Macrofossils from a Late-Glacial Deposit at Cambridge, Massachusetts

Macrofossils were isolated from late-glacial sediments exposed in open section in a building excavation at Cambridge, Massachusetts. The lower portion of the profile contained leaves of three species of herbaceous plant species now generally found in arctic or alpine regions, and fragments of a water beetle belonging to a species that now occurs characteristically in regions of boreal forest. The upper portion of the profile contained spruce needles, spruce wood and a spruce cone, and seeds and leaf fragments representing four species of water plants. Correlation by means of pollen analysis indicates' that the sediments may have been deposited between about 10,000 and 13,000 years ago. The occurrence of arctic-alpine species in the lower portion of the profile indicates that areas suitable for the survival of these species existed both beyond the margin of the Wisconsin ice sheet at the time of its maximum advance, and in Massachusetts at a time of glacial retreat.