GEOL 404 1st Edition Lecture 6 Outline of Last Lecture I. FaciesII. Facies AssociationIII. Hierarchy of Depositional UnitsIV. Limitations of FaciesV. Deposition EnvironmentsVI. Deposition Environments PaleocurrentsOutline of Current Lecture VII. Stress RegimesVIII. FaultsIX. FoldsX. Geometrical FoldXI. Mechanical FoldCurrent LectureVII. Stress Regimesa. Tension – Being pulled apart “normal” faultingb. Compression – Convergence “pushed together” and are involved with foldingc. Transform – Gliding plates past each other “shear stress”d. Elastic, Brittle, Ductilei. Depend on amount and rate of stress appliedii. Temperature and pressureiii. Degree of lithificatione. Stress Axes’si. Principal axes of stress1. Will be unequal in a normal situation, and causes deformationVIII. Faultsa. NomenclatureThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.i. Foot Wall -The higher piece in Tension or Comp stressii. Fault Scarp -The earth that’s uncovered in Tension or compiii. Fault Line -The line where both piece intersectiv. Fault Plane -The line of direction the pieces are movingv. Hanging Wall -From Comp or Tension stressvi. Fault Race -Only from Shear stressb. Real Situationsi. Horizontal Wells1. Horizontal wells have the chance to penetrate more vertical fractures, and usually produce more oil2. Austin Chalk – A reservoir that was examined and they found the Eagleford.3. Eagleford Shale – An example where horizontal wells are optimized for the strike direction of normal down to the faults4. Gas production per well is very high the closer you are to a fault. This occurs because faults are trapping the hydrocarbons.c. Listric Faultsi. Tensional Regimeii. Definition1. Curved normal faults in which the fault surface in concave upwards and it’s dip decreases with depth. iii. Occur in extension zones with main detachment fracture following a curved path rather than a planar path. iv. Nomenclature1. Growth Fault -Line that separates curved from horizontal faults2. Synthetic Fault-Top fold curves top left to bot right3. Antithetic Fault -Top fold curves top right to bot left4. Rollover Anticline -Contains both synthetic and antitheticd. Reverse Faultsi. Compressional Regimes1. The hanging wall is displaced up the fault plane relative to block2. Contain high angle and low angle reverse faults (THRUST FAULTS)e. Strike Slip Faultsi. San Andreas Fault Systemii. They can act as conduits for migration as well as trapping mechanismsiii. Can act as conduits for fluidization as well.f. Diagramsi. Fault Wall Juxtaposition Diagram1. They can become very complex and need very accurate depth structure maps on a good well defined datum2. It also requires the interval thickness to be near parallel.3. Depth vs Fault drawing4. Throw vs Depth5. 3D diagramsIX. Foldsa. 3 Categoriesi. Compressiveii. Tensileiii. Shearingb. Classificationi. Geometrical -Based on morphologic characteristics (Most Common)ii. Mechanical -Folds based upon origin and mechanisms that occurc. Magnitude of Forcei. Depends on the ability of some beds to resist deformation and the length of time that the forces are applied.d. Nomenclaturei. Non-cylindrical fold -Fault with no foldii. Interlimb angle -Bot of anticline where angles from faults meetiii. Cylindrical fold-Fault with foldiv. Amplitude -Height from bot anticline to inflection pointv. Limb -The outside of the faultvi. Inflection Point -Point at which slope changesvii. Axial Trace -Point connected to fault within the anticlineviii. Hinge Points -Point on top of anticlineix. Axial Surface -The plane on which the fault occursx. Hinge Line -Location of top anticlinexi. Hinge Zone -Location of top anticlinexii. Fold Axis -Top of anticlinexiii. Inflection Line -Location where fault changes slopexiv. Hinge Zone -Bottom of anticlinexv. Wavelength -Length of anticlineX. Geometrical Folda. Symmetric fold -Both limbs have the same angle of dip and axial plane is verticalb. Plunging folds -Will have an inclined axisc. Asymmetric fold -Has fold limbs with different anglesd. Overturned fold -Have limb dips in the same direction but not amounte. Recumbent fold -Has overturned folds where axial surface is horizontalf. Isoclinal folds -Have parallel limbs and axial plans have orientationg. Chevron folds -Have limbs with sharp v shaped juncture at crestsh. Box folds -Fold limbs make a box like shapei. Monocline -Single limb dips in one direction j. Fan fold -Crest and trough flare out at the axial planek. Kink folds -Fold with planar limbs and sharp hingel. Open folds -Fold with interlimb angle betwee 70 and 120 degreesm. Closed tight fold -Fold has interlimb angle between 30 to 70 degreesXI. Mechanical Folda. Flexure slip fold -Folding is slip along the bedding planesb. Shear slip folds -Fold which shearing or slipping is spaced planes parallelc. Domes -Uplift or anticlinal structure with rocks dippingd. Basins -Low area in crust where sediments