Preseli Pembrokeshire Pembrokeshire district. On 1 April 1996 the district was abolished by the Local Government (Wales) Act 1994 and merged into a reconstituted county of Pembrokeshire. Preseli Pembrokeshire Preseli Pembrokeshire (, ; ) was one of six local government districts of Dyfed in West Wales from 1974 to 1996. Until 1987 the name of the district was Preseli. The district took its name from the Preseli Hills. It was formed by the Local Government Act 1972 on 1 April 1974 from the northern part of the administrative county of Pembrokeshire - specifically, the municipal borough of Haverfordwest, the urban districts of
Pembrokeshire to its proximity to the relatively warm Atlantic Ocean. Inland, average temperatures tend to fall 0.5 °C for each 100 metres increase in height. The air pollution rating of Pembrokeshire is "Good", the lowest rating. The rocks in the county were formed between 600 and 290 million years ago. More recent rock formations were eroded when sea levels rose 80 million years ago, at the end of the Cretaceous Period. Around 60 million years ago, the Pembrokeshire landmass emerged through a combination of uplift and falling sea levels; the youngest rocks, from the Carboniferous Period, contain the Pembrokeshire Coalfield. The