1. Non-Terrigenous Sediments and Rocks
Carbonate-Chemical-Volcaniclastic
Sediments and Rocks

2. No “Simple” Classification Scheme

3. Importance of Volcaniclastics
Recognition of contemporaneous volcanism
Pyroclastic rocks and volcaniclastics with admixtures of proclasts
Voluminous strata at plate boundaries and hot spots

4. Classification of Volcaniclastic Rocks
Volcanic particulate material
Any fragmentation mechanism
Any transport process
Any environment
Pyroclastic
Particles broken by volcanism
Epiclastic (epiclasts)
Any fragment of volcanic (composition) origin

5. Classification of Volcaniclastic Rocks
Pyroclastic rock or sediment
>75% material fragmented by volcanic eruptions
Tephra: unconsolidated pyroclastic deposit
Hydroclastic rocks or sediment
Water interaction fragmentation
Pyroclastic Ejecta
Juvenile
Cognate
Accidental
Erupting magma,
Crystals and glass
Co-magmatic volcanic rock
Country rock inclusions

6. Classification of Pyroclastic Rocks
Basic classification otbo (on the basis of) particle size
Blocks (solid) and bombs (molten) (>64mm)
Volcanic breccia deposits
Lapilli (2-64mm)
Lapillistone
Ash (<2mm)
Tuff
Additional Classification otbo composition
Crystals
Lithic
Vitric fragments

7. Composition of Tuffs Crystals (intratelluric)
Euhedral +/- broken
Compositional zoning
Vitric (glassey) fragments
Bubble wall shards

8. Composition of Tuffs Vitric (glassy) fragments Lithic fragments
Bubble wall shards
Hydroclastic shards
Lithic fragments
Volcanic rock fragments (cognate?)

9. Fragmentation Processes
Explosive (gas expansion) comminution (fragmentation): mainly intermediate to silicic (high silica) magmas.
Ash fall; Laterally extensive air fall; Typically silicic and vitric rich.
Mantles topography.
Consists of glass (bubble-wall) shards.

10. Volcanic Fragmentation Processes and Products
Continental silicic (high silica) magmas; Calderas and pyroclastic sheet deposits
Ash flow {nuee ardante or ignimbrite, as in “great flaming ignimbrites”.
Follow topographic lows (high density fluid).
Create gigantic pyroclastic sheet deposits
Can be hot enough after deposition to weld, annealed vitric fragments welded tuff
Kaguyak volcano, Alaska

11. Volcanic Fragmentation Processes and Products
Hydroclastics; Water interaction fragmentation (typically basaltic lavas)
Great volumes of hydroclastics on the sea floor and in the edifice of submarine volcanoes
Highly subject to alteration –> clay minerals, microcrystalline silica, and zeolite

12. Significance of Volcaniclastic Rocks
Subject to extensive diagenetic alteration during burial
Typically occur in high heat flow geological settings
Typically poor fluid reservoir rocks

13. Orthochemical Sediment: Evaporites
Stratified rock consisting of minerals precipitated from high concentration brines, typically hypersaline sea water
Anhydrite (CaSO4)
Gypsum (CaSO4 )*H2O
Halite (NaCl)
Others

14. Evaporites Indicative of unusual climatic or oceanographic conditions
Severe circulation restriction
Climatic aridity
Highly subject to secondary alteration/solution
Anhydrite<--->gypsum due to hydration/dehydration
Physical deformation: enterolithic structure
Occurrence
Bedded
Nodular
Chicken wire

15. Siliceous Sediments/Rocks
Chert/diatomite (SiO2 );
Opaline tests
Chalcedony
microcrystalline quartz

16. Siliceous Sediments/Rocks
Bedded chert (most)
Pelagic sediment consisting of siliceous zoo- and phytoplanktonic tests
Siliceous sediment experience a predictable transformation from amorphous opal to chalcedony and eventually to microcrystalline quartz due to time/temperature dependant chemical reaction
C= lam chert, s= sandstone layers, f= fractures

17. Siliceous Sediments/Rocks
Nodular Chert; diagenetic origin (typical)
Silica derived from the solution of siliceous fossil material in predominantly carbonate rich successions
Sponge spicules and other siliceous bioclasts
N=chert nodules, b=bedded chert

18. Organic Rich Sedimentary Rock
Organic compound-rich rocks
Coal
Humic coal
vascular {land} plant derived organic compounds altered by elevated temperature and burial pressure
Sapropelic coal
Formed from non-vascular (algal) plant material

19. Organic Rich Sedimentary Rock
Oil Shale
Primary, organic carbon (OC)-rich shale (>2% to > 10% OC)
Formed in low energy environments through suspension and deposition in stagnant (anaerobic) conditions
Most common source of long chain, liquid and gaseous hydrocarbons that can migrate into porous reservoir rocks and from economic accumulations of petroleum
Spontaneous combustion of
Kimmeridge oil-shale, Dorset, UK.

