A palynological study of the Gustav Group from north-west James Ross Island Antarctica

The material from station DJ.1456/DJ.1504 at Brandy Bay is from the Lewis Hill and Brandy Bay members of the Whisky Bay Formation. The presence of Ascodinium acrophorum indicates a mid Vraconian (latest Albian) to early Cenomanian age for this succession. The occurrence of Ascodinium cf. serratum, and certain semi-quantitative data are strongly suggestive of the early Cenomanian. The palynological associations from station DJ.1502 at Brandy Bay are similar to those observed from station DJ.1456/DJ.1504. The station DJ.1502 succession is entirely within the Lewis Hill Member. Key dinoflagellate cyst taxa are indicative of the Vraconian (latest Albian) to early Cenomanian interval. The consistent occurrences of Ascodinium cf. serratum strongly suggest the early Cenomanian, but this cannot be deemed to be unequivocal evidence of this substage. Semi-quantitative dinoflagellate cyst data also suggest the early Cenomanian. Twelve samples from station DJ.1504 at Brandy Bay were studied. These are from the Lewis Hill and Brandy Bay members of the Whisky Bay Formation. The six Lewis Hill Member samples proved more palynologically-rich than the six samples from the overlying Brandy Bay Member. The assemblages from the Lewis Hill Member are similar to those from this unit at station DJ.1502, however, the occurrence of unequivocal Ascodinium serratum is indicative of the early Cenomanian. This study is the first definite palynological evidence for the Cenomanian Stage in the James Ross Basin. The material from the overlying Brandy Bay Member produced the key marker species Isabelidinium acuminatum and Isabelidinium glabrum, which is indicative of the early Turonian. This conclusion is consistent with previous palynological studies, but not strontium isotope stratigraphy that invoked a late Turonian age for the underlying uppermost Lewis Hill Member. The Hidden Lake Formation of station DJ.1507 at Brandy Bay yielded dinoflagellate cysts such as Conosphaeridium striatoconus and Spinidinium echinoideum subsp. rhombicum, which indicate a Coniacian age. This finding is in accord with previous studies.