STRATIGRAPHY AND SEDIMENTATION (LACUSTRINE) Flashcards
What controls the level of water in the lake and its chemistry?
Balance between inflow and outflow
Rate of evaporation
Five mechanisms of Lake Formation
Eruption of Volcano
Plate tectonics
Glacial Lake
Formed by matured rivers
Mudslides and landslides
The most common deposits in Lakes
Sand and Mud
Study of Modern Lakes
Limnology
what can more likely form a lake, Glacier or Stream?
Glacier
When a lake is filled to the spill point an there is a balance of water supply into and out of the basin and in which level of water is constant thus also means that the water is fresh
Hydrologically Open
If the rate of evaporation exeeds the rate of water supply and there is no outflow of water from the lake
Hydrolgically close
Lakes that have stable/fixed shroreline and is commonly dominated by siliciclastic sedimentation (If siliciclastic is low, carbonate or chemical seimentation may occur)
Open Lakes
Lakes that fluctuating shroreline and is predominated by chemical sedimentation
Closed Lakes
Lakes with low salinity and are either open or close with a low supply of dissolved ions allowing water to remain fresh
Freshwater Lakes
Hydrologically close and are perennial bodies of water in which dissolved ions have become concentrated by evaporation
Saline Lakes
Rain dependent lake which mainly occur in arid settings and only exist for few months or years after rainstorms in the catchement areas
Ephemeral lakes
Why are wave driven surface currents in lakes incompetent?
Because of limited fetch
Warm part of the lake that is relatively oxygen enriched
Epilimnion (Epi-surface)
Deposits that are usually in the upper column of lake?
Overflow (Low Density)
Fines suspended
Cold bottom part of the lake which are anoxic
Hypolimnion
What separates the upper and lower part of the lakes
Thermoclines
Deposits that are usually in the lower part of the lake
Underflow high density (Coarse turbidited)
Lake margin clastic deposits
Can resemble deltaic - Pragraiding Coarsening and Shallowing up
Lake margin marshy environment
Palustrine Environment
Deep lake facies
Alternating Finely Laminated Muds (Suspended Fines) and Thin Graded turbidites (Density)
In a varve suequence, at which season is the dark-organic rich deposits formed?
Summer
In a varve sequence, at which season is the paler clastic sediments deposited?
Spring Thaw
Milimiter scale laminae of alteranating dark and pale deposits which are used in chronostrat of holocene deposits
Varves
