general terms COPY Flashcards
3D QFL diagram
%mud: <5%= arenites, 5>%mud<50%=wackes, %mud>50%=mudstones QFL: %qtz: %qtz>90%=qtz arenite, 75-90%=sublithic, sub-arkosic, <75%-arkosic or lithic
A-Horizon
Zone of oxidation, leaching, organic reactions, humus, solutes, fine clay percolating. Approximately 5% rocks.
Actualism
The present processes approximate the past but it must be interpreted with a grain of salt.
Alfisols
Soils that are developped in moist, temperate climates. There is alot of insoluble cations (Fe + Al) in the alfisols. Examples include Georgia’s red clay or African soils.
Are physical, biological, and chemical weathering discrete things?
They are not. Salt crystallization is an example of both chemical and physical weathering. Root wedging and fungal breakdown are biophysical and biophysiochemical.
Arenites NEED PIC
Sandstones that are composed of distinct grains and cement with a maximum of 5% mud.
Aridsols
Soils that form in deserts. They are poorly developed, solutes are relatively static because evaporation offsets any percolation. Many evaporites and dust.
Authegenic minerals
Minerals produced at the surface. Minerals precipitated through biologic, supersaturation, oxidation, or other processes.
B-Horizon
Zone of accumulation (illuvial). Clay and solutes. Dark colors. ~80% mineral
Bed Shear Stress
tau0=SW*h*S
SW=specific weight
h=flow depth
S=slope (gradient)
This represents the shear stress a flow exerts onto a bed it is flowing over.
Bedforms
Mounds or troughs of loose sediment on a mobile bed forming @ sediment and fluid interface. They describe the relation of strata.
Bernoulli’s Principle
Derived from the conservation of energy and the principle of continuity where:
KE+PE+P(aka work)=Constant
If the path is obstructed by a grain and therefore V(flow) increases (see principle of continuity) and over a dx the PE is constant/~0 then the KE increases when traversing over the grain and therefore P (pressure) decreases. This forms hydraulic lift.
Biological Weathering
The influence of plant life of the weathering process. Examples include root wedging and bioturbation. It creates a significant part of the weathering scheme.
Biological Weathering Examples
Chelation: The Bonding of metals with organic compounds with the effect of increasing their solubility.
C-Horizon
Chunky Bedrock, regolith. 100% rock
Cataclastic Breccia
Refers to breccias formed due to land movement.
Landslide/Slump breccias form due to the tension of sliding material
Tectonic Breccias form from gouge
Collapse breccias are from cave-ins and other forms of ground failure
Chelation
Biogenic weathering through organic compounds. It forms a metal compund that increases the solubility of the metal.
Chemical Weathering
Break down of rock due to being at disequilibrium on Earth’s surface. Characterized by shifts in the chemical and/or mineralogic components of a rock.
7 Chemical Weathering Mechanisms
Carbonation because of rain being slightly acidic
Simple Solution: dissolution without precipitation
Hydrolysis: dissolution and precipitation of new minerals. Incurs a permanent composition/mineralogic shift.
REDOX: The oxidation of Mn and Fe to form hydro/oxides.
Hydration/dehydration: clays, hematite->goethite, and gypsum->anhydrite. Characterized by reversibility and impermanence.
Ion Exchange: shifting ions within clays/zeolites and solution
Chelation
Clay series
Clays constitute a significant potion of all grains in sedimentary rocks that host large metallic cations, strong, and stable structures.
illite alters to smectite (montmorillonite: expandable upon hydration)
kaolinite is a T-Oct Al-rich clay with the potential for bauxite (Al(OH)3) . It is the ultimate Alumino-silicate weathering product.
Climbing Ripples
During the de-escalation of flow ripples will stop migrating and start “mounding” Therefore downward flow will be up-dip. They form non-tangential and tabular cross-bredding.
Competence ADD FBD
The maximum particle size that a flow can move.
