Jurassic Jurassic The Jurassic (; from Jura Mountains) was a geologic period and system that spanned 56 million years from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period Mya. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles. The start of the period was marked by the major Triassic–Jurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian-Toarcian extinction in the Early Jurassic, and the Tithonian event at the end; however, neither event ranks among the "Big Five" mass extinctions. The
Partridge Island (Nova Scotia) geological period between 208 and 220 million years ago, rivers swollen by intense rains carried coarse sediments (now sedimentary rocks) from nearby highlands into the Fundy Basin. Other deposits came from wind-blown sand dunes. Later, large lakes formed on the central part of the basin depositing finer sediments up to 1,000 metres thick and, as they dried up periodically, they left behind salt and gypsum deposits. The red sedimentary sandstone base of Partridge Island dates from the late Triassic period. The covering layer of dark basalt was formed from magma and lava eruptions in the Jurassic period between 175 and