High-Frequency, Glacio-Eustatic Cyclicity in the Middle Pennsylvanian of the Paradox Basin: An Evaluation of Milankovitch Forcing

  1. P. L. de Boer2 and
  2. D. G. Smith3
  1. R. K. Goldhammer,
  2. E. J. Oswald and
  3. P. A. Dunn

Published Online: 29 APR 2009

DOI: 10.1002/9781444304039.ch18

Orbital Forcing and Cyclic Sequences

Orbital Forcing and Cyclic Sequences

How to Cite

Goldhammer, R. K., Oswald, E. J. and Dunn, P. A. (1994) High-Frequency, Glacio-Eustatic Cyclicity in the Middle Pennsylvanian of the Paradox Basin: An Evaluation of Milankovitch Forcing, in Orbital Forcing and Cyclic Sequences (eds P. L. de Boer and D. G. Smith), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304039.ch18

Editor Information

  1. 2

    Utrecht, The Netherlands

  2. 3

    London, UK

Author Information

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

Publication History

  1. Published Online: 29 APR 2009
  2. Published Print: 28 JAN 1994

ISBN Information

Print ISBN: 9780632037360

Online ISBN: 9781444304039



  • high frequency, glacio-eustatic cyclicity in Middle Pennsylvanian;
  • glacio-eustatic sea level fluctuations;
  • platform carbonate cyclicity;
  • depositional facies;
  • systems tract development of fourth order sequences


Middle Pennsylvanian (Desmoinesian) shelf carbonates in the SW Paradox Basin display three superimposed orders of stratigraphic cyclicity with a systematic, vertical succession of facies, cycle and sequence stacking patterns. Fifth-order cycles (34 cycles in 196-m section; average 6 m thick; mean period of 29 ka) are grouped into fourth-order sequences (average 35 m thick; mean period 257 ka), which in turn vertically stack to define a third-order sequence (196+ m thick; 2–3 Ma duration). Fifth-order cycles are composed of shallowing-upward packages of dominantly subtidal shelf carbonates with sharp cycle boundaries (either exposure or flooding surfaces). Fifth-order cycles are packaged into fourth-order sequences bounded by regionally correlative subaerial exposure surfaces. These type 1 sequences contain a down-dip, restricted low-stand wedge of evaporites and quartz clastics in topographic lows on the Paradox shelf (intra-shelf depressions). The low-stand systems tract is overlain by a regionally correlative transgressive shaley mudstone (condensed section), and a high-stand systems tract composed of thinning-upward, aggradational, fifth-order cycles. Systematic variation in the thickness of fourth-order sequences (thinning-upward followed by thickening-upward), as well as systematic variations in the number of fifth-order cycles/fourth-order sequences (decreasing followed by increasing number), define a third-order accommodation trend which is also regionally correlative.

High-frequency cycles and sequences are interpreted as dominantly aggradational allocycles generated in response to composite fourth- and fifth-order glacio-eustatic sea-level fluctuations. Two different orbital forcing (Milankovitch) scenarios are evaluated to explain the composite stratigraphic cyclicity of the Paradox sequences, each of which is plausible given Desmoinesian age date estimates. The cycle, sequence and facies stacking patterns have been replicated via computer by superimposing composite, high-frequency glacio-eustasy atop regional subsidence using depth-dependent sedimentation.