THE MID-NORIAN PALEOLANDSCAPE OF THE NEWSPAPER INTERVAL WITHIN THE BLUE MESA MEMBER OF THE CHINLE FORMATION IN PETRIFIED FOREST NATIONAL PARK, ARIZONA

The Triassic Chinle Formation present in the Petrified Forest National Park (PFNP) has been studied in many aspects but has not been subject to a paleolandscape study within the Newspaper interval of the Blue Mesa Member. This study utilized a laterally continuous paleoweathered surface with the purpose of reconstructing a paleolandscape existing prior to a Mid-Norian climate shift associated with a large floral and faunal turnover within PFNP. The landscape surface was identified via high resolution photopans of exposed slopes within the park. The study consisted of documenting fluvial aggredational cycles (FACs) and the stratigraphic hierarchy of each associated fluvial sequence in addition to paleosol development, features and biological associations of paleosols found along the exposed paleoweathered surface. The area of interest is a single fining upward deca-meter scale FAC-set, the Newspaper interval, that is divided into a series of 7 individual meter scale FACs deposited by a fine-grained meandering river belt. Each FAC is a fining upward sequence terminated by either paleosol development at its surface or an erosive contact with the overlying FAC. Twenty-three pedotypes represent 46 profiles trenched from paleosols developed along the single paleoweathered surface with pedogenic carbonate and organic matter collected when possible for isotopic analysis. Pedotypes include paleosols similar to modern well drained Entisols; well drained calcic and non calcic Inceptisols; and cambic, calcic and non-calcic well drained and poorly drained Vertisols. FAC thickness appears to be inversely related to paleosol maturity, and decreases away from the main channel complex. Paleosols seem to be more mature further from more frequent deposition of sediment in or near channels. Those similar to Inceptisols are proximal to channels while those similar to Vertisols are found in more stable distal areas. Paleosols formed at the surface of infilled channels appear to be the least mature and similar to Entisols and weakly developed Inceptisols. Trace fossils seem to indicate carbonate replaced cycad stumps make up the bulk of plant traces in most overbank facies with trees like Araucarioxylon and various Lycopods being more common in all riparian zones and infilled channels.