Lacustrine
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This document discusses lacustrine facies and lake sedimentation. It describes how factors like lake size, basin shape, climate, and tectonics control lacustrine sedimentation. Lacustrine facies can include sand, mud, carbonates, and evaporites. Characteristics are discussed like stratification in the water column, different facies like shoreline and delta deposits, and characteristics of lake deposits like thin bedding and rare fossils. Overall it provides an overview of the factors that influence lake sedimentation and the types of facies and deposits that can form in lacustrine environments.
Lacustrine
- 1. LACUSTRINE L ECTUR E 4#
- 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: oLake size oClosed Basin vs. Open Basin oChemistry of Water oAmount of sediment entering the basin oLatitude (Seasonality) oShape of basin (shallow vs. deep) oRegional tectonics oWater temperature (lake and inflow) oWind
- 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
- 8. LACUSTRINE CHARACTERISTICS Can be filled with sand, mud, calcareous or salty in fill Vary in size from small to very large Often similar processes to shallow marine environments, but: • Generally has lesser amount of wave energy • Generally close system, thus have a higher sedimentation rate • Have to tide (or almost no tide)
- 10. Fluvial – Lacustrine Fluctuating Profundal Evaporitic
- 11. 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
- 13. 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
- 15. • 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
- 17. 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
- 18. CHARACTERISTICS OF LAKE DEPOSITS Lithologies •sandstone, mudstone, fine-grained limestones and evaporites Mineralogy •variable Texture •sands moderately well sorted Bed geometry •Often very thin-bedded Sedimentary Structure •Wave ripple and very fine parallel lamination Paleocurrents •Few with paleo-environment significant Fossils •Algea and microbial plus uncommon shells Colour •Variable, but may be dark grey in deep lake deposits
- 19. CORE PHOTOS
- 21. FLOW REGIMES Flow velocity increase