The surface geology in Pembrokeshire tends to run in east – west bands and this is reflected in the landform.
The north of the parish comprises Ordovecian sedimentary rocks which are part of a broad band of rock spreading across much of central Pembrokeshire and widening into Carmarthenshire, at the western end this band of rock outcrops at Druidston Haven in the relatively soft cliffs in the middle part of the beach.
The ridge along the Haven road is comprised of a narrow band of (more resistant?) Silurian sedimentary rocks which seems to peter out without reaching the coast in the west but extends along the A48 in the East towards Narberth.
The south of the parish is comprised of the band of millstone grit (Carboniferous in age) which outcrops between Broadhaven and Druidstone and runs across the Rhos just south of Uzmaston and thence south east to Marros.
The south west corner of the parish includes an area of coal measure rocks which outcrop in the west between Little Haven and Broad Haven and then re-appear in the east at Hook and Landshipping before widening to the east and outcropping on the Coast between Amroth and Tenby. This was mined and quarried both East and west of the parish but not within Lambston? Why Not? Too deep?
A more detailed map of the Portfield Gate end of the parish shows a much more complex situation, still with an esat west alignment. The northern area as above is shown as Silurian mudstone extending as far south as Cuckoo Grove and well out of the parish to the north.
Then there are two east west bands of silurian gasworks mudstones (Named after a famous outcrop at the old gasworks below New Road in Haverfordwest and featuring in Richard Forey’s bbook – Check
es its names to rocks – there are both defined ‘Portfield Beds’ and ‘Cuckoo Shales’ in geological records ; From BGS website
along the Haven road.This then gives way to the broader belt of carniniferous sandstone. At the point where this map ends (192) the coal measures are further south than the parish boundary.