SEDIMENTARY PETROLOGY (CLASTIC SEDS) Flashcards
1
Q
How much of the seds and seds rocks are Gravelstones or Rudites?
A
5%
2
Q
Depositional Agent that forms Gravelstones
A
Glaciers and Debris Flows and some water-laid seds
3
Q
Whats the minimum percentage of Gravel-sized population to be considered as a rudite?
A
at least 30%
4
Q
Subrounded to rounded, gravel or sand supported, with one composition of clasts
A
Oligomictic Conglo
5
Q
Subrounded to rounded, gravel or sand supported, with multiple composition of clasts
A
Polymictic Conglo
6
Q
Subagular to angular, gravel or sand supported, with one composition of clasts
A
Oligomictic Breccia
7
Q
Subangular to angular, gravel or sand supported, with multiple composition of clasts
A
Polymictic Breccia
8
Q
Mud-supported Rudites
A
Diamictite
9
Q
Single composition clast mud supported rudite
A
Oligomictic Diamictite
10
Q
Angular Clasts
A
Breccia
11
Q
Rounded Clasts
A
Conglomerate
12
Q
Single Composition of clast
A
Oligomictic
13
Q
Multiple compositions of clast
A
Polymictic
14
Q
What does breccia texture suggest
A
Minimal Transport and nearby provenance
15
Q
Breccia Environemtns
A
1) Fault zones
2) Talus Slopes due to Rock Falls
3) Impact Craters- Impactities
4) Karst Collapse of Carbonate Rocks
5) Upper portions of Alluvial Fans where Debris Flows are Commons
6) Whereve cohesive mud clasts are eroded and transporte a short distance by streams, currents or gravity flows
16
Q
Clast-Supported Framwework where clasts are in contact and therefore support one another
A
ORTHOconglomerate/breccia
17
Q
Orthoconglo-forming environments
A
Principle: Dapat continuous ung travel ng sand and mud or finer particles and napagiwanan ang mga gravel
1) Aqueous envi - Stream Channels, Beaches and Marine Shoals where sand and mud is continuously tranposted while gravel accumulates
2) Alluvial Fans and Ephemeral Braided Rivers Stream in which fines are removed and settled as SIEVE DEPOSITS
3) In areas where sands are entrained by winds from the surface leaving Gravel as LAG DEPOSITS
18
Q
A matrix supported rudite with the matrix composed mostly of sand
A
Sand-Supported
19
Q
Environments of a sand Supported Rudite
A
Principle: Dapat pwedeng mag accumulate together si Sand and Gravel
1) Alluvial Fans
2) River Channels, Braid Bars, Point Bars
3) Beaches, Marine Shoals, Storm Deposits
4) High conc sed gravity flows
20
Q
Mud-supported Matrix
A
Diamictite or Paraconglomerate
21
Q
Environments of Mud-Supported/Diamictites/Paraconglo
A
1) Glaciers - Tillites (Gravel + mud rich till)
2) Mudflows and Debris Flows including Lahars
3) Gravel-bearing sed gravity flows deposited in mud rich areas
4) tectonic Melanges at Covergent Plate Boundaries
22
Q
Typical Composition of Oligomictic
A
Compositionally/Mineralogically Mature and so Quartz Rich
23
Q
Specific examples of Oligomictic Breccias
A
Fault, Collapse and Rockfall Breccias
24
Q
What infor can Polymictic conglo give?
