Fossil woods from the permian and triassic of Mozambique: taxonomy, palaeocology and geoconservation
Date
2021
Authors
Nhamutole, Nelson Ernesto
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Abstract
Despite the discovery of immense fossil forests in Mozambique over 150 years ago,
meager palaeontological research has been directed to this unique legacy of Earth’s
history. As a consequence, only one outdated genus was known to date in
Mozambique. To change this scenario, fossil woods from Permian and Triassic
formations from the Tete and Niassa Provinces, Centre and Northern of
Mozambique, were collected during three consecutive field campaigns in 2017, 2018
and 2019. Over 300 samples were sectioned and studied microscopically. As a
result, important insights on the taxonomy, palaeoecology, palaeoclimates and
geoconservation are provided and improve significantly our knowledge on one of the
largest fossil forests in the world. Taxonomically, six genera and seven species are
now identified, consisting of Agathoxylon africanum, Agathoxylon karooensis,
Australoxylon teixeirae, Prototaxoxylon uniseriale, Taxodioxylon sp.,
Cupressinoxylon sp. nov, Protaxodioxylon sp. nov. 1 and Protaxodioxylon sp. nov. 2.
The latter three taxa are assigned to new species but only the latter two have been
submitted for publication. Agathoxylon africanum and Australoxylon teixeirae seem
to be endemic to Gondwana, sustaining the idea of species-level provincialism
based on Glossopteris leaf fossils. With the addition of the Mozambican occurrence,
Australoxylon teixeirae represents the most widespread taxon in Gondwana. Based
on growth ring analysis, it is found that the trees sampled show well-marked, wide,
growth rings suggesting well-defined seasons. Most of the woods studied present
rings belonging to D-type and S-type. S-type growth rings indicate extreme
conditions dominated by very wet and hot climate with the possible occurrence of
disease or post-depositional compression. Four fossil forests were also analyzed
qualitatively and quantitatively. These forests, subdivided into Nhambando,
Mapembera, Cadzewe and Carangache, are interesting for geotourism. In
Mozambique, however, more straightforward decisions are needed to ensure the full
legal protection of such sites and the implementation of safe geotourism. Although
the number of specimens with good preservation is relatively low, this study
represents an important contribution to fill gaps in the understanding of the
Gondwana palaeoflora in the Southern Hemisphere as a whole
Description
A dissertation submitted in fulfilment of the requirements for the degree of Master of Science to the Faculty of Science, School of Geoscience, University of the Witwatersrand, Johannesburg, 2021