Palynological records of the Early Permian postglacial climate amelioration (Karoo Basin, South Africa)

Abstract

The Permian coal-bearing formations of the South African Karoo Basin play a crucial role in the study and interpretation of Gondwana’s climate history and biodiversity in this time of major global changes in terrestrial and marine ecosystems. Here, we report on new palynological data from the No. 2 coal seam of the Witbank coalfield, documenting the switch from icehouse to greenhouse conditions in the Early Permian. The studied postglacial fluvio-deltaic deposits of a highly proximal setting comprise coarse-grained to pebbly sandstones, partially with an abrupt upward transition into fine-grained sediments and coal, trough cross-stratified medium- to coarse-grained sandstones and horizontally laminated fine- to medium-grained sandstones and siltstones. The sedimentary organic matter content clearly documents stratal changes in the palynomorph assemblage and variations in the amount and in the type, size and shape of plant debris. Generally, palynofacies is characterized by a high amount of opaque phytoclasts. Amorphous organic matter is characteristic of laminated siltstones and coals. The palynological record indicates a cold climate, fern wetland community, characteristic of lowland alluvial plains, and an upland conifer community in the lower part of the coal seam. Up section, these communities are replaced by a cool-temperate cycad-like lowland vegetation and gymnospermous upland flora. The data presented herein, provide important information for (1) reconstructing palaeoenvironmental and climate change within the Lower Permian of the NE part of the South African Karoo, (2) intercontinental comparison of palaeofloral diversity patterns in adjacent sub-basins and (3) intra-Gondwanic correlations of coal-bearing basins (e.g. Australia), recording a major postglacial change associated with climate amelioration.