Mesozoic palynofloras from the Mac. Robertson shelf, East Antarctica: geological and phytogeographic implications

Abstract

Gravity cores taken from five sites in the Nielsen basin, a sinuous trough on the Mac. Robertson shelf of the East Antarctic continental margin, have yielded non-marine palynofloras of late Early Jurassic to Early Cretaceous age. The palynomorphs occur in glacimarine muds and are thus not in situ, but the composition of the samples indicates that no mixing of individual assemblages has occurred, and that the sediments were deposited very close to outcrop of the source of the palynomorphs. The sequence is oldest at the seaward end of the Nielsen basin, and youngest near the fault-bounded landward end. It is interpreted as reflecting pre-break-up deposition on a passive, rifted continental margin. The age of the assemblages has been established by comparison with the zonal scheme developed in the Perth Basin of Western Australia. Similarity of the Antarctic palynofloras with those known from basins on the east coast of India confirms continental reconstructions that show this part of East Antarctica to have been contiguous with eastern India prior to break-up. The non-marine character of the palynomorphs suggests that marine conditions in this region of the Antarctic margin did not develop until at least late Early Cretaceous time.