Margaret Formation | |
---|---|
Stratigraphic range: Wasatchian | |
Type | Formation |
Unit of | Eureka Sound Group |
Overlies | Mount Moore Formation |
Thickness | 140 m (460 ft) |
Lithology | |
Primary | Sandstone |
Other | Siltstone, coal, tuff |
Location | |
Coordinates | 78°42′N81°54′W / 78.7°N 81.9°W |
Approximate paleocoordinates | 76°06′N30°42′W / 76.1°N 30.7°W |
Region | Ellesmere Island, Northwest Territories, Nunavut |
Country | Canada |
Extent | Sverdrup Basin |
The Margaret Formation is a geologic formation of the Eureka Sound Group in the Sverdrup Basin in Northwest Territories and Nunavut, Canada. The unit belonging to the Eureka Sound Group which crops out at Ellesmere Island preserves fossils dating back to the Early Eocene period, or Wasatchian in the NALMA classification. [1]
The Margaret Formation comprises sandstones, sandy siltstones, clay-rich sandstones, coal seams and clay-rich coal seams and volcanic ash beds. The thickness of the formation, which overlies the Mount Moore Formation, reaches about 140 metres (460 ft). Radiometric dating of the formation provided ages of 52.6 ± 1.9 Ma (2010) and 53.7 ± 0.6 Ma (2017).
The area where the formation was deposited in the Early Eocene experienced a much warmer climate than the High Arctic today, with mean annual temperatures ranging from 7.6 to 12.9 °C (45.7 to 55.2 °F) and warmest month mean temperatures from 18.2 to 22.2 °C (64.8 to 72.0 °F). The deltaic to swamp environment of the Margaret Formation has provided a diverse fauna of various groups of mammals, birds ( Presbyornis and Gastornis ), reptiles (turtles, snakes, lizards and crocodiles) and fish.
The Margaret Formation comprises sandstones, sandy siltstones, clay-rich sandstones, coal seams and clay-rich coal seams and volcanic ash beds. The thickness of the formation, which overlies the Mount Moore Formation, reaches about 140 metres (460 ft). [2]
The formation was probably deposited in a lush proximal delta front to delta plain environment, with abundant channels and coal swamps. [3]
A volcanic ash layer containing crandallite in the middle of the formation was dated using U-Pb radiometric dating in 2017 to 53.7 ± 0.6 Ma. [2] In 2010, ashes of the formation were dated to 52.6 ± 1.9 Ma. [4]
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. [5]
Ensemble estimates of mean annual temperatures for the high-latitude fossil localities in Arctic Canada ranged from 7.6 to 12.9 °C (45.7 to 55.2 °F), with the range of coldest month mean temperature from 1.3 to 4.2 °C (34.3 to 39.6 °F) and warmest month mean temperatures from 18.2 to 22.2 °C (64.8 to 72.0 °F). Mean annual precipitation estimates for the Margaret Formation ranged between 131 and 180 centimetres (52 and 71 in). [6] The mean summer precipitation has been estimated at 1,134 millimetres (44.6 in) and mean winter precipitation at 366 millimetres (14.4 in). [7]
The fossils and sedimentology indicate a lush, rain forest community on a coastal delta plain. Multiple palaeoclimate proxies, ranging from oxygen isotope analysis of vertebrate bones and teeth to palaeofloral analyses, estimate a mild temperate climate for the Eocene High Arctic, where winters remained at or just above freezing and summer temperatures extended to 20 °C (68 °F) or higher. These temperatures are a far cry from today's High Arctic, where central Ellesmere Island experiences a mean annual temperature of −19 °C (−2 °F), a warm month mean temperature of about 6 °C (43 °F) and a cold month mean temperature of −38 °C (−36 °F) or colder. [8]
Despite the mild Eocene Arctic climate, the vertebrate fauna would have experienced months of total darkness and cooler temperatures during the winter. Recent isotopic work suggests that some mammals, including the hippo-like Coryphodon , were year-round residents in the High Arctic. Given that Gastornis was large (approaching 2 metres (6.6 ft)) and flightless, it likely also was a year-round resident of the Arctic. In contrast, the volant Presbyornis might have been a seasonal migrant to the Arctic. [8]
The formation has provided the following fossils: [1]
The formation has been correlated with the Allenby Formation and Kamloops Group of British Columbia, the Chickaloon Formation of Alaska, [24] and with the Wishbone, Chuckanut and Iceberg Bay Formations. [25] The upper Margaret Formation also has been correlated with the Buchanan Lake Formation of the Eastern Arctic Archipelago. [26]
Formation | Wasatch | DeBeque | Claron | Indian Meadows | Pass Peak | Tatman | Willwood | Golden Valley | Coldwater | Allenby | Kamloops | Ootsa Lake | Margaret | Nanjemoy | Hatchetigbee | Tetas de Cabra | Hannold Hill | Coalmont | Cuchara | Galisteo | San Jose | Ypresian (IUCS) • Itaboraian (SALMA) Bumbanian (ALMA) • Mangaorapan (NZ) |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Basin | Powder River Uinta Piceance Colorado Plateau Wind River Green River Bighorn | Piceance | Colorado Plateau | Wind River | Green River | Bighorn | Williston | Okanagan | Princeton | Buck Creek | Nechako | Sverdrup | Potomac | GoM | Laguna Salada | Rio Grande | North Park | Raton | Galisteo | San Juan | ||
Country | United States | Canada | United States | Mexico | United States | |||||||||||||||||
Copelemur | ||||||||||||||||||||||
Coryphodon | ||||||||||||||||||||||
Diacodexis | ||||||||||||||||||||||
Homogalax | ||||||||||||||||||||||
Oxyaena | ||||||||||||||||||||||
Paramys | ||||||||||||||||||||||
Primates | ||||||||||||||||||||||
Birds | ||||||||||||||||||||||
Reptiles | ||||||||||||||||||||||
Fish | ||||||||||||||||||||||
Insects | ||||||||||||||||||||||
Flora | ||||||||||||||||||||||
Environments | Alluvial-fluvio-lacustrine | Fluvial | Fluvial | Fluvio-lacustrine | Fluvial | Lacustrine | Fluvio-lacustrine | Deltaic-paludal | Shallow marine | Fluvial | Shallow marine | Fluvial | Fluvial | |||||||||
Volcanic | Yes | No | Yes | No | Yes | No | Yes | No | Yes | No | ||||||||||||
Ellesmere Island is Canada's northernmost and third largest island, and the tenth largest in the world. It comprises an area of 196,236 km2 (75,767 sq mi), slightly smaller than Great Britain, and the total length of the island is 830 km (520 mi).
