Natalie O'Toole

A section of Triassic strata is exposed at Carrs Brook, on the northern margin of the Minas Subbasin, Colchester County, Nova Scotia. A detailed map of the Carrs Brook section was made using a plane table survey. The 200-300 m long portion of the Triassic section consists of three facies. Facies 1 consists of coarse, red sandstone with and without mudstone intraclasts. Facies 2 consists of grey conglomerate and sandstone with mudstone intraclasts. Facies 3 consists of fine, red sandstone with and without mudstone intraclasts. The sedimentary features found in these facies include: erosional channel bases, large-scale trough cross-beds, small-scale cross-beds, iron- manganese concretions, calcite concretions, wavy bedding, convolute lamination, and green patches.

The paleoenvironment consisted of a braided river system in a semi-arid environment. The grey conglomerate and sandstone formed in the river channels, while the fine red sandstone formed eolian dunes which were blown into the river system. The coarse, red sandstone first formed part of the river system, and was then turned into an eolian deposit by the wind. The evidence for this is the lack of matrix in the thin section analysis of the coarse, red sandstone facies.

There was a lack of matrix in the fluvial grey conglomerate and sandstone. Fossilized vertebrate and plant material was found only in the grey conglomerate and sandstone of Facies 2. Sparse, fragmented bone material of several groups of dinosaurs and tetrapods were found. This indicated that the dinosaurs did not die in large herds, in flash floods. Rather, dinosaurs came to the river to use it as a waterhole and died. Their bones were then washed down the river as fragmented pieces.

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Pages: 56
Supervisor:Martin Gibling