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]

Quick Facts Type, Unit of ...
Portland Formation
Stratigraphic range: Hettangian-Sinemurian
~199–195 Ma
TypeGeological formation
Unit ofAgawam Group, Newark Supergroup
Sub-unitsTurners Falls Sandstone & Mount Toby Formation
OverliesEast Berlin Formation
Lithology
PrimarySandstone
OtherMudstone, siltstone, limestone
Location
Coordinates42.3°N 72.5°W / 42.3; -72.5
Approximate paleocoordinates24.0°N 18.6°W / 24.0; -18.6
RegionConnecticut, Massachusetts
Country USA
ExtentDeerfield & Hartford Basins
Thumb
Portland Formation
Portland Formation (the United States)
Thumb
Portland Formation
Portland Formation (Massachusetts)
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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]

Vertebrate paleofauna

Dinosaur coprolites are known from the formation.[2] This formation and the underlying East Berlin Formation are well-known for its numerous well-preserved dinosaur tracks, which represent ornithischians, theropods, and sauropodomorphs, which are preserved at sites such as Dinosaur Footprints Reservation.[2][5] Other tracks are also known representing animals such as pseudosuchians, turtles, and temnospondyls.[6]

More information Dinosaurs, Genus ...
Dinosaurs
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Anchisaurus[2] A. polyzelus[2]
  • Connecticut[2]
  • Massachusetts[2]
Several specimens. A relatively small basal Sauropodomorph. Many Otozoum tracks in the formation that may belong to Anchisaurus could have been made by potentially even larger specimens of the genus.[7]
Podokesaurus[2] P. holyokensis Massachusetts Partial postcranial skeleton.[8] A coelophysoid theropod. The only specimen was destroyed in a fire.
Neotheropoda sp.[9] Massachusetts Partial humerus. Estimated to have been 9 meters long, and possibly a semiaquatic piscivore.
Theropoda sp.[10] Connecticut Bones and tracks attributed to "Anchisauripus"
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More information Non-dinosaur archosaurs, Genus ...
Non-dinosaur archosaurs
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Stegomosuchus[11] S. longipes Hine's Quarry, Longmeadow Partial postcranial skeleton. Originally Stegomus. A small armored "protosuchian" crocodyliform.
Pterosauria sp.[12] South Hadley, Massachusetts Partial Wrist and tooth. Non-pterodactyloid pterosaur estimated to have a wingspan of 40 cm.
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More information Fish, Genus ...
Fish
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Acentrophorus[13] A. chicopensis Material initially referred to the genus Acentrophorus. Most researchers consider the species distinct from Acentrophorus.
Redfieldius[13] R. gracilis The last surviving redfieldiiform fish.
Semionotus[13] S. sp. A semionotid fish.
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Invertebrate paleofauna

More information Insects, Genus ...
Insects
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Holcoptera H. schlotheimi[14] A coptoclavid beetle. Thumb
H. giebeli[15]
Orthoptera sp.[15] An indeterminate orthopteran.
Blattaria sp.[15] An indeterminate cockroach.
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See also

References

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