Continental rift to back-arc basin: Jurassic-Cretaceous stratigraphical and structural evolution of the Larsen Basin, Antarctic Peninsula
The Larsen Basin developed in Jurassic times as a result of continental rifting during the early stages of Gondwana break‐up. Lower‐?Upper Jurassic non‐marine sedimentary and volcanic rocks constitute a syn‐rift megasequence recording initial largely amagmatic extension and subsequent widespread extension‐related silicic volcanism. A succeeding, Kimmeridgian–early Berriasian transgressive megasequence, consisting largely of anoxic‐dysoxic hemipelagic mudstones, is thought to have been deposited during a thermal subsidence phase when relative magmatic quiescence and peak Jurassic eustatic sea levels served to maximize sediment starvation. The fragmentary record for late Berriasian–Barremian times suggests that a ?regressive megasequence may have developed in the earlier part of this period, recording increased sediment yield to the Larsen Basin from the increasingly emergent Antarctic Peninsula arc. Subsequently, strata in the southern, but not the northern, part of the basin underwent relatively intense eastward‐verging deformation, possibly during the formation of a retro‐arc fold‐thrust belt. Where exposed, the lower part of the succeeding Aptian–Eocene megasequence consists of a deep‐marine clastic wedge deposited along the fault‐bounded western basin margin during a phase of arc uplift and related differential subsidence. Following partial basin inversion in Late Cretaceous times, regression took place as reduced basinal subsidence rates allowed shallow marine facies to prograde basinward.