The Pagodroma Group – a Cenozoic record of the East Antarctic ice sheet in the northern Prince Charles Mountains

Abstract

Abstract:The northern Prince Charles Mountains overlook the western side of the 700 km long Lambert Glacier-Amery Ice Shelf drainage system. Within these mountains, at Amery Oasis (7O05O'S, 68'00'E) and Fisher Massif (7 1' 3 1 'S, 67"40'E), the Cenozoic glaciomarine Pagodroma Group consists of four uplifted Miocene and Pliocene-early Pleistocene formations here named the Mount Johnston, Fisher Bench, Battye Glacier and Bardin Bluffs formations. These are composed of massive and stratified diamicts, boulder gravels and minor laminated sandstones, siltstones and mudstones. Each forniation rests on either Precambrian metamorphic rocks, or on Permo-Triassic fluvial strata. The unconfonnity surfaces are parts of the walls and floors ofpalaeofjords. TheMiocene FisherBenchFormationexceeds 350 minthickness at Fisher Massif, where the yet older Miocene (or Oligocene) Mount JohnstonFormation overlies basement rocks atup to 1400 mabove sea level. Individual formations contain either Miocene diatoms, or else Pliocene-early Pleistocene diatomforam assemblages. The diamicts are interpreted as fjordal ice-proximal or ice-contact sediments, deposited seawards of tidewater glacier fronts located some 250 to 300 km inland of the present ocean margin. Each formation records an ice recession following a glacial expansion.

New insights in the evolution of Antarctic glaciation from depth conversion of well-log calibrated seismic section of Prydz Bay

“…Conversely, the so-called ''Dynamicists'' have argued that the ice-sheet fluctuations, which are indicative of more temperate (polythermal) glacial regimes than the present one, lasted until about 2.5 Ma, i.e. the late Pliocene (Webb et al 1984;McKelvey et al 2001;Wilson 1995;Harwood and Webb 1998;Hambrey and McKelvey 2000;Hambrey et al 2003). Whitehead et al 2006 reviewed the Cenozoic stratigraphy of the whole Lambert Graben and Prydz Bay region providing a general overview of temporal and spatial history of ice sheet advance and retreat.…”

Records of past ice sheet fluctuations in interior East Antarctica

“…The Pliocene strata in both the Vestford Hills and Larsemann Hills are mainly marine deposit with deep water foraminifer fossils (Quilty et al, 2000;Harwood et al, 2000). There are fjordal deposits in the northern Prince Charles Mountains (Whitehead and McKelvey, 2000;McKelvey et al, 2001;Hambrey and McKelvey, 2000a,b). It was reported recently that the sedimentary facies of Pliocene glacial deposits in the southern Prince Charles Mountains was continental facies (Whitehead et al, 2000;Whitehead and McKelvey, 2002), and the corresponding strata in the Prydz Bay was deep water ooze (Barker et al, 1998).…”

Late Miocene paleoenvironment of the Lambert Graben embayment, East Antarctica, evident from: Mollusc paleontology, sedimentology and geochemistry

“…1). The Prince Charles Mountains flank the sides of the graben and are partly covered with glacimarine sediment of the Pagodroma Group, which comprises at least four geographically separated formations (Hambrey and McKelvey, 2000a;McKelvey et al, 2001). The northerly Battye Glacier and Bardin Bluffs formations occur on the Amery Oasis,~250 km from Prydz Bay.…”

“…Alternative fossil evidence suggests the EAIS continued to vary in size until the Late Pliocene and that a warm glacial regime had persisted long after the Middle Miocene (Hill et al, 1996;Harwood and Webb, 1998). Much of this debate has centred upon evidence found in the Transantarctic Mountains, but new evidence about the dynamics and paleoenvironment of the EAIS is emerging from research on the Pagodroma Group in the Prince Charles Mountains (Hambrey and McKelvey, 2000a,b;McKelvey et al, 2001;Whitehead and McKelvey, 2001;Bloemendal et al, 2003;Ehrmann et al, 2003;Whitehead et al, 2003).…”

“…The formation was first discovered from the Dragons Teeth exposures (McLeod, 1958), subsequent research describes the formation's geographic extent, lithostratigraphy, age and occurrence of mollusc fossils (Bardin and Kolosova, 1988;Hambrey and McKelvey, 2000a,b;McKelvey et al, 2001). At McLeod Massif the Battye Glacier Formation consists of two lithostratigraphic members: a brown, sand-rich Upper Member, and a grey, muddier Lower Member (Whitehead et al, 2003) (Figs.…”