The only sedimentologically significant correlation horizons are those that approximate [[time lines]] within and between sandstone bodies. This style of correlation requires an understanding of the succession of depositional environments and intervening [[Unconformities|unconformable surfaces]]. It often leads to nonparallel and nonhorizontal correlations. For example, in [[Lithofacies and environmental analysis of clastic depositional systems#Shoreline deposits|shoreface]] systems, time lines denoted by shale or silt breaks between shingled shoreface sheets and lenses are inclined in a seaward (depositional [[dip]]) direction ([[:file:lithofacies-and-environmental-analysis-of-clastic-depositional-systems_fig2.png|Figure 2]]). | The only sedimentologically significant correlation horizons are those that approximate [[time lines]] within and between sandstone bodies. This style of correlation requires an understanding of the succession of depositional environments and intervening [[Unconformities|unconformable surfaces]]. It often leads to nonparallel and nonhorizontal correlations. For example, in [[Lithofacies and environmental analysis of clastic depositional systems#Shoreline deposits|shoreface]] systems, time lines denoted by shale or silt breaks between shingled shoreface sheets and lenses are inclined in a seaward (depositional [[dip]]) direction ([[:file:lithofacies-and-environmental-analysis-of-clastic-depositional-systems_fig2.png|Figure 2]]). |