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Sedsim modelling of controls on confined mini basin fill by eustatic and halokinetic mechanisms (Gulf of Mexico) Tristan SALLES 1, Cedric GRIFFITHS 1,

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Presentation on theme: "Sedsim modelling of controls on confined mini basin fill by eustatic and halokinetic mechanisms (Gulf of Mexico) Tristan SALLES 1, Cedric GRIFFITHS 1,"— Presentation transcript:

1 Sedsim modelling of controls on confined mini basin fill by eustatic and halokinetic mechanisms (Gulf of Mexico) Tristan SALLES 1, Cedric GRIFFITHS 1, David MCGEE 2, Mihaela RYER 2

2 General Context Mini basin description and uncertainties Sedimentary filling interpretations Sedimentary structures Control mechanisms Numerical modelling Building the Sedsim model Testing scenarios Model results Processes through intervals Cross-sections Outline RST 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 ≈ 43 km What is the architecture of the basin fill? What depositional processes led to basin accumulation? Can we simulate the way the basin filled ? Can we reproduce the heterogeneity of the processes involved ? Presently the basins are confined but during deposition of the interval of interest, there is evidence for a more unconfined system ≈ 29 km RST Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

4 ≈ 29 km ≈ 43 km “Western Basin” “Elongate Basin” General context Basin introduction A A A’ Time /s ≈ 29 km 2 Simulation of the 5 intervals Pleistocene period (-940,000 to -460,000 years) RST Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient” after Heather MacDonald, (2009)

5 INTERPRETATION Transparent, wavy, mounded, erosional Fully chaotic OR blocky Debris Flows Mass Transport Complexes Variable to high reflectivity Wavy with erosional basal contact 0.2 ms 0.5 ms CHARACTER 0.2 ms 0.5 ms By Thinning Leveed Channel Overbank Muddy Turbidites 0.3 ms By Baselap Draping Ponded Mass Flows Basin Floor Fans Chaotic Convergent Draping Sedimentary filling interpretations Sedimentary structures RST Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient” after Heather MacDonald, (2009)

6 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 RST Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient” 1. Ponded sheets 2. Debris Flows 3. Channel complexes Interval 4 Sedimentary structure * Salt emergence 4. Confined channel after Heather MacDonald, (2009)

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

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

9 Building the model General 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 into cells of 250 m 3 types of flow 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) RST Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

10 From Ron Waszczak. Miller at al., Building the model Pleistocene sea level fluctuations RST Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

11 0.46 Ma 0.54 Ma 0.94 Ma Time /ms Age (Ma) Depth / ft 4500 m/Ma 2000 m/Ma Sea Level ? Building the model Interval Timing & Sedimentation Rates RST Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient” Average deposition rate: 3250 m/Ma

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

13 Sedsim results 1 st step mainly controlled by sea-level – Intervals 1 & 2 (beginning) Partially dominated by debris flows Turbidity flow dominated

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

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

16 RST Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient” Sedsim results 4 th step sea-level transition and lowstand – Intervals 4 & 5 Debris flows dominated Turbidity flows dominated

17 Sedsim results Halokinetic impact on deposit heterogeneity – Intervals 4 & 5 Slumped material induced by salt tectonic RST Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

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

19 Sedsim results Sections showing evolution in the mini-basin - End of interval 4 RST Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient”

20 Sedsim results Average deposition rate ≈ 150 m ≈ 200 m

21 RST Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient” Sedsim results Comparison to seismic Time /s

22 1.The model can simulate the different processes which filled the mini-basin: Unconfined Turbidites Channel Complexes Debris Flows 2. The mini-basin fill is cyclic in nature and the cyclicity is controlled by: (i) Salt interplay (ii) Sea level changes 3.The model can reproduce the sedimentary layer heterogeneity however the driving forces for tectonic activity is user imposed. RST Symposium ASF - Session 2.4 "Modelling of sedimentary processes. From continent to deep environment. From present to ancient” Conclusions

23 Contact Us Phone: or Web: Thank you… CSIRO Earth Science and Resource Engineering Dr Tristan Salles Research Scientist Phone: Web:


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