Paper No. 31-5
Presentation Time: 9:20 AM
PALEOBOTANICAL RECORD OF SANGAMONIAN INTERGLACIAL DEPOSITS FROM EASTERN NORTH AMERICA – INSIGHTS FOR THE 21ST CENTURY
Conditions at least as warm as today are recorded by pollen and plant macrofossils from a relatively small number of pre-Wisconsinan deposits in eastern North America. Recent re-investigation of pollen and plant macrofossils in the Don Formation confirms the interglacial character of these sediments (McCarthy and McAndrews, 2016), thought to represent sedimentation from MIS5e – 5c by comparison with the well-constrained record from the Ziegler Reservoir fossil site, central Colorado (Anderson et al. 2014). Common seeds of wetland and aquatic herbs in the Don Fm. (e.g., sedges, grasses, cattails) record accumulation in a shallow lake or floodplain environment. The lower 2 m of the Don beds exposed in the Brickworks section of Toronto correlate with strata assigned to the Sangamonian at the Sanford Mine and Fernbank sites in New York (Muller et al., 1993; Karrow et al., 2009) and the Smith Farm section in Indiana (Kapp and Gooding, 1964). The paleobotanical record does not, however, record conditions markedly warmer than today, with pollen-derived transfer functions reconstructing mean annual temperature ca. 1.5oC warmer than today in the lower 2 m of the Brickworks section cooling up-section to 3.5oC cooler than today. Similarly, pollen assemblages in the Pym beds and Albany River section of the James Bay Lowlands record a Sphagnum wetland with spruce and boreal woodland hardwoods, much like the modern “muskeg”vegetation. Algal palynomorphs (dinoflagellate cysts and green algal colonies) in the Pym beds, thought to be equivalent to the Missinaibi Fm., record deposition in a mesotrophic – eutrophic lake bordered by a fringing Sphagnum wetland, although marine dinoflagellate cysts record marine incursion in some samples during the MIS 5e highstand. This suggests that even slightly warmer conditions, such as those projected for AD 2050 by most climate models (IPCC, 2014) could negatively impact the quality of the abundant freshwater resources in Canada.