Determines by if the flow can exert a force that is greater than tauc
Conglomerates/Breccias:
Rocks that are primarily composed of lithic fragments over 2mm (>30%). If they are angular then it is considered a breccia. If they are more mature and rounded then they are conglomerates. Clast supported refers to if the individual clasts are touching and create the structure. Matrix supported refers to the concept of the clasts being suspended in the fine grained matrix material.
Continental Block Provenance
Typical exhumed continental material. It has a wide variety but primarily consists of quartzose, K-spar, sometimes volcanics.
Debris flow deposits
Unsorted, chaotic, matrix supported, lacks cross-stratification and occasionally shows reverse grading
Debris flows
A type of flow that is dominated by a high viscosity, like a bingham plastic, that forms an internal structure and develops matrix supported rocks. The base of the flow has a relatively low velocity and thus is non-erosive on the base. It is characterized by “freezing” when shear at the base is less than the critical shear.
This can commonly occur in arid regions and with volcaniclastic deposits and include mud flows (~50% mud), muddy debris flows, and debris flows (0% mud)
Density Flows
A fluid flow that is formed due to a non-homogenous density.
Diagenesis
The final step of lithification of sedimentary rocks that alters the rock due to pressure.
Name two forms of deformation
Plastic and Ductile Deformation: Characterized by the expansion of clays into adjacent quartz
Flexible Grain Deformation: Characterized by minerals restructuring and reducing the volume of other grains. Ex: mica forming a planar surface where a quartz grain once existed.
Dimensionless numbers
Numbers that describe a state change for the participants of the system.
E-Horizon
Zone of intense remove of cations (eluviation) and chelation. The soil is a light color and depleted of metallic cations. ~50% mineral
Entrainment
The process of grains losing contact with the bed below and is determined by the critical shear threshold.
Epiclastic Breccia/Conglomerate
FIND EXAMPLE
Epiclastic conglomerate/breccia: An extraformational/intraformational rock that formed from a non-specific weathering and transport process.
Example of hydrolysis
Alumino-silicate+ “acidified” water + water yields alkalai metal in solution + phyllosilicate + SiO2 (aq)
Ex: 2KAlSiO6(s) +H2CO3 + H2O-> K2CO3(aq) + Al2SiO5(OH)4 (s) + 8SiO2 (aq)
Orthoclase + carbonated rain + water -> Potassium carbonate + kaolinite + aqueous silica
Example of REDOX
2FeS2+15/2O2 + 4H2O -> Fe2O3 + 4SO4 2- + 8H+
Ferrous iron (soluble) forms ferric iron (3+) upon being exposed to the atmosphere and forms the hydrated Fe(OH)3 This then dehydrates to form hematite (above).
Factors of Weathering
Climate and Rock
Weathering in wet climates is dominated by chemical mechanisms. Low slope, higher grain size surface area, and warm climates all promote water retention and higher weathering.
Feature of immature clasts
Poor sorting, angular grains composed on relatively unstable minerals.
Features of mature clasts
homogenous composition, well rounded, well sorted
Feldspathic Arenite AKA Arkose
Less than 75% of the clasts are qtz and there is more spar than lith. They are generally immature and form clay-rich arenites. They often form on stable continental shelves/alluvial fans or in-situ when granite decays. They are promoted by arid/cold environments and were more common from Paleozoic and Mesozoic times.
Froude Number
A dimensionless unit that describes how a surface wave passes through a liquid. The denominator describes the velocity of a surface wave through water and the numerator is the velocity of flow. Therefore a Fr<1 means that the wave’s velocity is greater than the flow’s.
Fr=V/(gD).5 D=water depth
Grain flow deposits
Kinetic sieving causes reverse grading. Generally well sorted, and form wedge shapes with the upper surface = angle of repose
Grain Flows
These are relatively dry flows of individual grains that are induced when the weight exceeds the internal frictional cohesion. The dispersive pressure is derived from the collision of grains. Commonly is the “Avalanching” of grains on the lee-side of dunes.
tau/P=tan(a) where: a=angle of internal friction
P=dispersive pressure
Gravity Flows
Characterized by a mass of sediment forming a flow with or without significant fluid composition and is propelled by the particle mass.
