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from Conceptual Models to Outcrop-Based Forward Models Using Carb3d+: Preliminary Findings from La Molata, Cabo De Gata, SE Spain

Kaczmarek, Stephen E.1; Whitaker, Fiona F.2; Bova, John 1; Franseen, Evan 3; Smart, Peter L.4; Goldstein, Robert 5; Leadbeater, Tom 2
1 Upstream Research Company, ExxonMobil, Houston, TX.
2 Department of Earth Sciences, University of Bristol, Bristol, United Kingdom.
3 Kansas Geological Survey, Lawrence, KS.
4 Department of Geographical Sciences, University of Bristol, Bristol, United Kingdom.
5 Department of Geology, University of Kansas, Lawrence, KS.

Upper Miocene strata from the Cabo de Gata region of south-eastern Spain preserve a shallow temperate- to warm-water carbonate depositional sequence formed over 3.5 Ma under superimposed high-frequency sea-level cycles in an archipelago setting. Detailed outcrop work at Las Negras has provided high-resolution constraints on stratal geometry, lithological heterogeneity and relative sea-level history. Here we use this data to constrain numerical simulations of platform evolution using the 3D process-based forward model CARB3D+, which can predict the co-evolution of sedimentary facies and early diagenesis in a sequence stratigraphic context.

Whilst CARB3D+ lacks the functionality to incorporate input of volcaniclastics or megabreccia formation, the synthetic stratigraphy does honor most of the important aspects observed in outcrop, within the 5 unconformity-bound depositional sequences. This agreement enables us to perform numerical experiments to evaluate some of the significant local, regional and global constrains on sequence development. The synthetic stratigraphies generated using CARB3D+ are sensitive to changes in the character of the carbonate factory over time, the interactions between high-magnitude, high-frequency fluctuations in relative sea-level, and the substantial (~200m) and complex paleotopography of the Neogene volcanic substrate.

Simulations indicate a shift change in rate- and depth-dependence of production from cool-water heterozoan facies to warm-water photozoan facies. Heterozoan-dominated sequences (DS1A, DS1B, and DS2) are most accurately modeled using lower maximum carbonate production rates over a broad range of water depths. In contrast, photozoan-dominated units (DS3 and TCC) are best modeled with production - depth curves that have higher maximum values but lower depositional ranges. Sequence stratigraphy, pinning-point relative sea-level curves and magnetostratigraphy provide tight constraints on third- and fourth-order fluctuations which control sequence development. In addition, higher frequency fifth-order cyclicity is suggested by meter-scale cycles in both the lower heterozoan units, and the uppermost TCC sequence. Frequency and amplitude of sea level changes, as well as cyclicity and sea level asymmetry, dictate sequence boundary development and stratigraphic architecture at La Molata.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009