Although Whale Cove is just around the corner from Pettes Cove on Grand Manan Island, the beach stones and pebbles on the seashore are of a very different character. Not only do the beach stones and pebbles represent a whole new suite of rock types, but also at Whale Cove the stones are generally a lot bigger, more roughly shaped, and have been pushed up en masse by the sea into a large curving bank that extends right across the cove. This natural stone bank acts as a barrier that separates the sea on one side from the salt-marsh and lake on the other.
Whale Cove is geologically significant for a number of reasons – primarily it marks the location of the northernmost point of the fault line that extends the length of the island. However, the fault is not actually visible here – in contrast to Red Point, its southern extremity on the island, where it can be seen in low cliffs on the shore, with the Triassic volcanic rocks to the west and the older metamorphic rocks to the east.
The coastlines in both directions at Whale Cove do, however, respectively expose rocks of both sides of this major fault, so that representatives of both the younger and older rocks can end up amongst the beach stones. It is a place where valuable minerals and semi-precious stones can be found. For example, I think the dark blue-green spots and patches on some of the stones I photographed could be copper, which is found at Whale Cove within the South West Head Member of the Fundy Group of Late Triassic lava flows (0733); and also (with lead) in the North Head Formation (Airfield Copper 1321) from the Castalia Group dating from the Late Neoproterozoic to Early Cambrian.
Mineral crystals that formed in the spaces made by gas bubbles in cooling lava of the Triassic Dark Harbour Basalt and Seven Days Work Member – occur in rocks which outcrop on the western shore of Whale Cove. The minerals include many I have not heard of before, like the zeolite minerals chabazite, mesolite, stilbite, and heulandite, together with much more familiar quartz-related amethyst and agate. Unfortunately, I spent only a half hour near dusk at Whale Cove and had little opportunity to explore further and find some pebbles with these wonderful crystals.
There is a wealth of information available on the internet about the geology of Grand Manan, courtesy of J. Gregory McHone and Nancy W. McHone at the Grand Manan Museum. They provide a wonderful resource. They have also published the one book I would need to identify the beach stones on the island but unfortunately it seems to be no longer available (it used to be printed on demand): The McHone’s Guide to Grand Manan Beach Stones – if anyone reading this knows where I can obtain a copy, I would be delighted to hear from them.
COPYRIGHT JESSICA WINDER 2013
All Rights Reserved