Rip-Rap Rocks at Annapolis Royal

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Boulders for sea defence along a shoreline

At Annapolis Royal in Nova Scotia a wooden boardwalk winds around the shoreline behind the town, giving unhindered views across the water of the Annapolis Basin to Granville Ferry and Port Royal on the opposite shore. The shore is bordered by salt marsh and mud which are vulnerable to erosion by the significant tides pumping in and out of the confined area of the Basin from the Bay of Fundy beyond. The natural strength of the ebb and flow are used in a tidal power electricity generating system at the nearby head of the basin.

The shore at the water’s edge is covered with dark angular blocks of stone which do not seem native to the location. They look like volcanic basalt, possibly from the Early Jurassic North Mountain Basalt (JN) dating from about 206 million years ago, which occurs naturally on the other side of the basin on the stretch of land that extends down to the Digby Neck and Brier Island. You can see this basalt outcropping at Delaps Cove which was described in an earlier post. It seems as if these basalt blocks at Annapolis Royal have been imported and positioned to protect the shore.

The basalt blocks are backed by salt marsh riddled with pools and runways. The raised pathway that passes around the back of theatre, and which provides such a pleasant walk past the dalek-like red and white lighthouse, is built on the saltmarsh. The boardwalk structure is protected on the seaward side by a line of sea-defence rip-rap. The rip rap is made up of a variety of rock types and includes boulders of local granite or granodiorite (Dg) which forms the bedrock that underlies the town. These are volcanic rocks from the South Mountain Batholith created during the Mid to Late Devonian Period from about 382 – 360 million years ago. Some of these granite boulders are shown in close up in the gallery below. These are the type of rocks mentioned in the earlier posts about Peggy’s Cove.

Mid to Late Triassic rocks of the Blomidon Formation (TJB) and Wolfville Formation (T) (dating from about 250 to 206 million years ago) are the foundation underlying the land on the Port Royal shore of the Annapolis Basin. However, as far as I could see, none of the siltstones, sandstones (including red sandstones), mudstones, or conglomerates from these formations had been used as rip-rap boulders here.

I did wonder if one or two of the rip-rap boulders fringing the boardwalk, that were clearly not granite, may have belonged to the Halifax Formation that underlies the landscape just to the south of Annapolis Royal. These rocks date from the Late Cambrian to Early Ordovician Periods 499 – 470 million years ago, and include slates and schists. Rocks of the Halifax Formation have featured in some earlier posts.


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