A
Significant and easily accessible info concerning the nature of the rocks in the source areas
25
Info that a Rudite with large clasts can provide
1) Provenance infor source Rocks
2) Climate and Relief
3) duration and intensity of Transport
4) Tectonic Settings
26
A conglo with preserved unaltered rocks implies that
1) Clasts are highly durable and chemically stable (Quartz-rich)
2) Low Precipitation and Temp w/c inhibit chem decompostions
3) High Relief and Low Vegetative cover w/c promote rapid erosion and minimize duration of chemical decomposition and clast disintegration
4) Short Tranpo w/c promotes survival of mechaically unstable clasts
27
PLUTONIC CLASTS imply that
A relatively nearby source area
28
Presence of mafic fragments implies that
High Relief
Rapid Erosio
LowrT and Rainfall
29
Granitoid Rock Fragments are commonly derived from
Intracratonic Rift Settings
Magmatic Arc
30
What is the implication of Limestone-and-evaporite rich Conglo
Source area as high relief and high erossion rate and low T and Rainfall
31
Clasts are both rounded and angular
Breccio-Conglomerate
32
Direct deposits of melting ice by glaciers
Till or Tillites (Lithified Rock)
33
non-glacial til like deposits (Olistostrome or graiflow)
Tilloid
34
Sed chaotic deposits of intimately mixed heterogenous materials w/c accumulate as SEMIFLUID body by submarine gravity sliding or slumping of unconsolidated seds
Olistostrome
35
Percentage of matrix to be considered Orthoconglo/Clast supported
<15%
36
Clast supported with no matrix at all
Open Framework
37
Clast suppored with finer sed matrix
Closed Framework
38
more thant 90% of the clasts consist only of resistant rocks ad mienrals such as metaquartzite, vein quartz and chert and are usually formed in environemtns which promote chemical decomposition (Low Relief, not rapid transport, babad ang seds,) like stream channels, bar deposits, near shore marine settings
Oligomict
39
Clasts of many different composition of metable stable and ustable rocks and are more abundant than the former ad is mostly formed in High Relief Areas
Petromict
40
Boundary between Matrix supported Conglo and sand or mudstone
>50% fines
41
Clasts same material as the matrix ad was formed as a result of REWORKING of lithified sediment soon after deposition derived from Interior (Intrabasinal sources)
Intraformational Conglomerate
42
A conglo in which clasts are exotic and are normally well rounded and well sorted since the source rock are distant from the depositional area
Extraformational Conglomerate
43
Rocks that contain less thant 30% Gravel and >1:1 Sand to mud ratio
Sandstones
44
Folks Classification
Isang Triangle with Seven Divisons beased on %Q, %F , and %LF
45
Sandstone w/ 95% Q in Folks
Qtzarenite
46
75-95% Q, >1:1 F:L
Sub arkose
47
75-95% Q, <1:1 F:L
Sublitharenite
48
<75% Q, >3:1 F:L
Arkoses
49
<75% Q, <1:3 F:L
Litharenites
50
<75% Q, between 1:1 to 3:1 F:L
Lithic Arkose
51
<75% Q, between 1:1 to 1:3 F:L
Feldsphatic Litharenites
52
Sandstones with significant mud matrix
Wackes
53
Sandstones with neglibile matrix
Arenites
54
Pettijohn's Classification
May Percent matrix na kasama aside from QFL and arkosic and lithic arenite lang
55
How many percet mud matrix <30microns are needed to be considered wackes
15%
56
Boundary between Mudstone and Sandstone
75% Mud Matrix Content
57
95% Q with 15% Mud Matrix
Quartz Wacke
58
<95% w/ >1:1 F:L
Feldsphatic Graywacke
59
<95% w/ <1:1 F:L
Lithic Graywacke
60
A general term for matrix rich sandstones
Graywacke
61
For blatt and tracy, how much is needed to be considered as mudrock?
