Reconstructing the Dust Cycle During the Late Paleozoic Ice Age

The Late Paleozoic Ice Age (LPIA) (330-270 Ma) was the Earth's most recent icehouse climate prior to the Cenozoic. On land, it coincided with the evolutionary divergence of reptilian and mammalian ancestral groups and the beginning of fully terrestrial ecosystems, as vertebrate herbivores, carnivores, and trees all began to expand into drier habitats. It also coincided with active tectonics associated with the formation of Pangaea and widespread silicic volcanic activity. Substantial glacial-interglacial fluctuations in pCO2 and hints of high oxygen levels suggest that carbon cycle variability was much stronger than during the Plio-Pleistocene. CO2 drawdown during the first part of the LPIA was likely driven by carbon sequestration and/or weathering on land; surprisingly, however, a switch to marine sequestration seems to have occurred by the Early Permian. This enhanced marine productivity could have been driven by fertilization of the ocean, perhaps by atmospheric dust.

As it has been during the Plio-Pleistocene, the dust cycle seems to have been highly active during the LPIA. Most surprising is evidence for widespread atmospheric dust deposition. Deposits of character and thickness analogous to loess recently formed in the Plio-Pleistocene mid-latitudes have been found near the LPIA paleo-equator. These deposits have no good analogs in the recent past.

Here, we will present a new reconstruction of the dust cycle during the LPIA based on a concerted campaign of measurements of archives of LPIA dust deposition throughout the world synthesized with climate modeling.