Abstract
Abstract Oscillations in ice sheet extent during early and middle Miocene are intermittently preserved in the sedimentary record from the Antarctic continental shelf, with widespread erosion occurring during major ice sheet advances, and open marine deposition during times of ice sheet retreat. Data from seismic reflection surveys and drill sites from Deep Sea Drilling Project Leg 28 and International Ocean Discovery Program Expedition 374, located across the present-day middle continental shelf of the central Ross Sea (Antarctica), indicate the presence of expanded early to middle Miocene sedimentary sections. These include the Miocene climate optimum (MCO ca. 17–14.6 Ma) and the middle Miocene climate transition (MMCT ca. 14.6–13.9 Ma). Here, we correlate drill core records, wireline logs and reflection seismic data to elucidate the depositional architecture of the continental shelf and reconstruct the evolution and variability of dynamic ice sheets in the Ross Sea during the Miocene. Drill-site data are used to constrain seismic isopach maps that document the evolution of different ice sheets and ice caps which influenced sedimentary processes in the Ross Sea through the early to middle Miocene. In the early Miocene, periods of localized advance of the ice margin are revealed by the formation of thick sediment wedges prograding into the basins. At this time, morainal bank complexes are distinguished along the basin margins suggesting sediment supply derived from marine-terminating glaciers. During the MCO, biosiliceous-bearing sediments are regionally mapped within the depocenters of the major sedimentary basin across the Ross Sea, indicative of widespread open marine deposition with reduced glacimarine influence. At the MMCT, a distinct erosive surface is interpreted as representing large-scale marine-based ice sheet advance over most of the Ross Sea paleo-continental shelf. The regional mapping of the seismic stratigraphic architecture and its correlation to drilling data indicate a regional transition through the Miocene from growth of ice caps and inland ice sheets with marine-terminating margins, to widespread marine-based ice sheets extending across the outer continental shelf in the Ross Sea.
Highlights
Deep-sea benthic foraminifer δ18O isotopes exhibit ∼1‰ increase at ca. 14 Ma, termed the middle Miocene climate transition (MMCT), one of the three major climate transitions of the Cenozoic, which was accompanied by significant Southern Ocean cooling and inferred expansion of ice sheets in Antarctica (Shackleton and Kennett, 1975; Flower and Kennett, 1994; Zachos et al, 2001; Shevenell et al, 2004, 2008; Miller et al, 2020)
Seismic facies, and physical properties reveal open marine, ice-distal to ice-proximal glacimarine and subglacial conditions occurred in a heterogeneous manner across the continental shelf of the Ross Sea at various times through the past ∼23 m.y
Isolated ice-proximal and regional ice-distal conditions are interpreted to occur during the early Miocene prior to the formation of RSU5, i.e., before ca. 18 Ma
Summary
Discontinuity RSU5 forms the bottom boundary of RSS3-II and the Seismic Package B, and is identified as a high amplitude and laterally continuous reflection that is generally conformable with the underlying record In Pennell Basin (IODP Site U1521), Package B consists of bioturbated diatom-bearing/rich mudstone with bivalves and rare clasts in Lithostratigraphic Unit III (McKay et al, 2019), forming the upper part of the sequence that constitutes the interpreted Seismic Unit RSS4-I. The recovered Package C consists of silica cemented mudstones with rare clasts at DSDP Site 272 in the Glomar Challenger Basin (Hayes et al, 1975), while in the Pennell Basin the record is dominated by diamictite with carbonate concretions and occasional thin intervals of fine wavy mudstone laminations (Fig. 4), i.e., Lithostratigraphic Unit VII at IODP Site U1521 (McKay et al, 2019). The locations of the three considered sites are marked with red dots. (B) Reconstructions of the tentative most oceanwards extent of the grounded ice edge and marine terminating glaciers during periods of the ice advance from early to middle Miocene based on the depth and sediment distribution maps in Figures 7 and 9, and the features represented in
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