MOR weathering
A form of submarine chemical weathering where basalt reacts with seawater to form glaucanite (clay), phillipsite (zeolite), and palagamite.
Hjulstrom Diagram
A diagram that describes the maximum diameter of a particle that be entrained within a flow based on flow velocity. At small diameter the erosion potential decreases because the fine particle’s develop stronger van-der-waals cohesive forces. The curve is calibrated for h=1 m and SiO2 particles.
Hydraulic Lift
Derived from the principle of continuity which says that the flux within a pipe is constant.
Flux 1=Q1*A1=Flux 2=Q2*A2
where Q=velocity.
Therefore if A21 then Q2>Q1
Intraformational Conglomerates
These are conglomerates that form within a basin so the clasts are not from an external formation. Flat pebble conglomerates. Precontemporeneous clast formation includes the drying of mud, grain flows, and/or tides.
K-Horizon
A special form of the B-horizon for CaCO3 accumulation (caliche). It is a distinctly hard zone because of the cementing.
7 Key geothermometers
Color alteration
Vitrinite reflectance
graphitization of kerogen
clay mineralogy
zeolite assemblages
fluid inclusions
oxygen isotope ratios
Laminar flow
Particles move relatively parallel to each other and the overall flow vector. It is supported by a low reynolds number.
Liquified flow deposits
Dish structures (concave up “dishes”)
Convolute laminae (“mushroom” shapes)
Flame structures (similar to convolute but not yet wider at the peak)
Mounds and vertical structures: “mud volcanoes” where the water was escaping the sediment
Liquified flows
This is a broad term describing the upward exhumation of liquid from sand and mud. In the process sediment is “liquified/fludized” (effective loss of cohesion) by settling and water escapes the pore space.
Lithic Arenites
Siliclastic rocks with a large quantity of rock fragments.
Often immature, angular grains and indicates shallow marine enviroments or fold-thrust belts.
Magmatic Arc Provenance
Sediments are derived from igneous rocks, lith, plag, and typical volcanics. It includes less quartz and K-spar.
Maturity of sediment
Maturity is the extent to which grains have reached their final weathering product for a given environment.
Meteorite Impact Breccia
Breccias that form due to meteorite impacts.
Migration of Ripples
Ripples migrate due to the avalanching on the lee-side of the slope. They produce cross stratification that is either linear (2D ripples) or concave (3D ripples)
Components of Sediments and their meaning for provenance
SiO2: Overrepresented due to multi-cyclical nature and non-secondary alteration.
Spars: the most common mineral in the crust but underrepresented due to susceptibility to alter to clays. Feldspathic grain indicate that the rock is relatively immature.
clays: kaolinite is the most mature clay. Volumetrically clay is the majority of sed rocks and acts as an important reservoir for accumulating metals.
heavy minerals: Relatively stable high SG minerals. Zeolites and garnets are significant components of this.
mafic minerals: RARE indicates an extremely immature rock.
lithic fragments: commonly the most stable rocks like quartzite, volcanic glass, slate, phyllite, schist, or chert.
Mollisols
Temperate/Semi-Arid Soils. There is usually a thick humus, low water content. There is low removal of cations. The E-horizon is usually absent. The B-horizon has alot of caliche nodules.
Mudstones
Fine grained siliclastic rocks with more than 50% of the grains smaller than 1/256 mm. Phyllosilicates (kaolinite, illite, and smectite) and quartz are the primary mineral components. They are indicative of deep ocean/lakes where the turbulence is low.
Claystones (D<4 microm)
Siltstone (4-63 microns)
Shale: fissile bedded/brittle mudrocks. often with pyrites and other sulfides.
Argillite: a low-grade metamorphosed mudstone
Newton’s Laws of Motion
1: inertia, a body @rest is @ rest 2: F=ma 3: every action has an equal and opposite reaction
O-Horizon
Zone of organic accumulation. Leaf litter without any bedrock.
