Vertical variation of the Miocene sandstone mineralogy in the Kutei Basin has been recognized but the reasons for this remain unsaid. Deltaic-sandstone facies, parasequence sets, detrital mineralogy, and provenance of the uppermost Middle Miocene to the Upper Miocene strata in the Anamta and Amantu areas were analyzed using twenty-three wells and selected composite 2D and 3D seismic lines. Taxon indicators were correlated to build bio- and litho-stratigraphic markers: M50, M65, M66, and M70. The mineralogy dataset was derived from core and cuttings, while the detrital minerals were described, counted, normalized, and plotted in ternary diagrams. The four key markers were tied to the 3D-seismic data for seismic-stratigraphy analysis to observe the parasequences, system tracts, and sequence boundaries that correspond to the fluctuated relative sea-level. The parasequence sets are: (1) M65 aggradation and progradation, (2) M66 progradation, forced-regression, and back to another progradation, (3) M70 progradation, which interestingly demonstrate the detrital-mineral groupings. Qt-F-L suggests a gradual change up to the younger age from subarkose to sublitharenite towards feldspathic-litharenite to litharenite. Qp-Lv-Ls demonstrates the source was derived from collision-suture and folded-thrust belt. Qm-F-Lt diagram reveals the mature rocks with stable frameworks to the recycled-orogen provenance. The sediments maturity and stability are further confirmed by the Qm-P-K ternary chart. The most important finding is a significant shift of the paleo-shelf edge during the forced regression, as it separated the mineralogy composition of the M66 to the underlying M65 parasequence sets.