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carbonates final > carbonates 2 > Flashcards

carbonates 2 Flashcards

1
Q

reefs

A

having a rigid, wave-resistant organic framework; with topographic relief about the surrounding environment

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2
Q

reef mounds

A

fine grained, matrix dominated, frame - lacking buildups

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3
Q

bioherm;

A

a small, lends - shaped reef or mound

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4
Q

biostrome

A

a tabular rock body, usually a single bed of similar composition

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5
Q

buildup

A

generic name with no compositional, size or shape connotation

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6
Q

reef core

A

is massive and unbedded carbonate with or without skeletons; composed of the framework filled in by interstitial matrix of lime mud and skeletal sand

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7
Q

reef flank

A

composed of bedded limestone conglomerates made of reef debris that have washed down from reef during storms, dipping and thinning away from the core

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8
Q

inter reef

A

composed of subtitdal lime mudstone or terrigenous clastic sediment, unrelated to reef growth

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9
Q

construction

A

are the biological processes t, the direct growth of calcareous organisms

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10
Q

destruction

A

various processes that damage or destroy the growing reef

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11
Q

sedimentation

A

the biological activities on and around reefs leads to the accumulation of biogenic matter and reef - derived detritus

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12
Q

cementation

A

in many reefs, ancient and modern, extensive early cementation has occurred, directly from marine pore waters

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13
Q

major controls on reef morphology

A

topography

biological

sea - level

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14
Q

facies zonations

A

since reefs grew in shallow, high - energy settings, they show lateral and vertical facies zonations, a response to variations in water depth and energy.

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15
Q

stabilization stage

A

consists of shoal of skeletal lime sand; surface can be colonized by algae, plants and/ or animals that send down roots or hold - fast to bind and secure the substrate

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16
Q

colonization stage

A

characterized by monospecific (or low diversity) lamellar or branching fossils

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17
Q

diversification stage

A

diversity increases and a great variety of growth forms occur. this stage forms the bulk of reef

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18
Q

domination stage

A

limestones formed by a few taxa with one growth habit, encrusting to laminated

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19
Q

microbial mounds

A

founded by the action of microbes, namely cyanobacteria

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20
Q

skeletal mounds

A

the skeletal builders acted as mud bafflers, trappers, binders, and stabilizers

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21
Q

mud mounds

A

reliefs of lime mud that supported a variable benthic flora and / or it can be produced in situ by organisms (degradation of skeletons, microbial production

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22
Q

carbonate platform

A

a large edifice formed by the accumulation of sediments in an area of subsidence. have a flat top, steep sides and can be several km thick and extend over many hundreds of km2

23
Q

carbonate shelf

A

a platform tied to an adjacent continental landmass

24
Q

carbonate bank

A

an isolated platform surrounded by deep ocean water and cut off from terrigenous clastic sediments

25
Q

carbonate atoll

A

a specific type of bank developed on a subsiding volcano

26
Q

rimmed shelves

A

a carbonate platform that has segmented to continuous rampart of reefs and/or lime sand shoals along the margin that absorbs ocean waves

27
Q

stationary mode

A

the position of the rimmed margin does not change much through time

28
Q

offlap mode

A

the rimmed margin progrades basinwards connection with open ocean is poor, leading to evaporites and.or exposures

29
Q

onlap mode

A

shelfward migration of facies belts

30
Q

drowning mode

A

when sea-level rise is too fast for carbonte sedimentation to keep pase

31
Q

emergent mode

A

sea - level falls below the shelf - break and the shelf is subject to subaerial exposure

32
Q

unrimmed shelf

A

no barrier along the seaward margin

33
Q

erpiric carbonate platforms

A

epeiric carbonate platforms are very extensive areas of negligible topography

characteristics include:

1) equable, relatively warm climates
2) vast, shallow (<10m), well-lit, clear seas
3) little-exposed land
4) good organic and carbonate productivity
5) vast areas if carbonate sedimentation

34
Q

3 zones of epeiric platforms

A

zone x: open ocean below fair - weather wave base

zone Y: a narrow, high energy zone that was under the influence of tide

zone z: that platform that beyond the effect of tidal exchange

35
Q

isolated platform

A

a) a shallow - water carbonates surrounded by deep ocean water, with steep margins
b) cut off from terrigenous clastic sediments
c) ,rginal reefs and sand bodies, sandy mud and muds in the interior
d) possible sandy islands with tidal flats
e) water circulation controlled by tides and waves
f) sediment transportation influenced by storms

36
Q

platform response to eustasy

A

a) exposure: when sea level falls below the edge of the platform, the carbonate factory is shut down and sediments are subject to meteoric diagenesis
b) drowning: when the rate of sea - level rise outpaces the rate of vertical sediment accumulation and the carbonate factory is submerged below the photic zone.
c) flooding: in a steady state situation, water depth over the platform is just right for macimm production. the accumulation sace is maintained by combination of platform subsidence and sea level rise

37
Q

backstep (transgression)

A

the movement and reestablishment of a shelf margin toward the shelf interior due to a rapid sea level rise

38
Q

catch-up:

A

transgression - early highstand: an initial rapid increase n the rate of sea level rise is followed by a decrease

39
Q

keep - up

A

transgression the rate of sediment accumulation “keeps - up” with the rate of relative sea level rise.

40
Q

dissolution is controlled by the flux of…

A

co2 in and out of water

41
Q

simple dissolution

A

rainwater is in equilibrium with atm co2 and is in reality an extremely weak acid. thus simple dissolution is brought about by rainfall on bare rock surface.

42
Q

biogenic dissolution

A

air in the soil zone has much higher co2 because of plant respiration and decay of OM.

43
Q

mixing dissolution

A

mixing of two solutions which are both saturated with respect to calcite can lead to an undersaturated mixture

44
Q

water - controlled precipitation

A

because of Pco2 decrease in the meteoric water. Plants can take Co2 from water causing ppt.

45
Q

mineral - controlled precipitaiton

A

caused by differences in Caco3 mineral solubility.

46
Q

sea - floor diagenesis: zones

A

zone 1: precipitation warm shallow water platform carbonates

zone 2: zone of dissolution / precipitation: temperate water shelves, tropical carbonate slopes

zone 3: zone of active dissoultion, deep basin environments

zone 4: zone of no carbonate: wholly deep - sea settings

47
Q

Vadose zone

A

pore filled water and/ or air organically produced gas

48
Q

iniltration zone

A

soil on top of bedrock, carbonate precipitation due to biological activities and evaporation

49
Q

caliche

A

carbonate - lithified portion of the soil profile develeped commonly on carbonate sediments and rocks

modern caliche is vertically zoned and composed of 4 rock types:

1) a compact crust
2) beneath hardpan
3) caliche nodules with concentric lamination
4) massive chalky carbonate composed of uncementated silt - sized calcite microspar

50
Q

phreatic zone

A

can be subdivied into fresh water phreatic zone, mixing zone, and deep phreatic zone

51
Q

lenticular zone

A

horizontal water movement. the water are generally saturated with respect to calcite but undersaturated with respect to aragonite and mg calcite

52
Q

mixing zone

A

is dominated by dissolution without much precipitation

53
Q

deep phreatic zone

A

may be slow moving or almost stagneant ground water, or in case of young exposed carbonate platforms, it may be seawater

54
Q

factors that affect dolomitization

A

1) thernidynamics
2) kinetics
3) mass transfer
4) nature of host rock

carbonates final (1 decks)

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