The effect of siliceous sponge deposition on Permian paleocommunity structure

A dramatic shift from carbonate-rich to chert-rich marine strata occurred during the Permian and is frequently attributed to the increased activity of siliceous sponges and their biosiliceous sedimentation. The first-order ecological consequences of this transition, if any, remain opaque. We analyze fossil occurrence data from the Phosphoria Basin (western North America) to test whether the presence of siliceous sponges, which are correlated with basin-wide chert strata, influenced the recruitment of benthic fauna. We digitized occurrence data from Yochelson and Van Sickle (1968), with particular attention to 228 fossil collections with detailed lithologic descriptions. We categorized fossil collections by formation, facies, and lithology, and used these data to code DCA and NMDS ordinations. We also analyzed the clustering of taxa into faunal units termed biofacies.
Results from these analyses indicate that fossil collections occurring in chert and carbonate are closely associated in f...