Portland Formation

Not to be confused with Portland Group (geology) or Portland stone.

Portland Formation
Stratigraphic range: Hettangian-Sinemurian ~199–195  Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Geological formation
Unit of	Agawam Group, Newark Supergroup
Sub-units	Turners Falls Sandstone & Mount Toby Formation
Overlies	East Berlin Formation
Lithology
Primary	Sandstone
Other	Mudstone, siltstone, limestone
Location
Coordinates	42°18′N72°30′W / 42.3°N 72.5°W / 42.3; -72.5
Approximate paleocoordinates	24°00′N18°36′W / 24.0°N 18.6°W / 24.0; -18.6
Region	Connecticut, Massachusetts
Country	United States
Extent	Deerfield & Hartford Basins
Portland Formation (the United States) Show map of the United States Portland Formation (Massachusetts) Show map of Massachusetts

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]

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]

Dinosaurs
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
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"

Non-dinosaur archosaurs
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
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.

Fish
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Acentrophorus [13]	A. chicopensis				Material initially referred to the genus Acentrophorus . Most researchers consider the species distinct from Acentrophorus .
Redfieldius [14]	R. gracilis				The last surviving redfieldiiform fish.
Semionotus [14]	S. sp.				A semionotid fish.

Invertebrate paleofauna

Insects
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Holcoptera	H. schlotheimi [15]				A coptoclavid beetle.
	H. giebeli [16]
Orthoptera sp. [16]					An indeterminate orthopteran.
Blattaria sp. [16]					An indeterminate cockroach.

See also

• List of dinosaur-bearing rock formations

References

1. Portland Formation - USGS
2. Weishampel et al., 2004, pp.530–532
3. Olsen, P.E. (2002). "Stratigraphy and Age of the Early Jurassic Portland Formation of Connecticut and Massachusetts: A Contribution to the Time Scale of the Early Jurassic". Geological Society of America (Abstract). Archived from the original on 2018-11-28. Retrieved 2017-07-07.
4. Weems, R. E.; Tanner, L. H.; Lucas, S. G. (2016). "Synthesis and revision of the lithostratigraphic groups and formations in the Upper Permian?–Lower Jurassic Newark Supergroup of eastern North America" . Stratigraphy. 13 (2): 111–153. Bibcode:2016Strat..13..111W. doi:10.29041/strat.13.2.03.
5. Getty, Patrick (2004). "Ornithischian ichnites from Dinosaur Footprint Reservation (Early Jurassic Portland Formation), Holyoke, MA". Journal of Vertebrate Paleontology. 23 (Supp 3): 63A. doi:10.1080/02724634.2003.10010538. S2CID   220410105.
6. "PBDB". paleobiodb.org. Retrieved 2024-02-09.
7. Yates, Adam M. (2010). "A revision of the problematic sauropodomorph dinosaurs from Manchester, Connecticut and the status of Anchisaurus Marsh". Palaeontology. 53 (4): 739–752. Bibcode:2010Palgy..53..739Y. doi:10.1111/j.1475-4983.2010.00952.x.
8. "Table 3.1," in Weishampel et al., 2004, p.48
9. McMenamin, M. (2021). Large neotheropod from the Lower Jurassic of Massachusetts. AcademiaLetters, Article 3591. doi : 10.20935/AL3591.1©2021 by the author — Open Access — Distributed under CC BY 4.0
10. "A New Specimen of Sand Pseudomorph Dinosaur Bones with Tetrapod Tracks from the Early Jurassic, Hartford Basin, USA | Request PDF". Archived from the original on 2023-11-21. Retrieved 2025-04-03.
11. von Huene, Friedrich (1922). "The Triassic reptilian order Thecodontia". American Journal of Science. 4 (19): 22–26. Bibcode:1922AmJS....4...22H. doi:10.2475/ajs.s5-4.19.22.
12. "Early Jurassic pterosaur from Massachusetts". Archived from the original on 2023-11-21. Retrieved 2025-04-03.
13. "The first Upper Permian amphibian from the Dolomites". ResearchGate.
14. "PBDB". paleobiodb.org. Retrieved 2024-02-09.
15. "PBDB". paleobiodb.org. Retrieved 2024-02-09.
16. "PBDB". paleobiodb.org. Retrieved 2024-02-09.

Bibliography

• Weishampel, David B.; Dodson, Peter; Osmólska, Halszka, eds. (2004). The Dinosauria, 2nd edition. Berkeley: University of California Press. ISBN   0-520-24209-2 . Retrieved 2019-02-21.