Contrasting facies patterns in subtropical and temperate continental slopesediments: inferences from east Australian late Quaternary records

Studies of latest Quaternary continental slope sediments at two localities on the east Australian margin have revealed markedly different responses to late Quaternary sea level fluctuations. Offshore of Noosa, in the sub-trop ics, the sediment is predominantly a mixture of fine metastable carbonate, siliciclastic material, and pelagic carbonate. Important features of the st ratigraphy include a siliciclastic-dominated facies deposited relatively sl owly during the last glacial lowstand (sedimentation rate less than or equa l to8 cm/ka), and a calcareous facies, rich in metastable carbonate, deposi ted more rapidly during the late post-glacial transgression (sedimentation rates 15-24 cm/ka). Highstand and transgressive sedimentation rates are gre ater than lowstand rates by a factor of 2.5-6 due to increased shelf carbon ate productivity after flooding of the mid-shelf. Off Sydney, in temperate latitudes, continental slope sediment is largely a mixture of fine silicicl astic material and pelagic carbonate. Mean sedimentation rates range from 2 to 5 cm/ka over the last four oxygen isotope stages, with mean glacial/int erstadial rates higher than Holocene rates by a factor of similar to1.36. T his largely reflects the transfer of siliciclastic mud from the shelf to th e slope during sea level regression. In both localities, facies changes on the slope are not related to specific sea level states (e.g. lowstand facie s, transgressive facies, etc.), but reflect instead the interaction of chan ging sea level with shelf morphology. (C) 2001 Elsevier Science B.V. All ri ghts reserved.