Lakes

Question 1

lake diversity

Answer 1

acidic, dilute, saline, alkaline, meromictic, hypersaline, spring fed

Question 2

what controls lake sedimentation

Answer 2

climate, time, hydrology, geology, biology

Question 3

lake stratification

Answer 3

seds and facies strongly influenced by thermal regime of a lake

Question 4

lake classification

Answer 4

• by how often the surface and bottom water overtunes
  1. monomictic: winter summer mix
  2. dimictic: string, fall
  3. polymictic: temp strat, irregular mixing

Question 5

meromixes and permanent stratification

Answer 5

refer to notes

Question 6

lacustrine env and facies

Answer 6

• shoreline are highly variable to absent, siliciclastic or carbonate, or vegetated
• are common in great lakes and large glacial lakes

Question 7

carbonate shorelines

Answer 7

shoreline seds vary with slope and energy level

refer to notes

Question 8

carbonates in saline lakes

Answer 8

-refer to notes

Question 9

deltas

Answer 9

-usually small and diverse
-common in perinnial lakes
-doesnt show up in karsts or groundwater fed lakes
-sed style: depends on densities of inflow and lake water and how much sed supplied
-

Question 10

Gilberts

Answer 10

Hyperpycnal flow: in=lake density
high bedload-dilute water
-common in glacial fed lakes
-lakeward progradation

Question 11

deltas with underflow

Answer 11

• high susp load-dilute or saline
• hyperpycnal: in>lake density
• aggradation and slow progradation
• density currents leads to turbidites from river mouth

Question 12

deltas with sediment plumes

Answer 12

• dilute inflow to saline lake causes sediment plume at surface
• hyperpycnal: in>lake density
• aggradation and slow progradation
• clay flocculation

Question 13

what are lake center sediments mainly?

Answer 13

-pelagic (fine clastics and biological sediments)
diatoms exist and various carbonate shelled plankton (ostracods, etc)
-many carbonates are bioinduced by plankton
-organic muds
-authigenic minerals: iron oxides, chertz, zeolites, salts
-commonly laminated

Question 14

organic rich lake seds

Answer 14

ALLOGENIC

• org accum>rate of decay
• high organic material
• oxy poor bottom
• vegetation is waterborne
• clastic/carbonates in between dentrital matter

AUTOGENIC

• littoral wetlands (macrophytes)
• stable strat (meromixes)
• plankton
• anoxic bottom, oxic surface, organic rich laminites
• sapropelic oozes
• org matter accum>rate of decay

Question 15

Saline lakes

Answer 15

• semi-arid
• sandflats, mudflats, saline pan, saline mudflat, mountains, alluvial fans
• ephermal lakes: playas, playa lakes, saline pans

Question 16

saline pan cycle

Answer 16

FLOODING STAGE
EVAPORATIVE CONCENTRATION
DESICCATION

refer to notes

Question 17

types of lake basins

Answer 17

-overfilled (fluvio lacustrine facies association), balanced-filled, underfilled

Question 18

overfilled fluvial-lacustrine facies association

Answer 18

• deep basin
• stable water level
• prograding upward coarsening
• water/sed supply>accommodation space
• progradational parasequences
• not common in arid climates
• well mixed shallow basin
• marlstone, carbonates, coal, coaly shales
• org matter: terrigenous and microbial
• oil/gas
• open

Question 19

underfilled lakes

Answer 19

• too much accommodation space
• closed
• climatically driven
• evaporitic
• aggradating
• groundwater recharge
• micritic and dolomicritic mudstones, microbialites, travertine-tufa
• dominantly microbial
• oil

Question 20

balance-filled lakes

Answer 20

• alt between open and closed
• climatically controlled
• flucuating profundal facies
• aquatic org matter dominant
• progradation and aggradation (desiccation cycles and shoaling cycles)
• dominantly microbial