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
~199–195 Ma
↓
TypeGeological formation
Unit ofNewark Supergroup
Sub-unitsTurners Falls Sandstone & Mount Toby 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 located in Massachusetts, USA.[2] Ornithischian tracks located in Massachusetts and Connecticut, USA.[2] Theropod tracks located in Massachusetts and Connecticut, USA.[2] Prosauropod tracks located in Massachusetts and Connecticut, USA.[2]

Dinosaurs
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Anchisaurus[2] A. polyzelus[2]
  • Connecticut[2]
  • Massachusetts[2]
Podokesaurus[2] P. holyokensis Connecticut[2] Partial postcranial skeleton.[5] All known remains of this species have been destroyed.

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". Archived from the original on 2018-11-28. Retrieved 2017-07-07.CS1 maint: bot: original URL status unknown (link). Session No. 26 Studies of Depositional Systems and Sedimentary Rocks: In Honor of Edward Scudder Belt. 37th Annual Meeting (March 25-27, 2002).
  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. "Table 3.1," in Weishampel et al., 2004, p.48

Bibliography
  • Weishampel, David B.; Peter Dodson, and Halszka (eds.) Osmólska. 2004. The Dinosauria, 2nd edition, 1–880. Berkeley: University of California Press. Accessed 2019-02-21. ISBN 0-520-24209-2
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