Dr. Kathleen Ritterbush
09 January 17
Permian rocks outcropping across Utah contain surprising amounts of chert, which appear to be artifacts of the longest and largest regime of seafloor sponge meadows in Earth history. No one is sure why a belt of siliceous sponge meadows spanned from temperate to arctic Pangea for tens of millions of years. Weâ€™re mapping sponge rocks across the state to determine when and where sponges dominated coastal systems. We want to know what environmental and ecological conditions favored their establishment, perpetuation, and eventual decline. A cooling climate may have helped, but the deposits also required a huge flux of marine silica of dubious provenance. Utahâ€™s Permian cherts also span a critical spatial boundary. Northern units, like the Murdock Mountain Formation in the Great Salt Lake Desert, contain bedded cherts1000 m thick and may record persistent sponge accumulation associated with the northern sponge belt. Southern units, like the Kaibab Limestone around St. George, contain abundant cherty nodules, and
may reveal more similarities to biocalcifying tropical ecosystems recorded across Texas. Sponge rocks also influence critical economic deposits (including petroleum Kansas and polymetalic mining in Peru), increasing motivation to determine their general formation requirements.