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FUNDAMENTAL STRUCTURES (Text page 9, 645 – 662)

FUNDAMENTAL STRUCTURES (Text page 9, 645 – 662). We often approximate structures as lines and planes whenever possible. Three types of fundamental structures. CONTACTS between rock bodies (pages 645-656) Examples?????. (CONFORMABLE contact, or was formed during continuous deposition).

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FUNDAMENTAL STRUCTURES (Text page 9, 645 – 662)

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  1. FUNDAMENTAL STRUCTURES (Text page 9, 645 – 662)

  2. We often approximate structures as lines and planes whenever possible

  3. Three types of fundamental structures • CONTACTS between rock bodies (pages 645-656) Examples?????

  4. (CONFORMABLE contact, or was formed during continuous deposition) Sedimentary beds within a formation

  5. UNCONFORMABLE contacts (pages 645-649) Three types of unconformities Represent gaps in rock record

  6. Sandia Mountain, NM ~300 million year old limestone ~1400 million year old granite Nonconformity (page 647)

  7. Angular Unconformity (page 647) Siccar Point, Scotland

  8. http://www.searchanddiscovery.com/documents/geophysical/Abbott/index.htmhttp://www.searchanddiscovery.com/documents/geophysical/Abbott/index.htm Disconformity (page 647)

  9. http://www.searchanddiscovery.com/documents/geophysical/Abbott/index.htmhttp://www.searchanddiscovery.com/documents/geophysical/Abbott/index.htm

  10. Dike INTRUSIVE CONTACTS (pages 650-653)

  11. Sill

  12. See page 651, fig. B3

  13. FAULT CONTACTS (pages 653-654) http://libraryphoto.cr.usgs.gov/htmllib/btch205/btch205j/btch205z/wre00014.jpg

  14. SHEAR ZONE CONTACTS (pages 654-656) http://earth.leeds.ac.uk/shearzones/gallery/odhair.htm Faults and shear zones will show up as secondary structures later on

  15. PRIMARY STRUCTURES (pages 656-662) developed during rock formation

  16. Include: • Cross bedding • Graded bedding • Ripple marks • Mud cracks • Flow structures • Pillow structures… etc.

  17. SECONDARY STRUCTURES Developed after rock formation (NOW we’re talking!!!)

  18. We often approximate structures as lines and planes whenever possible

  19. ORIENTATIONS OF STRUCTURES (Pages 662 – 666) TREND (Azimuth or bearing with respect to north) Orientations of LINES in space (pages 663-664) PLUNGE (deviation from horizontal)

  20. Bearing Azimuth 315 045 N 45 E N 45 W 090 W E 270 S 45 W 225 S 45 E 135 180 S

  21. Orientation of PLANES can be defined by: • Strike and dip (pages 665-666) • Dip and line of dip/dip direction (ALWAYS perpendicular to the strike) • Orientation of at least two lines on the plane

  22. Orientation of a line on a plane can also be described as RAKE or PITCH (the acute angle between the line and the strike of the plane. Page 700)

  23. The geometric orientation of a plane or line in space is also called ATTITUDE Attitude is usually given in terms of: • Orientation measured on the HORIZONTAL plane (compass direction, either as AZIMUTH or BEARING) • Orientation measured on the VERTICAL plane (deviation from horizontal)

  24. Bearing Measured from North or south Azimuth (ALWAYS measured clockwise from north) 315 045 N 45 E N 45 W 090 W E 270 S 45 W 225 S 45 E 135 180 S

  25. N70W S10E N50E N35W S15W S70E N65W N47W S12W N81W S26E S52E N67W N52E Geolgy 318 lab 1a (1/23/12) The following orientations are given in BEARINGS. Express them as AZIMUTHS

  26. 215 025 120 235 190 330 285 228 317 067 162 112 293 157 Geolgy 318 lab 1a contd. (1/23/12) The following orientations are given in AZIMUTHS. Express them as BEARINGS

  27. Orientations of LINES in space (pages 663-664) PLUNGE (Angle between the horizontal plane and the line) Measured DOWNWARD on a vertical plane TREND (Azimuth or bearing with respect to north) Measured on a horizontal plane

  28. To measure plunge and trend of a line: Theoretical stuff • Identify the VERTICAL plane passing through the line • Find the horizontal line on that vertical plane • Angle between the original line and the horizontal line gives PLUNGE • Orientation of the horizontal line gives TREND

  29. Orientation of PLANES can be defined by: • STRIKE and DIP (pages 665-666) • Dip and line of dip/dip direction (ALWAYS perpendicular to the strike) • Orientations of at least two lines (any orientation will do) that lie on the plane

  30. Strike and dip (with dip direction, of course!) STRIKE is the orientation of the horizontal line on an inclined plane (Given in azimuth or bearing) DIP is the inclination of the line of greatest slope on an inclined plane (Measured downward on a vertical plane)

  31. Dip and dip direction or line of dip The direction in which a plane slopes downward is called the DIP DIRECTION (or LINE OF DIP)Measured as azimuth or bearing Dip direction is ALWAYS perpendicular to the strike of the plane

  32. Orientation of a line on a plane can also be described as RAKE or PITCH (the acute angle between the line and the strike of the plane. Page 700)

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