Paper No. 19
Presentation Time: 8:00 AM-12:00 PM
SEDIMENTARY RECORDS OF RURAL LAND USE CHANGE NEAR ASHFORD, CT
Eight sediment cores collected from a small (1.2 ha) pond near Ashford, CT are examined to characterize sedimentary records of nearby rural land use change. Archival records indicate that the pond formed in ≈1902 by damming of a small stream that flowed through a field used for haying and recreational purposes. Cores reported on here were collected along a (170 m) lengthwise transect along the axis of the pond. This includes five percussion cores (to 1.3 m) and 2 vibracores (2.3 m, 3.2 m) that were split and logged physically, along with 1 piston core (0.73 m) that was subsectioned for 210Pb dating and bulk sediment chemistry (data analyses ongoing). Preliminary analyses indicate that cores collected in a shallow (1.7 m) up-pond basin and a less shallow (1.3 m) down-pond basin differ at depth but are capped by similar near surface pond gyttja. The deeper basin cores contain >70 cm of basal rhythmically bedded (1 – 3 cm thick) brown to gray silt to fine sand beds (unit 1) which grade upwards to ≈45 cm of massive silty sand (unit 2) and overlying 30 cm of black silty sand with poorly decomposed wood and leaf detritus. These sediments are overlain by ≈7 cm of dark brown to black organic rich gyttja that clearly reflects recent deposition in the pond. The shallower up-pond cores generally lack bedded sediments of unit 1, but contain homogeneous fine sand and silt with discrete organic fragments (Unit 2) 60 cm thick and brown to black organic rich sand and silt with (unit 3) with large wood fragments and organic leaf detritus. Capping gyttja (unit 4) is thicker and contains more wood and peat detritus than was present at down-pond sites. Sediment characteristics reflect changing conditions at this rural farming location. Deeper rhythmic beds down gradient reflect either fluvial or lacustrine deposition likely associated either with local flooding or deglaciation. Overlying silts and sands at both sites have pedogenic overprinting that reflects a pre-pond farmer’s field depositional environment. Ongoing radiometric and bulk sediment analyses will provide constraint interpretations for more recent pond deposition since damming in 1902.