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New Oxford Formation

New Oxford Formation
Stratigraphic range: Late Triassic,
~230–205.6 Ma
Conglomerate of the New Oxford Formation from York County, Pennsylvania
Typesedimentary
Unit ofNewark Supergroup
UnderliesGettysburg Formation
Thickness6900 feet[1]
Lithology
Primaryshale, sandstone
Otherconglomerate
Location
ExtentPennsylvania, Maryland
Type section
Named byStose and Bascom, 1929[1]

The New Oxford Formation is a mapped bedrock unit consisting primarily of sandstones, conglomerates, and shales. The New Oxford Formation was first described in Adams County, Pennsylvania in 1929,[1] and over the following decade was mapped in adjacent York County, Pennsylvania[2] and Frederick County, Maryland.[3] It was described as "red shale and sandstone with beds of micaceous sandstone, arkose, and conglomerate." The majority of this early mapping was done by George Willis Stose, Anna Isabel Jonas, and Florence Bascom.

Depositional Environment

The New Oxford Formation and other formations of the Newark Supergroup were deposited in the Gettysburg Basin, just one of many Triassic rift basins existing on the east coast of North and South America, which formed as plate tectonics pulled apart Pangaea into the continents we see today.

Stratigraphy

The New Oxford Formation is overlain by the Gettysburg Formation in Frederick County, Maryland and in Adams, Cumberland, Lancaster, and York Counties in Pennsylvania. In all other areas to the northeast in Pennsylvania the New Oxford Formation is overlain by the Hammer Creek Formation.[4]

The New Oxford Formation overlies precambrian and paleozoic rocks at the bottom of the Gettysburg Basin.

The New Oxford Formation is not divided into members.

Paleofauna

Vertebrate paleofauna

The New Oxford Formation contains mainly tetrapod fossils, including dinosaur remains.[5]

Vertebrate paleofauna of the New Oxford Formation
Genus Species Location Stratigraphic position Material Notes Images
Archosauria[5] Indeterminate[5] "Footprints"[5]
Anaschisma[5] A. browni[5] "Several partial specimens, including a well-preserved skull"[5] Initially referred to the now obsolete taxon Koskinonodon
Anchisauripus[5] A. sillimani[5] "Footprints"[5] Possibly the same animal as Eubrontes
Atreipus[5] A. milfordensis[5] "Footprints"[5]
Clepsysaurus[5] C. veatleianus[5] "Tooth"[6]
Compsosaurus[5] C. priscus[5] "Teeth"[7]

Galtonia[5]

G. gibbidens[5]

"Teeth."[8]

Grallator[5] G. tenuis[5] "Footprints"[5]
Metoposauridae[5] Indeterminate[5]

?

Otozoum[5] O. minus[5] "Footprints"[5]
Palaeoctonus[5] P. appalachianus[5] "Teeth"[6]
P. aulacodus[5] "Teeth"[6]
Redondasaurus[5] Indeterminate[5] "Tooth"[5]
Rutiodon[9] R. carolinensis[5] "Holotype consists of five teeth, the vertebral centrum, vertebrae and ribs, the neural spine, and a fragment of interclavicle"[10]

Sauropodomorpha[5]

Indeterminate (originally "Palaeosaurus" fraserianus)[5]

"Tooth."[11]

Originally known as Palaeosaurus fraserianus

Sphodrosaurus[5] S. pennsylvanicus "Partial skeleton including the back of the skull, the spinal column, all of the ribs, all of the hindlimbs and parts of the upper forelimbs"[12] Originally believed to have been a member of the Procolophonidae and then a dinosaur, it is now believed to be a basal member of the Eosuchia
Suchoprion[5] S. cyphodon[5] "Teeth"[11]

Paleoflora

Age

Relative age dating of the New Oxford Formation places it in the Late Triassic period, around ~221.5–205.6 Ma (Norian-Rhaetian), possibly reaching as old as 230 Ma (Carnian) in some places.

See also

References

  1. ^ a b c Stose, G.W., and Bascom, Florence, 1929, Description of the Fairfield and Gettysburg quadrangles [Pennsylvania]: U.S. Geological Survey Geologic Atlas of the United States, Fairfield-Gettysburg folio, no. 225, 22 p.
  2. ^ Stose, G.W., and Jonas, A.I., 1939, Geology and mineral resources of York County, Pennsylvania: Pennsylvania Geological Survey County Report, 4th series, no. 67, 199 p.
  3. ^ Jonas, A.I., and Stose, G.W., 1938, Geologic map of Frederick County and adjacent parts of Washington and Carroll Counties (Maryland): Maryland Geological Survey County Geologic Map, 1 sheet, scale 1:62,500
  4. ^ Wood, C. R., 1980, Groundwater resources of the Gettysburg and Hammer Creek Formations, southeastern Pennsylvania: Pennsylvania Geological Survey, 4th ser., Water Resource Report 49, 87 p. (see W 49).
  5. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Triassic, North America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 518–521. ISBN 0-520-24209-2.
  6. ^ a b c Cope, E. D. (1877). Descriptions of extinct Vertebrata from the Permian and Triassic formations of the United States. Proceedings of the American Philosophical Society 17(100):182-193
  7. ^ Leidy, J. (1856). Notice of some remains of extinct vertebrated animals. Proceedings of the Academy of Natural Sciences of Philadelphia 163-165
  8. ^ "Table 14.1," in Weishampel, et al. (2004). Page 326.
  9. ^ Emmons, E. (1856). Geological Report of the Midland Counties of North Carolina xx-351
  10. ^ Emmons, E. (1856). Geological Report of the Midland Counties of North Carolina xx-351
  11. ^ a b "Table 12.1," in Weishampel, et al. (2004). Page 236.
  12. ^ E. H. Colbert. 1960. A New Triassic Procolophonid from Pennsylvania. American Museum Novitates 2022:1-19


Quelle: http://en.wikipedia.org/wiki/New_Oxford_Formation