50%
62
Feldspathic Sandstone
Arkoses
63
Information which can be revealed by Sanstone composition
1. Exposed rock types in source areas
2. Chemical stability and decompositio history of rock types
3. Climate, relief, and rates of erosion
4. Proximity to Source area, and intensity and duration of transport
5. Tectonic Settings
64
Tectonic settings in which sediments are derived from arcs over subduction zones along CPBs
Magmatic Arcs
65
Sediments are derived from orogenic mountiain belts which formed at collision plate boundaries
Recycled Orogens
66
Sediments are derived from stable cratonic source rocks from shields, and/or platforms or Continental rift systems
Contintental Blocks
67
Compositional range of Volcanic-Magmatic Arc-derived arenites
Litharenites,
Feldsphatic Litharenites,
Lithic arkose
68
Progressive Erosion of Volcanic-Magmatic Arc Fragments results to a trend of
Increasing Q and F, Decrreasing L
69
Differentiate Young undissected volcanic arc to dissected plutonic arc
The former generates a huge number of Aphanitic Rocks fragments while the latter produces Phaneritic Rocks which contain sand size F and Q
70
Divisions of Recycled Orogen by Dickenson and Suczek
1) Subuction Complexes
2) Collision Orogen
3) Foreland Uplifts
71
Areas which contain Sed rocks, Met rocks and Recycled Volcanic-Magmatic Arc Seds from uplifted recyced Accretionary complexes
Subduction Complexes
72
Contain sed and met rocks of both continental and oceanic origin uplifted during the continental collision that close ocean basins
Collision Orogens
73
Consist of diverse sed, met, and plutonic ign rocks assmeblages exposed in orogenic belts some distance from convergent plate boundaries
foreland uplits
74
Sandstones which are situated or formed in orogenic belts
Mostly Litharenite, Sublitharenites w/ Subordinate subarkoses and some lithic arkoses
75
Trend in Orogenic Belt Erosion
High Q, Low F and L
76
Consists of primarily Precambrian plutonics and high grade met rocks such as granitoids, gneiss and granulite
Shields
77
Relatively thin veneer of largely mature detrital sed rocks and or carbonate sed rocks that overlie the shields
Platforms
78
Sediments are derived from pre-existing, generally mature, sed rocks that overly plutonic basements (Shields) in a stable platform with VERY LOW RELIEF (PLATFORM ONLY)
Craton Interior
79
Both platform sed rocks and plutonic basement shield are exposed as source rock type with LOW to Moderate RELIEF (Shield + Platform w/ Low-Mod Relief)
Transitional Cratons
80
Basement Plutons (Shields) are exposed in area of high relief resulting from uplift esp in continental Rift Settings (Shield+High Relief)
Uplifted Basements
81
Sandstone which usually form in Cratonic Settings
Less Mature Arkoses and subarkise to more mature qtzarenites
82
Trend in Cratonic or Cotinental Block Souce Areas
The higher the Relief, The Rapid the erosion, the higher the Felds
The lower the relief the slower the erosion higher chem decomposition, higher qtz content
83
How much of the sed record is constituted by Mudrocks?
60-65%
84
Differentiate silt and clay
Clay are much smaller and are produced thru decompostion while silt is larger and is mostly formed by disintegration
85
Detrital fractions of mud
<30% Gravel
<1:1 S:M
86
Mudrocks with more than 5% gravel
Gravelly mudrocks
87
Mudrocks with >1:9 Sand to Mud Ratio
Sandy mudrocks
88
Traction transportation
Bed load
89
Coarse mudrocks w. >2:1 Silt to mud fraction or more than 2/3s
Siltstones
90
Fine mudrocks that contain <1:2 or less than 1/3 silt and more than 2/3s Clay
Claystone
91
Constains substantial amts of both clay and silt
Mudstone
92
the tendency of certain mudstones and claystones to split into thin layers parallel to the stratification
Fissility
93
Fissile Mudstones and Claystones
Shale
94
Why is there fissility in Mudstones and Claystones
Because there is subparallel alignment of clay and mica minerals
95
Techniques which can be employed to examine mudrocks
XRD
96
Decomposition of Ferrogmag in
ALKALINE soils with
LOW DRAINAGE,LOW TEMP in HIGH LATTITUDES
Chlorite
97
Product of weathering of ferromag minerals + plagioclase and is favored by impeded drainage in ALKALINE Conditions and SEMIR ARID Climates
Smectite (Montmorillonite)
98
weathering of Feldspars especially K-felds common in TEMPERATE REGIONS with NEAR NEUTRAL pH
Illite
99
MID LATITUDES SEMI-ARID - TEMPERATE slightly ALKALINE pH
