(360-290 million years ago)
The Carboniferous Period is divided into two parts. The Lower Carboniferous, also called the Mississippian, began approximately 360 mya and ended 310 mya. The Upper Carboniferous, or Pennsylvanian, extended from about 310 to 290 mya, the beginning of the Permian Period.
Global View - Where was Nova Scotia?
Nova Scotia was located near the equator, wedged between the ancient North American and African continents. It was part of the supercontinent Pangea, which had formed in the Devonian Period.
Rocks of Nova Scotia
In the Lower Carboniferous, continued movement along the fault lines uplifted parts of Nova Scotia and trapped reservoirs of magma in the crust to form large subterranean deposits of granite. These deposits are found mainly in the Cumberland and Colchester counties near the Chedabucto-Cobequid fault line.
Initially, the Appalachian valleys were steep enough to have braided streams, which permitted little ground-stabilising vegetation. Erosion gradually reduced the topography of the mountains as the streams transported gravel, sand and mud into the adjacent basins. These sediments are preserved today as rocks of the Horton Group which are 1000 to 2000 m (3280 - 6560 ft) thick.
Where a basin lay below sea level and there was access to the sea, the basin was flooded. This created a new branch of the sea, often shallow and with relatively poor circulation to deeper water. In such circumstances, evaporation of sea water led to the precipitation of thick layers of limestone, salt, gypsum and anhydrite, all important minerals that are mined today from the Windsor Group.
The climate of the Lower Carboniferous had evolved into hot, desert-like conditions, perhaps similar to the area around the present day Dead Sea. In the later part of the Lower Carboniferous (315-310 mya) the climate changed from dry to very wet, as the sea flooded some low lying areas and evaporated into the hot air.
Plants became important ground cover in this lush new environment. The first animals with backbones (amphibians and reptiles) ventured onto land, leaving their trackways for us to find at sites such as Horton Bluff.
Rocks of Nova Scotia
The coal age was born in a burst of prolific, lush vegetation. Wetlands in the vast floodbasins of Nova Scotia had a subdued topography of low hills separated by broad river valleys and freshwater lakes. As the plants died and decayed, they became buried and compressed by new organic material growing on top of them, forming thick layers of peat.
Some of these environments were stable for millions of years, experiencing only gentle subsidence or rhythmic oscillations in elevation. In these locations, such as the Sydney coalfields, tremendous thicknesses of organic material accumulated and were eventually turned into coal.
Vegetation flourished in the warm climate of the Upper Carboniferous Period, particularly the large trees which could reach heights of 30 metres and swamp plants found at Joggins. Some of the swamp plants had large tops and laterally spreading roots which were ideally suited to the wide, flat, poorly drained land surfaces. These plants grew densely in bogs and swamps along the floodplains, estuaries and shorelines of lakes, and possibly in coastal areas.