Fluvial architectural analysis and longitudinal variance of the Castlegate Sandstone, Book Cliffs, Utah

The Castlegate Sandstone is among the most-studied fluvial deposits in the world due to its world-class continuous exposure in the Book Cliffs of Utah. Despite this, there has yet to be a comprehensive and detailed fluvial architecture analysis study considering the complete longitudinal variance within the system and all scales of architectural elements. This study uses methods of analysis of fluvial architectural elements, lithofacies, and calculation of backwater length. Nine outcrops, primarily along depositional dip, are utilized in this study with measured sections and thousands of drone photographs to create large-scale 3D outcrop models. Orthomosaics derived from 3D models are used to track and order bounding surfaces and assign architectural elements in order to reconstruct the depositional history of the Castlegate Sandstone. This study recognizes valley-scale scours in the Castlegate, a frequently overlooked surface within the hierarchy of fluvial bounding surfaces, but no evidence of an incised-valley system. Data collected was compared and supplemented with the numerous previous studies on this rock unit. This study determines the lack of trackable surfaces from the proximal to distal reaches of the Castlegate as well as lateral variation in architecture along strike within the system due to the unique regional controls on fluvial architecture. Observations made in this study add insight into driving factors of varying fluvial architecture and channel style observed along the lateral and longitudinal profile of the Castlegate Sandstone including climate, discharge, sediment supply, eustacy, and tectonics.