Phanerozoic Onlap Charts

Compilation of Phanerozoic sea-level change, coastal onlaps and recommended sequence designations*
Compiled by John W. Snedden (Inst. Geophysics UT Austin) and Chengjie Liu, (ExxonMobil Exploration)


Following is a compilation of published information on Phanerozic sea-level change and coastal onlaps (click on thumbnail image above for access to pdf of charts). These coastal onlap curves for the Paleozoic are derived from Haq and Schutter (2008) and that for the Mesozoic-Cenozoic are from Hardenbol et al. (1998), with minor revisions to accommodate absolute age revision and redefinition of stages. We also made age recalibrations for the Mesozoic-Cenozoic interval to the 2004/2008 timescale. The sea level trends are derived from Haq et al. (1987).

The time scale used here is from 2008; it is the current consensus time scale, but we expect future revisions with improved age data. The magnitudes of sea-level change in this chart follow the estimation of Haq and Schutter (2008) and Hardenbol et al. (1998). However, there is little consensus on the range of sea-level changes, though most believe that the sea-level position during most of the Phanerozoic was within ±100 meters of the present-day level.

The sequence designations are derived from a combination of abbreviated stage names and a sequential numerical appendix similar to the sequence boundary names of Hardenbol et al. (1998)*.   A sequence is designated by the sequence boundary name at its base. These are useful for chronostratigraphic designations of both depositional sequences and sequence stratigraphic surfacesThe methodology for using this chronostratigraphic designation system is included in Snedden and Liu (2011). Based on the AAPG paper referenced below the attached powerpoint file explains the methodology used in building the onlap chart. It is annotated with text in the notes pages explaining each figure

We thank Jim Ogg and Gabi Ogg at the Purdue University and the International Commission on stratigraphy
for their assistance in age recalibration of the Mesozoic-Cenozoic depositional sequences of Hardenbol et al. (1998) into the 2004/2008 time scale.

* Sequence names for 19 Cambrian sequences are temporary because six stages containing these sequences have not yet been ratified by the International Commission on stratigraphy.
Note that the science of time and biostratigraphic markers is constantly advancing. Currently while the absolute ages change with new time scales, the stage boundaries have remained relatively stable with regard to biohorizons that are used in used in the chart presented above. Users are advised to check for updated ages and biostratigraphy that may have been superseded by using the International Chronostratigraphic Chart 2015 .  This can be downloaded from:


Haq, B.U. and S.R. Schutter, 2008, A chronology of Paleozoic sea-level changes: Science, v. 322, October 2008, p. 64-68.

Haq, B.U. and A.M. Al-Qahtani, 2005, Phanerozoic cycles of sea-level change on the Arabian Platform: GeoArabia, v. 10/2, p. 127-160.

Hardenbol, J., J. Thierry, M.B. Farley, T. Jacquin, P.C. de Graciansky, and P. Vail, 1998, Mesozoic and Cenozoic sequence chronostratigraphic framework of European Basins, in P.C. Graciansky, et al. (eds) Mesozoic and Cenozoic sequence stratigraphy of European basins: SEPM Special Publication 60, p. 3-13, charts 1-8.

Snedden, J. W. and C. Liu, 2011, Recommendations for a uniform chronostratigraphic designation system for Phanerozoic depositional sequences: American Asssociation of Petroleum Geologists Bulletin, v. 95, no. 7, p. 1095-1122.

Contact for authors
Institute for Geophysics, The University of Texas at Austin. Email:
ExxonMobil Exploration Co. (
Monday, May 16, 2016
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