Tides can not be a dominant factor, as cross-stratification is abundant; storm beds, recognised by hummocky cross-stratification, are also common, suggesting that storms were important in shaping the landscape.
Because of this association, studies must take account of the geographical and ethnical background of participants by controlling for what is called population stratification.
Virtually every society has age-stratification, meaning that the age structure in a society changes as people begin to live longer and the population becomes older.
