Figure 5 - uploaded by Stephen Phillips
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Selected facies from the Vermillion Creek area. (A) Interbedded sandstone and silty mudstone which includes facies M, Ss1, Ss3, Ss4, and Ss7. (B) Symmetrical rippled sandstone (Ss3). (C) Trough cross-stratified sandstone (Ss1). (D) Asymmetrical rippled sandstone (Ss2). (E) Small-scale soft-sediment deformed sandstone (Ss6). (F) Large-scale softsediment deformed sandstone (Ss6) within distributary channel deposits. Note that F has been rotated to horizontal (top is to the right) to highlight that this slump feature occurred at the base of the sandstone.
Source publication
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...
Contexts in source publication
Context 1
... were located based on accessibility. Facies were then defined by grain size, sedimentary structure, and/or bioturbation (table 1; figure 5) and subsequently grouped into associations. Additionally, one scintillometer (Radiation Solutions Inc. RS-230 BGO Super-Spec handheld gamma-ray spectrometer) survey was undertaken to measure the natural radioactivity of the rock along the same path as the measured section in the NW outcrop area (figures 1 and 4) . ...
Context 2
... deposits are composed of heterolithic very fine grained sandstone and silty shale (10% to 60% sandstone) ( figure 5A). Sandstone beds increase in thickness from laminated (< 1 cm) to thick bedded (30 to100 cm) upsection. ...
Context 3
... range from thin to thick bedded. The dominant sedimentary structure is unidirectional trough cross-stratification ( figure 5C), but asymmetrical rippled (including climbing ripples; figure 5D) and soft-sediment deformed sandstone (figures 5E and 5F) is common. Sandstone can sometimes appear structureless. ...
Context 4
... range from thin to thick bedded. The dominant sedimentary structure is unidirectional trough cross-stratification ( figure 5C), but asymmetrical rippled (including climbing ripples; figure 5D) and soft-sediment deformed sandstone (figures 5E and 5F) is common. Sandstone can sometimes appear structureless. ...
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Citations
One of the goals of sequence stratigraphy is to model the conditions that generate stratigraphic architecture at outcrop to basin scales. Accommodation and sedimentation are the principal variables included in sequence-stratigraphic models that describe facies architecture in marine successions. Similar models exist to describe wholly nonmarine architecture. Distinct models are commonly applied to basins containing predominantly lacustrine or predominantly fluvial facies, which can make it difficult to apply models to the entire history of a basin that may include both lacustrine-dominated or fluvial-dominated phases, depending on climatic and tectonic conditions. To account for these changing conditions over the history of nonmarine basins, we present a conceptual three-dimensional model that describes the potential architectural patterns under specific combinations of accommodation, sediment flux, and water balance. Sectors of the model delineate where basins are underfilled or overfilled with respect to accommodation and limited with respect to sediment and water, creating eight zones with different implications for the development of facies architecture. Different types of basins (e.g., foreland, extensional, pull-apart, intracratonic) show broadly different trends in architecture through time. Subtle changes in accommodation, sedimentation, and water balance in the model correspond to shifts in facies architecture between lithostratigraphic units, but architectural transitions within individual basins are more important indicators of evolving basin conditions than comparisons among all basins. This model may serve as a guide for comparing the influence of distinct drivers of architecture among different types of basins as well as identifying important intervals of change during the history of basin filling. The availability of commensurate data on the history of accommodation, sedimentation, and water balance is, however, an ongoing challenge to reconstructing complete basin histories. Future analyses will test how well predicted facies stacking patterns compare to observed nonmarine stratigraphic successions resulting from the combination of accommodation, sediment flux, and water balance during the history of basin filling.