Eureka is a small research base on Fosheim Peninsula, Ellesmere Island, Qikiqtaaluk Region, in the Canadian territory of Nunavut. It is located on the north side of Slidre Fiord, which enters Eureka Sound farther west. It is the third-northernmost permanent research community in the world. The only two farther north are Alert, which is also on Ellesmere Island, and Nord, in Greenland. Eureka has the lowest average annual temperature and the lowest amount of precipitation of any weather station in Canada.
Mary R. Dawson was a vertebrate paleontologist and curator emeritus at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania.
Presbyornis is an extinct genus of presbyornithid bird from North America during the Paleogene period, between the Late Paleocene and Early Eocene.
Coryphodon is an extinct genus of pantodonts of the family Coryphodontidae.
Pachyaena was a genus of heavily built, relatively short-legged mesonychids, early Cenozoic mammals that evolved before the origin of either modern hoofed animals or carnivores, and combined characteristics similar to both. The genus likely originated from Asia and spread to Europe, and from there to North America across a land bridge in what is now the North Atlantic ocean. Various described species of Pachyaena ranged in size from a coyote to a bear. However, recent work indicates that Pachyaena is paraphyletic, with P. ossifraga being closer to Synoplotherium, Harpagolestes and Mesonyx than to P. gigantea.
Strathcona Fiord is a fiord on the west central coast of Ellesmere Island, the most northern island within the Arctic Archipelago, Nunavut, Canada.
Tapirus merriami, commonly called Merriam's tapir, is an extinct species of tapir which inhabited North America during the Pleistocene.
The Hannold Hill Formation is an Early Eocene (Wasatchian) geologic unit in the western United States. It preserves the fossilized remains of the ray Myliobatis and gar.
The Wasatch Formation (Tw) is an extensive highly fossiliferous geologic formation stretching across several basins in Idaho, Montana, Wyoming, Utah and western Colorado. It preserves fossils dating back to the Early Eocene period. The formation defines the Wasatchian or Lostcabinian, a period of time used within the NALMA classification, but the formation ranges in age from the Clarkforkian to Bridgerian.
The Indian Meadows Formation is a Wasatchian geologic formation in Wyoming. It preserves fossils dating back to the Ypresian stage of the Eocene period.
The Galisteo Formation is a geologic formation in New Mexico. It contains fossils characteristic of the Bartonian stage of the Eocene epoch, Duchesnean in the NALMA classification.
The San Jose Formation is an Early Eocene geologic formation in the San Juan Basin of New Mexico and Colorado.
The Mint Canyon Formation (Tm) is a Miocene geologic formation in the Sierra Pelona Mountains of Los Angeles County, southern California. The formation preserves fossils dating back to the Middle to Late Miocene.
The Eureka Sound Formation is a geologic formation found in the Canadian Territory of Nunavut on Ellesmere Island, which is part of the Canadian Arctic Archipelago. The Eureka Sound Formation is Tertiary in age.
The Coldwater Beds are a geologic formation of the Okanagan Highlands in British Columbia, Canada. They preserve fossils dating back to the Ypresian stage of the Eocene period, or Wasatchian in the NALMA classification.
The Argiles d'lignite du Soissonnais is a geologic formation in the Oise department of northern France. The formation has provided fossil mammals, reptiles and fish as well as arthropods in the amber of the formation. The Argiles d'lignite du Soissonnais dates back to the Ypresian stage of the Eocene period.
Ignacius is a genus of extinct mammal from the early Cenozoic era. This genus is present in the fossil record from around 62-33 Ma. The earliest known specimens of Ignacius come from the Torrejonian of the Fort Union Formation, Wyoming and the most recent known specimens from Ellesmere Island in northern Canada. Ignacius is one of ten genera within the family Paromomyidae, the longest living family of any plesiadapiforms, persisting for around 30 Ma during the Paleocene and Eocene epochs. The analyses of postcranial fossils by paleontologists suggest that members of the family Paromomyidae, including the genus Ignacius, most likely possessed adaptations for arboreality.
Comptonia columbiana is an extinct species of sweet fern in the flowering plant family Myricaceae. The species is known from fossil leaves found in the early Eocene deposits of central to southern British Columbia, Canada, plus northern Washington state, United States, and, tentatively, the late Eocene of Southern Idaho and Earliest Oligocene of Oregon, United States.
Equisetum similkamense is an extinct horsetail species in the family Equisetaceae described from a group of whole plant fossils including rhizomes, stems, and leaves. The species is known from Ypresian sediments exposed in British Columbia, Canada. It is one of several extinct species placed in the living genus Equisetum.