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]
| Portland Formation | |
|---|---|
| Stratigraphic range: Hettangian-Sinemurian ~ | |
| 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′N 72°30′W / 42.3°N 72.5°W |
| Approximate paleocoordinates | 24°00′N 18°36′W / 24.0°N 18.6°W |
| Region | Connecticut, Massachusetts |
| Country |  USA |
| Extent | Deerfield & 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
editDinosaur 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] | 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. | _(18125938496).jpg) | |
| 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[13] | R. gracilis | The last surviving redfieldiiform fish. | 
| |||
| Semionotus[13] | S. sp. | A semionotid fish. | 
| |||
Invertebrate paleofauna
edit| Insects | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Holcoptera | H. schlotheimi[14] | A coptoclavid beetle. | 
| |||
| H. giebeli[15] | ||||||
| Orthoptera sp.[15] | An indeterminate orthopteran. | |||||
| Blattaria sp.[15] | An indeterminate cockroach. | |||||
See also
editReferences
edit- ^ Portland Formation - USGS
- ^ a b c d e f g h Weishampel et al., 2004, pp.530–532
- ^ 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.
- ^ 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. doi:10.29041/strat.13.2.03.
- ^ 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.
- ^ "PBDB". paleobiodb.org. Retrieved 2024-02-09.
- ^ 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.
- ^ "Table 3.1," in Weishampel et al., 2004, p.48
- ^ 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
- ^ https://www.researchgate.net/publication/372010039_A_New_Specimen_of_Sand_Pseudomorph_Dinosaur_Bones_with_Tetrapod_Tracks_from_the_Early_Jurassic_Hartford_Basin_USA
- ^ 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.
- ^ https://www.researchgate.net/publication/355340350_Early_Jurassic_pterosaur_from_Massachusetts [bare URL]
- ^ a b c https://www.researchgate.net/publication/351559379_The_first_Upper_Permian_amphibian_from_the_Dolomites Cite error: The named reference ":0" was defined multiple times with different content (see the help page).
- ^ "PBDB". paleobiodb.org. Retrieved 2024-02-09.
- ^ a b c "PBDB". paleobiodb.org. Retrieved 2024-02-09.
Bibliography
edit- 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.