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Canadian Pleistocene fossils

23 December 2015
Geology

I'm not sure if this was sent in by somebody at the contact email address or I picked it up when reading something at a web site but at www.thecanadianencyclopedia.ca/en/article/quaternary-vertebrate-fossils/ … we have a wonderful resource as this concerns the Pleistocene fauna of North America. The Canadian Shield is virtually fossil free – even geology free as it has been wiped clean of everything down to the Pre-Cambrian base as a result of the ice sheet during the Late Glacial Maximum, and outwash as a result of meltwaters. Does such a clean sheet require rapid breakdown of the ice sheet?

In spite of that Canada still has a remarkable number of fossil assemblages – beyond the Shield. In the Yukon fossils are common, especially in the mountains. In fact, fossils abound in British Columbia and the praire provinces – where meltwaters have played a role in shaping the modern landscape. About three quarters of Pleistocene animals found in the Yukon had a connection with Asia, across the Bering Straits, and just a quarter with N America south of Canada. Woolly mammoth, mastodon, horse and steppe bison became extinct towards the end of the Pleistocene – exacerbated by climate change (it says). In a Catastrophic model climate change in this instance would equate with an upheaval in nature in which the Yukon became cold and the Shield was rinsed clean. The Yukon has also preserved traces of human activity (artifacts made of stone and bone) at Bluefish Cave, Old Crow and excavations near Dawson city. At Old Crow Basin 50,000 specimens representing 60 mammal species has been dug out of the sediments and range in age from 1.4 million years ago to just 12,000 years ago. Old Crow Basin includes the remains from an interglacial episode which has been dated 1.4 million years but at 180,000 years ago there are fish, birds, shrew, beavers, rabbits, the weasel, wolf, fox, as well as the mammoth, bison, caribou and horse. At 130,000 years ago there are fish, birds and 31 mammal species (many of them being sub aquatic creatures suggesting  marshy environment with nearby ponds. And so on.

Placer mining for gold at Dawson City revealed Ice Age fossils (from 20,000 to 15,000 years ago). At Nuggest Guch a volcanic ash layer covered an original grassy surface on which lay indirect human evidence dating back 30,000 years. At Sixty Mile on the Alaskan border placer mining for gold revealed hundreds of specimens dated between 50,000 and 25,000 years ago – including grizzly bear, woolly mammoth, horse, camel, caribou, steppe bison, musk ox and wild sheep etc.

At Charlie Lake Cave in British Columbia, near Fort St John, late glacial fossils were found dated 10,500 to 9000 years ago. The site was visited by people with stone and bone tools – some of which were left behind.

Caves on Vancouver Island, sometimes located at raised cliff locations, have also turned up lots of fossils – fish, birds, animals, dated beween 18 to 16,000 years ago. The assemblage indicates an open environment, possibly a bit cooler than in modern times, but not glacial.

Caves in Alberta, on the praire side of the mountains, turned up fossils from a dry climate between 33 and 23,000 years ago, while in eastern Canada, in the northern part of the Appalachian chain of mountains, sediments on cave floors have included fossils from the early Holocene (between 10,000 and 8,000 years ago).

However, many important Ice Age assemblages actually lie within the flood sedimentary zone – usually described as glacial during the Late Glacial Maximum (LGM). In southern Alberta thick sequences of glacial and interglacial deposits exist, dating from 1 million years to the Holocene, exposed in bluffs along the South Saskatchewan River. Gravel pits near Edmonton have dredged up lots of Pleistocene mammal remains. This was a steppe environment over a long period of time. The encyclopedia then adds, there was a break in the sequence between 20,000 and 11,000 years ago, for whatever reason, which they attribute to the LGM phase. However, the LGM came into existence after 30,000 years ago and culminated in the Oldest Dryas episode, 18,000 to 15,000 years ago – so the facts do not fit the excuse. This is a perfect point in time for a C14 plateau event as we know one existed during the Younger Dryas episode. The gap actually exists at the end of the LGM rather than contemporary with LGM. At Wally's Beach in Alberta there are human made bone and stone tools together with an assemblage of mammal remains, varied, and the preserved tracks in sediments of mammoth, bison, horse, camel and caribou etc. In Saskatchewan there are Early Pleistocene fossil deposits from 1.7 million years ago includes what is described as a bone-eating dog. What was that as dogs are supposed to have evolved after 33,000 years ago.

A quarry near Winnepeg in Manitoba possessed evidence of fauna from a steppe like environment indicating the steppe (praire) existed from Edmonton in Alberta, across Saskatchewan into Manitoba – during the Ice Age era (around 40,000 years ago).

At Toronto remains of fish and mammals such as groundhogs, bears, and deer are dated to the last interglacial when temperatures were 3 degrees warmer than in modern Toronto (or that is how the Eemian is perceived as a worldwide phenomenon). Other interglacial cave sites exist in Ontario – which is surprising as it was supposed to have been buried under a mile of ice during the LGM.

The lowlands of Quebec and Ontario were covered by a watery extension of the Atlantic Ocean between 12,— and 9400 years ago, it is claimed. One reason is that ice had melted after the LGM ended but this part of N America had not as yet bounced back from the weight of ice – but gradually rose so that by the early Holocene the ocean had receded. There is no reason to doubt this version of events but the hypothesis is used to account for the fossils found in the region during the latter stages of the Younger Dryas event. Whales, seals, walrus fossils are found and the idea they could have been washed up in a tidal wave isn't actually a consideration – or is not mentioned. At St Nicholas in Quebec sand formations said to be tidal in origin, also dating from the late glacial era, 10,000 to 8500 years ago, includes lots of marine fossils such as fish, seabirds, and marine mammals such as seals and whales etc. Some 400 C14 dated whales remains have been catalogued in raised beach locations.

A history of sea ice levels in Canadian Arctic waters and the islands during the Holocene have show that sea ice restricted the movement of whales between 8500 to 5000 years ago (between 6500 and 3000BC). Summers during this period were colder than the historical period as from 5000 to 3000 years ago temperatures seem to have been warmer on the whole in the Canadian Arctic – suggesting warmer summers than today (the Bronze Age in the ancient near east). From 3000 years ago to the present se aice again presented whales with a challenge over large parts of the Arctic Ocean and this is still the case nowadays.

All in all a revealing article but what to make of it – that is the leading question.

 

 

 

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