Eocene palynology of the Mulga Rocks deposits,southern Gunbarrel Basin,Western Australia

Mack, C.L. & Milne, L.A., 19.2.2015. Eocene palynology of the Mulga Rocks deposits, southern Gunbarrel Basin, Western Australia. Alcheringa 39, xxx–xxx. ISSN 0311-5518

Late Eocene palynomorph assemblages have been recovered from carbonaceous sediments within a tenement centred on the Mulga Rocks uranium deposits, currently under exploration by Energy and Minerals Australia. The Mulga Rocks deposits occur in a palaeovalley incised into rocks of the Cretaceous southern Gunbarrel Basin, and the underlying Neoproterozoic to Late Devonian southern Officer Basin, Western Australia. The palynomorph assemblages recovered from the Mulga Rocks deposits most closely resemble the Middle Nothofagidites asperus Zone equivalent of the Murray Basin. Many of the species recovered, and the abundance and diversity at which they are present, are considerably different from most of the southeastern Australian palynoassemblages of similar age. Common in the assemblages are species belonging to Nothofagus, Casuarinaceae, Myrtaceae and Picrodendraceae. Proteaceous species are diverse, with Banksia affiliates being prominent. Of most significance are assemblages dominated by Myrtaceidites species, which also contain affiliates of Petrophile and Xylomelum that occur in modern heathland, woodland and dry sclerophyll forests. The prominence of these taxa, and their co-occurrence, suggests that sclerophylly, at present linked closely with xeromorphy and now ubiquitous in the vegetation of Western Australia, was present in the late Eocene of southern Australia and suggests that at that time this trait may have been more prevalent than previously interpreted.

Charlotte Mack [charlotte.mack@postgrad.curtin.edu.au] and Lynne Milne [l.milne@curtin.edu.au], Department of Applied Geology, Curtin University of Technology, GPO Box U1987, Perth, WA 6845, Australia. Received 4.7.2014; revised 11.2.2015; accepted 19.2.2015.     

Palynology of the Jurassic-Cretaceous transition in the Rajmahal Formation,West Bengal,India

Borehole PGD-1A penetrated Cretaceous Rajmahal Formation and underlying Triassic Panchet Formation between 288–423.51 m. Palynoassemblages recovered within the Mesozoic sequence are assigned to three palynozones closely comparable to Australian assemblages. The oldest palynozone is the Verrucosisporites-Lundbladispora zone, which occurs between 373.5–376 m in the uppermost Panchet Formation. The first occurrence of Callialasporites turbatus occurs at 373.5 m and signals the presence of Jurassic deposits. The overlying Infratrappean greyshales (371.5–354 m) of the Rajmahal Formation is represented by the Murospora florida palynozone of Late Jurassic age. The youngest palynozone identified is the Cicatricosisporites australiensis zone which occurs within the Inter-trappeans (346.35–295.0 m) of the Rajmahal Formation. Based on ages assigned to the M. florida and C. australiensis zones in Australia, the Rajmahal Formation is dated as Oxfordian-Berriasian. The first appearance datums (FADs) of Cicatricosisporites australiensis, Crybelosporites stylolsus, Aequitriradites spinulosus and Lycopodiacidites dettmannae suggest that the Jurassic-Cretaceous boundary probably lies just within the interval 346.35–328.81 m in Inter-trappean bed II.