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General Context Mini basin description and uncertainties Sedimentary filling interpretations

Sedsim modeling of confined mini basin filling control by eustatic and halokinetic mechanisms (Gulf of Mexico) Tristan SALLES 1 , Cedric GRIFFITHS 1 , David MCGEE 2 , Mihaela RYER 2. Outline. General Context Mini basin description and uncertainties Sedimentary filling interpretations

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General Context Mini basin description and uncertainties Sedimentary filling interpretations

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  1. Sedsim modeling of confined mini basin filling control by eustatic and halokinetic mechanisms (Gulf of Mexico) Tristan SALLES1, Cedric GRIFFITHS1, David MCGEE2, Mihaela RYER2

  2. Outline • General Context • Mini basin description and uncertainties • Sedimentary filling interpretations • Sedimentary structures • Control mechanisms • Numerical modeling • Building Sedsim model • Testing scenarios • Model results • Processes through intervals • Cross-sections RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  3. General context Localization Northern Gulf of Mexico Bathymetry • What is the architecture of the basin fill? • What depositional processes led to basin accumulation? • Can we simulate the way the basin fill? • Can we reproduce the heterogeneity of the processes involve? ≈ 43 km ≈ 29 km Presently the basins are confined but during deposition of the interval of interest, that was much less true RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  4. 0 1 Time /s 2 3 4 5 General context Basin introduction “Western Basin” A A’ 5 4 3 2 1 A A’ ≈ 43 km ≈ 29 km • Simulation of the 5 intervals • Pleistocene period (-940,000 to -460,000 years) 2 “Elongate Basin” ≈ 29 km RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  5. Sedimentary filling interpretations Interval 3 Sedimentary structures summary • Drape 2. Channel complex 3. Spillover 4. Unconfined sheet flows RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  6. Sedimentary filling interpretations Interval 4 Sedimentary structures summary 1. Ponded sheets 2. Debris Flows 3. Channel complexes * Salt emergence 4. Confined channel RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  7. 0.2 ms 0.5 ms Sedimentary filling interpretations Sedimentary structures CHARACTER INTERPRETATION Chaotic Variable to high reflectivity Wavy with erosional basal contact Transparent, wavy, mounded, erosional Fully chaotic OR blocky Debris Flows Mass Transport Complexes Convergent Leveed Channel Overbank Muddy Turbidites By Thinning 0.2 ms Ponded Mass Flows Basin Floor Fans By Baselap 0.5 ms Draping 0.3 ms Draping RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  8. Sedimentary filling interpretations Intervals summary • Interval 2 – Weakly Confined • Ponded sheets, MTDs, Channel complexes • -Salt emergence • -Increased channel confinement • -No fault movement • Interval 3 – Intermediate? • Draped sheet deposits, fault-steered channel complex • -Continued salt emergence • -Presence of fault • -Fault movement negligible • Interval 4 – Confined • Alternating sheet and mass-transport deposits • - Basin-wide deposition • -Extreme cyclicity in deposits • -Considerable fault movement RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  9. Controls on depositional styleSea level change Relative sea level High Lowstand interval Time Low condensed section interval when shoreline is located near the shelf edge (turbidity flows dominate) interval of upper slope instability (debris flows dominate) leveed channels dominate (relatively low sand:mud) frontal splays dominate (relatively high sand:mud) Posamentier & Kolla, 2003. interval of upper slope instability (debris flows dominate) condensed section RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  10. Controls on depositional styleHalokinetic autocyclicity Salt controlled structural high Hemipelagites and muddy turbidites mute topography Pre-existing hemipelagites and muddy turbidites Intrabasinal MTC (pre- existing hemipelagites and muddy turbidites) Head scarp Run-up Antecedent sea floor Madof et al., 2009. RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  11. Potential basin fill driving mechanisms • Eustatic Control • Would expect to see alternating deposits punctuated by condensed sections: • MTD • Frontal Splay • Channel Complexes • MTD • Halokinetic Control • Patterns of sedimentation governed by 3D motion of salt: • HP & Muddy turbidites • Intrabasinal MTDs RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  12. Building the modelGeneral input and assumptions • 4 siliclastic grainsizes : • 1. coarsest 300 μm with a density of 2650 kg.m−3 • 2. medium 150 μm with a density of 2650 kg.m−3 • 3. fine 70 μm with a density of 2700 kg.m−3 • 4. finest 4 μm with a density of 2700 kg.m−3 • 28 × 41 km plane divided in cells of 250 m • 3 types of flows regime : • Highstand linear sources composed of fine material (5% of fine and • 95% of finest) • Transition  point sources corresponding to debris flows (high flow rate, • high flow velocity, high concentration, mainly coarsest and medium) • Lowstand  point sources corresponding to turbidity flows (medium flow • rate, high to medium flow velocity, medium to low concentration, • medium to fine grainsize) RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  13. Building the modelPleistocene sea level fluctuations From Ron Waszczak. Miller at al., 2005. RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  14. Building the modelInterval Timing & Sedimentation Rates Age /Ma 0.46 Ma Sea Level 0.54 Ma 4500 m/Ma Time /ms ? 0.94 Ma 2000 m/Ma Depth / ft Average deposition rate: 3250 m/Ma RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  15. Building the modelSalt tectonic scenarios High tectonic activity during deposition Low tectonic activity during deposition RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  16. Sedsim results1st step mainly control by sea-level – Interval 1 & 2 (beginning) Partially dominated by debris flows Turbidity flow dominated RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  17. Sedsim results2nd step sea-level highstand and salt emergence – Interval 2 Muddy turbidity flows due to salt emergence Muddy turbidity flows due to salt emergence RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  18. Sedsim results3rd step sea-level transition and lowstand – Interval 3 Debris flows dominated Turbidity flow dominated RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  19. Sedsim results4th step sea-level transition and lowstand – Interval 4 & 5 Debris flows dominated Turbidity flows dominated RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  20. Sedsim resultsHalokinetic impact on deposit heterogeneity – Interval 4 & 5 Slumped material induced by salt tectonic RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  21. Sedsim results Sections evolution in the basin - Interval 2 RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  22. Sedsim resultsSections evolution in the basin - End of interval 4 RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  23. Sedsim resultsAverage deposition rate ≈ 150 m ≈ 200 m Average deposition rate of: 3500 m/Ma RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  24. Sedsim resultsComparison to seismic 0 1 Time /s 2 5 4 3 2 2 1 4 5 RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  25. Conclusions • The model can simulate the different processes which fill the basin: • Unconfined Turbidites • Channel Complexes • Debris Flows • 2. The basin fill is cyclic in nature and the cyclicity is controlled by: • (i) Salt interplay • (ii) Sea level changes • The model can reproduce the sedimentary layers heterogeneity however • the driving forces for tectonic activity is user imposed. RST2010 - Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

  26. Contact Us Phone: 1300 363 400 or +61 3 9545 2176 Email: enquiries@csiro.au Web: www.csiro.au Thank you… CSIRO Earth Science and Resource Engineering Dr Tristan Salles Research Scientist Phone: +61 8 6436 8779 Email: tristan.salles-taing@csiro.au Web: www.csiro.au/cesre

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