A high‐resolution record of early Miocene Antarctic glacial history from ODP Site 1165, Prydz Bay

Abstract

[1] ODP Site 1165, located 400 km northwest of Prydz Bay, contains a high-resolution early Miocene record of pulses of ice-rafted debris (IRD) originating from the ancestral Lambert Glacier system and the Antarctic coast to the east. The 520 m of early Miocene sediments consist of dark gray claystone with silt laminae (contourites) alternating with decimeter-scale layers of greenish-gray bioturbated claystone that commonly contain ice-rafted debris. Downhole logs also record the alternations between the two facies: the IRD-bearing greenish-grey claystone corresponds to high resistivity and density values because of increased cementation by silica, and corresponds to lower natural gamma radiation values because of diluted clay content. The downhole logs thus allow a continuous and detailed stratigraphic record of the IRD-bearing layers to be obtained. The IRD-bearing layers represent deglaciations and interglacials, when a high flux of icebergs with incorporated material were melting out over the site; the contourite-rich layers represent glacials, when the Polar Current over the site was relatively strong. The sequence is dated by magnetostratigraphy, and the timing of the major IRD pulses is paced by orbital eccentricity, indicating that the volume of the East Antarctic ice sheet also fluctuates on this timescale. After 19.7 Ma, minor precessional and subprecessional IRD layers appear in the record, indicating that the ice sheet becomes more prone to deglaciation through this interval, perhaps associated with the gradual warming trend through the early Miocene.

Characterisation of long-term climate change by dimension estimates of multivariate palaeoclimatic proxy data

“…The age associated to the corresponding layer is about 20.3 to 20.4 Myr BP. In another study from Prydz Bay (ODP Site 1165) (Williams and Handwerger, 2005), this age interval was found to correspond to the probably most pronounced layer of ice-rafted debris during the Early Miocene, which indicates that the transition found in the Cape Roberts data is probably related to a major deglaciation event on the Antarctic continent.…”

“…Map of the Antarctic continent including the locations of the Cape Roberts project drill sites and the preceeding MSSTS-1 and CIROS-1 drillings. In addition, the location of ODP site 1165 (Williams and Handwerger, 2005), the site of collection of what is probably the best studied Antarctic offshore marine core, is displayed.…”

Late Oligocene obliquity-paced contourite sedimentation in the Wilkes Land margin of East Antarctica: implications for paleoceanographic and ice sheet configurations

“…In this 455 study, we have further characterized these facies on the basis of sedimentological data (visual core description, facies analysis, CT-scans, HRSEM), physical properties (magnetic susceptibility, NGR); and geochemical data (X-ray Fluorescence-XRF), which allow us to construct a sedimentation model for the depositional setting of Site U1356 during the late Oligocene that is dominated by bottom-current reworking of both, glacial and interglacial deposits. 460 Laminated, fossil-barren, glaciogenic deposits consistent with those of Facies F1 have been observed on younger sedimentary sections from other polar margins and interpreted as contour current modified turbidite deposits and as muddy contourites (Anderson et al, 1979;Mackensen et al, 1989;Grobe and Mackensen, 1992;Pudsey, 1992;Gilbert et al, 1998;Pudsey and Howe, 1998;Pudsey and 465 Camerlenghi, 1998;Anderson, 1999;Williams and Handwerger, 2005;Rebesco, 2007, Escutia et al, 2009). This particular type of glaciogenic contourite facies is associated with glacimarine deposition during glacial times, and has been interpreted to result from unusual, climate-related, environmental conditions of suppressed primary productivity and oxygen-poor deep-waters (Lucchi and Rebesco, 2007).…”

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“…Recent evidence from ice-proximal drill sites indicates that Antarctic ice sheets did advance and retreat with 40 and 100 ky cyclicity in the Neogene (Grützner et al, 2003;Patterson et al, 2014;Williams and Handwerger, 2005). However, these records are from single locations.…”