Abstract:
This study has three purposes: to establish a chronologically
controlled vegetational history for a number of sites
in south Southwestern Ontario; to utilize the resulting data
to support and/or add to the current understanding of Quaternary
geology and stratigraphy, and the glacial and postglacial
history of the Great Lakes in south Southwestern Ontario; and
to attempt to propose a possible explanation for the extinction
of the mastodon in Southern Ontario.
Palynological and geochronological analyses were conducted
on material collected from eleven sites (east to west):
Verbeke Mastodon Site, Woloshko Mastodon Site, Walker Pond II,
Pond Mills I, Lake Hunger Bog, Bouckaert Site. Mabee Site,
Cornell Bog. Colles Lake I, Folden Mastodon Site and Forest
Pond. Individual geochronologically controlled (where possible)
vegetational histories were reconstructed for each of the sites
investigated.
The results of the individual studies, when considered in
overview. indicated the existance of an established closed
boreal forest throughout south Southwestern Ontario by 10,000
years B.P. This evidence for a significant climatic change
coincident throughout south Southwestern Ontario supports the
proposed age of 10,000 years B.P. for the Pleistocene/Holocene
Boundary (Terasmae, 1972).
Remnant patches of 'open spruce parkland' persisted in
small local 'wet' areas. It was in these areas that the mastodon
was restricted during early Holocene time. With continued
encroachment by the surrounding boreal forest, possibly speeded up by this browser's destructive feeding habits, the spruce
enclaves shrank and the mastodon became extinct in south
Southwestern Ontario.
The results of this thesis basically support Dreimanis'
(1967, 1968) proposed 'Environmental-Climatic' theory for
mastodon extinction.
It is suggested that increased dryness during the present
interglacial compared to the climate of earlier interglacials
may be the key to unravelling the problem of mastodon extinction
in eastern North America.