Oligomect vs. polymict conglomerates/breccias
Oligoment conglomerates are composed of a single clast type whereas polyment have several types of clasts present.
paleosols
Lithified, ancient soils. Most commonly from the Quaternary but determined by the paleoclimate of the time/area.
Petramict conglomerate nomenclature
Named by the primary clast type
Physical Weathering
Disintegration of rocks without significant chemical or mineralogic changes occurring. Mechanical degradation.
Physical Weathering Examples w/ mechanisms
freeze-thaw: Ice has a volume of 1.09*Vol(liq) which wedges rocks and produces large angular blocks or granular disintegration within granites. Insulation weathering: Solar expansion and contraction Hydration-dehydration cycles: oscillating pore pressures “Sheeting”: exfoliation due t decreasing P of exhumation
Provenence
The paleosetting of a sediment used to derive its origin.
Proximal vs. Distal Turbidites
Proximal turbidites refers to turbidites that have prominent A-C horizons and form on or near the continental shelf. They are up to a meter thick.
Distal turbidites have more intense C-E layers and refers to deeper ocean turbidites.
R-horizon
Bedrock layer
Recognizing paleosols GET A PHOTO for cutons and peds
Traces of life, soil horizons, soil structures (bioturbation, preciptation of nodules…), cutons and peds (irregular bedding within a granular “matrix”)
Recycled Orogen
this provenance indicates continental collisions and has a great deal of meta-sed lith, and quartz.
Regolith
Physically broken rock debris. Cracked and fractured but still chonky.
Reynolds Number
=inertial F/Viscosity= U(flow)*L*rho/(dynamic viscosity)
where: L~depth of flow
Fi = intertial forces and is related to the momentum of the fluid.
U=avg velocity
It is a dimensionless unit describing laminar (re<500) and turbulent flow (500
Sandstones
Primarily mineral grains of sand size. Arenites are sand+cement, wackes are sand+silt/mud.
Sediment Classes
Clastic: Physically transported and accumulated sediment
Carbonates: chemical/biorganic carbonate formation and consists of either unaltered primary sediments or secondary, altered, sediments.
Other biogenic sediments: cherts, diatomites
Chemical Sediments: Evaporites
Sediment Load Types (4 types)
Fluvial:
Bed Load: this includes large particles being transported by saltation or traction transport.
Suspended load: This is the layer that is within the turbulent part of the flow and has infrequent impact with the bed.
Wash load: This is silt and dissolved particles.
Elluvial:
Dustload: The fine particles that act as the air’s “wash load”
Sequence of bedforms in laminar flow
planar beds, ripples, sand waves, dunes. Steep side shows flow direction.
Shield’s Diagram
A similar diagram to the Hjulstrom diagram with greater applicability.
Shooting/supercritical flow
When Fr> 1 and there is not upward flow.
Siliciclastic Sedimentary Rocks
A broad group of sedimentary rocks (~75% of all) that are primarily composed of silica rich minerals. These include sandstones, shales, and conglomerates.
Siliciclastic cements
Silica overgrowths: These are characterized by the quartz grains having extended, slightly modified boundaries, but also exhibit homogenous extinction angles.
Microcrystalline fabric: “mini-geodes”
Soil
A complex material with physical and chemical composition that is derived from weathering.
Soil Horizons
Internal soil structure derived from regolith-atmosphere interactions
Solution Breccia
When a solution dissolves the host rock and only the insoluble rocks remain to form the fragments present within the breccia.
Stages of Diagenesis
- ) Eogenisis: 0
- ) Mesodiagensis: z<2000 m Characterized by increased compaction and thinning of beds. The expulsion of water may create structures. Cementation and dissolution. The grains react with the groundwater to form new compounds like oil.
- ) Telediagenisis Z>2000m this is characterized by the exhumation of the rock. Characterized by chemical weathering and decompression.
Stoke’s Law
The terminal velocity of a settling particle determined from the balance of gravity and drag forces.
