INITIAL PALYNOLOGICAL AND PALEOMAGNETIC RESULTS FROM GLACIAL VARVES FROM LAKE SUPERIOR

We have succeeded in separating pollen from samples of red and grey glacial varves from a core from Lake Superior. We find that the pollen grains are well-preserved and that the pollen concentration is three to four times higher in the summer (red) layers compared to the winter (grey) layers. The winter layers show a detectably higher ratio of grass pollen to conifer pollen than the summer layers, and there is also evidence for upcore climatic amelioration. Overall, the pollen record suggests a warmer, more temperate climate than has been found in contemporaneous deposits from large European glacial lakes. We also examined the paleomagnetic and environmental magnetic properties of the cores using u-channels. The sediments appear to carry a stable magnetic remanence which suggests that it should be possible to date them using a master curve of geomagnetic paleosecular variation. In addition, there are variations in environmental magnetic parameters that probably reflect changes in both paleoclimatic conditions and sedimentologic regime. For example, magnetic hardness indicates that the magnetic mineralogy is quite uniform. On the other hand, there are significant fluctuations in both magnetic grain size and magnetic concentration although there appears to be an overall decrease in concentration upcore. Thus, a combination of pollen and magnetic studies should provide new insights into the paleoenvironmental history of Lake Superior.