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GLE 2024 (Day 1) > STRATIGRAPHY AND SEDIMENTATION (LACUSTRINE) > Flashcards

STRATIGRAPHY AND SEDIMENTATION (LACUSTRINE) Flashcards

1
Q

What controls the level of water in the lake and its chemistry?

A

Balance between inflow and outflow
Rate of evaporation

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2
Q

Five mechanisms of Lake Formation

A

Eruption of Volcano
Plate tectonics
Glacial Lake
Formed by matured rivers
Mudslides and landslides

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3
Q

The most common deposits in Lakes

A

Sand and Mud

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4
Q

Study of Modern Lakes

A

Limnology

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5
Q

what can more likely form a lake, Glacier or Stream?

A

Glacier

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6
Q

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

A

Hydrologically Open

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7
Q

If the rate of evaporation exeeds the rate of water supply and there is no outflow of water from the lake

A

Hydrolgically close

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8
Q

Lakes that have stable/fixed shroreline and is commonly dominated by siliciclastic sedimentation (If siliciclastic is low, carbonate or chemical seimentation may occur)

A

Open Lakes

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9
Q

Lakes that fluctuating shroreline and is predominated by chemical sedimentation

A

Closed Lakes

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10
Q

Lakes with low salinity and are either open or close with a low supply of dissolved ions allowing water to remain fresh

A

Freshwater Lakes

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11
Q

Hydrologically close and are perennial bodies of water in which dissolved ions have become concentrated by evaporation

A

Saline Lakes

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12
Q

Rain dependent lake which mainly occur in arid settings and only exist for few months or years after rainstorms in the catchement areas

A

Ephemeral lakes

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13
Q

Why are wave driven surface currents in lakes incompetent?

A

Because of limited fetch

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14
Q

Warm part of the lake that is relatively oxygen enriched

A

Epilimnion (Epi-surface)

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15
Q

Deposits that are usually in the upper column of lake?

A

Overflow (Low Density)
Fines suspended

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16
Q

Cold bottom part of the lake which are anoxic

A

Hypolimnion

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17
Q

What separates the upper and lower part of the lakes

A

Thermoclines

18
Q

Deposits that are usually in the lower part of the lake

A

Underflow high density (Coarse turbidited)

19
Q

Lake margin clastic deposits

A

Can resemble deltaic - Pragraiding Coarsening and Shallowing up

20
Q

Lake margin marshy environment

A

Palustrine Environment

21
Q

Deep lake facies

A

Alternating Finely Laminated Muds (Suspended Fines) and Thin Graded turbidites (Density)

22
Q

In a varve suequence, at which season is the dark-organic rich deposits formed?

23
Q

In a varve sequence, at which season is the paler clastic sediments deposited?

A

Spring Thaw

24
Q

Milimiter scale laminae of alteranating dark and pale deposits which are used in chronostrat of holocene deposits

25
Q

saline lakes are classified according to

A

Brine Composition (Ion-Rich waters)

26
Q

Lakes with brines of Bicarbonate and Sodium Carbonate represented by TRONA and NATRON which are exclusively freshwater evaporites

A

Soda Lakes

27
Q

Lakes with brine enriched with Magnesium and Calcium and lower rates of Bicarbonate represented by precipiation of Gypsum and Mirabilite (NaSulphate)

A

Sulphate Lakes

28
Q

Saline lakes that have same classification as Marine Evaporites

A

Saline or Chloride Lakes

29
Q

Other names of Ephemeral Lakes

A

Playa Lake
Saline Pan

30
Q

whats is the characteristics of Ephemeral Lake deposits

A

Layer of Mud overlain by Layer of Evaporite (nung may water pa syempre mud yung idedeposit then nung matuyo nagkaevaporite)

31
Q

Regions around ephemeral lakes were saeidments are saturated with saline groundwater

A

Inland Sabkhas

32
Q

Most common mineral in such settings

A

Derset Rose Gypsum

33
Q

assemablege of fossils that belongs to the same species

A

Monospecific

34
Q

Usual fossils in Lakes

A

Gastropods
Bivalvaes
Ostracods
Arthropods

35
Q

An Arthropod which may tolerate perrenial saline lakes

A

Brine Shrimp

36
Q

A green alage related fossil or organism that is an indicative of a freshwater or brackish water due to its intolerant to high salinity

A

Charophytes

37
Q

This type of siliceous ooze is dominant in cold sediment starved lakes in mountainous and polar regions

38
Q

deposits of diatoms

39
Q

Lake filling is transgressive or regressive?

A

Regressive

40
Q

What is the characteristics of a regresive deposit?

A

Coarser nearshore and finer along the basins which willl be covered by fluvial seds

41
Q

Texture of Lacustrine deposits

A

Mod Well sorted Sands

GLE 2024 (Day 1) (34 decks)

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