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Rockwood Park, Saint John

Much of Rockwood Park is underlain by a karst landscape formed in Precambrian marble of the Green Head Group. Karst topography is created when soluble bedrock is dissolved by mildly acidic water. Soluble bedrock is usually carbonate rock such as limestone, dolomite or marble. Marble is a metamorphic rock, meaning the original sedimentary limestone has been altered by heat and pressure. Acidic water (rainwater and groundwater) dissolves the bedrock along cracks or bedding planes. Over long periods of time the cracks enlarge and the size of the openings in the rock increases. As the acidic water drains through the cracks into the bedrock, the landscape develops sinkholes, underground streams and caves. The park also includes outcrops of metamorphic Brookville Gneiss and igneous rock, like the Rockwood Park Granodiorite, produced during the plate tectonic processes that created the Iapetus Ocean.

There are a few ‘large’ caves in Rockwood Park including Howe’s Cave and Harbell’s Cave. A man named Oliver reportedly discovered Howe’s Cave, also known as Oliver’s Cave, in the 1860s. Two members of the Natural History Society of New Brunswick, Robert Matthew and I. Allen Jack soon after explored it. George Matthew wrote a description of the cave in 1904 for the Bulletin of the Natural History Society of New Brunswick. The landscape and karst features that include Howe’s Cave are a unique feature in the geology of Saint John.

Along with the underground caves, other karst features are seen at Rockwood Park. These features include flutes, runnels, sinkholes, vertical shafts, disappearing and reappearing springs, limestone pavements and spring fed lakes, like Lily Lake.