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Tectonic Elements and Fault Styles: A Geological Interpretation Guide

Understand large tectonic elements and fault styles with regional maps, focusing on rifts, margins, orogens, and cratons. Explore characteristic fault patterns during extensional and contractional plate motions. Learn how faulting ages influence tectonic analysis.

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Tectonic Elements and Fault Styles: A Geological Interpretation Guide

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  1. What is a “tectonic analog”? Figure A13–1 • (1) Mmax implies large L, W. • Most SCRs are best examined with regional geologic and tectonic maps (1:2,500,000 – 1:10,000,000 scale) • (2) Large tectonic elements (rifts, passive margins, orogens, cratons) are easiest to identify on regional maps. • (1) + (2): Do any kinds of large tectonic elements have characteristic fault styles that favor large rupture L, W? • (Most useful if represented in CEUS and adjacent Canada) • Mmax = large Mo release on large faults

  2. Figure A13–2

  3. Characteristic fault styles Figure A13–3 • Extensional plate motions (rifts, passive margins) • Rift-parallel & margin-parallel faults are long • Steep dips, deep penetration (alkaline igneous rocks) • Large L, W: large Mo • Thick, restricted sandstones, then widespread limestones • Contractional plate motions (orogens) • Low-dip thrust faults, long, wide, above most seismicity • Faults steepen into hot cores (healing, folding, offsetting faults) • Large L, W, where low dips; smaller W where steeper: smaller Mo? • Sandstones, shales, limestones; thicker closer to rising mountains • Precambrian plate motions (cratons) • Old: rifting, folding, thrusting overprinted on each other repeatedly • Faults of all L and orientations, older faults can be healed and deformed; small effective L, W: smaller Mo • Tectonically quiet: few associated sedimentary, igneous rocks

  4. Figure A13–4

  5. Analogs Figure A13–5 • Rifts & margins have distinctive fault styles and associated igneous and sedimentary rocks. • Ditto for orogens. Ditto for cratons. • Rifts & margins are recognizable from one SCR to another, ditto for orogens, cratons • Rifts & margins, orogens, cratons are distinguishable from each other within same SCR • Differences within an SCR >> differences between SCRs • Faults heal so faulting age matters

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