Coldwater Beds
| Coldwater Beds | |
|---|---|
| Stratigraphic range: Ypresian (Wasatchian) ~ | |
| Type | Formation |
| Thickness | 230 m (750 ft) |
| Lithology | |
| Primary | Mudstone |
| Other | Shale, tuff |
| Location | |
| Coordinates | 50°06′N 120°30′W / 50.1°N 120.5°W |
| Approximate paleocoordinates | 54°48′N 103°30′W / 54.8°N 103.5°W |
| Region | British Columbia |
| Country |  Canada |
| Extent | Okanagan Highlands |
| Type section | |
| Named for | Coldwater River |
| Named by | Dawson |
| Year defined | 1895 |
  Coldwater Beds (Canada)  Coldwater Beds (British Columbia) | |
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]
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
_MAT_and_(b)_MAP_estimates.png)
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
- 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
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
- ^ a b c Coldwater Beds at Fossilworks.org
- ^ Quilchena at Fossilworks.org
- ^ Pearson & Obradovich, 1977, p.9
- ^ Tribe, 2004, p.41
- ^ Tribe, 2004, p.67
- ^ Tribe, 2004, p.112
- ^ West et al., 2020, p.1387
- ^ Mathewes, 2015, p.2
- ^ a b c Handlirsch, 1910
- ^ 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 Archibald & Mathewes, 2000
- ^ a b Rice, 1959
- ^ Archibald et al., 2014
- ^ Pulawski et al., 2000
- ^ Engel & Archibald, 2003
- ^ a b c Archibald et al., 2018
- ^ a b Archibald et al., 2013
- ^ a b Archibald & Makarkin, 2006
- ^ Makarkin & Archibald, 2003
- ^ Makarkin et al., 2003
- ^ a b Greenwood et al., 2015, p.19
- ^ Manchester, 1992
- ^ Greenwood et al., 2015, p.15
- ^ West et al., 2020, p.1390
- ^ West et al., 2020, p.1391
- ^ Greenwood et al., 2015, p.18
- ^ Pearson & Obradovich, 1977, p.10