jura-trias

from The Century Dictionary.

• noun In geology, a rock series which is regarded as representing, in part or whole, deposits of both Triassic and Jurassic time (as in the ease of the Red or Newark sandstones of the Connecticut valley, New Jersey, Pennsylvania, and southward), or in which the distinction of age is obscure (as in the Burrum and Ipswich formations of Queensland).

from the GNU version of the Collaborative International Dictionary of English.

• noun (Geol.) A term applied to many American Mesozoic strata, in which the characteristics of the Jurassic and Triassic periods appear to be blended.