The Paleosalinity Context for the Ecological Pattern of the Chengjiang Biota

Abstract

The Chengjiang biota provides critical insights into metazoan diversification during the Cambrian Explosion, preserved at multiple localities with varying fossil abundances across the Chengjiang Bay. This work reports new B/Ga and B/K data from three drill cores near fossil localities, to evaluate salinity influences on ecological distribution of the biota. The results document a pronounced B/Ga and B/K decline at the biota's basal horizon, alongside a southwestward‐increasing B/Ga gradient from <6 to ∼13. These findings suggest significant freshwater influx into the Chengjiang Bay and the Chengjiang biota was deposited under a temporally decreasing salinity context. Enhanced freshwater input likely promoted turbiditic deposition of the event beds preserving the Chengjiang biota. Crucially, our data demonstrate a southwestward‐increasing salinity gradient in the Chengjiang Bay that governed ecological distribution of the Chengjiang Biota, with brackish waters suppressing marine animal development in the northeast, whereas stable marine conditions sustained elevated biodiversity in the southwest.