Illite-Smectite Mixed Layer
100
Warm, Humid Climate in SUBTROPICS
ACIDIC SOIL
Leaching
Degraded Illites
Kandites - Kaolinite
101
Warm and Humid in Tropical Latitudes
Very High Acidity, Low pH
Intense Decomposition of Silica
Gibbsite - Bauxite
102
Chlorite
High latitudes
103
Kaolinites
Low Latitudes
104
Illites, Smectites
Common elsewehere
105
Younger Clays
Smectite and Mixed Smectite-Illite
106
Older Clays
Illite
107
Smectite and Kaolinite alters to
Illite and/or chlorite
108
Generally green-colored K-Fe-rich Illite produced in Marine Envi formed by slow precipitation in agitated, oxidizing, marine envi and replacements of fecal pellets in reducing conditions
Glauconite
109
Red and Purple mudrocks contains
Hematite
110
Ths commonly form in Iron rich mudrocks around decomposing organic matter that reduces iron which results in the removl of red coloration
Reduction Spots
111
Yellow to rusty colored contain
Limonite
112
Brown Mudrocs have
Goethite
113
Meidium to dk gray and black mudrocks ower their color to
Presnce of carbon rich organic Material w/ finely divided pyrite
114
Most widely distrbuted sed rocks
Mudrocks
115
Mudrock depositional Envi
Magsesettle lang si Mud kapag Calm na ang lahat
1) Calm Environments
116
Smectite rich claystones formed by the alteration of volcanic ash deposits generated by explosive eruptions with lumpy popcorn-like appearance since they swell and shrink
Bentonites
117
Mudstones that contain sufficient carbon-rich organic material to substantially influence their properties
Carbonaceous Mudrocks
118
A carbonaceous mudrock with a black color due to elevated (>2%) of incompletely decomposed, carbon-rich organic matter
Black Shales
119
Used to denote organic-rich mudstones and claystone especially by oceanographers and paleoceanographers
Sapropel (Organic - Mud)
120
Characterized by Organic mineral content of 15-30% that have potential to yield profitable amounts of petroleum and/or natural gas when heated sufficiently
Oil Shales
121
The process of extracting oil and gas by crushing shale (source rock) and heating it in anoxic conditions to 500 deg cel
Pyrolysis
122
Bituminous organic material in mudrocks that makes one a source rock
Kerogen
123
Oil window for kerogen to be converted to Oil
100-140 deg cel
124
Gas Window for kerogen to be converted to Gas
160deg cel
125
Factors that favor formation of Carbonaceous mudrocks
1)high Bio Prouctivity in the surface water
2) Sluggish Circulatio w/c impedes coarse detritues and oxygen replenishment
3) Anoxic-Reducing Bottom water conditions
126
BOD stands for
Biological Oxygen Demand
127
environments favorable for Carbonaecous mudrock formations
Lake
Marginal Sea
Epeiric Sea
Deep Ocean Basin
128
Includes all submetamorphic, post depositional changes that affect sediments after accumulation
Diagenesis
129
T and P of Diagenesis
0-3Kbar
150+/-50 deg cel
130
early shallow diagensis that occurs shortly after burial
Eodiagenesis
131
Later, deeper diagenesis
MesoDiagenesis
132
Much later, shallow diageneses that occurs as sed rocks approach surface due to erosion
Telogenesis
133
Factors Affecting Diagenesis
1) Temp (increses at depths)
2) Pressure (increases with depth)
3) Fluid Chemistry (conc of dissolved solids, gases, PH, and Oxidation-reduction potential (Eh)
4) Aqueous fluid circulation rates and patterns w/c depend on porosity, permeability, hdraulic head and rock structure
134
Occurs as a result of increasing confining pressures as sediments are buried progressively deeper beneath the surface
Compaction
135
Can act as excellent aquifers or water bearing horizons due to well sorting and retainment of substantial porosity and permeability even after burial
Quartzarenite
Arkosic Sandstones
136
Excellent Aquicludes or Aquitards
Mudrocks or Siltsones ot Claystones
137
Aquicluide
No Flow At all Very Low Hydr. Conductivity
138
Aquitard
May allow flow but very slow
139
Are lithic Sandstones and Conglomerates efficient storers and transmitters of fluid?
Better than mudorck but much lesser than arkosic sandstones
140
Solubility of minerals increases with increasing
pressure
141
Highest stress in a matrix of detrital grains are situated in
Point contacts between rigid grains
142
Dissolution caused by increase in pressure within contact points and presence of thin film of water
Pressure Solution
143
Pressolution is common in grains of?
