A HIGH RESOLUTION SEDIMENT RECORD OF THE LAST ~11,240 ¹⁴C YR FROM A LAMINATED LAKE CORE FROM BALLSTON LAKE, EASTERN NEW YORK STATE

Ballston Lake, located in eastern New York State (~42°55’N; 73°52’W), is long (~5 km), narrow (<0.5 km) and eutrophic, and occupies an avulsed reach of the Mohawk River. The Lake formed at the onset of the Younger Dryas (~11,000 14C yr BP) and most of the lake is <15 m deep, however, the southernmost end of the lake reaches depths of >30 m. This southern basin is meromictic and permanently anoxic below 18 meters; all other parts of the lake are dimictic and are only anoxic for part of the year. The anoxic state of the South Basin enables preservation of organic matter and millimeter-thick annual varves. Cores from northern and central parts of the lake are not laminated and terminate in sand and gravel deposited in the paleo-Mohawk river bed.

In February 2002, we retrieved an ~15.5 meter-long core from the deep southern basin. The varved sections of Holocene mud are sporadically interspersed with massive sediment layers between 4 and 30 cm thick, which may reflect intervals of increased frequency of climatically-driven turnover events, or slumping of organic-rich mud from shallow water zones into the deep basin. Eight AMS radiocarbon analyses have been performed on macrovegetal material in the core. The base of the core dates to ~11,240 ± 40 14C yr BP (~13,200 calendar ybp). Sedimentation rates begin low (~2.9 cm 100yr-1) in the early Holocene and increase rather steadily to ~13..2 cm 100yr-1 in the late Holocene and are currently at ~40.1 cm 100yr-1. High-resolution measurement of organic carbon content and flux reveals a first order trend of increasing organic carbon levels from the late glacial (<0.0037 g cm-2) to the early Holocene (~.0045 g cm-2), a near constant early to mid-Holocene organic carbon flux of ~.0038-.0070 g cm-2, and a sharp increase in organic carbon over the last two centuries due to European settlement to ~.067 g cm-2. Ballston Lake is responding to climatic change and drainage basin changes as humans occupy the surrounding area.