How does this cross section indicates that the Stockton sandstone is the oldest rock layer?

In a geological cross-section, the principle of superposition states that in undisturbed sedimentary layers, the oldest layers are at the bottom and the younger layers are deposited on top. If the Stockton sandstone is depicted at the lowest level of the cross-section, it indicates that it was formed first, before the overlying layers. Additionally, if there are no intrusions or significant folding that would disrupt this order, it further supports the conclusion that the Stockton sandstone is the oldest rock layer.