Early Eocene fossil plants from the Mwadui kimberlite pipe, Tanzania

An early Eocene (52 ± 2 Ma) flora from the Mwadui kimberlite pipe in Tanzania includes ten leaf morphotypes, small seeds, fossil wood putatively related to Cynometra (Detarieae, Fabaceae), and a sparse palynoflora. The leaf flora is characterised by microphyllous and notophyllous entire margined leaves that are suggested to be related to the Euphorbiaceae and Fabaceae, although many cannot be firmly placed in modern families. The wood is the oldest member of Cynometroxylon and confirms that the Detarieae were diverse by the early Paleogene. The palynoflora is dominated by Ailanthipites daedaleus and Triporopollenites mwaduiensis with lesser amounts of small tricolpate (Tricolpites) and monosulcate (Lilliacidites) grains together with spores (Cyathidites spp., Triporoletes laevigatus) and freshwater algal cysts. Other components of the palynoresidue include abundant charcoalified tracheids and fungal hyphae. The low diversity and sparse palynoflora suggests a restricted catchment with little input from the regional vegetation. The sediments accumulated in a freshwater lacustrine environment with palynological input from the crater walls that were covered by low diversity vegetation. This is supported by the leaf floras. Although the leaf floras are more diverse with nine morphotypes identified, the small leaves (microphyll to notophyll) suggest a water-limited palaeoenvironment. This is supported by the low diversity and abundance of fern and bryophyte spores. The presence of a single wood taxon not only indicates that there were large trees around the crater-lake but that the aboreal component was of low diversity. These observations suggest an open woodland-like setting, while the taxonomic affinities of the wood (Cynometra) suggest a humid microclimate possibly with marked wet-dry seasonal contrasts. © 2013.