20. Non-Terrigenous Sediments and Rocks
Carbonate Sediments and Rocks

21. No “Simple” Classification Scheme

22. Most Common non-Terrigenous Sedimentary Rocks
Carbonates (>50% primary carbonate minerals)
Limestone (CaCO3)
Chemical
biochemical
Dolomite (CaMg(CO3)2)

23. The Origin of Carbonate Sediments
Most form as biogenic particles (essentially the only source) in
warm (tropical; 30oN to 30oS latitude),
shallow (shelf; within the photic zone), (mostly <10-20 m)
marine water
Also accumulate in deepwater
ooze
limestone (fine-grained) made up of skeletons of pelagic microorganisms such as Globigerina

24. The Origin of Carbonate Sediments
Why?
Any process that decreases [CO3] forces rxn (2) to the left, CO2 is less soluble in warm water; CaCO3 has retrograde solubility
(1) H2O + CO2 <---> 2H2CO3 <–->H+ + HCO3- <-->H+ + CO3-2
CaCO3 <-–> Ca+2 + CO3-2
(pH dependant reaction)

25. Carbonates: General Characteristics
The majority of carbonate sediment forms in subtidal to supratidal environments and gives rise to widespread tabular deposits along continental (trailing edge) margins and epicontinental seas
Important occurrence in reefs, mounds or banks (bio-buildups)

26. Carbonate Minerals in Sedimentary Rocks
The physical and chemical conditions of the environment in which calcites, dolomites and aragonites are formed are reflected in their composition.
bivalent metal cations
Ca+2
Calcite, aragonite
Mg+2
Magnesite, dolomite
Fe +2
Siderite, ankerite
+ CO3 -2

27. Carbonate Minerals in Sedimentary Rocks
Several factors control the crystal habits and crystal sizes of these minerals, most important:
salinity
ratio of magnesium to calcium of in the solution (time dependant)
bivalent metal cations
Ca+2
Calcite, aragonite
Mg+2
Magnesite, dolomite
Fe +2
Siderite, ankerite
+ CO3 -2

28. Most modern Carbonate sediments (mostly biogenic)
Magnesian Calcite = small crystals > 4% Mg++ (4-9%),
Mg++ = 3 x Ca++ in normal sea water (main site of CaCo3 ppt)
“poisons” (interferes with calcite crystallization) and results in formation of meta-stable Aragonite (neomorphosis)
Aragonite (orthorhombic polymorph of CaCo3)
(Mg,Ca)CO3
(Mg,Fe,Ca)CO3
(Aragonite)

29. Most ancient carbonate rock is
Calcite:
<4% Mg++ (CaCO3)
Dolomite
(CaMg{Co3}2) 42% - 58% CaCo3.
Not readily formed at low temperatures; almost always 2nd ary mineral or very rare primary ppt “the dolomite problem”:
Primary or Secondary/Authigenic??
(Mg,Ca)CO3
(Mg,Fe,Ca)CO3
(Aragonite)

30. Other, (mainly diagenetic) Sedimentary Carbonate Minerals
Siderite
Fe Co3
Ankerite:
Ca(Mg,Fe)Co3

31. Carbonates: General Characteristics
An antipathetic relationship exists between carbonate sediments and siliciclastic sediments due in large part to the biology of carbonate sediment-forming organisms
high terrigenous sedimentation rates increase turbidity, which inhibits photosynthesis by benthic organisms
gill breathers (such as the coral) get clogged up and die
The structures and textures of carbonate rocks mostly reflect intrabasinal, biological AND physical factors

32. Carbonates: General Characteristics
Carbonate sediments are particulate and subject to physical processes at the site of deposition just like TC sediments
Kinetic energy (currents) in the depositional environment influence:
grain size and sorting
BUT, carbonate sediments are mostly biogenic (“born” not “made”) and may not experience physical transport
This can confound grain size-sorting / depositional energy relationship

34. Source and Type of Sediments Produced in Modern and Ancient Carbonate Environments

35. Carbonate Rock Classification
Allochems
Carbonate sand
Micrite
Micro Crystalline calcite
Cement (spar)

36. Carbonate Rocks Constituents
The sand-sized grains that occur in carbonate rocks are called allochemical particles or allochems.
Intraclasts (rock fragments):
formed, transported and redeposited within the basin
Ooliths: concentrically laminated carbonate structures, including:
oolites -concentrically laminated structures,less than 2mm in diameter, thought to be abiogenic in origin
pisolites - same as oolites, but greater than 2mm in diameter
oncolites - spheroidal stromatolites (> 1-2 cm)
Peloids:
silt to fine grained sand sized carbonate particles with no distinctive internal structure; most thought to be fecal pellets
Skeletal particles (bioclasts):
whole microfossils, whole megafossils, broken shell fragments
algae, forams, corals, bryozoans, brachiopods, gastropods, pelecypods, ostracods, etc.

