Portland Formation

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]

Not to be confused with Portland Group (geology) or Portland stone.
Portland Formation
Stratigraphic range: Hettangian-Sinemurian
~
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
Portland Formation (the United States)
Portland Formation (Massachusetts)

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
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Anchisaurus[2] A. polyzelus[2]
  • Connecticut[2]
  • Massachusetts[2]
Podokesaurus[2] P. holyokensis Massachusetts Partial postcranial skeleton.[7] All known remains of this species have been destroyed.
Neotheropoda sp.[8] Massachusetts Partial humerus. Estimated to have been 9 meters long, and possibly a semiaquatic piscivore.
Non-Dinosaur Archosaurs
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Stegomosuchus[9] S. longipes Hine's Quarry, Longmeadow Partial postcranial skeleton. Originally Stegomus. A small armored "protosuchian" crocodyliform.
Pterosauria sp.[10] South Hadley, Massachusetts Partial Wrist and tooth. Non-pterodactyloid pterosaur estimated to have a wingspan of 40 cm.
Fish
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Redfieldius[11] R. gracilis The last surviving redfieldiiform fish.
Semionotus[11] S. sp. A semionotid fish.

Invertebrate paleofauna
Insects
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Holcoptera H. schlotheimi[12] A coptoclavid beetle.
H. giebeli[13]
Orthoptera sp.[13] An indeterminate orthopteran
Blattaria sp.[13] An indeterminate cockroach

See also

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.
  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. "Table 3.1," in Weishampel et al., 2004, p.48
  8. 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
  9. 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.
  10. https://www.researchgate.net/publication/355340350_Early_Jurassic_pterosaur_from_Massachusetts
  11. "PBDB". paleobiodb.org. Retrieved 2024-02-09.
  12. "PBDB". paleobiodb.org. Retrieved 2024-02-09.
  13. "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.
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