Method description:Sample depths, ages, and Th concentrations have been previously published for the both the late Quaternary (Abell et al., 2023; Kinsley et al., 2022) and Pliocene-early Pleistocene (Abell et al., 2021). For consistency between datasets, Th is used to correct for the detrital components of Mn and U.Excess/authigenic components are determined via:[Mnxs] = [Mnmeas] – ([Thmeas] * (Mn/Th)lith)[Uauth] = [Umeas] – ([Thmeas] * (U/Th)lith)where [Mnmeas] and [Umeas] represent the total measured concentration of Mn and U, [Thmeas] indicates the total measured concentration of Th, (Mn/Th)lith is the ratio of Mn/Th in an assumed detrital endmember, and (U/Th)lith is the corresponding ratio for U. We set (Mn/Th)lith to be approximately 43 using the values from upper continental crust for Mn (600 ppm; Taylor & McLennan, 1995) and fine-grained dust for Th (14 ppm; McGee et al., 2016).