• During the Paleozoic and Mesozoic, the seas rose over the continents.
  • This is called a marine transgression.
  • During a marine regression, the sea level retreats.
  • These events leave characteristic rock layers known as sedimentary facies.
  • Facies are characteristicrock layers, such as sandstone, shale, limestone for a marinetransgression.
  • The reverse indicates a marine regress.
  • The Paleozoics had four complete cycles of marine transgressions and regressions.
  • The MesozoIC had two (Figure below).
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