FOSSILIZED FORESTS OF THE LOWER CARBONIFEROUS HORTON BLUFF FORMATION, NOVA SCOTIA

The Hurd Creek and Blue Beach members of the Horton Bluff Formation (Tournaisian) at Horton Bluff on the Bay of Fundy contain several forested levels. Evidence for standing trees is found in the form of molds and casts of the base of trunks and in preserved scours around the base of the trees. The casts and scours are preserved as sandstone/siltstone fills surrounded by shale, primarily within horizons of green shale. These shales are paleosols that cap progradational cycles formed by the infilling of mud-dominated brackish bays. The molds are found in a sandstone/siltstone bed exposed on the wave cut platform. Abundant fossilized plant debris indicates the presence of Lepidodendropsis and of pterophytes, and potentially of Archeocalamites.

At least two forested levels have been identified in the Horton Bluff Formation. An 11-meter (horizontal distance) section of sandstone/siltstone exposed on the wave-cut platform contains 163 standing tree fossils spaced tens of centimeters apart. These trees range from 3 to 35 cm in diameter. A prominent 117-meter (horizontal distance) green shale observed in two dimensions contains 13 casts and 8 scours. The casts narrow upwards at approximately 58° from vertical, and have a maximum width and height of 88 cm and 22 cm, respectively.

The fossilized forests at Horton Bluff may be the oldest well-preserved forests in Nova Scotia. Similar structures could potentially be identified at previously overlooked locations, such as in older rocks with poor vegetative preservation. Additionally, an understanding of the vegetative cover in the late Devonian and early Carboniferous could lead to further understanding of the paleo-environment and ecology at that time.