Recognition of the Kellwasser Event (Late Devonian) in the Hongguleleng Formation, Xinjiang Province, China

The Hongguleleng Formation records the rapid rebound from the Frasnian-Famennian (F/F) extinction event in a highly fossiliferous shallow marine setting associated with a Devonian oceanic island arc complex. Samples were collected from the basal six meters of shale and limestone in the Hongguleleng Formation and the upper one meter of shale and volcaniclastic sandstone in the underlying Zhulumute Formation. This interval also spans the linguiformis / triangularis conodont zone boundary which forms the F/F boundary. Although the Kellwasser event is not recognizable in outcrop by evidence of black shale, it can be recognized geochemically as series of dysoxic and anoxic events that span three meters of section below the F/F boundary. The same interval also shows high levels of biological productivity based on excess Ba and P2 O5 proxies. The upper limestone surfaces in this interval often have large concentrations of brachiopods. In contrast, limestones and shales in the lower Famennian show oxic to slightly dysoxic conditions. Pulses of volcaniclastic and hydrothermal components to detrital sedimentation are common throughout the interval. The analysis of multiple geochemical proxies allows us to confirm the presence of the Kellwasser event in the open oceanic part of Paleotethys. The tectonic setting of the Hongguleleng Formation is in contrast to the sections previously studied, which were located near Laurussia, Gondwana, Siberia, and the South China plate.