Abstract

This study describes the foraminifera and facies of a large submarine canyon: the Bass Canyon, in the Gippsland Basin off the coast of southeastern Australia. The study incorporates facies analyses and interpretations of three types of foraminiferal distributional data: forms alive at time of collection, recently dead forms and relict forms. Four principle biofacies types occur: (1) middle shelf to shelf-break carbonate sand; (2) oxic upper to middle bathyal carbonate sand and gravel, with abundant bryozoans; (3) reduced oxic middle bathyal carbonate sand and gravel and (4) lower bathyal oxic muddy sand to Globigerina Ooze.

Correspondence Analysis of the 61 parameters (percentage abundance of foraminifera and % carbonate) in 36 samples yielded a clear depth-related pattern, although other related parameters such as dissolved oxygen and substrate also exert control on the foraminiferal assemblages.

Relict foraminifera are restricted to shelfal depths, shallower than 145 m. This pattern is similar to other shelf regions in Australia, where shelf areas were exposed during the Last Glacial Maximum, reworking shelf facies shallower than 150 m. The distribution of living foraminifera is similar to the distribution of the total assemblage, suggesting that the region has not been significantly mixed by wave, slump or bioturbation processes.

The majority of the modern Bass Canyon foraminiferal assemblages are cosmopolitan species, with few (semi-)endemic taxa that are mostly restricted to the shelf. These modern deeper-living forms are more conservative since they evolved in relatively lower stress eutrophic environments than their shallower oligotrophic dwelling contemporaries.

The foraminiferal and facies analogues of this study on the Bass Canyon may be used as a modern palaeoenvironmental analyses of the Gippsland and Otway Neogene sedimentary deep-sea successions. This will lead ultimately to a better understanding of the evolution of the basins in southeastern Australia, in an area influenced by the Southern Ocean during the Cenozoic.

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