Dale Fort Blog Number 4

18 04 2012

The History of Dale Fort (Part 2)

This post is the second in a series that describe the history and pre-history of Dale Fort.  It deals with the rocks the buildings are actually constructed from.

Although Dale Fort is made mostly from rock quarried no more than 20 miles away, its stones are very different to the Old Red Sandstone they sit on. The main body of the fort comprises grey limestone blocks.  They were formed when the Rheic Ocean (see Blog Number 3) expanded and covered most of what was left of the Caledonian Mountains.  At that time, our part of what was to become Britain was located around the equator, so the sea was warm.  These conditions encouraged the deposition of calcium carbonate.  Ultimately this formed the limestone of South Pembrokeshire.  300 million years later these deposits were quarried from West Williamston on the Carew River and transported down the River Cleddau to be used in the construction of Dale Fort.

Some buildings and the battery at Dale Point are capped with granite.  This comes from Lundy Island in the Bristol Channel and is the youngest of Dale Fort’s rocks. It probably emerged as an intrusion (a hot up thrust from below (Ooh err missuss…) around 30 million years ago, in association with the Flimstone Fault which runs along the line of the Bristol Channel.

The remnant of the courtyard fronting the former Officer’s Quarters (St. Brides) is paved with thick slate flags. These probably came from Abereiddy or Rosebush in North Pembrokeshire. They were formed around 500 million years ago, when fine sedimentary shales were metamorphosed into slate as a result of heat produced by earth movements and the intrusion of molten material from below.

The bricks used in the construction of the fort probably came from the works at Bridgewater in Somerset and Goodwick near Fishguard.  The gravel and sand used for concrete and mortar probably came from the glacial deposit at The Gann, a mile or so from Dale Point.

 

Don’t miss the next historical blog which will deal with the first humans

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