AN ICEHOUSE DUST CYCLICITY RECORD PRESERVED FROM THE CARBONIFEROUS-PERMIAN AKIYOSHI LIMESTONE (JAPAN)

The Akiyoshi Belt is defined as a Late Permian subduction-generated accretionary complex in southwest Japan that is best characterized by Viséan to Guadalupian atoll-type limestone underlain by basaltic rocks of a seamount origin, and includes deep-water chert and terrigenous clastic rocks with minor siliceous tuff. The oceanic rock assemblage of the carbonates, siliceous rocks, and basaltic rocks were formed in an equatorial region of Panthalassic ocean far removed from any terrigenous siliciclastic influx, excepting that related to eolian delivery (atmospheric dust). Limestone of the Akiyoshi atoll archives climatic and eustatic changes during Early Carboniferous to Middle Permian time, spanning the onset, peak, and demise of the Late Paleozoic Ice Age (LPIA). We are investigating links between atmospheric dust (flux, size, composition, provenance) and icehouse- and glacial-interglacial climate modes, specifically at the Carboniferous-Permian boundary (Gzhelian-Asselian—hypothesized peak icehouse conditions) and Moscovian (diminished icehouse conditions). We hypothesize that dust flux varies systematically, with generally colder climates linked to higher dust fluxes.

The Gzhelian-Asselian interval studied to date exhibits pronounced cyclicity, expressed as upwardly shallowing sequences of wacke-/packstone to grainstone, with possible exposure (signaling glacial phases). We will present data on variations in dust flux and grain size with respect to this glacial-interglacial cyclicity to further explore atmospheric dust loading during the LPIA.