The Portland Formation is a geological
formation in
Connecticut and
Massachusetts in the northeastern United States.[1] It dates back to the
Early Jurassic period.[2] The formation consists mainly of
sandstone laid down by a series of lakes (in the older half of the formation) and the floodplain of a river (in the younger half). The sedimentary rock layers representing the entire Portland Formation are over 4 kilometres (2.5 mi) thick and were formed over about 4 million years of time, from the
Hettangian age (lower half) to the late Hettangian and
Sinemurian ages (upper half).[3]
In 2016, the paleontologist Robert E. Weems and colleagues suggested the Portland Formation should be elevated to a
geological group within the Newark Supergroup (as the Portland Group), and thereby replacing the former name "Agawam Group". They also reinstated the Longmeadow Sandstone as a formation (within the uppermost Portland Group); it had earlier been considered identical to the Portland Formation.[4]
Weishampel, David B.; Dodson, Peter; Osmólska, Halszka, eds. (2004).
The Dinosauria, 2nd edition. Berkeley: University of California Press.
ISBN0-520-24209-2. Retrieved 2019-02-21.
The Portland Formation is a geological
formation in
Connecticut and
Massachusetts in the northeastern United States.[1] It dates back to the
Early Jurassic period.[2] The formation consists mainly of
sandstone laid down by a series of lakes (in the older half of the formation) and the floodplain of a river (in the younger half). The sedimentary rock layers representing the entire Portland Formation are over 4 kilometres (2.5 mi) thick and were formed over about 4 million years of time, from the
Hettangian age (lower half) to the late Hettangian and
Sinemurian ages (upper half).[3]
In 2016, the paleontologist Robert E. Weems and colleagues suggested the Portland Formation should be elevated to a
geological group within the Newark Supergroup (as the Portland Group), and thereby replacing the former name "Agawam Group". They also reinstated the Longmeadow Sandstone as a formation (within the uppermost Portland Group); it had earlier been considered identical to the Portland Formation.[4]
Weishampel, David B.; Dodson, Peter; Osmólska, Halszka, eds. (2004).
The Dinosauria, 2nd edition. Berkeley: University of California Press.
ISBN0-520-24209-2. Retrieved 2019-02-21.