SBWM

• Younger Dryas wetlands from Calumet County, WI • Late Holocene charcoal record of amplified aridity ca. AD 1290 Abundant deposition of plant macrofossils was found in pond sediment and peat exposed at a farm-pond on the Schneider Farm, Calumet Co., east-central Wisconsin (Photo). Stratigraphy of a 15-m section yields the Holocene history of this area starting from a basal till unit dated ca. 14,000 years ago (Chilton Member till). Over 180 specimens of wood were collected in 2005 along with charcoal from the 2 m topsoil gyttja underlying brown clay. The Younger Dryas event was represented with two spruce records spanning 184 and 145 years dated between 11,500 (larch) and 11, 100 cal Yr. BP (spruce), deposited at the 30-45 cm depth level of the peat. There are two other tree-ring records dated ca. AD 660 cal Yrs BP in the top peat unit (185 years) and 13,200 cal Yrs BP (159 years) in the low pond sediment unit associated with the Older Dryas cooling. The Two Creekan-age wood does not seem to be overrun by a glacier lobe at this location and is represented by float logs in the pond sediments. Most clear evidence of hydrological change results from the tree-ring records of spruce and larch growing on the wetland, which suggest two independent episodes of tree colonization toward the end of the Younger Dryas. The hydrological shift from aquatic environment to wetland occurred ca. 10,740 cal Yrs BP. The charcoal record indicates a shift to drying climate dated after ca. AD 1290.