The Effect of Tectonic and Eustatic Cycles on Accommodation and Sequence-Stratigraphic Framework in the Upper Cretaceous Foreland Basin of Southwestern Wyoming

  1. Henry W. Posamentier2,
  2. Colin P. Summerhayes3,
  3. Bilal U. Haq4 and
  4. George P. Allen5
  1. W. J. Devlin,
  2. K. W. Rudolph,
  3. C. A. Shaw and
  4. K. D. Ehman

Published Online: 15 APR 2009

DOI: 10.1002/9781444304015.ch25

Sequence Stratigraphy and Facies Associations

Sequence Stratigraphy and Facies Associations

How to Cite

Devlin, W. J., Rudolph, K. W., Shaw, C. A. and Ehman, K. D. (1993) The Effect of Tectonic and Eustatic Cycles on Accommodation and Sequence-Stratigraphic Framework in the Upper Cretaceous Foreland Basin of Southwestern Wyoming, in Sequence Stratigraphy and Facies Associations (eds H. W. Posamentier, C. P. Summerhayes, B. U. Haq and G. P. Allen), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304015.ch25

Editor Information

  1. 2

    Plano, Texas, USA

  2. 3

    Godalming, UK

  3. 4

    Washington, DC, USA

  4. 5

    St Remy les Chevreuses, France

Author Information

  1. Exxon Production Research Co., PO Box 2189, Houston, TX, 77252-2189, USA

Publication History

  1. Published Online: 15 APR 2009
  2. Published Print: 17 NOV 1993

ISBN Information

Print ISBN: 9780632035489

Online ISBN: 9781444304015

SEARCH

Keywords:

  • effect of tectonic and eustatic cycles on accommodation and sequence-stratigraphic framework;
  • sequence stratigraphy relating sedimentary strata - variations in accommodation through interpretation of stratal geometry;
  • stratigraphic relationships of Upper Cretaceous strata in southwestern Wyoming;
  • basin subsidence, thrust belt tectonics and tectonic component of accommodation;
  • stratigraphic expression of basin tectonics;
  • thrust belt-foreland response model;
  • sedimentation associated with out-of-phase tectonism in southern Wyoming foreland basin;
  • higher order sequence possible mechanisms;
  • control on higher order cycles by larger scale cycles

Summary

Both tectonics and eustasy contribute to a basin's accommodation, and hence, to observed cyclic stratal patterns, but distinguishing between the relative contribution of these components is not always straightforward. This paper addresses this problem with an example from the Upper Cretaceous foreland basin of southwestern Wyoming. Three large-scale sedimentation cycles, 500 m to 1500 m in thickness, are present in the Upper Cretaceous section, and these cycles consist of two parts. The lower part is characterized by a relatively deep-water shale succession that exhibits an abruptly deepening or retrogradational stacking pattern. The upper part consists of shallow-marine to non-marine sandstone units which exhibit an overall progradational stacking pattern. Geohistory analysis from a stratigraphic section at Rock Springs, Wyoming indicates that the onset of deposition of the lower, shale-prone part of each cycle corresponds with an acceleration in subsidence rate. The increases in subsidence rate were caused by thrust movements in the Sevier Fold-Thrust Belt. Deposition of the upper, progradational part of each cycle occurred during times of decreased subsidence rate and can be tied to periods of relative quiescence in the thrust belt. Independent evidence for the timing of thrust movements is provided by palynologically dated, syntectonic deposits in the thrust belt.

Basement-involved, Laramide-style uplifts also affected the foreland basin in the Late Cretaceous, and were responsible for dramatic changes in depositional style and palaeogeography. The relative timing between thrusting in the fold-thrust belt and basement-involved tectonism in the foreland basin determined stratigraphic patterns within the sedimentary fill. When the uplift of basement structures occurs during times of relative quiescence in the thrust belt, the tectonic movements are said to be ‘out-of-phase’. In basins where thrusting and basement-involved movements occur simultaneously, the events are said to occur ‘in-phase’. Thick, aggradational braided stream sediments were deposited in the vicinity of Rock Springs in association with out-of-phase movements. A period of in-phase tectonism was associated with the progradation of deltaic complexes that were supplied with abundant sediment from uplifted areas and deposited in adjacent, differentially subsiding sub-basins. The sub-basins were also the site of basinally restricted lowstand deposition during higher order sea-level fluctuations.

Superimposed on the larger scale, subsidence-related stratal packages are third- and fourth-order depositional sequences. The expression of the higher order sequences and their component systems tracts was controlled by the larger scale, subsidence-related accommodation cycles. However when both the regional and local tectonic controls in the basin are accounted for, a shorter duration, higher order control on relative sea-level fluctuations is still needed to account for the deposition of these sequences. Our working model is that the controlling mechanism, at least for the third-order sequences, is eustasy. However, other mechanisms may account for some of the observed depositional cyclicity, and these are discussed. Regardless of the mechanism, the observed stratigraphic relationships indicate that higher order fluctuations in relative sea level occurred in the Late Cretaceous that cannot be directly attributed to thrust-belt tectonics or intra-foreland basement-involved uplifts.