INTERPRETATION OF A PALUSTRINE DEPOSITIONAL ENVIRONMENT FOR THE PINK MEMBER OF THE CLARON FORMATION: BRYCE CANYON NATIONAL PARK, UTAH

Distributed across the high plateaus of southwestern Utah, the late Paleocene to Eocene age Claron Formation has been described as clastic and carbonate sediments deposited in a fluvial-lacustrine system within an intermontane basin formed during the Laramide orogeny. Recent lithologic and paleontological studies of the lower pink member of the Claron Formation at Bryce National Park suggest the carbonates are primarily associated with a palustrine system, defined as shallow, hard-water [high Ca(HCO₃)₂ content] perennial lakes subjected to subaerial exposure during which pedogenesis modifies the fine-grained carbonate substrates. Four palustrine facies and one lacustrine facies are recognized. The palustrine facies are: (1) mottled limestone, consisting of carbonate mud, with minor detrital grains; (2) nodular and brecciated limestone characterized by irregular micritic nodules embedded in a soft, chalky matrix; (3) rooted limestone with large, tapering root casts; and (4) peloidal/pisoid limestone containing hymenopteran trace fossils (cocoons). A sparry limestone facies is interpreted as a normal lacustrine environment. The mottled and nodular limestone facies are the products of desiccation and iron mobilization, whereas the rooted facies indicates a well-established plant community with more intense soil modification and longer periods of subaerial exposure. The peloidal/pisoid facies is associated with repeated wet and dry conditions associated with fluctuating water tables. The sparry limestone facies is indicative of longer periods of true lacustrine influence.