Sedimentary Petrology Flashcards
It is a branch of study concerned with the composition, characteristics and origins of sedimentary rocks
Sedimentary Petrology
these are particles that have been mechanically transported by water, wind or ice or chemically precipitated from solution or secreted by organisms and deposited in loose layers on the Earth’s surface
Sediment
Originates and is transported as solid particles from both mechanical and chemical weathering
Detrital Material
or
Clastic Material
these are produced largely by chemical weathering
Soluble Material
rocks that formed at low temperature and pressure, found at or near the Earth’s surface
Sedimentary Rocks
these are formed from cemented sediment grains that are fragmented of pre-existing rocks
Detrital or Clastic Sedimentary Rocks
These are deposited by precipitation of minerals from solution
Chemical Sedimentary Rocks
these are formed by the accumulation of the remains of organisms
Organic Sedimentary Rock
The physical breakdown and chemical alteration of rocks at or near the Earth’s surface
Weathering
disintegrated rock particles are transported from the source or parent rock to its site of deposition
Transportation
occurs when the transported material settles or comes to rest as the medium of transport loses energy and can no longer transport its load
Deposition
as material precipitates from water tthat percolates through the sediment, open spaces are filled and particles are joined together into a solid mass
Cementation
the weight of the overlying material compresses more deeply buried sediment
Compaction
complex process whereby freshly deposited loose grains of sediment are converted into rock
Lithification
a collective term for all changes that take place in texture, composition, and other physical properties after sediments are deposited
Diagenesis
a grade scale for classifying the diameters of sediments.
Udden-Wentworth Scale or Wentworth Scale
Particles with
a. <1/256mm
b. 1/256 - 1/16mm
c. 1/16 - 2 mm
d. >2 mm
Clay
Silt
Sand
Gravel
Particle with the grain diameter of
a. 2 - 1 mm
b. 1/4 - 1/8 mm
c. 32 mm
d. 1/64 - 1/128mm
Very Coarse Sand
Fine Sand
Cobble
Fine Silt
consolidated gravel; composed of well-rounded pebbles
Conglomerate
term used if most of the clasts are between 64mm and 256mm in diameter of rock
Cobble Conglomerate
mixture of rounded and angular clasts
Breccio-Conglomerate
clasts that are angular in shape
Breccia
a gravelstone with a mud-supported matric, commonly deposited from glaciers, sediment gravity flows, particularly debris flows.
Diamictite
All clasts have the same material
Monomictic
composed of clasts of the same material as the matrix and is formed as a result of reworking of lithified sediment soon after deposition
Intraformational Conglomerate
rocks with equally spaced fracture planes in all directions, which will form spherical clasts when the edges are rounded off
Cubic (Equant)
rock that is clast-supported; A conglomerate in which all clasts are in contact with other clasts
Orthoconglomerate
used where there are just two or three clasts types present
Oligomictic
a matrix-supported texturel; A conglomerate in which most clasts are not in contact
Paraconglomerate
conglomerate that contains clasts of many different lithologies
Polymictic
a conglomerate in which clasts are exotic. Clasts are derived from a distant source
Extraformational Conglomerate
bedrock lithologies that break up into slabs form clasts with one axis shorter than the other
Oblate (Discoid)
when a discoid clasts are moved into a flow of water, these are preferentially oriented and may stack up in a form called ____________
Imbrication
those which are less susceptible to physical and chemical breakdown have a higher chance of being preserved as a clast in a conglomerate
Resistant Lithologies
clasts are less common, forming mainly from metamorphic rocks with a strong linear fabric
Rod-Shaped (Prolate)
grains that form within the depositional environment, they are pieces of plant or animal, but there are some which are formed by chemical reactions
Biogenic Particle
grains in the size of 1/16 - 2mm
Sand
Components of sand and sandstone
Detrital Minerals Authigenic Materials Matrix Lithic Fragments Biogenic Particles
Minerals that grow as crystals
Authigenic Materials
a rock if the amount of matrix is >15%
Arenite
a method whereby a thin section on a petrographic microscope is examined by stepping across thin sections at equal intervals
Point Counting
is defined as the grain suze of material between 4 and 62 microns in diameter
Silt
are group pf phyllosilicate minerals that are main constituents if clay-sized particles
Clay Minerals
general term for any indurated sediment made up of silt and/or clay
Mudrock
If the rock has
a. ≥2/3 clay
b. ≥2/3 silt
c. >1/3 silt + >1/3 clay
Claystone
Siltstone
Mudstone
strong tendency to break in one direction, parallel to bedding
Fissility
applied to any mudrock that shows fissility
Shale
is a textural term to define the finest grade of clastic sedimentary particles
Clay
most common mineral seen in silt deposits
Quartz
these are the deposist from strong, persistent winds that carry silt-sized dust thousands of kilometers
Loess Deposit
most common member of the Kandite Group
Kaolinite
a product of more moderate temperature conditions in soils with neutraal to alkaline pH
Montmorillonite
swelling or expanding clay
Montmorillonite
generally formed in soil profiles in warm, humid environments where acidic waters intensely leach bedrock lithologies such as granite
