LAB2_outcrop_patterns - Structural Geology Lab 2: Outcrop...

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8 Structural Geology Lab 2: Outcrop Patterns and Structure Contours I. Geologic Map Symbols A. Refer to Appendix F in back of lab manual for list of commonly used geologic map symbols 1. Emphasis: a. strike and dip of bedding (1) inclined (2) horizontal (3) vertical (4) overturned b. Fold axes (1) syncline (2) antincline (3) plunging folds c. strike and dip of joints d. strike and dip of foliation e. fault symbols (1) thrust (2) vertical II. Outcrop, structure and age relationships A. Folding of rocks 1. Inclined sequence of sedimentary beds a. layer cake relations (1) oldest on bottom, youngest on top b. Fold Types (1) Anticlines -upfolded forms, results in older rocks becoming enclosed within younger strata (2) synclines -downfolded forms, results in younger rocks becoming enclosed within older strata. (3) symmetrical folds - both limbs of the fold dipping at same angle away from fold axis (4) asymmetrical folds - both limbs of the fold not dipping at same angle away from fold axis (5) overturned folds - condition in which one limb of fold has been tilted beyond vertical (6) plunging folds - axis of fold is tilted (7) Domes - more or less circular equivalent of anticline, oldest rocks exposed in center of dome
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9 (8) Structural Basin - more or less circular equivalent of syncline, youngest rocks exposed in center of dome (not to be confused with depositional basin) c. Outcrops Patterns Associated with Folded Rocks (1) As rocks are folded, and subsequently subjected to erosion, regular patterns become evident in relation to type of rock that outcrops and age of the rock that outcrops in an area of folded strata. In essence, erosion exposes the interiors of the folds (2) Non-plunging Folds - axis of fold is horizontal, results in parallel bands of dipping strata about the fold axis (a) anticlines- oldest strata exposed along fold axis (b) synclines- youngest strata exposed along fold axis (3) Plunging Folds -axis of fold is tilted, results in alternating V-shaped bands of dipping strata oriented about the fold axis. (a)
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This note was uploaded on 10/02/2011 for the course GEOLOGY 406 taught by Professor Taylor during the Spring '11 term at Western Oregon University.

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LAB2_outcrop_patterns - Structural Geology Lab 2: Outcrop...

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