structural Flashcards
real number reflecting temp mass density speed or any physcial magnitude that has no direction
scalar
has both magnitufe and direction such as for e traction or verlocity
vector
same length and of the same amgbitude in 2 different cooridnate systems dofferent numbers has bith magnitutude and direction such as force traction or velocity
vector
linear stylolitic structures form a lineation that parallels the movement direction direction quite precisely
stylolites
name often used for small extension fractures open are more commonly mineralized qirh quartz or carbonates and do not show dtriation typically dip around 45 degrees in teh slip direction witj respect to a horizontally oriented
T fractures
set of fractures sometiomes dip in the opposite direction
p fractures
low angle normal faults and
anthithetic reverse faults make high anfle
r fractures
r prime fractures
gibes the orientation of the prinicple atresswa and the shape of the stress sllipsoid
inversion of slip data
datasets may contain slop curfsces formed under teo or more stress fields that must be separated to obtain useful tejlts
complex failt slip
vacancies or less impurities in the form of extea atoms in the lattice point defect interes missing atom
point defects
movement of vacancies
diffusion
referred to as dislocations
line defects
a mobile line defect that contributes to intracrystalline deformation by a mechanical callep slip
dislocations
implies movements of dislocation front within ad plane plane in a crustal that has the highest density of atoms had the highest desity of atoms
slip
includes structures such as grain boundaries subgrain bpudnaries and twon planes
plane defects
volume diffusion is also called
nabarro herring creep
also called grain boundary diffusion
coble creep
less energy demanidng than nabarro hearinfg
cobble creep
dislocation line oriented parallel to the slip direction bit like teating a pirce of paper
screw dialocations
effect of non recrystallizing minerals such as small mica grains in quartzite or quartz rich mylonites
pinning
non cylindrical upright antiform sometimes
doubly plunging
can dorm attractice traps of oul and gas wolrds largest hydrocarbon
doubly plunging antiform
implies slip along layer interfaces or very thin layers during folding produces class 1b or parallel folds
flexural slip
competent rock layers tah thave been stretched into segmetbs much longer in one fimension than the other two and thus define lineation appear ob the limbs of thw fold with their long axes oriented in the direction kf the fd axiseasily recognized in sections perpendicular to the long axis
boudinage
linear deformations structures that are restricted the interface between a competent and a an incompetent rock striations on failt surfaces layer interfaces structures formed during layer parlel extension as well as contracriln
mullion
place to find mullion
structures in metamorphic to ks at boudbaey between quartzite and phyllite or micaschist occur on the surface of quartz pods in micaschists
result of discrete interference between compaction cleavage an a subsequent tectonic cleavage brtween teo eually developed tectonic cleavages
pencil structures
unmetamorphosed very low grade emtamorphic rocks
relate to he irregular or corrugates shape of a slip surface
geometric stria
special type of geometric striae seen on walls of the deformation band cluster zones
cigar shape
intersected by secondary fracturws such as ried fractures or twnsile fractures high angle to laip direction
intersection lineations
tabular stur tures tend to point int he direction of contraction and slickentolites are thus a kind of lineation kinematically differet from other lineations
slickolites
a very pronounced stretching lineation indicate
prolate strain
in plastic tegime lineations form
penetrative fabrics alone L favrics
together with foliatoond
LS fabrics
max lohest
extensional structures formed by layer parallel extension
single competent layers extended into separate pieces through plastic brittle combinationmore or less regulary shaped
boudins
process that leads to the formation of boudins from originally continuos layers deforms plastically
boudinage
regularly shaped areas pf thinning in many extended comptent layers without the separation into isolated fragments are boudin like elements that are barely connected
pinch and swell structures
process where a pinch and swell is formed
necking
magnitude thicker than the microlayering represented bu the foliatio but fo i many ways resemble classic boudins a strong planar anistorpy in deformed rocks
foliation boudinage
separated by tensile fractures filled with quartz or other hydrothermal mienrlas nad or by flow of adjacent rock layers foliation within the boudin pinched toward the extnesion fracture
dymmetric foliation boudin
separate dby brittle shear fracturws or by ductile shear bands showing relative movement along the fractures/bands found in single conjugate sets
