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Lecture 7

ENVIRSC 2E03 Lecture Notes - Lecture 7: Turbidite, Wave Base, Halophyte

Environmental Science
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Lecture 7:
Sedimentary Facies
Thermohaline Currents: difference in temperature of water in oceans along continental rise
where cold water is returned to bottom of ocean and warm surface flow moves along the
continental edge.
Delta: Mixture of sub-environments; lagoons, marshes, estuaries, floodplains, beaches, dunes
-any deposit sub-aerial or sub-aqueous formed by fluid sediment that build into a
standing body of water.
-oceans, semi-enclosed seas, lakes lagoons
-sediment supply is higher than the distributional processes from waves and tides that
carry sediment away
-point sources of continental sediments entering the coastal and shelf areas
-characterized by river systems which carry heavy sediment in the water
Sorting occurs as sediment enters basin and then becomes finer and finer down slope and
further out into the ocean
Brackish Water: dilution of ocean salt water with continental fresh water
Clams and molluscs form that can stand both brackish and sea and fresh water conditions
Estuary: a semi enclosed coastal body of water which has free access to the ocean and where
seawater is measurably diluted by freshwater from land drainage.
-flooded river valleys with lower sedimentation rates than deltas
-sediment accumulation is low, water depth is too deep compared to a delta where
water depth is shallow and/or sediment accumulation is high.
Fluvial: Gravel, sand, mud, crossbedding, graded, coarse lags, Freshwater shells
Mixed Marine Fluvial: Sand, mud, crossbedding, bioturbated, graded, ripples, organic rich,
brackish shells
Marine: Mostly sandy, crossbedded, bioturbated graded, marine shells
Lagoons form where coastal embayments or depressions are separated from the sea by a
barrier. Barriers form by:
-Sediment material
-coral reef growth
Lagoons: muddy to sandy, poorly sorted, abundant marine or brackish shells, shell beds are
common, bioturbated. Potential organic rich, sand beds may be common.
Dunes: high angle cross-bedding well sorted fine sands, root casts.
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