Quartz Sands and Gravels w/ little to no plastic matrix
144
Long grain contact formed from differential dissolution when 1 grain is more soluble than the other
Concavo-Convex
145
Formed when dissoluton rates are equal
Straight Contact
146
Differential dissolution is caused by imperfections in the grain contact
Sutured Contact
147
occurs when crystalline solids partially or completely dissolve in pore fluids which migrates through fractures and between grains where they may be precipitated as veins and mineral cements
Dissolution
148
Occurs when pore fluids precipitate intergranular mineral or mienraloid cements that bind grains together
Cementation
149
Major Cements in Detrital Sed Rocks
1) Silica
2) Carbonates
3) Iron Oxides and Hydroxides
4) Feldspars
5) Clay Minerals
150
Type of cement overgrowths in which the silica that precipitates intially nucleates on a pre-xiting detrital qtz grain which both go extinct at the same time under the microscope
Syntaxial Qtz
151
IN what type of envi is Quartz Cement usually formed
Qtzarenite, Gravelstones that accumulated in beach, dune, and shallow marine envi assoc with Intracratonic basins and passive margins
152
An amorphous mineraloids that contains various amounts of water an is a common cement in Volcanoclastic Seds
Opal
153
how are opals formed?
Silica by product of devitrification of glass shards and pumice to betonties
154
at what T and P are opal cements precipitated
Low T and P since Opal Solubility increases with temp and Depth (EODIAGENESIS)
155
Whats the pH conditions in which OPAL tends to form
Alkaline (High pH)
156
Cryptocrystalline silica chracterized by microscopic EQUANT Crystals
Chert
157
Microcrystalline Silica which are bladed with radiating to Divergent habit under the microscope
Chalcedony
158
The most abundant mineral cement
Calcite
159
Addition of CO2 though respiration and bacterial decomposition makes pore solutions
Acidic (Lowe Ph)
160
Favorable conditions for Calcite precipitation
HIGHLY ALKALINE (HIGH Ph) LOW CO2
161
calcite cement composed of one or more cystals that occupy small pore spaces between detrital grains
Blocky Cement
162
composed of single, large calcite crystal that nucleates and grows to fill multiple pore spaces that it completely envelops several detrital grains that appear as inclusions (POIKILS) within a single clacite
Poikiloptic Cement
163
Iron-rich oxide cements
Hematite
Goethite and
Limonite
164
Where does IRON that forms these cements come from?
Alteration of Ferromag Silicates during weathering and diagenesis
165
Where is hematite cementation common?
Arid Terrestrial Envi
Alluvial fans
Braided Streams
Meandering streamsm flood plains, deserts
166
Rare cement which occur in fedlspar-rich detrtal sed rocks such as arkosic sandstones and gravelstones and apeear as optically clear overgrowths that nucleated on felspar hosts grains (Orthoclase in K felds) (Albite in Plag)
Feldspar Cement
167
Type of clay cements which occur as stacks of platy layers called books that precipitate at fairly shallow depths from Low K. acidic pore waters in Terrestrial envi (Eo and Telodiagenesis)
Kaolinite cements
168
clay cements which forms at higher temp and depth from high potassium, alkaline ppore waters esp. in Marine Envi (Late Eodiagenesis and Mesodiagenesis)
Illite Cement
169
K felds alter to this finegrained mica
Sericite
170
Ca and K felds at higher temperatures alter to
Albite
171
Volcanic Fragments typically alter to
Zeolites
172
Temperature at which mixed layer clay transformed into more ordered Illite
200 deg cel
173
Temp at which clay minerals transform into Chlorite and Mica
300 deg cel
174
Zeolite minerals stable at below 100 deg cel
Analcime and Heulandite
175
Stable from 100-200
Laumontite
176
Stable above 200
Prehnite - Pumpellyite
177
What are frequently significant Diagenetic Structures in Detrital seds rocks
1) Conretions
2) Nodules
3) Geodes
4) Liesegang Rings or Bands
178
Cannonball-like structures Formed by precipitation around a NUCLEATION SURFACE (Fossil, Sand Grain, Shale chip) and which multiple periods can form a concentric structure and a roughly spherhical shape
Concretions
179
Similar to concretions but lack a well defined nucleus and generally do not have concentric growth rings which are commonly chert nodules in limesones or dolostones
Nodules
180
A nodule with mineral-filed cracks whose origins are still controversial
Septarian Nodules
181
Nodules that were or are partly hallow and have roughly spherical to more irregular outer layers of chalcedony and a cavity lined with crystals
Geodes
182
Common in many detrital rocks esp. Carbonate or Fe-rich cements bands which are often truncated against prominent joint surfaces and are formed by precipitation by various FeO minerals moving through bodies of rocks separated by fractures from the outside-in that prodcues ring-like patterns of bands
Liesegang Rings
