Seismic stratigraphy of the Finger Lakes: A continental record of Heinrich event H-1 and Laurentide ice sheet instability
Article
Mullins, HT, Hinchey, EJ, Wellner, RW et al. (1996). Seismic stratigraphy of the Finger Lakes: A continental record of Heinrich event H-1 and Laurentide ice sheet instability
. 311 1-35. 10.1130/0-8137-2311-6.1
Mullins, HT, Hinchey, EJ, Wellner, RW et al. (1996). Seismic stratigraphy of the Finger Lakes: A continental record of Heinrich event H-1 and Laurentide ice sheet instability
. 311 1-35. 10.1130/0-8137-2311-6.1
Seismic reflection surveys of 8 of the 11 Finger Lakes of central New York State have documented the deep (as much as 306 m below sea level) glacial scour of these lake basins and their subsequent infill by thick (up to 270 m) unconsolidated sediment. Drill data indicate that sediment infill occurred rapidly during a short interval between ∼14,400 and 13,900 14C yr ago, coeval with Heinrich event H-1 when large volumes of icebergs and meltwater were discharged into the North Atlantic during an unstable phase of the Laurentide ice sheet. Six acoustically defined depositional sequences beneath the lakes, correlated with drillcore and piston core samples, record the infill history of the Finger Lakes during the late Wisconsin. Depositional sequence I is equivalent to thick, water-laid sands and gravels of the Valley Heads moraine deposited ∼14.4 ka. During retreat of the ice margin from its Valley Heads position, subglacial meltwaters transported large volumes of fine-grained sediment into the Finger Lake basins (sequences II and III). Sequence IV records a phase of high-level proglacial lakes when ice blocked northern outlets of the Finger Lakes and fine-grained sediments continued to be transported into the basins from the north. An abrupt drop of proglacial lake levels and a drainage reversal is recorded by sequence V when sediments first began to enter the Finger Lakes from the south following retreat of the ice margin past the northern outlets of the lakes. The well-known modern glens and waterfalls of the Finger Lakes region formed at this time when lateral streams adjusted to dramatically lowered local base levels. Radiocarbon dates across the sequence V/VI boundary indicate that proglacial lake levels dropped ∼13.9 ka. Depositional sequence VI represents thin (<15 m) postglacial sediments that have accumulated in the Finger Lakes following the establishment of "modern" drainage. Definition of deep scour and a rapid phase of sediment infill beneath the Finger Lakes 14.4 to 13.9 ka not only provide a continental record of Heinrich event H-1 but also support models of rapid ice flow and large-scale instability of the Laurentide ice sheet at this time.
