Late Paleozoic stromatolites: new insights from the Lower Permian of Kansas

Carboniferous to Permian marine stromatolites are widely dispersed across t he Pangaean margins and embayments and are typified by the 'Ottonosia-grade stromatolite' (designated herein). This stromatolite type consists of a we ll-laminated oncoid or domical stromatoid that developed into branching, la minated columns in the upper reaches. To develop a model for the global pat tern, we investigated Lower Permian stromatolites from Kansas (Howe Limesto ne Member, Red Eagle Limestone). Stromatoids from the Lyon County locality typify the Ottonosia-grade stromatolites. The laminae are sharp throughout the stromatoid and are defined by an increase in cornuspirid foraminfera an d algal filaments. The upper zone of the stromatoid is composed of well-lam inated branching and brecciated columns ('pseudo-thrombolitic'). Coeval str omatolites From a new exposure at the Tuttle Creek Dam spillway possess a m ore massive mesostructure. These stromatolites are composed of a turbinate stromatoid or oncoid base and an overlying domical stromatoid, and are rimm ed by smaller meandering columns. Only the basal stromatoid, oncoids, and u pper columns are well laminated. In both localities, the microbial-construc ting ecosystem is dominated by cornuspirids and calcifying filamentous alga e (?Girvanella). The mesostructural differences of the stromatolites are du e to different environments of formation. The Tuttle Creek stromatolites fo rmed in a shallow-subtidal to intertidal open marine setting. The coeval Ly on County stromatolites formed in a semi-restricted, marginal marine enviro nment such as a lagoon or supratidal zone. Based on this information and in dependent sedimentological data, we conclude that lagoonal or supratidal zo nes were common features in the late Paleozoic intracratonal zones of the P angaean supercontinent and account for Ottonosia-grade stromatolites occurr ing in the Laurentian mid-continent, the Zechstein Basin. Japan, Brazil, an d Tunisia.