Criteria for differentiating microbial-caddisfly bioherms from those of marine polychaetes in a lacustrine setting: Paleocene second member, Funing Formation, Subei Basin, East China

摘要

Paleogene carbonate successions from lacustrine basins across East China yield microbial bioherms containing abundant agglutinated fossil tubes. Historically, these have been interpreted as the dwellings of polychaetes introduced by marine incursions. This is problematic, because these tubes are associated with abundant non-marine fauna and algae. Diverse and exceptionally well-preserved fossil tubes from carbonate microbial bioherms were studied in outcrops and drill cores of the second member of the Paleocene Funing Formation, Subei Basin, East China. Detailed macro-, meso-, and micro-structural investigations of these tube-dominated bioherms reveal that the putative "marine polychaete tubes" better fit the morphologies and construction styles of lacustrine caddisfly (Insecta: Trichoptera) larval cases, eliminating the need for a marine influence on this lacustrine setting.