Ain't my fault, but I was "anticline"d to do it! EarthCache
Ain't my fault, but I was "anticline"d to do it!
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This area is a geological fold, these folds can occur for many different reasons, including oil deposits, earthquakes and many other reasons. The Fold has interested me for a long time and I love to look at all the features of the area anytime I have the chance. features of the fold can be viewed from Quail Creek State Park, thought the south side of St. George Ut. and then North west to Gunlock State Park.
The term fold is used in geology when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur singly as isolated folds and in extensive fold trains of different sizes, on a variety of scales. Folds form under varied conditions of stress, hydrostatic pressure, pore pressure, and temperature - hydrothermal gradient, as evidenced by their presence in soft sediments, the full spectrum of metamorphic rocks, and even as primary flow structures in some igneous rocks. Folds are classified by their size, fold shape, tightness, dip of the axial plane.
Fold terminology in two dimensions
Looking at a fold surface in profile the fold can be divided into hinge and limb portions. The limbs are the flanks of the fold and the hinge is where the flanks join together. The hinge point is the point of minimum radius of curvature for a fold. The crest of the fold is the highest point of the fold surface, and the trough is the lowest point. The inflection point of a fold is the point on a limb at which the concavity reverses, on regular folds this is the mid-point of the limb.
Fold terminology in three dimensions
The hinge points along an entire folded surface form a hinge line, which can be either a crest line or a trough line. The trend and plunge of a linear hinge line gives you information about the orientation of the fold. To more completely describe the orientation of a fold, one must describe the axial surface. The axial surface is the surface defined by connecting all the hinge lines of stacked folding surfaces. If the axial surface is a planar surface then it is called the axial plane and can be described by the strike and dip of the plane. An axial trace is the line of intersection of the axial surface with any other surface (ground, side of mountain, geological cross-section). Finally, folds can have, but don’t necessarily have a fold axis. A fold axis, is the closest approximation to a straight line that when moved parallel to itself, generates the form of the fold. A fold that can be generated by a fold axis is called a cylindrical fold. This term has been broadened to include near-cylindrical folds. Often, the fold axis is the same as the hinge line.
Fold shape
It is necessary to convey a sense of the shape of the fold. A fold can be shaped as a chevron, with planar limbs meeting at an angular axis, as cuspate with curved limbs, as circular with a curved axis, or as elliptical with unequal wavelength.
Fold tightness
Fold tightness is defined by the angle between the fold's limbs, called the interlimb angle. Gentle folds have an interlimb angle of between 180° and 120°, open folds range from 120° to 70°, close folds from 70° to 30°, and tight folds from 30° to 0°. Isoclines, or isoclinal folds, have an interlimb angle of between 10° and zero, with essentially parallel limbs.
Fold symmetry
Not all folds are equal on both sides of the axis of the fold. Those with limbs of relatively equal length are termed symmetrical, and those with highly unequal limbs are asymmetrical. Asymmetrical folds generally have an axis at an angle to the original unfolded surface they formed on. Deformation style classes Folds that maintain uniform layer thickness are classed as concentric folds. Those that do not are called similar folds. Similar folds tend to display thinning of the limbs and thickening of the hinge zone. Concentric folds are caused by warping from active buckling of the layers, whereas similar folds usually form by some form of shear flow where the layers are not mechanically active.
Fold types
Anticline: linear, strata normally dip away from axial center, oldest strata in center.
Syncline: linear, strata normally dip toward axial center, youngest strata in center.
Antiform: linear, strata dip away from axial center, age unknown, or inverted.
Synform: linear, strata dip toward axial centre, age unknown, or inverted.
Dome: nonlinear, strata dip away from center in all directions, oldest strata in center.
Basin: nonlinear, strata dip toward center in all directions, youngest strata in center.
Monocline: linear, strata dip in one direction between horizontal layers on each side.
Chevron: angular fold with straight limbs and small hinges
Recumbent: linear, fold axial plane oriented at low angle resulting in overturned strata in one limb of the fold.
Slump: typically monoclinal, result of differential compaction or dissolution during sedimentation and lithification.
Ptygmatic: Folds are chaotic, random and disconnected. Typical of sedimentary slump folding, migmatites and decollement detachment zones.
Parasitic: short wavelength folds formed within a larger wavelength fold structure - normally associated with differences in bed thickness.
Disharmonic: Folds in adjacent layers with different wavelengths and shapes A homocline involves strata dipping in the same direction, though not necessarily any folding.
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Fig 7.
To get credit for this cache Email me the answers to these Questions. please no answers in logs or the log will be deleted.
1. Using Fig 5, as a reference, Determine what type of fold you are viewing at the posted coords. (this fold is 1 mile wide at these Coordinates)
2. Using Fig 4, Determine if the fold is, Symmetrical, Asymmetrical, or Overturned fold.
3. Using Fig 6, Which of the 4 attributes can you see looking toward the NE? (Fig 7 is a arial view of the location which may help)
4. Names of all people in your group.
5. Extra credit, Post a Picture of your group!
Additional Hints
(No hints available.)