U=cD2 = (1/(18*dynamic viscosity)[(rhos-rhof)*g*d2]
Where: U=terminal V
D=spherical diameter
c=constant=f(viscosity, rho(fluid),rho(solid)
Substantive Uniformatarianism
Hutton and Lyell’s idea where the present processes of geomorphology perfectly mimic the past.
Terms of bedforms (flow separation, attachment, eddy erosion)
Flow separation: The point where the flow lines depart from the peak of the ripple
Attachment: the intersection of the falling flow line with the proceeding ripple
Tranquil flow
When Fr < 1 and waves can move up the flow
turbidite anatomy
Head: The erosive part of the flow that scours the base of the bed.
Body: A steady and uniform portion of flow that begins depositing a and b layers of the bouma sequence. It flows faster than the head.
Tail: Dilute part of the flow that can auto suspend fine particles.
Turbidite/Bouma Sequence
.2-.4 m deposits derived form turbidity currents with an a-layer that has a scoured base, and normal grading of coarse particles. b layer is planar bedding from the upper flow regime. c layer has ripple strcutures and represents the shift from upper to lower flow regimes. d is laminated silts. e is pelogic and hemipelogic muds.
turbidity flows
A type of gravity flow derived from sediment accumulation following seasonal floods, storms, quakes, or tsunamis and characterized by a shift from plastic to fluid flow. It has low viscosity, high turbulence, and lacks an internal structure.
Turbulent flow
A field of the flow lines created within this type of flow show no pattern of molecular flow and may not align with the average flow vector. It is characterized by lower rates of settling and increased erosive capacity.
These flows are characterized by an eddy viscosity which is their “apparent viscosity” where n=mew*10x and tau=(mew+n)(du/dy)
Types of Chemical Weathering
Simple solution: The dissolution of nutrients and metallic ions. Hydration/Dehydration: Gypsum->anhydrite Hydrolosis: the formation of clays RedOx: Fe/Mg alternate between 2+ and 3+ during hydration and dehydration.
Types of contacts
Sutured Contacts: This is where the cement creates a jagged look like they have been crudely stitched together.
Concavo-Convex: Where the rounded grain has a “bite” taken out of it by the cement.
Long Contact: This is where the cement does not create a spherical indent into the grain but follows a smooth curve.
Ultisols/oxisols/ferrosols
Tropical soils that rapidly recycle the nutrients. There is typically a very large A-horizon. Red soils indicating only insoluble Al and Fe reside.
Upper flow regime bedforms
planar beds, antidunes, chutes+pools. Steep side towards flow direction.
Volcanic Breccias
Pyroclastic: Quenching due to air and depositied within ashy formations
autobreccia: due to the fragmentation of highly viscous lava at the front of a continuous flow
Hyaloclastic: Quenching of hot magma
Volcanoclastic sandstones
A form of lithic arenites that are pyroclastic material like euhedral spars, pumice, glass, and low qtz.
Wackes NEED PIC
Sandstones with grains that are surrounded by mud/silt
Weathering
A process which breaks down rock at the Earth’s surface. It produces discrete sedimentary particles and dissolved solutes. It includes physical, chemical, and biological weathering.
What to red rocks indicate?
Red rocks indicate that the iron was in an oxidizing enviroment. Black/green indicate that the iron is reduced to ferric iron and was formed within a anoxic or low oxygen enviroment.
Udden-Wentworth Scale
A geometric scale for measuring grain sizes that uses the rule 2*(n-1) so each size is two times the prior.
Phi-scale
phi=-log2d so d=2(-phi)
In general when phi>0 the size decreases reflecting the tendency to see small and not large particles.
Name the size range for clay, silt, and sand
Clay: D8 (too small to see)
Silt: .004
Sand: .06
Methods for Measuring Grain Size (6 kinds)
Pippette Analysis, Photohydrometer (transmission=F(settling)), Sedigraph (x-ray), laser diffraction, electroresistance, semi-autoimaging
Sediment Maturity
Sphericity, Roundness/angularity (wind is very effective and depleting angles), and composition.
