Coldwater Beds

The Coldwater Beds is a geologic formation of the Okanagan Highlands in British Columbia, Canada. It preserves fossils dating back to the Ypresian stage of the Eocene period, or Wasatchian in the NALMA classification.[1]

Not to be confused with Coldwater Sandstone.
Coldwater Beds
Stratigraphic range: Ypresian (Wasatchian)
~51.9–51.1 Ma
↓
TypeFormation
Thickness230 m (750 ft)
Lithology
PrimaryMudstone
OtherShale, tuff
Location
Coordinates50.1°N 120.5°W / 50.1; -120.5
Approximate paleocoordinates54.8°N 103.5°W / 54.8; -103.5
RegionBritish Columbia
Country Canada
ExtentOkanagan Highlands
Type section
Named forColdwater River
Named byDawson
Year defined1895
Coldwater Beds (Canada)
Coldwater Beds (British Columbia)

The formation comprises mudstones, shales and tuff deposited in a lacustrine environment and has provided many insect fossils, as well as indeterminate birds and fossil flora assigned to Florissantia quilchenensis, named after Quilchena, the fossil locality where the fossils have been found.[2]

Description

The Coldwater Beds were defined by Dawson in 1895 based on a section along the Coldwater River in the Okanagan Highlands.[3] The formation reaches a thickness of 230 metres (750 ft),[4][5][6] and comprises mudstones, shales and tuff deposited in a lacustrine environment. U-Pb dating of thick tephra, combined with Ar-Ar dates of sanidine from same bed provided an Early Eocene age. The tephra was deposited within insect-bearing shales.[1]

Climate
Early Eocene proxy ensemble data from fossil localities showing (a) MAT and (b) MAP estimates with the Coldwater Beds indicated with (2)

During the Early Eocene, the climate of much of northern North America was warm and wet, with mean annual temperatures (MAT) as high as 20 °C (68 °F), mean annual precipitation (MAP) of 100 to 150 centimetres (39 to 59 in), mild frost-free winters (coldest month mean temperature >5 °C (41 °F)), and climatic conditions that supported extensive temperate forest ecosystems.[7]

The Quilchena fossil locality is dated to 51.5 ± 0.4 Ma corresponding to the Early Eocene Climatic Optimum (EECO), and is reconstructed as the warmest and wettest of the Early Eocene upland sites from the Okanagan Highlands of British Columbia and northern Washington State. Mean annual temperature (MAT) is estimated from leaf margin analysis as 16.2 ± 2.1 °C (61.2 ± 3.8 °F) and 14.6 ± 4.8 °C (58.3 ± 8.6 °F). Using bioclimatic analysis of 45 nearest living relatives, a moist mesothermal climate is indicated (MAT 12.7 to 16.6 °C (54.9 to 61.9 °F); cold month mean temperature (CMMT) 3.5 to 7.9 °C (38.3 to 46.2 °F) and mean annual precipitation (MAP) of 103 to 157 centimetres (41 to 62 in)/yr. Leaf size analysis estimates MAP at 121 ± 39 centimetres (48 ± 15 in)/y.[8]

Fossil content

A wide variety of fossils occur in the formation, including abundant fish remains, insects, and plants, and rare occurrences of molluscs, ostracods, and birds:[1]

Birds

Insects
Blattaria
  • Diplopterinae indet.[10]
Coleoptera
Dermaptera
Diptera
Hemiptera
Hymenoptera
Mecoptera
Neuroptera
Orthoptera
Trichoptera

Flora

Fossil plants were first reported from the Coldwater Beds at the Quilchena site and nearby by Penhallow (1908).[20]

Correlations
Correlation of the Coldwater Beds with other Early Eocene formations in northern North America

The formation has been correlated with the Allenby Formation and Kamloops Group of British Columbia, the Margaret Formation of Ellesmere Island, Nunavut, the Chickaloon Formation of Alaska,[23] and with the Wishbone, Chuckanut and Iceberg Bay Formations.[24] The flora of the Coldwater Beds has been correlated to the Chu Chua Formation of eastern Canada.[25] The formation also correlates with the Springbrook, Kettle River and O'Brien Creek Formations in Washington, United States.[26]

