EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Timing, Magnitude, Rate, and Drivers of Eustasy: A Review of the Cretaceous Period

Andrew Davies, Mike Simmons, David Ray, Benjamin Gréselle, Frans van Buchem, and Chris Robson
Andrew Davies et al.
  • Halliburton, Landmark, Abingdon, United Kingdom of Great Britain and Northern Ireland (

Isolating the eustatic signal from the sedimentary record remains challenging, yet much progress is being made toward understanding the timing, magnitude, and rate of eustasy on both long-term (107-108 yr) and short-term (105-106 yr) scales throughout the Phanerozoic. Knowledge of timing, magnitude, and rate, in turn, provides insights into driving mechanisms (tectono-eustasy vs. climatically mediated eustasy; e.g., glacio- or aquifer-eustasy). As an example, we review the current state of knowledge of Cretaceous eustasy. A literature-based review of sea-level change estimates has been conducted, and the results were evaluated against the different driving mechanisms. A further evaluation of driving mechanisms has been derived from a global geodynamic and associated paleoclimate model.

An analysis of short-term sea-level cycles reveals four broad episodes of magnitude change. Three of these episodes reflect trends of increasing sea-level change magnitudes from the Berriasian to early Hauterivian, late Hauterivian to Aptian, and Santonian to Maastrichtian. The fourth episode reflects a decreasing magnitude trend from the Albian to Coniacian. In addition, the maximum magnitude of sea-level change, at an approximate stage level, has been identified and categorised as slight (less than 10 m), modest (10 to 40 m), or significant (41 to 65 m). Significant magnitudes are inferred for the Valanginian, Aptian, Albian, and Maastrichtian; exclusively slight magnitudes are restricted to the Berriasian.

Because climatically driven eustasy is the likely cause of short-term sea-level change, an assessment of the characteristic maximum magnitude limits of the principal climatic drivers (thermo‑, aquifer-, and glacio-eustasy) has been made. Such a comparison argues for glacio-eustasy as the driver of significant short-term sea-level change and is supported by climate proxy data demonstrating that the Valanginian, Aptian, Albian, and Maastrichtian are intervals of cooling.

While the mechanisms, frequency, and magnitude short-term sea-level cycles linked to thermo- and glacio-eustasy are understood, the likely contribution of aquifer-eustasy remains enigmatic and, for the most part, untested. To better understand the role of aquifer-eustasy, paleoclimate simulations aimed at assessing the spatio-temporal pattern of aridity and humidity under differing CO2 forcing have been undertaken during time slices considered reflective of the differing Cretaceous climates and paleogeographic configurations (Valanginian, Turonian, and Maastrichtian). Only modest changes in the spatial extent of arid and humid zones are observed in response to large changes in CO2 forcing. The simulations also demonstrate that the greatest aquifer charge is more likely during lower CO2/cooler intervals, indicating that aquifer-eustasy works in phase with both glacio- and thermo-eustasy in contrast to the aquifer-eustasy paradigm. Additionally, using information on modern water table depths, we estimate that aquifer eustasy would be unable to contribute significantly to Cretaceous sea-level change. Indeed, even in the most optimistic case, the largest possible total aquifer-eustasy response remains smaller than 7 m. Our results indicate that glacio-eustasy is the most likely driver of Cretaceous short-term eustatic cycles because aquifer-eustasy is unable to account for the estimated Cretaceous magnitudes.

How to cite: Davies, A., Simmons, M., Ray, D., Gréselle, B., van Buchem, F., and Robson, C.: Timing, Magnitude, Rate, and Drivers of Eustasy: A Review of the Cretaceous Period, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3088,, 2020


Display file

Comments on the display

AC: Author Comment | CC: Community Comment | Report abuse

displays version 1 – uploaded on 03 May 2020
  • CC1: Comment on EGU2020-3088, Yiwei Xu, 04 May 2020

    Your work is excellent. I have three questions to consult you :

    1. The data include many 3rd-4th sea-level changes, so the maximum magnitude refers 3rd or 4th eustasy?

    2. Your work show that the glacio-eustasy is the main driver. However, recently, an mid-Cretaceous rain forest  in the antarctic has been reported, which imply an ice-free world. How do you explain the contradiction?

    3. You have collect so much data of sea-level changes, is there any posssible to use those data to reconstructed a curve of 2nd-3rd global sea-level changes?

    • AC1: Reply to CC1, Andrew Davies, 04 May 2020

      Thank you for your comment and questions. My answers are below:

      1.  Yes - we only captured sea level estimates where the duration of the rise and subsequent fall of sea-level is in the order of 3 Ma or less.


      2.  It is undeniable that the Cretaceous was generally warmer than today and during some time periods much warmer and likely ice-free. The presence of mid-Cretaceous forests in Antarctica (Klages et al., 2020) is a fantastic example of this. However, we must be careful not to extrapolate individual data points to the Cretaceous more generally. The core used in the study of Klages et al., 2020 only contains ~3m of Cretaceous material, which can only be constrained to a 9 million year window somewhere in the Turonian-Santonian. Therefore the data may only capture conditions during a hyperthermal (e.g. ~OAE2) and not one of the many the cooler episodes that are known to occur in that 9 Ma time period, when small inland ice sheets may have existed.


      3.  Yes, our ambition is to generate a transparent, data-derived global sea-level curve. However, whilst the data provide insights into the temporal changes in the pattern of short-term eustatic cycles, it is another matter to make a long-term global sea level curve. We focused on short-term cycles to reduce the influence of local, non-eustatic factors (tectonics, sedimentation rate). These local factors hinder the generation of long-term, 3rd/2nd order curves and so need to be removed using techniques like backstripping. For a reliable eustatic curve, it is also necessary to know the exact timing of each sea level high and low, which requires good stratigraphic precision (e.g. good biostratigraphic control). It also requires a good understanding of how the stratigraphy in each section correlates, which is often trickier than it sounds!

    • AC2: Reply to CC1, Mike Simmons, 04 May 2020

      I would just add to Andy's reply, that a growing body exists for episodic Cretaceous polar glaction see

      Alley, N.F., Hore, S.B., Frakes, L.A., 2019. Glaciations at high-latitude Southern Australia during the Early Cretaceous. Australian Journal of Earth Sciences 2019, 1-51.

      For a good recent example.

  • CC2: Comment on EGU2020-3088, Yiwei Xu, 04 May 2020

    One more question, is there any possible that the maxium magnitude is still influenced by tectonics, not the real eustatic signal?

    • AC3: Reply to CC2, Mike Simmons, 04 May 2020

      Check the full paper by Ray et al. (2019) but the synthesis approach, the data selection, the short-term duration of the events and their relative synchronicity suggests the dominant signal is eustastic.