37. Carbonate Rocks Constituents
The sand-sized grains that occur in carbonate rocks are called allochemical particles or allochems.
Intraclasts
Ooliths
Peloids
Skeletal particles (bioclasts)
The interpretation of the depositional setting of carbonates is based on grain types, grain packing or fabric, sedimentary structures, and early diagenetic changes.

38. Carbonate Rocks Constituents
The sand-sized grains that occur in carbonate rocks are called allochemical particles or allochems.
Intraclasts (early lithified carbonate fragments):
irregularly-shaped grains that form by syndepositional erosion of partially lithified sediment.

39. Carbonate Rocks Constituents
The sand-sized grains that occur in carbonate rocks are called allochemical particles or allochems.
Ooliths: concentrically laminated carbonate structures, including:
oolites -concentrically laminated structures,less than 2mm in diameter, thought to be abiogenic in origin
pisolites - same as oolites, but greater than 2mm in diameter
oncolites - spheroidal stromatolites (> 1-2 cm)

40. Carbonate Rocks Constituents
The sand-sized grains that occur in carbonate rocks are called allochemical particles or allochems.
Pelloids:
silt to fine grained sand sized carbonate particles with no distinctive internal structure; most thought to be fecal pellets

41. Carbonate Rocks Constituents
The sand-sized grains that occur in carbonate rocks are called allochemical particles or allochems.
Skeletal particles (bioclasts):
whole microfossils, whole megafossils, broken shell fragments
algae, forams, corals, bryozoans, brachiopods, gastropods, pelecypods, ostracods, etc.
Standard microfacies (fossil fragment type -> environment)

42. Carbonate Rocks Constituents
Micrite:
microcrystalline carbonate particles of clay (<1-4 micron) size (subtranslucent matrix) formed by
chemical or biochemical ppt
abrasion of allochems
implies deposition in a low energy environment just like in terrigenous mudstones

43. Carbonate Rocks Constituents
Cement:
sparry (twinkling crystalline) orthochemical material formed in interstitial pore spaces of “grainy” carbonate sediment
cement in pores indicates original void space
also recrystallized allochems or micrite

44. Carbonate Rocks Constituents
Insoluble Residues –
minor amounts of clay minerals and quartz occur in limestones, as insoluble residues, (so called because they do not dissolve in HCl)
Most insoluble material is chert (siliceous)
chert mostly originates from the shells of silica secreting organisms including diatoms, radiolarians, and some sponges.

45. Classification Schemes: Folk Classification
Type I limestone,
Sparry Allochemical rocks: allochems > 50%, spar cement > micrite mud [4 rock types]
more energetic environment, some sorting
Type II limestone,
Micritic Allochemical rocks: allochems >10%, micrite mud > spar cement [4 rock types]lower energy environment, more poorly sorted than Type I
Type III limestone: Micrite: allochems < 10%
very low energy at the site of deposition (carbonate mudrock)
“Biolithite”: Reef rock

46. Classification Schemes: Dunham Classification
Texture and allochem type incorporated into classification
sediment deposited in calm vs agitated waters
mud-bearing vs mud-free sediment
grain vs mud support
bound (biologically)
depositional texture recognizable

47. 5 Principles of Dunham Classification
Presence or absence of lime mud; is there any mud at all. Calm waters allow for the accumulation of lime mud and indicates the absence of current induced agitation
Grain Support: self supporting framework:
fluid circulation, diagenesis
Grain kind: standard microfacies types
Grain size, rounding, and coating: hydrologic interpretations
Biogenically ppt masses bound at time of deposition:
Boundstone
organic framework
laminations not consistent with gravity (stromatolite)
roof over sediment filled cavities

48. Folk Textural Spectrum Classification
Concocted to incorporate textural characteristics comparable to textural maturity in TC sediments
Mud component
Sorting
Rounding

49. Dolomitic Rocks
Typically devoid of primary textures and structures; if primary textures are preserved
<10% dolomite: “dolomitized” (rock name)
>10% dolomite: dolomitic (rock name)
recrystallized carbonate: dolostone
saddle dolomite: “burial” dolomite of hydrothermal origin