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

• Measured stratigraphic

sections are marked with red dots

100 km

8.19 km

Cape Town

Study Area Pienaarsfontein Se Berg Grasberg Meideberg N (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

Unit 0

N

METHODS

• Followed 3 Units
• Measured 18 Stratigraphic sections
• Walked out key surfaces and packages
• Measured paleocurrents

Unit 1 Unit 2 Unit 3 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

Cross Section

Unit 1 Unit 2 Unit 3

DIP STRIKE DIP

W E Mouth Bars Delta Front Pro Delta

9 8 2 7 12 13 17 16 15

N

PRO DELTA – THINLY- BEDDED SILTSTONES

Thinly Bedded Turbidites Tidal Influence Bioturbation?

DELTA FRONT - TURBIDITES

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

DELTA FRONT – ALTERNATING DEFORMED BEDS

Alternating deformed and un- deformed siltstone and sandstone Very thinly bedded siltstone Slump? Heterolithic deformed bed

DELTA FRONT - DEFORMED BEDS

Thick turbidite bed In Situ deformed siltstone In Situ deformed sandstone Slump? Deformed sandstone

MOUTH BARS

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

MOUTH BARS

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

EVIDENCE FOR TIDAL INFLUENCE

• Mud Drapes
• Bidirectional Paleocurrents
• Heterolithic Sediment
• Flaser, Lenticular, and Wavy Bedding
• Double Mud Drapes
• Reactivation Surfaces

Mud Drapes in Sandstone

Flaser Bedding Lenticular Bedding Dominant paleocurrent direction

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

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)

• Recognition of

tidal features can impact reservoir characterization and quality

Sediment Morphology

SCIENTIFIC IMPLICATIONS AND CONCLUSIONS

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)

Unit 1 Composite Section

FACIES ASSOCIATIONS

Thinly Bedded Siltstone

In Situ Deformed Siltstone and Sandstone

Heterolithic Slump Deposit Alternating Deformed or Undeformed Siltstone and Sandstone Thick Sandstones

m

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).

VERTICAL TIDAL DISTRIBUTION

• Tidal features can be

found throughout each Unit

Tidal Features Decrease

• Thinly-bedded

siltstones exhibit the most tidal features

• Abundance and variety
• f features decreases

upward

Unit 1 Composite Section m