assetric foliation boudins
boudinage in two directions of finite extension within the layer
chocolate tablet boudinage
layer thickness and viscosity contrast extensional conuterpart to buckling
classic boudinage
less dependent on viscosit contrasts strongly dependent on a foliation anisotropy not to he considered a direct counterpart to passive folding
foliation boudinage
used for shear sense evaluation if original layer orientation aspect ratio and viscosity contrast
boudins
tabular zone which strain is notably higher than in the surrounding rock
shear zone
no internal diacontinuities marker layers crossed vy the shear zone can be traced continuously throug hthe zonr at the mesoscopic scale
prefectly ductile shear zone
two perfectly planat blundaries separating it from completwly udneformws wall rocks ductile so the slip surfaces or other diacontinuities are non existent
ideal shear zone
deviates fro
thw idela ductile shear zone
general shear zone
cover the plane strai spectrum of simultaneous sinple shear and lure shear
subsimple shear zone
where is mylonite derived from
scottish moine thrust zone
where are mylonites common
thrusts extensional shear zones and stepp basement shear zones
<50%
50-90%
>90%
protomylonite
mylonite
ultramylonite
remains of the original texture or original minerals found as large lenses or fragments wrapped in the mylonitix foliation
protolithic lenses
fragments of single crystals or minerlas and feldspar forms in deformwd grnaitic rocks during greenschist facies shearing temp is too low for feldspar to deform by cystalloplastic deformation mechanisms
porphyroclasts
shear bands french for shear which relates to the movement of scissors
cisaillement
structurws relatwd to partcile acceleration/deceleration
quarter structures
veins forming under non coaxial deformation will rotate the moment they form results in a
sigmoidal geometry that can be used to determine the sense of shear
shear zone are strain hardeningsheae zones deformation in the central part slows down as the zone thickens central part this records the dirst part kf the deformation history wbile ghe marginal parts only record the last part develop wide plateu thpe displacement progiles
type I
shear zoneshave the same development as tpy i entire shear zone remaind active throughour the deformation history zone grows in wifth anc fhe strain increases from ghe margins toward the center margins obly record the last increment of shearing while ghe central parg has experienced the entire shearing history
type IV
strain softenjng zones that quickly estbalish cerain thickness atter a while tue deformation localizes to the cnetral part margins become inactive and the actuve part of the shear zone gets thinner result is thin shear zones airh high shear strain
type II
shear zones develop a fized thickness and the entire zone keep sdefor ing without any sign of itbernal localization shear zone maibtains its thickness which equals its active thickness model perhaps the elast tealistic one works on kink bands
type III
generally reverse or thrust faults
contractional faults
bring older rocks on top and higher metamorphic horizontal displacement
thrust faults
charac features of contractional orognes such as the caledonian appalachian orogen and the alps
theust nappe
area in the central portion of the collision zone
hinterland
marginal part thus farthest into the continent
foreland
smallest units in a thrust nappe are
horses
thrust naloes that share common lithological and structural fratures referred to as a
nappe complex
bounded by a basal fault
sole thrust or floor thrust and overlying roof thrust
separates entire stack of thrust nalpes from a less deformwd or undeformed basement fundamental low angle extensional faults and significant or shear zones of uncertain sense of movement
detachment or decollement
erosional remnant of nappe same in scandinavian caledonies erosional hole
klippe
controlled by mantle plumes
controlled by plate tectonic stress
active faulting
passive faulting
sequence is the sedimentary package deposited prior to extension
prerift
sequence is constitues of sediments deposited during the rifting show thockness and facies variations across growth faults
synrift
pure and shear model
mcKenzie model
Wernicke model
geomtric form can be divided into smaller parts where each part has a form corresponding to the larger one called self similar one or more of their properties reparts at different scales
fractal
plot along a fairly stright segment implies or self similar relation implies the data define mote or less straigjt line
powerlaw distribution
deeper versions dominated by plastic deformation mechanism
strike slip shear zo es
2 most famous strike slip
san andreas fault in california
north anarolian fault in turkey
term used for strike slip faults in continental crust tht have free tips not constrained by oyher structures free tips move to that the fault i creases as displacementaccumulates have free tips and grow in length as they accumulate strike slip displacement
