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PASSIVE MARGIN STRATIGRAPHY FOR NUMERICAL MODELS CALIBRATION: COEFFICIENT OF DIFFUSION MEASUREMENT IN THE OGOOUÉ DELTA (GABON)

Abstract : One major and undepreciated point in diffusion process-based stratigraphic modelling is the large range of coefficients of diffusion used to reproduce natural examples without considering their meaning and their validity in term of transport and deposition processes. Most of the time, present-day stratigraphic models are not used as real forward models but more as a tool to make semi-inversion based on a “best-fit” approach to reproduce well-constrained sedimentary systems. The aim of this work is to consolidate inputs of stratigraphic numerical modelling by calibrations based a natural passive margin deltaic system: the relative small and structurally well delimited Cenozoic post-rift Ogooué Delta in Gabon. From seismic and wells analyses, this system evolves from Paleogene aggrading ramp to a significant deltaic progradation resulting from a major Lower Miocene uplift. Calculations from high resolution seismic stratigraphy and wells analysis are performed in three steps: (1) measurement of the sand/shale ratio evolution (calibrated on wells) along the depositional profile; (2) restoration of the slope at time of deposition (including correction of differential compaction); (3) calculation of depositional fluxes using a basin-scale age model at the highest time resolution possible and quantification of uncompacted volumes for each time slice and stratigraphic context considered (ratio between accommodation and sedimentation). Diffusion coefficient values range over one order of magnitude (0.1 to 1 km2/Ka), that is to say, show less variability than values classically used in published diffusion processed-based stratigraphic modelling (x0.0001 to x10 km2/Ka). These results also suggest (1) low influence of stratigraphic context on coefficient of diffusion values, (2) higher values of coefficients for the most proximal (shelf) and distal (basin floor) parts of the depositional profile and (2) an increase of coefficient values for clayey dominated facies.
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https://hal-insu.archives-ouvertes.fr/insu-01718200
Contributor : Isabelle Dubigeon <>
Submitted on : Tuesday, February 27, 2018 - 11:02:10 AM
Last modification on : Friday, November 6, 2020 - 2:28:02 PM

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  • HAL Id : insu-01718200, version 1

Citation

Brendan Simon, Cécile Robin, Delphine Rouby, François Guillocheau, Jean Braun, et al.. PASSIVE MARGIN STRATIGRAPHY FOR NUMERICAL MODELS CALIBRATION: COEFFICIENT OF DIFFUSION MEASUREMENT IN THE OGOOUÉ DELTA (GABON). International Meeting of Sedimentology 2017, Oct 2017, Toulouse, France. pp.832. ⟨insu-01718200⟩

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