FLUVIAL TO MARINE FACIES SUCCESSION IN A COMPOUND INCISED VALLEY IN THE FERRON-NOTOM DELTA, UTAH

The Turonian age Ferron sandstone formed in multiple deltas which empty into the Western Interior Seaway, including the Notom delta, which has been shown to contain 6 sequences. A compound incised valley system has been well documented at the base of the youngest sequence 1 in outcrops of the Cretaceous Ferron Notom delta complex in central Utah. That valley was shown to have undergone multiple episodes of cut and fill at high frequency Milankovich scale cyclicity, but correlative marine facies are not exposed. Directly beneath sequence 1, sequence 2 also contains a fluvial valley system. This valley system is particularly well exposed in the most basinward fluvial deposits within parasequence set 6 and can be correlated to coeval marine facies. Previously these deposits had only been documented in regional scale maps and cross sections, and it was interpreted as a single, versus compound valley. This study shows that the older valley is also compound, and more detailed data document the downstream succession of depositional facies comprising the valley fill. Correlation of 11 measured sections illustrates a basinward increase in tidal facies and reveals distinct lower and upper fluvial valleys, the lower of which feeds a previously documented shoreface facies. This confirms the compound nature of the valley fill in sequence 2. This suggests that the Ferron valleys are compound in nature and correlate with stepped forced regressive shoreline deposits that can be seen in the older shallow-marine strata. This finding demonstrates the importance of non-linear accommodation change in the context of traditional valley fill models.