Portland Formation

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°18′N 72°30′W / 42.3°N 72.5°W / 42.3; -72.5
Approximate paleocoordinates24°00′N 18°36′W / 24.0°N 18.6°W / 24.0; -18.6
RegionConnecticut, Massachusetts
CountryUnited States
ExtentDeerfield & Hartford Basins
Portland Formation is located in the United States
Portland Formation
Portland Formation (the United States)
Portland Formation is located in Massachusetts
Portland Formation
Portland Formation (Massachusetts)

The Portland Formation is a geological formation in Connecticut and Massachusetts in the northeastern United States. It dates back to the Early Jurassic period. 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).

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.

Vertebrate paleofauna

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

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon

Notes
Uncertain or tentative taxa are in small text
crossed out taxa are discredited.

Dinosaurs
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Anomoepus A. sp.
  • Massachusetts
  • Connecticut
 Hundreds of ornithischian footprints and trackways. Tracks made by small Ornithischians.
Eubrontes E. sp.
  • Massachusetts
  • Connecticut
 Many theropod footprints and trackways. Tracks made by medium to large sized theropods likely similar to Dilophosaurus.
Grallator G. sp.
  • Massachusetts
  • Connecticut
 Many theropod footprints and trackways. Tracks made by small to medium sized theropods likely similar to Coelophysis.
Otozoum O. sp
  • Massachusetts
  • Connecticut
 Many sauropodomorph trackways. Tracks made by medium sized Sauropodomorphs. Likely made by animals such as Anchisaurus.
Anchisaurus A. polyzelus
  • Connecticut
  • Massachusetts
 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.
Podokesaurus P. holyokensis Massachusetts Partial postcranial skeleton. A coelophysoid theropod. The only specimen was destroyed in a fire.
Neotheropoda indet. indeterminate Massachusetts Partial humerus. Estimated to have been 9 meters long, and possibly a semiaquatic piscivore.
Theropoda indet. indeterminate Connecticut Two specimens and tracks attributed to "Anchisauripus" The animal was noted as being similar to Coelophysis as well as being slightly larger than some of the largest specimens attributed to Coelophysis.
Non-dinosaur archosaurs
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Stegomosuchus S. longipes Hine's Quarry, Longmeadow Partial postcranial skeleton. Originally Stegomus. A small armored "protosuchian" crocodyliform.
Pterosauria indet, indeterminate South Hadley, Massachusetts Partial wrist bone and tooth. Non-pterodactyloid pterosaur estimated to have a wingspan of 40 cm.
Fish
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Acentrophorus A. chicopensis Material initially referred to the genus Acentrophorus. Most researchers consider the species distinct from Acentrophorus.
Redfieldius R. gracilis The last surviving redfieldiiform fish.
Semionotus S. sp. A semionotid fish.

Invertebrate paleofauna

Insects
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Holcoptera H. schlotheimi A coptoclavid beetle known with distinct color pattern.
H. giebeli
Orthoptera indeterminate
Blattaria indeterminate
Polyphaga indeterminate An indeterminate polyphagan larvae. Similar to Mormolucoides but larger.

See also

References

  1. ↑ Portland Formation - USGS
  2. 1 2 3 4 5 6 7 8 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. ↑ Olsen, Rainforth (2003). "The Early Jurassic Ornithischian Dinosaurian Ichnogenus Anomoepus" (PDF).
  8. 1 2 Olsen, Paul E.; Smith, Joshua B.; McDonald, Nicholas G. (15 September 1998). "Type material of the type species of the classic theropod footprint genera Eubrontes, Anchisauripus , and Grallator (Early Jurassic, Hartford and Deerfield basins, Connecticut and Massachusetts, U.S.A.)". Journal of Vertebrate Paleontology. 18 (3): 586–601. doi:10.1080/02724634.1998.10011086.
  9. ↑ Olsen, Whiteside (2005). "Jurassic cyclostratigraphy and paleontology of the Hartford basin".
  10. ↑ 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.
  11. ↑ "Table 3.1," in Weishampel et al., 2004, p.48
  12. ↑ 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
  13. ↑ "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.
  14. ↑ 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.
  15. ↑ "Early Jurassic pterosaur from Massachusetts". Archived from the original on 2023-11-21. Retrieved 2025-04-03.
  16. ↑ "The first Upper Permian amphibian from the Dolomites". ResearchGate.
  17. 1 2 "PBDB". paleobiodb.org. Retrieved 2024-02-09.
  18. 1 2 Thomson, Ulysses; Ross, Andrew J.; Davidson, Philip (August 2017). "Mesozoic Holcoptera (Coleoptera: Coptoclavidae) from England and the United States". Proceedings of the Geologists' Association. 128 (4): 659–674. doi:10.1016/j.pgeola.2017.05.009.
  19. 1 2 3 4 Huber, Phillip; McDonald, Nicholas G.; Olsen, Paul E. (2003). The Great Rift Valleys of Pangea in Eastern North America, Volume 2: Sedimentology, Stratigraphy, and Paleontology (PDF). Columbia University Press. pp. 206–223.

Bibliography