A DYNAMIC MODEL FOR CHINLE DEPOSYSTEM SUBSIDENCE

The Chinle Formation outcrops across the Colorado Plateau and represents a series of predominantly fluvial channel and floodplain deposits of Upper Triassic age, containing abundant silicified wood and terrestrial fauna. Traditionally, the accommodation space for the basin has been attributed to dynamic subsidence. However, despite extensive research of the formation and regional tectonics, there exists limited attempts to model the nature of the subsidence and no clear consensus on the nature of the basin. Additionally, there has been limited fieldwork with a view to synthesising data across the area of the entire plateau in recent years, with studies focussing on more limited geographic areas. Presented herein are preliminary results of a basin-wide sedimentological survey with the aim of creating a multifaceted dataset for basin modelling. Initial modelling results demonstrate the applicability of long wavelength subsidence for deposition of the Chinle Formation in the back-arc of the Cordilleran Magmatic Arc and in the absence of a major flexural load or fault-driven subsidence and highlight the importance of tight stratigraphic controls when modelling basins with relatively low succession thicknesses. Future work must emphasise the use of geochronological methods to provide more precise timescales for the creation of accommodation space. Areas for further exploration include the evolution of forces influencing the transition from the Lower Triassic Moenkopi Formation to the Chinle, including the timing of the abatement of flexural influence on the basin.