A pollen study of a late Quaternary peat bog, south-central Adirondack Mountains, New York

Abstract

A series of cores from a 7-ha glacial kettle, 600 m above sea level, provides information on the development of a Sphagnum peat bog and the late Quaternary vegetation and climate history of the south-central Adirondack Mountains, New York. Within the kettle, stratified drift that dates to about 11,000 yr B.P. is overlain by varved glacial-lake sediment, gyttja, and peat. The fossil pollen samples at Brandreth Bog were compared with 1,618 modern pollen samples using squared chord distance. The degree of similarity between fossil and modern pollen samples was calibrated using comparisons among modern samples from different vegetation regions. Modern pollen analogs were identified for all of the fossil samples at Brandreth Bog, and the vegetation and climate associated with these modern analogs were used to interpret the vegetation and climate history near the site. The numerically derived pollen assemblage zones at Brandreth Bog are broadly similar to those for other sites in the region. A forest similar to the current boreal forest succeeded treeless vegetation and spruce woodland around Brandreth Bog before about 10,200 yr B.P. A pine-dominated forest was present by 9,600 yr B.P. Continued warming of the climate allowed a hemlock-rich mixed conifer-hardwood forest to grow around Brandreth Bog after 7,000 yr B.P., and spruce and fir became less plentiful. After a sharp decline in the amount of hemlock around Brandreth Bog at 4,700 yr B.P., birch, maple, beech, and pine became the primary forest constituents. Spruce and fir trees increased in number near Brandreth Bog after 4,000 yr B.P., a development indicative of a reversal of the general warming trend that typified the early Holocene. By 2,000 yr B.P., a bog mat had closed over the lake basin. A rise in the abundance of ragweed pollen about 125 yr B.P. reflected European settlement, probably to the south. Correlation among five cores at the study site provided evidence of sediment focusing in the former lake basin.