Capistrano Formation
Stratigraphic range: Miocene to Pliocene
TypeFormation
Sub-unitsOso Member, unnamed siltstone member
UnderliesNiguel Formation
OverliesMonterey Formation
Thickness850 m
Lithology
PrimarySiltstone, Arkose
OtherBreccia, Mudstone
Location
RegionOrange County, California
CountryUnited States
Type section
Named forSan Juan Capistrano
Named byAlfred Oswald Woodford
Year defined1925

Outcrops of the Oso Member, with the type locality of Titanotaria highlighted

The Capistrano Formation is a geologic formation in coastal southern Orange County, California. It preserves fossils dating back to the late Miocene to early Pliocene, with the Oso Member representing a near-shore environment. Fifty-nine species and varieties of foraminifera are recognized from the Capistrano Formation[1] alongside a diverse array of marine mammals including up to five species of walrus.

Geography

The Capistrano Formation, named for the town of San Juan Capistrano, is located in southern California, specifically the northern extent of the Peninsular Ranges, which stretch from the Los Angeles Basin to Baja California. [2] It crops out along the coast from Dana Point to San Clemente, and inland for seven miles.[1]

Geology and Stratigraphy

The Capistrano Formation is a heterogenous marine formation that can be differentiated into two distinct but adjacent units. One of these units is the Oso Member, which is composed of arkosic sandstone and preserves a nearshore environment. This unit shows outcrops across Orange County, which are recognizable as medium to coarse grained, white to tan rock. The second member primarily consists of siltstone, preserves an environment that would have been located further out at sea in deeper waters and has not yet been named. At the southwestern border of the Oso Member the two units connect.

Depending on the locality, the Oso Member of the Capistrano Formation either conformably overlies the Puente Formation (specifically Soquel Member), while in other areas it unconformably overlies the Monterey Formation and is succeeded by the Niguel Formation. The Oso Member has been dated to the early late Hemphillian (6.6 to 5.8 Ma) based on the presence of Dinohippus interpolatus and absence of older or younger taxa, but the formation as a whole extends into the Pliocene, rendering the Oso Member coeval with only the lower strata of the unnamed siltstone member. Foraminifers and microfossils have also previously been used to date the formation, which indicate an early Pliocene age (5.6 to 4.9 Ma) for its upper boundary.[3]

Paleoenvironment

The two units of the Capistrano Formation preserve environments of difference distance from the shore. The Oso Member preserves a near-shore environment, thought to be submarine delta deposits situated in a shallow embayment of the Pacific Ocean. The presence of marlin fossils could indicate that parts of the formation deposited at bathyal depths, between 200 and 2.000 meters deep,[3] and Fierstine argues that the preservation of the material suggests that it was not subject to extensive postmortem transportation. He also argues that the presence of this fish suggests warm water temperatures during the Miocene, with Marlins typically preferring average surface temperatures of 24 °C.[4] Barboza and colleagues meanwhile argue that this alone is not sufficient evidence for depth, citing the preservation of marlin fossils in much shallower waters including one specimen found in deposits of the supralittoral zone.[2] The proximity to the shore is apparent due to the presence of terrestrial fauna.

Paleofauna

Chondrichthyes

Name Species Member Material Notes Image
Cosmopolitodus C. hastalis[2] Oso Member also known as the broad-toothed mako
Cosmopolitodus hastalis tooth
Myliobatis M. sp. [2] Oso Member a species of ray
Otodus O. megalodon [5] Oso Member

Siltstone Member

 teeth
Megalodon restoration

Osteichthyes

Name Species Member Material Notes Image
Acipenseridae indet.[6] Oso Member a type of sturgeon
Makaira M. nigricans [4] Oso Member a nearly complete skull an early specimen of the extant blue marlin
Blue marlin
Oncorhynchus O. rastrosus[7] Oso Member the sabertoothed salmon
Oncorhynchus rastrosus

Reptilia

Name Species Member Material Notes Image
Crocodilia indet.[2] Oso Member A tooth and an osteoderm
Dermochelyidae indet.[2] Oso Member
Testudinidae indet.[2] Oso Member

Aves

Name Species Member Material Notes Image
Mancallinae indet.[8][9] Oso Member a type of flightless auk
Uria U. sp. [8]

Mammalia

Afrotheria

Name Species Member Material Notes Image
Desmostylus D. sp.[2] Oso Member
Desmostylus
Hydrodamalis H. cuestae[2] Oso Member a close relative of Steller's Sea Cow
Proboscidea indet.[2] Oso Member

Artiodactyla

Name Species Member Material Notes Image
Antilocapridae indet.[2] Oso Member
cf. Balaenoptera [2] cf. Balaenoptera sp. Oso Member
Camelidae indet.[2] Oso Member
Delphinidae indet.[2] Oso Member
Herpetocetus[10] Oso Member a cetotheriid whale
Herpetocetus bramblei
Parapontoporia P. pacifica [11] Oso Member a skull with associated petrotympanic a relative of the Chinese river dolphin
Parapontoporia sternbergi (left), a related species
Physeteroidea Species A[2] Oso Member
Physeteroidea Species B[2] Oso Member
Tayassuidae indet.[2] Oso Member

