Palynology and correlation of the Upper Pennsylvanian Tobra Formation from Zaluch Nala, Salt Range, Pakistan

Abstract

Samples from the upper 84 m of a 125 m thick section of the Tobra Formation at Zaluch Nala, western Salt Range, Pakistan yielded palynomorph taxa including the spores Horriditriletes sp. and Microbaculispora tentula, abundant monosaccate pollen including Barakarites cf. rotatus, Cannanoropollis janakii and Plicatipollenites malabarensis, and rare taeniate and non-taeniate bisaccate pollen. Converrucosisporites grandegranulatus, Cycadopites cymbatus, Horriditriletes ramosus, Horriditriletes tereteangulatus and Microbaculispora tentula indicate the South Oman 2165B Biozone (Late Pennsylvanian), suggesting that the Tobra Formation in Zaluch Nala is equivalent to the middle part of the Al Khlata Formation of South Oman (Petroleum Development Oman (PDO) Al Khlata production unit AK P5). Brevitriletes leptoacaina, Brevitriletes parmatus, Horriditriletes ramosus and Microbaculispora tentula indicate the lower part of the Oman and Saudi Arabia Palynological Zone 2 (OSPZ2). The Tobra Formation assemblages are also correlated with those from Stage 2 and the eastern Australian Microbaculispora tentula Oppel-zone, based on the occurrence of Brevitriletes cornutus, Brevitriletes parmatus, Cycadopites cymbatus, Horriditriletes ramosus, Horriditriletes tereteangulatus and Microbaculispora tentula. The Tobra Formation in Zaluch Nala lacks the deglaciation sequence that is present in several other palaeogeographically nearby basins such as those of south Arabia and Western Australia. This is an indication of either non-deposition during the deglaciation period or erosion associated with the unconformity between the Tobra Formation and the overlying Warchha Formation.

Keywords:

• Carboniferous
• pollen
• spores
• Tobra Formation
• Zaluch Nala
• Salt Range
• Pakistan

Acknowledgements

Irfan U. Jan thanks the Higher Education Commission of Pakistan, the British Geological Survey and the University of Leicester for supporting this research. Dr Asif Khan (Director, National Centre of Excellence in Geology, University of Peshawar, Pakistan) and Professor Muhammad Haneef (Chairman, Department of Geology, University of Peshawar, Pakistan) are thanked for the organisational support during the fieldwork in Pakistan. Dr Michael Petterson, Professor of Applied and Environmental Geosciences, University of Leicester is cordially thanked for helping to arrange the collaboration among the above-mentioned institutes (via BUFI and British Council DelPHE grants) that facilitated the successful completion of this work. Dr Sarah Davies and Dr Jan Zalasiewicz, University of Leicester are thanked for useful suggestions during the work. Irfan U. Jan thanks Mr Muntazer Abbas, Research Associate (NCEG), Mr Suleman Afridi (University of Peshawar), Mr M. Nauman and Mr Shah Azam (MS geology students) for pre-field discussion and field support. M.H. Stephenson publishes with the permission of the Director of the British Geological Survey (NERC). Bernard Owens and John E. Williams are thanked for their constructive reviews.