See also

References
  1. Coldwater Beds at Fossilworks.org
  2. Quilchena at Fossilworks.org
  3. Pearson & Obradovich, 1977, p.9
  4. Tribe, 2004, p.41
  5. Tribe, 2004, p.67
  6. Tribe, 2004, p.112
  7. West et al., 2020, p.1387
  8. Mathewes, 2015, p.2
  9. Handlirsch, 1910
  10. Archibald & Mathewes, 2000
  11. Rice, 1959
  12. Archibald et al., 2014
  13. Pulawski et al., 2000
  14. Engel & Archibald, 2003
  15. Archibald et al., 2018
  16. Archibald et al., 2013
  17. Archibald & Makarkin, 2006
  18. Makarkin & Archibald, 2003
  19. Makarkin et al., 2003
  20. Greenwood et al., 2015, p.19
  21. Manchester, 1992
  22. Greenwood et al., 2015, p.15
  23. West et al., 2020, p.1390
  24. West et al., 2020, p.1391
  25. Greenwood et al., 2015, p.18
  26. Pearson & Obradovich, 1977, p.10

Bibliography
  • West, Christopher K.; David R. Greenwood; Tammo Reichgelt; Alexander J. Lowe; Janelle M. Vachon, and James F. Basinger. 2020. Paleobotanical proxies for early Eocene climates and ecosystems in northern North America from middle to high latitudes. Climate of the Past 16. 1387–1410. Accessed 2020-09-05.
  • Archibald, S. B.; A. P. Rasnitsyn; D. J. Brothers, and R. W. Mathewes. 2018. Modernisation of the Hymenoptera: ants, bees, wasps, and sawflies of the early Eocene Okanagan Highlands of western North America. The Canadian Entomologist 150. 250–257.
  • Greenwood, David R.; Kathleen B. Pigg; James F. Basinger, and Melanie L. DeVore. 2015. A review of paleobotanical studies of the Early Eocene Okanagan Highlands floras of British Columbia, Canada and Washington, USA. Canadian Journal of Earth Sciences . 1–70.
  • Archibald, S. B.; C. Kehlmaier, and R. W. Mathewes. 2014. Early Eocene big headed flies (Diptera: Pipunculidae) from the Okanagan Highlands, western North America. The Canadian Entomologist 146. 429–443.
  • Archibald, S. B.; R. W. Mathewes, and D. R. Greenwood. 2013. The Eocene apex of panorpoid scorpionfly family diversity. Journal of Paleontology 87. 677–695.
  • Archibald, S. B., and V. N. Makarkin. 2006. Tertiary Giant Lacewings (Neuroptera: Polystoechotidae): revision and description of new taxa from Western North America and Denmark. Journal of Systematic Palaeontology 4. 119–155.
  • Tribe, Selina. 2004. Cenozoic Drainage History of Southern British Columbia - PhD thesis, 1–147. Simon Fraser University.
  • Engel, M. S., and S. B. Archibald. 2003. An Early Eocene bee (Hymenoptera: Halictidae) from Quilchena, British Columbia. The Canadian Entomologist 135. 63–69.
  • Makarkin, V. N., and S. B. Archibald. 2003. Family affinity of the genus Palaeopsychops Andersen with description of a new species from the Early Eocene of British Columbia, Canada (Neuroptera: Polystoechotidae). Annals of the Entomological Society of America 96. 171–180.
  • Makarkin, V. N.; S. B. Archibald, and J. D. Oswald. 2003. New Early Eocene brown lacewings (Neuroptera: Hemerobiidae) from western North America. The Canadian Entomologist 135. 637–653.
  • Archibald, S. B., and R. W. Mathewes. 2000. Early Eocene insects from Quilchena, British Columbia, and their paleoclimatic implications. Canadian Journal of Zoology 78. 1441–1462.
  • Pulawski, W. J.; A. P. Rasnitsyn; D. J. Brothers, and S. B. Archibald. 2000. New genera of Angarosphecinae: Cretosphecium from Early Cretaceous of Mongolia and Eosphecium from Early Eocene of Canada (Hymenoptera: Sphecidae). Journal of Hymenoptera Research 9. 34–40.
  • Manchester, S. R. 1992. Flowers, fruits, and pollen of Florissantia, an extinct Malvalean genus from the Eocene and Oligocene of western North America. American Journal of Botany 79. 996–1008.
  • Pearson, R. C., and D. Obradovich. 1977. Eocene Rocks in Northeast Washington- Radiometric Ages and Correlation. United States Geological Survey Bulletin 1433. 1–41.
  • Rice, H. M. A. 1959. Fossil Bibionidae (Diptera) from British Columbia. Geological Survey of Canada Bulletin 55. 1–36.
  • Handlirsch, A. 1910. Canadian fossil Insects. 5. Insects from the Tertiary lake deposits of the southern interior of British Columbia, collected by Mr. Lawrence M. Lambe. Contributions to Canadian Palaeontology 2. 93–129.
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.