Radiometric Dating Techniques
Carbon-14 or Radiocarbon
Date organic material up to 60,000 y/o
Normal Fault
The hanging wall will move downward in relation to the footwall
They characterize extensional tectonic environments
FW is 60°
Heave
Horizontal movement along a fault
Fault
Thicker line than a geologic contact
Fault Scarp
an escarpment or break in normal erosional topography caused by a line of faulting
a linear ridge caused by the upthrown side of a fault
Potassium-argon Isotope
Date geologic materials greater than 100,000 years in age
Reverse Fault
The upper hanging wall is displaced upward past the footwall
Suggest compressional tectonic regimes
FW is 30°
Throw
Vertical movement along a fault
Offset on faults
A bar or ball on downthrown side of the fault or placing a "D" or "U" on the downthrown and upthrown
Scarplet
a small fault scarp
Uranium-thorium
Date carbonate materials that are younger than 500,000 years
Strike-Slip Fault
The movement is parallel to the strike of the fault plane with no relative up or down displacement of headwall or footwall
Appears to move side-to-side
Net slip
The measure of the distance between two points that are adjacent before the first movement in a fault
Thrust Faults
Teeth on the upper plate
Slickensides
parallel grooves formed on the surface of a fault plane attributable to opposite movement of fault surfaces
are striations or grooves on a fault surface
Rubidium-strontium Isotope
Whole rock dating technique used for igneous materials over 10 million years old
Growth Fault
Similar to a normal fault, except that it occurs simultaneously with the deposition of sedimentary rock
Characterized by on-going sedimentation such as river deltas or any other region in which the sediments are subsiding at a fast pace
Vector
The distance and direction of fault displacement
Outcrop Patterns
In absence of map symbols, these can be useful in determining fault orientation and dip
Breccia
a course-grained, unsorted, clastic rock composed of highly angular broken rock fragments in a fine-grained matrix
typically lithified by secondary minerals
can occur within the fault zone
Uranium-lead Isotopes
Date geologic materials between 1 million and 4.5 billion years old
Detachment Faults
Low angle regional normal faults with displacement in the tens of km range
Extensional tectonism and usually juxtapose unmetamorphosed headwall rocks against mildly to high metamorphosed footwall rocks
Strike separation
Measure across the strike of the fault and is defined as the horizontal distance between each side of the fault
Rule of V's
The outcrop pattern of faults in relation to the topography can be used to determine fault characteristics
Mylonite
a dense chert-like metamorphic rock with a streaky or banded structure formed by shear stress
lacking cleavage
produced by the extreme pulverization and shearing of rocks that have been involved in thrust faulting or intense dynamic metamorphism
Radiometric
aka absolute dating - a specific age or range of ages is obtained
Listric Fault
Curved shape with the angle of the curve greatest near the surface
Offset
The component of displacement measured perpendicular to the strike of the disrupted side of the fault
Cross Sections
Display a vertical representation of sub-surface structure and are frequently laid out to show the attitude or style of major faulting
Oblique-Slip Fault
Both strike-slip and dip-slip components
The footwall and hanging wall do not move exclusively along the fault's strike or dip, but instead move in a diagonal direction
Equal Area Stereo Net
Plots surface and subsurface data that is useful in interpreting faults
Thrust Fault
A low angle reverse fault in which the plane of the fault is between zero and 45°