al, ; Spell et al, ). (b) Time‐temperature plot shows cooling paths derived from the Marie Byrd Land and Thurston Island crustal blocks.…”

“…In any case, mid‐Cretaceous crustal extension of the WARS was associated with granulite facies metamorphism and crustal anatexis, with compressed isotherms in western MBL (Richard et al, ; Yakymchuk et al, ). This setting triggered the intrusion of the Byrd Coast Granite suite at ~115–95 Ma (Brown et al, ) and the rapid exhumation of shallow to mid‐crustal rocks between ~102 and 94 Ma (McFadden et al, ; Richard et al, ; Siddoway et al, ). Over the same interval, metamorphic core complexes developed in Zealandia and the opening of the Tasman Sea commenced in contiguous areas of east Gondwana.…”

“…HT thermochronological dating (e.g., K‐Ar and Ar‐Ar) of rocks of the Ford Ranges and Edward VII Peninsula predominantly yielded mid‐Cretaceous ages (Adams et al, ; McFadden et al, ; Richard et al, ; Siddoway, et al, ). These ages closely correspond with published LT thermochronology dates.…”