Morphology and acoustic character of the antarctic Wilkes Land turbidite systems: Ice-sheet-sourced versus river-sourced fans

The Wilkes Land continental slope contains an intricate network of submarin e canyons that on the continental rise develop into a series of channel and overbank deposits of turbidite systems, We can define upper-fan, middle-fa n, and loner-fan provinces. The Wilkes Land upper fans are characterized by large channels with relief up to 900 m, distances between levee crests up to 18 km, and channel-floor widths up to 6 km, Middle-fan channels also hav e high relief (similar to 300 m), and locally, interchannel areas exhibit m ounded contourite-style deposits with high relief (up to 490 m), Within mid dle-fan sediment mounds there are acoustic facies of channel-overbank depos its from turbidity currents, and of sediment waves from contour-current sed imentation. The lower rise is characterized hg small, shallow channels (50- 75 m relief) and by interchannel areas of low relief, both characteristic o f a lon er-fan environment, The Wilkes Land turbidite systems show the foll owing significant morphological differences compared to most river-sourced fans: (1) multiple large tributary channels across the upper and middle fan , (2) channel relief several times greater (900 m) than typical relief (100 -200 m) for channels on fans less than 300 km in diameter. and (3) steep mi ddle-fan and lower-fan gradients. We interpret the differences in channel n etwork patterns, channel size, and middle-fan and lower-fan gradients beta een the Wilkes Land fans and other fans to result from the continental ice sheet feeding glacial ice streams that reached the outer continental shelf at times of glacial maxima. The Wilkes Land canyon-channel network patterns are comparable with the high-latitude Laurentian Fan and Labrador Sea chan nels, The Laurentian Fan also has large upper-fan channels with larger reli ef (800 m) than typical relief (200-300 m) expected for fans that are 600 k m in diameter. Both the Labrador Sea and Laurentian Fan are fed by continen tal ice sheets at the shelf edge.