Integrated Study of Ancient Delta-Front Deposits, Using Outcrop, Ground-Penetrating Radar, and Three-Dimensional Photorealistic Data: Cretaceous Panther Tongue Sandstone, Utah, U.S.A.

The detailed 3-D facies architecture of “terminal” distributary channels in proximal delta-front deposits of the Cretaceous Panther Tongue delta in central Utah is imaged using digital mapping techniques and ground-penetrating radar (GPR). Four lithofacies were identified: massive sandstone, parallel-laminated sandstone, rippled heterolithics, and bioturbated heterolithics. Lithofacies interpretations suggest shallow water in a delta-front environment where river processes dominate deposition, but with seasonal wave and storm influence. “Terminal” distributary channels and upstream-accreting bars were observed on cliffs oriented both
perpendicular and parallel to the paleoflow direction. The terminal distributary-channel facies die out over less than 100 m distally into heterolithic deposits representing distal mouth bars of the delta front.

GPR and 3-D photorealistic techniques, together with sedimentary section measurements document the 3-D facies architecture. The 3-D photorealistic technique consists of draping oblique, close-range photographic images on 3-D terrain models of outcrops to generate a digital three-dimensional model of the outcrop. 2-D GPR profiles, collected parallel to cliff faces, are tied to the 3-D outcrop model using Global Positioning System (GPS). GPR lines are correlated with bedding diagrams of cliff-face exposures to extend mapping of sedimentary features behind the outcrop into three dimensions. Scours elongate downcurrent represent the bases of "terminal" distributary channels and show maximum relief of 5 m.