Physical Features
Mer Bleue is located in the southern melt water channel of the post-glacial Ottawa River. This channel was eroded into the floor of the Champlain Sea, which invaded the Ottawa Valley some 12 000 years ago. Bedrock topography consists of two north north-east/south south-west trending ridges. Surficial material consists of some glacial till, thick marine clay, and freshwater and deltaic deposits grading from coarse sand to clay. Peat deposits in the bog proper are up to 6 metres (20 ft) thick.
There are two sand ridges that extend from the west towards the center of the conservation area. These two parallel ridges divide the bog in three sections. The northern ridge (Dolman Ridge) used to have farms which were expropriated in 1958 and subsequently removed, while the southern ridge (Borthwick Ridge) continues to have a few farms on it and provides access to the visitor boardwalk.
The hydrological features at this site are most unusual. Being a domed bog, water enters the bog mainly from natural precipitation creating oligotrophic conditions. The periphery of the bog is encircled by a mineral-enriched lagg which maintains a base water level for the bog. Drainage is poor due to underlying clay deposits as well as numerous beaver dams. Water eventually drains slowly both westward into Greens Creek and eastward into Bear Brook. However, water levels remain at or near the surface of the bog for most of the year. Saline ground-water sources are found under the organic overburden. A number of artificial ditches were dug in the bog for land reclamation or drainage of adjacent lands, however, most are no longer functioning efficiently due to the many beaver impoundments and gradual sedimentation that has occurred along their lengths.
Read more about this topic: Mer Bleue Conservation Area
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