The Growth and Ecology of Upper Cambrian Microbialite Biostromes from the Notch Peak Formation in Utah

Exposure of carbonate rocks within the uplifted mountains of southwestern Utah presents a unique opportunity to study the growth, morphology and ecology of two upper Cambrian microbialite reefs located within the Hellnmaria Member of the Notch Peak Formation. The first reef contains meter-length, strongly elongate microbialites that grew in a deep, subtidal marine environment. These elongate microbialites formed as a result of coalescence of round ‘algal’ heads, a process known to produce compound microbialite structures in shallow water, but seldom explored as a key factor in the elongation of deep, subtidal forms that grew in ancient environments. The second reef contains lithistid sponge-microbial ‘stromatolites,’ a new type of metazoan bio-structure that has only been described from the Carboniferous and Triassic periods. This discovery has important implications when reconstructing middle to upper Cambrian reef-building communities, as these periods are assumed to have a very low diversity of metazoan reefal components. Taken together, both reefs shed light on the paleoecology and paleoenvironment of upper Cambrian microbialite reef-building communities