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Thin Bed and Sandstone Dike Architecture of Cretaceous Ferron Prodelta Shales, Utah

Abstract

This study examines the facies architecture of thin bedded prodelta shales, and compaction factor of a sandstone dike located within the Cretaceous Ferron Notom Delta Complex in Central Utah. Thin beds primarily form as a result of ignitive turbidites, tempestites, and hyperpycnal flows. The thin beds, in this study, were measured on a millimeter to centimeter scale, and were recorded in three measured sections. These measured sections were located at three different outcrop exposures between Hanksville and Cainville, Utah. For each measured section, sedimentological data including sedimentary structures, grain size, lithofacies, bed thickness, ichnofacies, and paleocurrents was collected.

In measured section 1, the compilation of facies shows that the environment is fluvial-dominated and wave-influenced, while measured sections 2 and 3 show a wave-dominated and fluvial-influenced environment. Facies produced by wave processes were dominant in all three measured sections, indicating that the distal area of the prodelta is wave influenced. This suggests that sediment gravity flows and tempestites are the main processes forming thin beds in the area. Low bioturbation and lack of inverse grading in these measured sections also supports this idea. Wave-enhanced sediment gravity flows also may have had an impact in the distal area. This is evident from the southeast migration of current ripples, which differs from the northeast migration of current ripples found in more proximal facies.

The sandstone dike located in the study area is a ptygmatically folded, vertical vein of very fine lower sandstone, which crosscuts horizontally bedded mudstones and sandstones. The dike was originally implaced as a planar, vertical sheet that was later folded to its present shape during compaction. The dike underwent 18% compaction (compaction factor of 1.21). Compaction of individual units of the dike ranged from 0 to 71% (compaction factors ranging from 1 to 3.44). The burial depth of this sandstone dike was likely greater than 300 m. It was also concluded that there is no relationship between facies and compaction within the dike.