Geoscience Reference
In-Depth Information
The Bay of Fundy shoreline (left) holds a unique record of an extinction event that marked the Triassic-Jurassic
boundary, roughly 200 million years ago; ferns (right) are the first plants to colonize a disturbed environment.
Along with the first dinosaurs, the early crocodilians, pterosaurs, turtles, and mammals survived this extinc-
tion. In the Jurassic, this assemblage of survivors constituted the modern world in embryo. For the next 100
million years, however, dinosaurs dominated the Earth's biota, and our own lineage, the mammals, survived in
the shadows.
The supercontinent Pangaea began to break apart in the Jurassic, causing the massive volcanism that created
the North Mountain in Nova Scotia as the crust weakened and magma welled up. Even though the continental
plates began to pull apart, the fossils in the Fundy Basin indicate that in earliest Jurassic times the landmasses
remained connected. For example, the sphenodontids found in Fundy, sturdily built little reptiles with parrot-
like beaks, are identical to fossils from England, suggesting that, 200 million years ago, the Atlantic Ocean had
not yet sufficiently opened to isolate these two populations. Similarly, the long-legged crocodilian Protosuchus
from Fundy is identical to specimens from China and South America, strongly suggesting that the continents
still formed a single landmass at least into the earliest Jurassic.
Ice and the Modern Coast
But the modern-day Atlantic Ocean was inexorably being born. As Eastern Canada drifted away from what is
now southern Europe and northwest Africa, parts of those now-distant continents remained welded to eastern
North America (such fragments of crustal material are called terranes). The pieces left behind form the Avalon
Terrane and today include eastern Newfoundland and parts of Nova Scotia and Maine. Other remnants of Ava-
lonia can be seen in Ireland, England, continental Europe, and North Africa.
Throughout the Jurassic and Cretaceous, the Appalachians continued to be worn down, and the sediments
were deposited as a coastal plain in the Gulf of Maine and on the Scotian Shelf. The sea level rose and fell dur-
ing this period, so the seashore was sometimes 100 kilometers (60 miles) or more south of Nova Scotia and at
other times only a few kilometers from the current coastline. The erosion of the Appalachians created a shal-
low, seaward-sloping shelf like that found today south of Long Island.
There are very few exposed rocks along the contemporary Atlantic coast from the Tertiary period, 65 to 2
million years ago, that followed the demise of the dinosaurs at the end of the Cretaceous. The disappearance of
the dinosaurs paved the way for the rise of the mammals, and so the Tertiary became known as the Age of