Kaolinite
a clay mineral with two patterns of layering
Kandite group
most common clay mineral in sediments
form in soils in temperate areas where leaching is limited
illite
forms in soils in arid climate with moderate leaching
fairly acidic groundwater conditions
Chlorite
an equipment that scans the surface of the sample which features micro imaging technique
Scanning Electron Microscope (SEM)
cohesive properties of clay minerals in suspension tend to form small aggregates of individual particles, it is called as ________
Flocculation
fragments that make up a sedimentary rock are called
Clasts
the distribution of clast sizes present
Sorting
During sediment transport, sharp edges tend to be chipped off first, the abrasion smoothens the surface of the clast
Clast Roundness
a relatively quick and easy method of semi-quantitatively determining the mineral composition of fine-grained sediment
X-Ray Diffractometer
is an inherited feature, that is, it depends on the shapes of the fragments which formed during weathering
Sphericity
describing individual clasts, the dimensions can be considered in terms of closeness to sphere
Clast Sphericity
tendency to break in a certain direction or show a strong alignment of elongate clasts
Fabric
quantitative assessment of the percentages of different grain sizes in clastic sediments and sedimentary rocks is called
Granulometric Analysis
is laid over the loose material or on a surface of conglomerate and each clast measured within its area
Quadrant
indicator of whether the grain-size histogram is symmetrical or is skewed to a higher percentage of coarser or finer material
Skewness
the extent to which the material has changed when compared with the starting material of the bedrock it was derived from
Maturity
a measure of the proportion of resistant or stable minerals present in the sediment
Compositional Maturity
there has been one cycle of erosion, transport and deposition
First Cycle
general term for solid sedimentary particles regardless of origin
Clastic or Detrital
Used for clastic sediment that is transported as solid particle across Earth’s surface
Epiclastic
used for clastic particles or organic origin such as shell fragments transported by waves or currents
Bioclastic
_____ refers to redeposited material
Second Cycle
the texture of sediment or sedimentary rock can be used to indicate information about the erosion, transport, and depositional history.
Textural Maturity
used for clastic particles produced initially by volcanic processes
Volcaniclastic
used for clastic particles composed of silicate minerals
Siliclastic
% of Mg in
a. Low Mg Calcite
b. High Mg Calcite
a. <4%
b. 11-19%
large group of organisms that have a fossil record back to the Cambrian and commonly have calcareous hard parts
Molluscs
have a distinctive layered shell structure consisting of two or three layers of calcite, or aragonite, or both
Bivalve Molluscs
shelly organisms with two shells and hence superficially similar to bivalves
Brachiopods
have a calcite or aragonite layered structure and are distinctive for their coiled form
Gastropods
layered shell structure and in common with most other molluscs, this is a feature that may be recognizable in fragments of shell under the microscope
Cephalopods
cephalopods that had a cigar-shaped guard of radial, fibrous calcite
Belemnites
hard body parts out of whole low-magnesium calcite crystals
Echinoids
they reconstruct their body parts out of whole calcite crystals, with discs that make up the stem or a ______ forming sizeable accumulations in Carboniferous sediments
Crinoids
small, single-celled marine organisms that range from a few tens of microns in diameter to tens of millimeters across
Foraminifera
largest calcium carbonate biogenic structure
Cnidaria (Corals_)
have a symbiotic relationship with algae that require clear, warm, shallow marine waters.
Hermatypic Corals
do not have algae and can exist in colder, deeper water
ahermatypic Corals
Single-celled protozoans are seen mainly as encrusting organisms today but in the past they formed large colonies
Bryozoa
they are an important source of biogenic carbonate and are important contributors of fine-grained sediment in carbonate environment through much of the geologic record
Algae & Microbial Organisms
known as the coralline algae
Red Algae (Photophyta)
have calcified stems and branches, often segmented that contribute fine rods and grains of calcium carbonate to the sediment when the organism dies
Green Algae (Chlorophyta)
they are extremely important contributors to marine sediments in parts of the stratigraphic record
Yellow Algae (Nanoplankton)
these organisms are not classified separately to algae
Cyanobacteria
the algal mats formed by these organisms
Microbial/Bacterial Mats
the filaments an sticky surfaces of the cyanobacteria act as traps for fine-grained carbonate and as the structure grows it forms layered, flat or domes structures called ___
Stromatolites
cyanobacterial communities that have an irregular rather than layered form
Thrombolites
they are irregular concentric structures mm to cm across formed of layers bound by cyanobacteria found as clasts within carbonate sediments
Oncoids
spherical bodies of CaCO3 less than 2mm
Ooids
concentrically layered carbonate particles over 2mm across,
Pisoids
commonly fecal pellets of marine organisms, mostly particles less than a mm across
Peloids
fragments of CaCO3 material that has been partly lithified and then broken up and reworked to form a clast which is incorporated into the sediment
