Incised Valley Systems and Sequence Stratigraphy of the Ferron Sandstone, Notom Delta, Henry Mountains Region, Utah

The Notom fluvial-deltaic complex is one of the Ferron wedges deposited in the foreland basin of the Western Interior Seaway during Mid-late Turonian and is exposed three dimensionally in the Henry Mountains region, Utah.

The complex is built upon dark colored, un-laminated, and highly burrowed shelf mudstone and culminates in pebbly coarse sandstone sourced mainly from the northwest. The wedge is capped by a transgressive lag which is in turn overlain by shelf mudstone.

Sixty measured sections along both depositional dip and strike recognized 12 north- to northeast-ward-prograding parasequences within the complex. Four high-order (fourth-order) sequences are recognized based on the continuous tracing of key surfaces and the stacking patterns of parasequences. Two of them include valleys. Regional correlation and mapping showed two erosional surfaces in the upper valley, each of which shows over 10 meters of erosional relief and which partition the valley fill into two unconformity-bounded sequences, marked as V1and V2 respectively in a stratigraphic higher order. A major change in valley sedimentology from V1 to V2 is indicated by changes in fluvial paleocurrent direction, grain size, formative channel dimension, and overall facies type between the two.

The Notom fluvial deltaic complex is formed under a long-term relative sea level fall after the Greenhorn transgression and relative sea level maximum. The high-order sequences recognized in the study are interpreted as the product of high-order sea level fluctuations superimposed on this long-term relative sea level fall. The major change in valley sedimentology is interpreted as the result of climate change which leads to the marked change in formative river dimension and discharge as evaluated using different techniques.