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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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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) Sedimentary beds within a formation
UNCONFORMABLE contacts (pages 645-649) Three types of unconformities Represent gaps in rock record
Sandia Mountain, NM ~300 million year old limestone ~1400 million year old granite Nonconformity (page 647)
Angular Unconformity (page 647) Siccar Point, Scotland
http://www.searchanddiscovery.com/documents/geophysical/Abbott/index.htmhttp://www.searchanddiscovery.com/documents/geophysical/Abbott/index.htm Disconformity (page 647)
http://www.searchanddiscovery.com/documents/geophysical/Abbott/index.htmhttp://www.searchanddiscovery.com/documents/geophysical/Abbott/index.htm
Dike INTRUSIVE CONTACTS (pages 650-653)
FAULT CONTACTS (pages 653-654) http://libraryphoto.cr.usgs.gov/htmllib/btch205/btch205j/btch205z/wre00014.jpg
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
PRIMARY STRUCTURES (pages 656-662) developed during rock formation
Include: • Cross bedding • Graded bedding • Ripple marks • Mud cracks • Flow structures • Pillow structures… etc.
SECONDARY STRUCTURES Developed after rock formation (NOW we’re talking!!!)
We often approximate structures as lines and planes whenever possible
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)
Bearing Azimuth 315 045 N 45 E N 45 W 090 W E 270 S 45 W 225 S 45 E 135 180 S
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
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)