Wave-formed ripples

From Wikipedia, the free encyclopedia

Ancient water ripple marks in sandstone, Moenkopi Formation, Capitol Reef National Park, Utah
Ancient water ripple marks in sandstone, Moenkopi Formation, Capitol Reef National Park, Utah

In sedimentology, wave-formed ripples or wave-formed ripple marks are a feature of sediments (sandstones, limestones, siltstones) and dunes. These ripple marks are often characterised (and thus distinguished from current ripples) by symmetric cross-sections and long relatively straight crests, which may commonly bifurcate. Their wavelength (periodicity) depends on the sediment grain size, water depth and water-particle orbits in the waves. On tidal flats the pattern of wave-formed ripples may be complicated, as a product of changing depth and wind and tidal runoff directions. [1]

While wave-formed ripples are traditionally described as symmetrical, asymmetric wave ripples are common in shallow waters along sandy shores. They are produced by bottom oscillations generated by passing breaker waves, which have unequal intensity in opposite directions.[2]

Wave-formed ripples indicate an environment with weak currents where water motion is dominated by wave oscillations.[3]

[edit] References

  1. ^ Maurice E. Tucker (2001) "Sedimentary Petrology",ISBN 0632057351
  2. ^ O. F. Evans, "The Classification of Wave-formed Ripple Marks", Journal of Sedimentary Research, Volume 11 (1941), doi:10.1306/D42690DF-2B26-11D7-8648000102C1865D
  3. ^ Monroe, James S., and Reed Wicander. The Changing Earth: Exploring Geology and Evolution, 2nd ed. Belmont: West Publishing Company, 1997. ISBN 0-314-09577-2 pp. 114-15, 352.