# Sequence stratigraphy: hierarchy of sequences

Exploring for Oil and Gas Traps | |

Series | Treatise in Petroleum Geology |
---|---|

Part | Predicting the occurrence of oil and gas traps |

Chapter | Exploring for stratigraphic traps |

Author | John C. Dolson, Mike S. Bahorich, Rick C. Tobin, Edward A. Beaumont, Louis J. Terlikoski, Michael L. Hendricks |

Link | Web page |

Store | AAPG Store |

Global sea level changes (eustacy) are cyclic phenomena. Six orders of sea level cycles are recognized from stratigraphic evidence.^{[1]} Third-, fourth-, and fifth-order sea level cycles model sequence deposition for petroleum exploration. A third-order sequence is a composite of fourth- and fifth-order sequences.

The table below shows sea level cycle frequencies, thickness ranges, and stratigraphic names for third-, fourth-, and fifth-order sequences.

Sequence order | Cycle frequency, m.y. | Thickness, m | Stratigraphic name |
---|---|---|---|

Third | 0.5–5 | 100–1000 | Sequence |

Fourth | 0.1–0.5 | 1–10 | Parasequence |

Fifth | 0.01–0.1 | 1–10 | Parasequence |

## Superimposition of cycles

Several frequencies, representing different orders of sea level cycles, are superimposed on one another to make a composite sea level cycle curve. For stratigraphic trap exploration, cycles that impact trap location are usually third-, fourth-, and fifth-order sea level cycles. Figure 1 shows how adding third-, fourth-, and fifth-order cycles together will produce a composite curve.

## See also

- Sequence stratigraphy
- Third-order sequences
- Fourth- and fifth-order sequences (Parasequences)
- Traps in a framework of sequence stratigraphy

## References

- ↑
^{1.0}^{1.1}Van Wagoner, J. C., Mitchum, R. M., Campion, K. M., Rahmanian, V. D., 1990, Siliciclastic Sequence stratigraphy in Well Logs, Cores and Outcrops: Concepts for High-Resolution Correlation of Time and Facies: AAPG Methods in Exploration Series No. 7, 55 p.