Stephen Phillips

Brigham Young University | BYU · Department of Geological Sciences

The Upper Cretaceous Rock Springs Formation of the Mesaverde Group in northwestern Colorado, southwestern Wyoming, and northeastern Utah is composed of fluvial, deltaic, and marine sediments that record the regression of the Western Interior Seaway during the Early to Middle Campanian. Contemporaneous deposits are present along the eastern and sout...

The analysis of downstream changes in ancient fluvial systems can better inform depositional models for foreland-basin systems. Herein we analyze the basal deposits of the Early Cretaceous Cedar Mountain Formation of Utah to better understand the variety of fluvial deposits present and to develop a depositional model for the Sevier foreland basin....

An analysis of the sedimentary fill of a foreland basin can provide information on the relative effect of tectonics, base‐level fluctuations and climate during basin development. This study analyzes fluvial strata from the upper Cedar Mountain and Naturita formations of the mid‐Cretaceous foreland basin of Utah (USA) to determine the effects of spa...

Thin tidal estuarine deposits of the Naturita Formation (0–23 m) of the San Rafael Swell record the initial flooding of the Cretaceous Western Interior Seaway, Utah, and capture the transition from inland fluvial systems to fully marine conditions over a time period of 5 My or less. A tide-dominated estuarine environment is favored due to the combi...

The Dakota Sandstone/Naturita Formation (D/N) of the San Rafael Swell (SRS), Utah contains extensive tidal deposits that, in part, record the initial transgression of the Cretaceous Western Interior Seaway (WIS). On the San Rafael Swell, there are comparatively few studies dedicated to this formation. The focus of this poster is to introduce data a...

Distinguishing different lithostratigraphic formations that are in contact with each other can be problematic when they are of like facies, appearance, and provenance. For example, formations of like facies that are vertically separated by a subtle unconformable surface are difficult to distinguish, especially if multiple candidate surfaces exist....

The placement of an unconformable surface within a stratal succession affects the interpreted thickness of units and sequences in contact with that surface. Unit thickness influences the interpretation of basin subsidence, paleotopography, diagenesis, and depositional style. Accurate placement of an unconformity results in true formational thicknes...

When the Navajo Sandstone was deposited, Utah resembled the present-day Sahara. Over time, deposition in this sand sea ceased and erosion ensued creating the surface on top of the Navajo Sandstone called the J-1, or Jurassic 1 unconformity. After this erosional period, deposition resumed with an interior seaway in Utah called the Carmel Seaway. Sho...

The Navajo Sandstone in south-central Utah is overlaid by the White Throne Member of the Temple Cap Formation in the west, and the Page Sandstone in the east. All three of these sandstones are Jurassic in age and were deposited in an arid, eolian setting. The Page Sandstone and the White Throne Member of the Temple Cap Formation are separated from...

The Temple Cap Formation and Page Sandstone are stratigraphically positioned above the Jurassic-1 (J-1) unconformity in south-central Utah. Radiometric ages have recently demonstrated that these formations are, in part, time equivalent. To conform to these new dates, a new sequence stratigraphic interpretation is necessary. This interpretation cann...