A fold which has the younger rocks at its core. A synclinal fold can be either symmetrical or asymmetrical. The symmetrical folds form a U-shape.

A symmetrical syncline:

------------------------------------------
#####\*****\=====/*****/#####
######\*****\===/*****/######
#######\*****\=/*****/######
########\****\/*****/#######
#########\********/#######
##########\*****/########
###########\***/########
############\/#########