Regional Geology of the Maritime Provinces

Pangea began to break up about 250 million years ago, an event that led to the formation of the continents and oceans that are so familiar to us today (Fig. 10).
Figure 10. Global paleogeography of the Jurassic, about 165 milloion years ago; Cretaceous, about 100 million years ago and Paleocene, about 50 million years ago. From Atlantic Geoscience Society (2001). Courtesy of C. Scotese, see Website No.9.

As Pangea stretched, depressions in the Earth's crust formed, similar to those in parts of today's East African Rift Valley: the ancient depressions included the Fundy Basin (precursor of much of today's Bay of Fundy) and, offshore, the Scotian Basin where oil and gas deposits subsequently developed to become the focus of modern exploration (Fig. 11).

Figure 11. Section across the Scotian Margin showing how the bedrock on land if buried offshore by a several kilometre-thick blanket of Mesozoic and Cenozoic sedimentary rocks and sediments. From Atlantic Geoscience Society (2001); courtesy of J. Wade, GSC(Atlantic).

The Fundy Basin is essentially a rejuvenated and stretched southernmost part of the Maritimes Basin, that filled with deposits from about 225 to 195 million years ago (Fig. 12) sediments were eroded mainly from the ancestral Appalachian Mountains to the northwest - although some derived from the area of the present day South Mountain, to the southeast. These sediments (now forming the Wolfville Formation) were transported and deposited by water - rivers, streams and lakes - and sometimes also by winds that formed sand dunes.

This was a time of ferns, cycads, horsetails and araucarians (related to the modern Norfolk Island pine). The equatorial clubmoss forests of the Carboniferous were gone forever as the region moved into the Northern Hemisphere (a fact confirmed by paleomagnetic studies). Gone too were the primitive amphibians and reptiles of the Joggins tree stumps and Blue Beach trackways, their places taken by protomammals and crocodile-like amphibians and reptiles.

Figure 12. The different rock formations of the Fundy Basin. Note that not all the time is represented by rock - for example, no rocks are currently known in the Fundy Basin that date from late Carnian to early Norian times.

The rock record passed upwards from the Wolfville Formation into the Blomidon Formation, dominated by soft sandstones and mudstones in laterally extensive thin layers, as seen in the cliffs at places like Blomidon (near Wolfville) and Rossway (near Digby). These thin-layered sediments bear the characteristics of lake, playa and sand flat

deposits; playas are ephemeral lakes that dry up in arid seasons. The interplay of permanent lake and playa sediments (and in places, gypsum deposits and dunes) shows that climate fluctuated between wet and dry. But it was consistently hot - the area was still only 10-20 degrees north of the equator, after all. Among the reptiles, dinosaurs were present, as testified by their occasional footprints, but were not yet dominant or huge.

A dramatic volcanic episode also punctuated the history of the Fundy Basin - and episode that only lasted about a half million years (it has been called a "mantle belch"). The basalt that was produced in this earliest Jurassic volcanic event is seen today, for example, in Nova Scotia's North Mountain (for which it is responsible), and at Five Islands, Wasson Bluff and Partridge Island, near Parrsboro, and Grand Manan Island in New Brunswick. But this volcanic event is traceable well beyond the Fundy Basin, to Morocco, Brazil and even southern France. Indeed, it may have been the most widespread volcanic event of all time. This event has been dated radiometrically at about 200 million years ago and has been proven by fossil evidence to be just within the Jurassic Period. The "belch" was thus immediately above the Triassic-Jurassic boundary, the time of a major extinction event - although this cataclysm, unlike the more famous Cretaceous-Tertiary event, represents a paving of the the way for dinosaurs rather than a dinosaur debacle. Did the volcanic episode have anything to do with the extinction? What about the Manicoagen impact crater in northern Quebec, which has been dated to around about the this time interval? Could the two disasters have had a cumulative destructive effect on the latest Triassic animals? A combination of disasters is now looked upon as a definite possibility as the cause of at least some mass extinction events.

Above the North Mountain Basalt is the youngest of the Fundy Basin formations, the McCoy Brook Formation, of Early Jurassic age. This formations consists of mostly red sandstones and mudstones of river and lake deposition. Immediately above the basalt, there is also much fossil scree - "paleotalus", and occasional rubble flows ("lahars") that reflect the unstable landscape in the millenia following the volcanic episode. Paleotalus is well seen at Blue Sac near Five Islands, and at Wasson Bluff, where it is the source of many small reptile fossils. Other fossils at Wasson Bluff, such as the dinosaurs, have been found in sand dune, river and lake deposits.

Off shore, the gap between Nova Scotia and Morocco continued to widen over the next 200 million years, a process that continues to this day. True basaltic ocean floor began to form about 180 million years ago, and the Scotian Basin continued to fill with several kilometres depth of mostly marine sediments. However, onshore in Nova Scotia and in the Fundy Basin region, rocks representing the last 200 million years are largely absent. This gap is filled only by a few scattered and intriguing deposits - of mostly river and lake origin - of Early Cretaceous age, from about 100-125 million years ago. The two largest known onshore Cretaceous outcrops underlie the Upper Musquodoboit Valley and the village of Shubenacadie, and are the source of commercial silica sands and potential kaolin clay deposits.