Neogene to Quaternary stratigraphic evolution of the Antarctic Peninsula, Pacific Margin offshore of Adelaide Island: Transitions from a non-glacial, through glacially-influenced to a fully glacial state

Abstract

A detailed morphologic and seismic stratigraphic analysis of the continental margin offshore of Adelaide Island on the Pacific Margin of the Antarctic Peninsula (PMAP) is described based on the study of a regular network of reflection multichannel seismic profiles and swath bathymetry. We present an integrated study of the margin spanning the shelf to the continental rise and establish novel chronologic constraints and offer new interpretations on tectonic evolution and environmental changes affecting the PMAP. The stratigraphic stacking patterns record major shifts in the depositional style of the margin that outline three intervals in its evolution. The first non-glacial interval (Early Cretaceous to middle Miocene) encompasses a transition from an active to a passive margin (early Miocene). The second glacially-influenced interval (middle to late Miocene) is marked by pronounced aggradational sedimentary stacking and subsidence. Ice sheets advanced over the middle shelf of the margin at the end of this second interval, while the outer shelf experienced rare progradational events. The third, fully glaciated interval shows clear evidence of glacially dominated conditions on the margin. This interval divides into three minor stages. During the first stage (late Miocene to the beginning of the early Pliocene), frequent grounded ice advances to the shelf break began, depositing an initial progradational unit. A major truncation surface marked the end of this stage, which coincided with extensive mass transport deposits at the base of the slope. During the second progradational glacial margin stage (early Pliocene to middle Pleistocene), stacking patterns record clearly prograding glacial sequences. The beginning of the third aggradational glacial margin stage (middle Pleistocene to present) corresponded to an important shift in global climate during the Mid-Pleistocene Transition. Morphosedimentary characteristics observed along the margin today began to develop during the latest Miocene but did not become fully established until sometime during the interval between the end of the Pliocene and middle Pleistocene. Between these two time intervals, the northeast lateral migration of the Marguerite Trough also played a critical role in margin evolution, as it controlled ice sheet drainage pathways across the shelf, which in turn influenced development of slope and rise morphologies. Areas offshore from Adelaide Island differ from other areas of the PMAP due to changes in sedimentary processes that resulted from migration of the trough. This study confirms that the PMAP represents an exceptional locality for decoding, reconstructing and linking past tectonic and climatic changes. The study area specifically records not only the most relevant changes in depositional style, but also the relative importance of persistent along-and down-slope sedimentary processes. Our study approach can be extended to other areas and integrated with additional techniques to understand the evolution and the global linkages of the entire An...

Subglacial hydrological control on flow of an Antarctic Peninsula palaeo-ice stream

“…Ó Cofaigh et al, 2005a;Reinardy et al, 2011). A homogenous, terrigenous diamicton with moderate shear strength, which was recovered in marine sediment cores from AHT, documents the presence of the soft till there (Pudsey et al, 1994;Heroy and Anderson, 2005). Each of the sub-bottom profiles shows three depressions in this high amplitude reflector that are 8-10 m deep and 400-800 m wide and contain an acoustically transparent fill, above which a reflector is usually observed separating the fill from the overlying soft till layer (Fig.…”

“…1), was a recurring ice stream pathway during glacial maxima (Larter and Cunningham, 1993;Larter and Vanneste, 1995). The most recent grounding zone advance to the shelf edge along the AHT occurred during the LGM (Pudsey et al, 1994;Heroy and Anderson, 2005;Ó Cofaigh et al, 2014). To the southeast of the trough, the inner shelf is incised by an erosional basin, Palmer Deep (PD), that measures 26 km east to west and 10 km north to south at the 800 m depth contour (Domack et al, 2006;Fig.…”

Subglacial hydrological control on flow of an Antarctic Peninsula palaeo-ice stream

“…Drilling results and seismic reflection profiles indicate that the Antarctic Peninsula Ice Sheet has advanced to its western continental shelf edge many times since the late Miocene (Larter et al, 1997;Barker and Camerlenghi, 2002). Through repeated glaciations the ice sheet has eroded and over-deepened the inner shelf, extended the outer shelf through progradation and delivered large volumes of sediment to the deep ocean (Barker and Camerlenghi, 2002;Bart and Iwai, 2012;Hernández-Molina et al, 2017). The AHT, a 140 km-long by 50 km-wide cross-shelf trough (Fig.…”

Relative paleointensity (RPI) and age control in Quaternary sediment drifts off the Antarctic Peninsula

“…The muds were derived from turbidity currents that are sourced from glacial sediments on the continental margin and flow along large channels between the drifts. Fine-grained components of the turbidity currents are entrained within a southwestward-flowing bottom current and deposited on the drifts (Rebesco et al 1996(Rebesco et al , 2002Hernández-Molina et al, 2017).…”