FAYETTEVILLE GREEN LAKE (NY) MID-HOLOCENE LOWSTAND CORRELATIVE TO GREAT LAKES' LOWSTAND?

Fayetteville Green Lake, NY, has long been known as a unique lake that contains a high-resolution package of Holocene sediments. Previous work, however, has only been able to recover about the last 2.5 ka (~0.5 meters) of material from the lakefloor. In this study, we have recovered a 6.7-meter piston core of sediment from the deep hole of the lake. A full suite of paleomagnetic and mineral magnetic analysis as well as Geotek® physical property logging and digital imaging were run on this core in order to look at environmental changes that have occurred in the watershed throughout the Holocene.

The upper unit of the core consists of ~1.23 meters of brown varved sediment. Below the varves is a massive brown unit 0.37 meters thick underlain by 0.25 meters of brown mud with a high percentage of reworked submerged aquatic vegetation (SAV) throughout the unit. Below the SAV unit is a 1.1-meter thick massive sandy marl unit, with small concentrations of reworked SAV near the bottom. The remainder of the core consists of laminated sediment with intermittent turbidites. The marl unit is interpreted as representing a period of major lake lowering in which carbonate material from the margins of the lake mass-wasted into the deeper zone of the lake, and varves were not able to form due to reduced stratification and increased physical disturbance.

Magnetic paleosecular variation (PSV) results suggest that the marl unit was deposited between 7.8 and >6.6 ka. The increase of SAV and overlying massive brown unit are observed from >6.6 to 6.0 ka, and represent the gradual increase in water level until the stratification was strong enough to resume the preservation of varved sediments at ~6.0 ka. The preliminary age constraints afforded by our PSV model suggest that Fayetteville Green Lake's major lowstand is correlated to a major lowstand in the nearby Great Lakes (7.9 to 7.0 ka). It is hypothesized that these correlative lowstands are due to regional atmospheric shifts, which brought dry air to the middle of the continent first from Arctic sources and subsequently from Pacific sources.