A HIGH-RESOLUTION PALYNOLOGICAL TIMESCALE OF GONDWANAN VEGETATION CHANGE AND PERMIAN DEGLACIATION

Pollen and spore assemblages from the Permian of Gondwana constitute the only high-resolution prior record of high-latitude plant communities during an icehouse-to-greenhouse transition. However, the difficulty of precisely correlating these palynological records across Gondwana obscures the tempo of floral change during this crucial interval. No quantitative model capable of detecting rapid vegetation fluctuations contemporaneous with the Gondwanan deglaciation presently exists.

We here offer a tool suitable for the task: a high-precision, palynologically-derived timescale of the Permian of Gondwana. The timescale is derived via constrained optimization algorithms, implemented in the software CONOP9. These algorithms first draw upon palynological records to assemble a scaled composite sequence of palynotaxon first and last appearance datums; next, high-precision U-Pb CA-TIMS dates directly associated with those palynological records calibrate the timescale, yielding a high-resolution record of vegetation change.

A preliminary iteration of the timescale encompasses 33 stratigraphic sections from across Australia and Antarctica, 399 taxa representing pollen, spores, algal remains, and acritarchs, and 37 U-Pb CA-TIMS dates. The timescale has a mean resolving power of 0.25 m.y.—an order of magnitude greater than the latest published Australian palynological scheme. This degree of precision allows the model to uniquely illustrate trends in the diversity and biogeography of high-latitude vegetation during an unparalleled historical precedent to the ongoing modern human-induced icehouse-to-greenhouse transition.