A marine
transgression is a
geologic event during which
sea level rises relative to the land and the shoreline moves toward higher ground, resulting in flooding. Transgressions can be caused either by the land sinking or the ocean basins filling with water (or decreasing in capacity). Transgressions and
regressions may be caused by
tectonic events such as
orogenies, severe
climate change such as
ice ages or
isostatic adjustments following removal of ice or sediment load.