Thursday, June 16, 2016

The age of Madumabisa (Zambia) Fossil Vertebrates From Permian

Resolving the age of Madumabisa fossil vertebrates: Palynological evidence from the mid-Zambezi Basin of Zambia


Barbolini et al


Age estimates for Permian rocks in the mid-Zambezi Basin of Zambia have thus far yielded ambiguous results. Previously studied palynoassemblages from the Madumabisa Formation resemble spore-pollen suites from both the Cistecephalus Zone of North Luangwa (Lopingian) and the palynological Assemblage Sub-Zone IV H of Zimbabwe, proposed as Guadalupian. In order to improve age estimates and refine the biostratigraphy of the Madumabisa Formation, this formation together with the underlying Gwembe Formation, were sampled for palynomorphs. Assemblages from the Gwembe Formation are dominated by trilete spores with less common striate and non-striate bisaccate pollen, whereas the overlying Madumabisa Formation palaeoflora is composed predominantly of striate bisaccates. Ferns, pteridosperms, lycopods, sphenophytes, glossopterids and conifers are represented in the palynofloras. The upper Gwembe Formation palynoassemblage can be correlated with the Didecitriletes ericianus Zone of Backhouse (1991), the Guttulapollenites hannonicus–Protohaploxypinus rugatus Zone (Zone VI) of Aitken (1998), Assemblage Zone III of the mid-Zambezi Basin, Zimbabwe and Biozone KK 3 in the Kalahari Karoo Basin, Botswana, suggesting a Guadalupian (Wordian–Capitanian) age. The upper Madumabisa Formation palynoassemblage can be placed in the upper Dulhuntyispora parvithola Zone of Backhouse (1991)/APP5 of Price (1997), dated as Wuchiapingian (Lopingian) and correlates with Assemblage 2 of the Moatize–Minjova Basin, Mozambique and the McKinnon Member palynofloras of East Antarctica. It also resembles Daptocephalus (formerly Dicynodon) Assemblage Zone palynofloras of the lower and middle Balfour Formation in the Karoo Basin, South Africa, and is suggested to be Lopingian (Wuchiapingian–Changhsingian) in age. Although these palynological assemblages place lower and upper age constraints on Madumabisa Formation vertebrate fossils, uncertainty remains as to the exact correlation between the Madumabisa vertebrate assemblages and the assemblage zones of the main Karoo Basin.

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