SCIENTIFIC QUESTIONS Q How do facies vary three-dimensionally in - PowerPoint PPT Presentation

SCIENTIFIC QUESTIONS Q How do facies vary three-dimensionally in shelf- margin systems? Q How do tidal features vary vertically and laterally across shelf-margins?

FIELD AREA N Pienaarsfontein Se Berg Grasberg 8.19 km Meideberg Study Area  Measured stratigraphic Cape Town sections are marked with red dots 100 km ( Google Earth and Google Map images)

PREVIOUS WORKS  Kookfontein: Wild, 2005 - detailed study of • Unit 5 (deepwater) –regional study of Kookfontein Fm Wild’s cycles C5-C8 correspond • to the Stratigraphic Units 1, 2, and 3 of this study Green, 2009 – up-dip detailed • study of Units 1, 2, and 3 Strat. column(Green, 2009), diagrams (Wild, 2005), photos courtesy of Asle Strom, Statoil

METHODS  Followed 3 Units  Measured 18 Stratigraphic sections  Walked out key surfaces and packages  Measured paleocurrents N Unit 0 Unit 3 Unit 2 Unit 1 Unit 0 Top of Josh’s work

CHALLENGES  Schedule Coordination and Time Management  Language Barriers  Semi- Continuous and Weathered Outcrops  Rugged Terrain  Dangerous Animals www.wildlife-pictures-online.com/200707.html

N Cross Section E W DIP STRIKE DIP Mouth Bars Delta Front Pro Delta Unit 3 Unit 2 Unit 1 17 13 12 7 2 8 9 16 15

PRO DELTA – THINLY- BEDDED SILTSTONES Bioturbation? Tidal Influence Thinly Bedded Turbidites

DELTA FRONT - TURBIDITES Coaly fragments Alternating deformed and un-deformed siltstones and sandstones Decimeter-scale sandstones with rippled tops

DELTA FRONT – ALTERNATING DEFORMED BEDS Slump? Heterolithic deformed bed Alternating deformed and un- deformed siltstone and sandstone Very thinly bedded siltstone

DELTA FRONT - DEFORMED BEDS Slump? Deformed sandstone In Situ deformed sandstone In Situ deformed siltstone Thick turbidite bed

MOUTH BARS Accretion wedge Heterolithic deformed package 1.5 m Concretions Meter-scale sandstone with scour and fill Mouth bar toe with tidal influence

MOUTH BARS Decimeter-scale sandstones with inclined bedding Meter-scale sandstone with concretions Concretions Thick turbidite bed Thinly-bedded turbidites

EVIDENCE FOR TIDAL INFLUENCE  Mud Drapes  Bidirectional Paleocurrents  Heterolithic Sediment  Flaser, Lenticular, and Wavy Bedding  Double Mud Drapes  Reactivation Surfaces

Dominant paleocurrent direction Flaser Bedding Lenticular Bedding Preserved Mud Drapes in In Situ Deformed Sediment Weathered-out Mud Drapes in Thick Sandstones Flaser and Lenticular Bedding in Thinly Mud Drapes in Sandstone Bedded Siltstone

PLANS FOR FUTURE WORK  Further define vertical and horizontal facies variability  Construct strike and dip cross sections  Create block diagrams to further illustrate facies distribution  Establish criteria for recognizing shelf-edge facies  Compare my findings to work done up-dip  Write, Write, Write!!!!!

QUESTIONS?

SHELF-EDGE DELTA MODEL (from Plink-Björklund et al., 2001)

SCIENTIFIC IMPLICATIONS AND CONCLUSIONS  Recognition of tidal features can impact reservoir characterization and quality  Sediment  Morphology

SCIENTIFIC IMPLICATIONS AND CONCLUSIONS  Detailed 3D outcrop studies can help characterize shelf-edge delta facies.  Understanding shelf –margin facies can help us understand shelf-margin progradation, slope accretion, and their relationship to deep water sands. (Seybold et al., 2007)

m FACIES ASSOCIATIONS Unit 1 Composite Section In Situ Deformed Siltstone and Sandstone Heterolithic Slump Deposit Thinly Bedded Siltstone Thick Sandstones Alternating Deformed or Undeformed Siltstone and Sandstone

CONCLUSIONS  Packages are mainly prograding or aggrading  Units coarsen-upward  Tidal-influence decreases upward

GEOLOGICAL AND STRATIGRAPHIC BACKGROUND  Retroarc Foreland Basin  Karoo Basin -Tanqua depocenter  Kookfontein Formation: ~250 m of stacked coarsening-upward intervals  Slope to shelf deltaic deposits ( Compiled and modified from Visser, 1993; Hancox & Rubidge, 2001; Andersson et al., 2004; Gradstein & Ogg, 2004; Wild, 2005; Scheffler et al., 2006; Fildani et al., 2007; Herbert & Compton, 2007;Fildani et al., 2009; Tankard et al., 2009).

m VERTICAL TIDAL DISTRIBUTION Tidal Features Decrease  Tidal features can be Unit 1 Composite Section found throughout each Unit  Abundance and variety of features decreases upward  Thinly-bedded siltstones exhibit the most tidal features