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
South German Jurassic South German Jurassic The term South German Jurassic () in earth history is used to refer to a lithostratigraphic rock unit at the hierarchical level of a super group. The rocks of the South German Jurassic were mainly deposited during the Jurassic period about 199 to 146 million years ago. The boundaries of the South German Jurassic and those of the chronostratigraphic or international Jurassic are not, however, exactly coincident. The depositions began rather later than the date of the international Triassic/Jurassic boundary and end as a result of erosion of the uppermost strata at various times during the Upper