What Grain Surface Texture relates to littoral (coastal) environments?
V-shaped fractures and conchoidal fractures.
What are the four types of grain textures?
- ) parallel flow orientations: The lengthwise of the grains indicates the direction and occurs within turbidites, gravity flows, and glacial transport.
- ) Perpindicular Orientation The grains align perpindicular to the flow vector and is common for river pebbles.
- ) Imbricated (Shingled): Similar to perpindicular where the grains “stack” upon each other. Occurs in turbidits, grain flows, and conglomerates.
- ) Random: Enough Said
Beds
Tabular or lenticular layers of sediment that share lithological, textural, or structural unity and have a heterogeneous nature when compared to other beds.
These include Sediment units, subdivisions, and amalgamation surfaces.
laminae<1cm thick
Reading Cross Sections
Grain Size: The wider the base the larger the grains.
Beds: Dark lines indicate beds.
Amalgamation Surface: Indicated by a dotted line
Bedding Structure Matrix
Beds are either Parallel or Nonparallel and either Continuous or discontinuous. The three kinds of lineations apparent are Even, Wavy, and curved.
Grading
Normal Grading describes beds that are larger grained at the base and grade into finer sediments.
Reverse grading indicates that the largest grains are at the top of the bed and can occur due to kinetic sieving and dispersive pressures.
Structureless/Massive Bedding
Bedding that shows a lack of internal structure that have little viable explanations to their creation. Oftentimes apparent massive bedding shows structures following x-ray analysis or acid staining.
Ripple Classification
2D ripples: Parallel lines without lee-side indicates oscillatory motion.
3D ripples: Tangential, trough lines, indicates turbulence.
Flaser Bedding
This is describes a bedding form where mud accumulates in the troughs of the cross strata. Indicates that the hydraulic conditions favored sand preservation.
Lenticular Bedding
This is characterized by discontinuous mud lenses and can indicate tidal planes, deltas, shallow shelfs, that favor mud preservation.
hummocky
Undulating cross-stratification that are both concave-up (swales) and convex-up (hummocks) with beds gently cutting one another and bounded by bioturbation. Includes large circular surface features.
Convolute Bedding and Laminations
Folding and crumpling of beds with irregular mircro anti/synclines that are restricted to a finite subdivision of the bed (~.05-.25 m) and the upper/lower bounds are clearly not convolute.
Ball and Pillow Structures
Seemingly abnormal ball or kidney shaped bulbous structures protruding the base of a bed and likely derived from the liquification of surrounding sediment.
Slump Structures
Also known as synsedimentary folds/faults that are derived from less compacted sand/mudstones.
Erosional Structures
Paleochannels: These cross-cut bedding
Scour and Fill: These are small lenses of coarse material whose long axis indicates flow direction where the bulbous end of the lens exists.
4 types of erosional bedding plane markings
- ) Sole markings: These are extruding features on the base of sandstones into shales (non-exclusive) and derived from erosional tools scraping the bed bottom.
- ) groove casts: “scraping” of tools along the floor, creates chevron or v shape dipping down-current.
- ) Saltation: bouncing…
- ) flute casts: These are shaped like yardangs and form in a similar way. The fat tail indicates flow direction.
Biogenic Structures
These are the trace fossils of burrowing, boring, feeding, locomotion, cut-and-fill caving, and arise from bioturbation, biostratification (stromalites), bioersion, and excrement.
Vertical trace fossils indicate harsher environments that are more likely to be eroded.
Ichnofacies
These are trace fossil assemblages that reflect unique depositional enviroments
stomalites
These are organic silt laminations within LS that form from algal plumes. If the laminations are too poor to recognize it is called a thrombalite.
Synesis and mudcracks
Subaqueous and subariel mudcracks that form from the alignment of clay minerals.
Rose Diagrams
A tool for identifying directional trends of sedimentary structures. The proportion of total fluid flow direction measures are plotted to show the primary flow direction.