Carnivora

Name Species Member Material Notes Image
Borophagus[2] Oso Member a large genus of canid
Borophagus skull
Mustelidae indet.[2] Oso Member
Gomphotaria G. pugnax[8] Oso Member a species of walrus
Gomphotaria pugnax life restoration
Osodobenus O. eodon[12] Oso Member three skulls representing an adult male, adult female and juvenile specimen the first known walrus with tusks
Pontolis cf. P. magnus

P. kohnoi[12]

 Oso Member a giant early walrus
Pontolis magnus mandible
Thalassoleon T. mexicanus[3] Siltstone Member multiple skulls and postcranial material a basal eared seal
Thalassoleon mexicanus skull
Titanotaria T. orangensis [13] Oso Member skull and postcranial material of multiple individuals a basal walrus
Lateral view of Titanotaria orangensis

Lagomorpha

Name Species Member Material Notes Image
Leporidae indet.[2] Oso Member

Perissodactyla

Name Species Member Material Notes Image
Dinohippus[2] D. interpolatus Oso Member isolated teeth
Rhinocerotidae indet.[2] Oso Member

See also

References

  1. 1 2 White, W.R. (1956). "Pliocene and Miocene Foraminifera from the Capistrano Formation, Orange County, California". Journal of Paleontology. 30 (2): 237–260. JSTOR 1300262.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Barboza, M.M.; Parham, J.F.; Santos, G.; Kussman, B.N.; Velez-Juarbe, J. (2017). "The age of the Oso Member, Capistrano Formation, and a review of fossil crocodylians from California". PaleoBios. 34. doi:10.5070/P9341033797.
  3. 1 2 3 Deméré, T.A.; Berta, A. (2005). "New skeletal material of Thalassoleon (Otariidae Pinnipedia) from the late Miocene-early Pliocene (Hemphillian) of California". Bulletin of the Florida Museum of Natural History. 45 (4): 379–411.
  4. 1 2 Fierstine, H. L. (2008). "A Fossil Skull of the Extant Blue Marlin (Makaira nigricans Lacepède, 1802) from the Late Miocene of Orange County, California". Bulletin, Southern California Academy of Sciences. 107 (2): 45–56. doi:10.3160/0038-3872(2008)107[45:AFSOTE]2.0.CO;2. S2CID 26337210.
  5. ↑ Boessenecker, R.W.; Ehret, D.J.; Long, D.J.; Churchill, M.; Martin, E.; Boessenecker, S.J. (2019). "The Early Pliocene extinction of the mega-toothed shark Otodus megalodon: a view from the eastern North Pacific". PeerJ. 7: e6088. doi:10.7717/peerj.6088. PMC 6377595. PMID 30783558. S2CID 67750037.
  6. ↑ Hilton, E.J.; Grande, L. (2017). "Review of the fossil record of sturgeons, family Acipenseridae (Actinopterygii: Acipenseriformes), from North America". Journal of Paleontology. 80 (4): 672–683. doi:10.1666/0022-3360(2006)80[672:ROTFRO]2.0.CO;2. S2CID 53583501.
  7. ↑ Sankey, J.; Biewer, J.; Basuga, J.; Palacios, F.; Wagner, H.; Garber, D. (2016). "The giant, spike-toothed salmon, Oncorhynchus rastrosus and the "Proto-Tuolumne River" (early Pliocene) of Central California" (PDF). PaleoBios. 33. doi:10.5070/P9331033123.
  8. 1 2 3 Smith, N. A.; Boessenecker, R.; Long, D.; Powell, C. "A new marine vertebrate assemblage from the Wilson Grove Formation at Bloomfield Quarry (late Miocene), Sonoma County, California". Journal of Vertebrate Paleontology, Programs and Abstracts 2017, 37:195.
  9. ↑ Morales, D.; Kloess, P.A.; Parham, J.F. (2015). "On the abundance of flightless auks from the middle Miocene to early Pliocene" (PDF). PaleoBios. 23 (1).
  10. ↑ Tanaka, Y.; Furusawa, H.; Barnes, L. G. (2018). "Fossil Herpetocetine Baleen Whales (Cetacea, Mysticeti, Cetotheriidae) from the Lower Pliocene Horokaoshirarika Formation at Numata, Hokkaido, Northern Japan". Paleontological Research. 22 (4): 295–306. doi:10.2517/2017pr025. S2CID 134686678.
  11. ↑ Boessenecker, R.W.; Poust, A.W. (2015). "Freshwater occurrence of the extinct dolphin Parapontoporia (Cetacea: Lipotidae) from the upper Pliocene nonmarine Tulare Formation of California". Palaeontology. 58 (3): 489–496. doi:10.1111/pala.12153. S2CID 128980362.
  12. 1 2 Biewer, Jacob N.; Velez-Juarbe, Jorge; Parham, James F. (2020-12-01). "Insights on the Dental Evolution of Walruses Based on New Fossil Specimens from California". Journal of Vertebrate Paleontology. 40 (5): e1833896. doi:10.1080/02724634.2020.1833896. ISSN 0272-4634. S2CID 228814992.
  13. ↑ Magallanes, I.; Parham, J.F.; Santos, G.; Velez-Juarbe, J. (2018). "A new tuskless walrus from the Miocene of Orange County, California, with comments on the diversity and taxonomy of odobenids". PeerJ. 6: e5708. doi:10.7717/peerj.5708. PMC 6188011. PMID 30345169. S2CID 53020427.
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