Road Log, Day Four: Nonmarine Sequence Stratigraphy and Facies Architecture of the Downdip Castlegate Sandstone in the Book Cliffs of Western Colorado and Eastern Utah
John C. Van Wagoner, 1991. "Road Log, Day Four: Nonmarine Sequence Stratigraphy and Facies Architecture of the Downdip Castlegate Sandstone in the Book Cliffs of Western Colorado and Eastern Utah", Sequence Stratigraphy Applications to Shelf Sandstone Reservoirs: Outcrop to Subsurface Examples, J. C. Van Wagoner, C. R. Jones, D. R. Taylor, D. Nummedal, D. C. Jennette, G. W. Riley
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OBJECTIVES: Today the Castlegate will be traced to the most basinward facies exposed in the Book Cliffs completing an updip to downdip analysis of the Castlegate sequence boundary and systems tracts. The Desert will be seen only at STOP ONE. As the Castlegate sequence boundary is traced basinward, changes in the sequence-boundary expression will be examined. These expressions will be compared with the expression of the sequence boundary seen yesterday. Changes in incised-valley geometry will also be studied, especially in the Horsepasture area of STOP THREE, time and weather permitting. Laramide deformation appeared to influence the Castlegate sequence boundary around the Colorado-Utah border. This influence will be examined later in the day.
Leave the motel parking lot in Moab. Drive north on Highway 191. The road log begins at the bridge crossing the Colorado River outside of Moab.
0.0 Crossing the Colorado River on the north side of Moab.
2.7 Passing the entrance to Arches National Park. This park contains the greatest density of natural arches in the world from a three-foot opening to the largest, Landscape Arch. This 105-foot high ribbon of rock measures 291 feet across. Much of the faulting in the Jurassic and Triassic rocks around Moab is controlled by movement of Pennsylvanian salt, 1000's of feet thick in some places.
8.6 Pass the turnoff to Dead Horse Point.
25.0 The Mancos, Desert, and Castlegate can be seen along the Book Cliffs to the north.
29.1 Turn right onto the access road for 1-70. Drive east toward
Figures & Tables
The Lower Sego provides an opportunity to study well-exposed, high-frequency sequences and their systems tracts. Criteria for identification of sequence boundaries will presented. Sequences and their boundaries will be contrasted with parasequences and their bounding surfaces. The Upper and Lower Sego contain well-exposed tidal deposits within the lowstand systems tracts of high-frequency sequences. These tidal deposits and their relationship to incised valleys and systems tracts will be examined. The incised valley interpreted to form during relative falls in sea level will be contrasted with distributary channels related to autocyclic mechanisms.
0.0 Leave the parking lot of the Grand Junction Hilton. Grand Junction , Colorado. Turn left onto Horizon Drive. Pass under the 1-70 bridge, Turn left into the entrance ramp for 1-70 west.
0.2 Enter 1-70 heading west toward the Colorado –Utah State line. For the next 20 miles the Interstate will parallel the Colorado River flowing along the west side of the Grand Valley. The Interstate is built on the gray Cretaceous Mancos Shale. To the west of the Colorado River are the red cliffs of the Colorado National Monument. The Monument is operated by the National Park Service. These cliffs are the eastern edge of the Uncomahgre Uplift. As you drive north along the Interstate, the steeply dipping eastern limb of the Uncomahgre is clearly visible. This tight monoclinal fold is the result of horizontal compressional tectonics associated with Laramide deformation (Heyman, 1983). The red rocks in the Mounment include, from stratigraphically oldest to youngest: the Chinle Formation forming the lower, less resistant slops, the Wingate formation forming the massive cliffs up to 400 feet thick , the Kayenta Formation overlain by an unconformity along which the Navajo and Curtis Formations are missing , the Summerville and Entrada Formations, and the Morrison Formation consisting of fluvial sandstones and associated mudstones, within which some of the earliest dinosaur bones in North America were discovered in the late 19th century. The Jurassic Morrison Formation is unconformably overlain by the brown, Cretaceous, coal-bearing Dakota Sandstone. The Dakota caps many of the high mesas within the Mounment and forms well-exposed dip slopes along the Interstate in the vicinity of the exit to Mack, Co..