New Mexico Segment
1991. "New Mexico Segment", 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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OBJECTIVE: For the next two days we will examine the stratigraphy and lithofacies of Turanian- and Coniacian-age strata in northwestern New Mexico, on the lands of the Navajo Nation (see location map Figure 6-1). We will focus on the Gallup (shallow marine and coastal plain), Torrivio (predominantly braided-fluvial) and Tocito (estuarine to shallow marine) sandstone formations. An overview of the stratigraphy, lithofacies and hydrocarbon-trapping styles pertaining to these sandstones, in outcrop and from extensive subsurface well-log correlations, is presented in the accompanying paper entitled ‘High- resolution sequence stratigraphy of the Upper Cretaceous Tocito Sandstone…’. A briefer overview is also presented under STOP 1 below. The stratigraphy of the San Juan Basin is summarized in Figures 6-2, 6-3 and 6-4. These are increasingly higher resolution stratigraphic columns, with Figure 6-4, being specifically designed for this field trip. This figure reflects some of the latest ideas on the distribution of significant sequence-stratigraphic surfaces in the Late Turanian and Coniacian parts of the section.
The discussion in the text at each of the field stops is designed to present two somewhat different sequence-stratigraphic interpretations of the rocks; an Exxon (Jones, Van Wagoner and Jennette) and L.S.U. (Nummedal and Riley) interpretation. The reader can draw his/her own conclusions from the observations made at outcrop and in the subsurface (see accompanying papers).
Any person wishing to conduct geological investigations on the Navajo Reservation, including visiting the stops described in this guidebook, must first obtain a permit from the Navajo Nation Minerals Department, P.O. Box 146,
Figures & Tables
Sequence Stratigraphy Applications to Shelf Sandstone Reservoirs: Outcrop to Subsurface Examples
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..