transcurrwnt faults
make a low angle with the overall shear zone and show tha same sense of slip shown together with another fracture
riedel shear fractures
develop after t fractures and their developments is probably related to ttemporal variations iny eh local stress field along the shear zone as offset accumulates
p shear fractures
blue fractures can occur in the shear zone setting of riedels clay model form perpendiculat tocthe maximum instantaneous stretching axis
t shear fractures
were active at about the same time under the same regional stress field acute angle between the two sets is bisected examples is himalaya
conjugate strike slip
famous straight fault traces and stepp dips acted as strike slip faults toward the end of the caledonian orogeny
great glen fault in scotland
bollefjorden fault in svalbard
lovated where a sinistr fault steps to the right
restraining beds
subparallel reverse or oblique slip contractional faults vlunded butje two strike slip segmetbs can form
contraxtional strike slip duplexes
form where a sinistral strike slip fault steps to the left or a dextral fault steps to the right
releasing bends
created in an overlap zone between teo syike slip transforms
dead sea
located in a releasing bend where normal faults have lowered the otherwise mountainous tegion to a level close to and locally under sea level
death valley
releasing bend basins along strike slip faults
pull apart basins
assoc sirh restraining beds
releasing beds
pos
neg flower structure
results in oblate ellipsoids flattening
generates prolate ellipsoids
transpression
transtension
internal decomposition of the total strain across a deformwd zone i to zones or domains of sifferent types of strain
strain partitioning
movent of subsurface salt and the formation of salt diapirs
halokinesis
low density of 2.160 g/cm3 less dense than other carbonate rocks denser than unlithified siliciclastic sefiments
pure salt
viscoelastic medium used as waste repositories and two deformation wet diffusion and dislocation creep
salt
involves simple shearing withing the salt layer as the overburden is translated relative to the substrate salt layers acting as decollmenys
couette flow
plug like shapes
salt stocks
slongted salt structures that appear as stocks in perpendicular cross sections
salt walls
known as bulb
stem
isolated salt bulbs
teardrop diapirs
diapirs flatten out and join sg one and less commonly stratigraphic levels
salt stock canopies
centrifuge skeme
hans ramberg
contains carboniferoues age caused a series of salt anticlines notably in moab and arches national park area
upheaval dome in canyonlans national park utak marginal parts of the paradox basin
similar structure in the north sea ocntaining circular faults
silverit crater
lateral variationd in the state of stress created in the salt layer intiates flow of salt toward low presur eareas effective even at very shallow depths
differential loading
causes salt to flow
vertica sed
lateral tectonic
separated by unconformities near the salt structure results stackingh
halokinetic cycle
exposed or very shllow dipairs that rise continually at a rate that morw or less keeps pace with sedimentaion
pssive diapirism
assymetruc sturcutes trinagular shaped volume of salt in the footwall
salt roller
known for their salt glaciers with estimate dflow rates of 0.3-16 m/yr
zagros mountains
several submarine salt glaciers have been mapped
gulf of mexico
where is salt wing i trusion found
southern norht sea
main slat layer permian zechsfein salt intruded higher and relatively thin traiassic evaporite layer
implies discrete deformation phases while progressive deformation involves more continuous and gradula development at a lov regional scale
polyphasal
temp and pressur eincrease
prograde metamorphism while retro is the opposite
crystals latger than genral grin size common in mica bearing schists and gneisses
porphyroblasts
syraight hence the striagjt central part pf tje inclusion pwttwrn seen
pre tectonic
sinoly overgro the present fabric traced continuously thorugh the porphyroblasts
posttectonic
direct dating of metamorphosm done nu and gives the age of zircon growth
U-Pb dating of zircon, monazite or sphene that has grown during metamorphism
amphibole and white mica giving cooling agws and k fless
argon 40
constrained by early middle devonian seds 425 Ma deposited in oceanic crust now found ophiolitic fragments in the collision zone
norway caledonides
presefve in rifts orogens and strike slip settings reflects the tectonic history of the atea with regard tovtiming of dault movements salt growth or collapse exhumation metamorphic event sor other local regional tectonic events
syntectonic
appraranc eof chromite has been interpreted as evidence for ophiolitic allochtons apporaching the basincfrom the hinterland
caledonian foreland
