The collision of the micro-continent of Avalonia with the Laurentian continent during the middle Palaeozoic caused the Caledonian orogeny which led to the formation and rapid erosion of sizeable mountain ranges across what is now the north of Britain.
[2] The early part of the Carboniferous period (359 - 330 million years ago) saw the deposition of a considerable thickness of limestones of differing characteristics in Gower and the wider region.
Many of the formations into which the Pembroke Limestone Group is divided, and which are in use across the country, take their name from localities in Gower due to the superb exposure within the southern coastal cliffs which more readily enables details of their stratigraphy to be worked out.
The Lower Coal Measures occur in a mile wide band running WNW from Sketty beneath Upper Killay to Wernffrwd though are little exposed.
Further north again, the stratigraphically lower parts of the Pennant Sandstone, a division of the Warwickshire Group form slightly higher ground along the margin of peninsular Gower such as that at Three Crosses.
The syncline 'tightens' westwards, resulting in the northward dip of the rocks of much of the peninsula towards that axis, being steeper than further east in the main part of the coalfield.
The dip is reversed to the south of the Cefn Bryn anticline which runs ESE-WNW through Gower, whilst further folds, particularly in the southwest, affect the strata locally.
A series of north-northeasterly directed thrust faults are associated with the fold structures, together bringing about a degree of crustal shortening as would be expected with the lateral compression of the crust effective during the continental collision.
Raised beach and cave deposits and erosional benches within the cliffs relate to varying sea-levels through the Pleistocene and have been the subject of a lot of research.
A ridge of weathered material which extends along the plateau surface in the southwest has been postulated to be an end-moraine of the Anglian Glaciation though doubt persists as to its age.
Though affected by urban development there are also sand deposits along the east coast from Black Pill eastwards to Swansea, behind the modern tidal flats.