Interclasts
are fine-grained siliceous sedimentary rocks made up of silt-sized interlocking quartz crystals
Cherts
it is considered carbonaceous if it contains a proportion of organic materials
___% for mudrock
___% limestone
___% sandstone
> 2% mudrock
0.2% limestone
0.05% sandstone
long-term preservation of dead vegetation is favoured by the wet, anaerobic conditions of mires, bogs, and swamps
Peat
if >2/3 of a rock is solid organic matter if may be called ____
economic ___ have less than ___% non-organic, noncombustible material
Coal
10%
bright, shiny black coal that usually breaks cubically and mostly consists of woody tissues
Vitrain
black or grey in color, dull and rough coal that usually contains a lot of spore and detrital plant material
Durain
black, fibrous with a silky luster, friable and soft coal that represents fossil charcoal
Fusain
banded, layered coal that consists of alternations of other 3 types
Clarain
microscopic examination of these lithotypes reveals that a number of different particle types can be recognized
macerals
origin of which is mainly cell walls of woody tissue and leaves
Vitrinite
mainly comes from spores, cuticles and resins
Liptinite
burnt, oxidized or degraded plant material
Inertinite
mudrocks that contain a high proportion of organic material that can be driven off as a liquid or gas by heating
Oil Shales
are clastic sediments that are saturated with HC and they are the exposed equivalents of subsurface of oil reservoirs
Tar Sands
Oil Sands
% Marine Evaporites
a. CaCO3
b. CaSO4
c. NaCl
d. KCl
a. 0.3%
b. 3.5%
c. 78
d. 18%
Sequence of Precipitation of marine Evaporites
CaCO3
CaSO4
NaCl
KCl and MgCl
precipitated from seawater once evaporation has concentrated the water to __% of its original volume
a. 19%
b. 9.5%
a. Calcium Sulphate
b. Halite
an important source of industrial potash and is interpreted as the product of of extreme evaporation of marine water
Sylvite
rocks with concentrations of phosphate (5-35% P2O5) are called ____
Phosphorites
Phosphorites are composed of _____, which is Fluorapatite
Francolite
Sedimentary rocks that contain at least 15% Iron ore referred to as
Ironstone
or
Iron Formation
are black to dark brown in color and range from a few mm to many cm across as _____ or as extensive laminated crusts on hard substrates
Nodules
method for representing a series of beds of sedimentary or sedimentary rocks
Sedimentary Logs
features that give the direction of flow
Unidirectional Indicator
structures that provide information about the axis of the current but do no differentiate between upstream and downstream directions
Flow Axis Indicator
information about the source of sediment
Provenance
used to determine the average chemical composition of large continental areas
Mud and Mudrock Analysis
sum of the characteristics of a sedimentary unit
Facies
confined to the physical and chemical characteristics of a rock
Lithofacies
Observation concentrate on the fauna and flora present
biofacies
focuses on trace fossils
Trace Fossils
temporal and spatial relationships between depositional facies as observed in the present day and recorded in sedimentary rocks
Walther’s law
provides a framework of understanding the processes that lead to the formation of mountains as well as providing for how all the main morphological features of the crust have been formed throughout most of earth history
Plate Tectonic Theory
is a consequence of the movement of any body travelling towards or away from the poles over the surface of a rotating sphere
Coriolis Force
is an important stage in the transformation of bedrock and regolith into detritus available for transport and deposition
Soil Formation
a coherent mass of bedrock moving downslope without significantly breaking
Landslide
with significant breaking of the bedrock accumulates as a chaotic mass at the bass of slope
Rock Fall
Regolith is lubricated with water as it moves down the slope, almost imperceptible
Soil Creep
intermediate between landslides and soil creep, instantaneous events like landslides but has plastic material due to water saturation forms an internallt deformed masss
Slumping
laminar flow, similar to a slump but with more water involved
Debris Flow
weathered detritus in mountain areas that accumulated near the bottom of the slope
Scree
initial erosion by water on hillsides, unconfined surface run-off down a slope following rain
Sheet Wasg
The result of atmospheric differences that are partly due to global distribution and local variations in pressure complex shifting patterns
Wind
is most effective on land surfaces with sparse vegetation
Wind Erosion
occurs by frictional action of block of materials in ice on the bedrock
Abrasion
occurs when glaciers flow over an obstacle
Plucking
lowering of land surface by a combination of weathering and erosion
denudation
change in the height of the ground over the sea
Relief
essential to all chemical processes
Water
presence of acids enhances hydrolysis and dissolved oxidizing agents facilitate oxidation reactions
Water Chemistry
high discharge in streams but dense vegetation reduces soil erosion even on steep slopes
High Rainfall
effectively protects the bedrock and overlying regolith from rain impact and overland water flow; stabilizes mountain slopes; bind fine detritus into soil protecting it from wind
Dense Vegetation Cover
Removal of mass from an uplifted bedrock
Isostatic Uplift
an orographic effect resulting to a sharp climatic division across a mountain range
Thermochronology
