Ph.D. student Thomas Farrell and Dr. Mark Schmitz joined a rafting expedition through the Grand Canyon of the Colorado River in May, 2021. The scientific goals of this trip centered around the Cambrian Tonto Group, a transgressive fluvial to marine sequence of rocks that formed the ‘Great Unconformity’ of the Grand Canyon. This sea level rise is recorded globally, but is only poorly constrained in its timing and tempo. Our sampling for detrital zircons along with carbon isotope chemostratigraphy and trilobite biostratigraphy will aid in understanding this important event in the Cambrian Earth system.