The cliffs and shoreline of Blue Beach expose beautifully bedded layers of sedimentary rocks. These consist mostly of sandstones, siltstones, and shales, which were laid down as sand, silt, and mud by rivers, lagoons, and along the ancient shores of a large marine bay or estuary, in brackish- (partially salty) to fresh-water conditions. The nearby landscapes were carpeted in dense, early forests and there were numerous swamps in the area. Primeval streams kept the landscape and the shoreline supplied with abundant sand and silt.
The main body of water in the former region filled a large depression of the Earth’s crust, known as the Maritimes Basin, which had formed at least 370 Million years (mya) ago. The depression was the result of a slow collision of continents, when what we today call Africa began to collide with Nova Scotia. This was the beginning of the formation of the supercontinent called ‘Pangea’.
Like all good sedimentary basins, the Maritimes Basin provided an ideal place for eroding sediments from nearby mountains that were thrust up by continental collision to collect, and for trackways to be buried and bones to accumulate.
The Maritimes Basin continued to gather sediments for over 70-million years. There are no sediments known from about the first 10-million years of the basin’s evolution. The Horton Group, represented best by the type-section at Blue Beach, are the oldest or lowest sediments found in the bottom of the basin, with an Early Carboniferous age of about 350 mya. Following the Horton Group come several later periods of sedimentation, each represented by differently-named rock groups, ultimately leading to the Upper Carboniferous rocks of Joggins and Sydney Mines in Nova Scotia. The incredibly complete succession of Carboniferous rocks seen in Nova Scotia has no parallel anyplace else on Earth.
Today, the sedimentary strata at Blue Beach have been slightly tilted from the horizontal and lifted into view. The entire section of rocks exposed in the 4 km of cliffs have suffered neither serious folding nor faulting, so their fossil contents have suffered virtually no distortion or damage. Other Horton Group exposures of rock contain nothing like the kind of fossil variety or density seen at the Blue Beach locality. Indeed, few other exposures yield more than plants or invertebrates.