Syncline, in structural geology, a syncline is a fold, with younger layers closer to the center of the structure.
The Ternoise valley is the most northerly flowing in the syncline to the south of the Variscan front.
All the strata are tilted in a generally southerly direction towards the axis of the South Wales Coalfield syncline though there is significant local variation, due in part to the proximity of the eastern slopes of the hill to the Neath Disturbance.
The peninsula, itself, is the southeastern side of a large syncline beneath Lake Superior.