Lacustrine

Lacustrine

1. Lecture 4# Lacustrine

2. Lake/Pond

3. Lacustrine Facies Lake = Hole (water + sediment) Variable : i. shape of lake (change with time) ii. Supply of water & sediment - ratio of water to sediment - supply rate in relation to lake change

4. Factors Control on sedimentation: Lake size Closed Basin vs. Open Basin Chemistry of Water Amount of sediment entering the basin Latitude (Seasonality) Shape of basin (shallow vs. deep) Regional tectonics Water temperature (lake and inflow) Wind

5. CONTROL OF Geometry & Hydrology Tectonics Crustal extension: deep & narrow; cratonic sags & foreland basins: shallow Climate Variations in temperature, seasonal differences, seasonal changes in surface energy Base level change Similar to marine basins Higher periodicities => greater facies complexity

6. Lacustrine Facies

7. LACUSTRINE CHARACTERISTICS

8. Evaporitic Fluctuating Profundal Fluvial – Lacustrine

9. Water Column Stratification More towards significance of source quality and quantity Stratified Lake Epilimnion - top of the lake . Metalimnion (or thermocline ) - middle layer that may change depth throughout the day . Hypolimnion - the bottom layer . High quality type-I kerogen Un-stratified Lake Seasonal overturn and mixing Limit preservation of organic material

10. Lacustrine Facies Epilimnic Facies Oxygenated lake facies Display evidence of wave or current processes Occasionally pervasive bioturbation & plant fossils Hypolimnic facies Fine-laminated terrigenous , biogenic, and authigenic minerals Occasionally turbidite sands

11. Ephermal facies Reflect climatically controlled changes in depth and extent Dessication cracks, evaporites Lake-shore facies Represent shallow or ramped margins Deltaic & shore-zone facies Fluvial influx versus reworking from wind-generated waves

12. Sublacustrine turbidites Likely in deep-lake Aerially restricted Subject to multidirectional sediment influx Display enormous bathymetric variability Facies : Sublacustrine channels, mounded turbidite lobes, channel-lobe complexes

13. Characteristics of lake deposits Bed geometry Often very thin-bedded Sedimentary Structure Wave ripple and very fine parallel lamination Paleocurrents Few with paleo -environment significant Fossil s Algea and microbial plus uncommon shells Colour Variable, but may be dark grey in deep lake deposits

14. Core Photos

15. Questions…

16. FLOW REGIMES Flow velocity increase