Flecker, R.1, P. J. Valdes1
(1) Bristol University, Bristol, United Kingdom
ABSTRACT: Assessing the Amplitude of Climate-Driven Sea Level Fluctuations using Global Climate Model Simulations and their Implications for Sequence Stratigraphic Interpretation
Two and a half decades after the first global eustatic sea level curves for the
Mesozoic were published, there is still debate about the nature and cause of the high
frequency (< 1 million years), low amplitude (a few tens of metres), "third
order" cycles. Elsewhere in the stratigraphic record, third order sequence boundaries
have been correlated with d18O increases and attributed to glacioeustatic processes. In
the Jurassic and Cretaceous this interpretation is fraught by the absence of evidence for
ice. Despite this, climate driven processes remain the favoured mechanism, although some
researchers advocate geoid deformation or plate tectonics. In addition, because
quantifying sea level change by analysing stratal geometries and interpreting oxygen
isotope records is inherently difficult, the amplitude of sea level change specified by
different published curves varies considerably.
We use global climate model (GCM) simulations to provide an independent evaluation of the amplitude of climate-driven sea level change. This takes into account not only the glacioeustatic component, but also the volumetric importance of thermal expansion and soil moisture storage. Mesozoic climate scenarios with no ice sheets and those with dynamic ice sheets of small areal extent are both considered. These simulations demonstrate how much sea level fluctuation could have been attributable to Mesozoic climate variation. We also use them to illustrate the climate implications of published eustatic amplitudes. In the light of these results we examine the effect of routinely integrating GCM simulations into the process of sequence stratigraphic analysis.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.