52 Reconstructing Past Climate from the Geologic Record of Ice Sheets and Mountain Glaciers (Posters)

Tuesday, 19 March 2019
8:00 AM - 12:00 PM
Casco Bay Hall

SUBGLACIAL KARST DEVELOPMENT IN EAST-CENTRAL NEW YORK STATE

Paper number: 52-5
Program: Theme Sessions
Time: 8:00 AM – 12:00 PM

Authors

  • Paul A. Rubin Presenting Author
    Northeastern Cave Conservancy, Tivoli, NY

Abstract

Conduit geometry, wall scallops, and surface topography provide evidence that much of Clarksville Cave in Albany County, NY developed in a subglacial setting toward the end of two or more glacial periods. This interpretation is confirmed by Beta Analytic Accelerator Mass Spectrometry (AMS) radiocarbon dating of charcoal located within a 2.7 cm thick silty clay loam layer situated above two in-cave debris flows. The AMS date of > 43,500 years BP exceeds the dating method limit, likely placing charcoal influx into the cave during late Marine Isotope Stage 6 or early MIS 5e (~ 140 ka to 110 ka; Sangamonian interglacial) coincident with a fire in newly developed upland forest. Cosmogenic radionuclide dating of sediment may further elucidate the Quaternary chronology of the region.

The potential catchment area required to develop large-diameter vadose infeeder conduits and a large phreatic conduit in the cave is not available from the present-day watershed. Seasonal variation in the quantity of warm-based subglacial meltwater, over tens of thousands of years, has resulted in alternating vadose and epiphreatic conditions developed behind a hydraulically inefficient or occluded outlet (not multiple phreatic conduits graded to changing base levels). At a second conduit constriction at a three-chert bed sequence (~ 75 cm thick), downward flow of high velocity meltwater has resulted in floodwater passage development elevationally above most of the cave (Pixie Passages).

A number of lines of evidence support substantial subglacial cave development from the influx of glacial meltwater. Factors supporting this interpretation include 1) numerous high-volume water and sediment inflow locations that have no relation to the surrounding hydrologic setting, 2) master phreatic conduit dimensions too large to have solely formed from existing watershed inflow (~ 9 m2), 3) small wavelength scallops on infeeder canyon walls that document high-velocity inflow (e.g., 1 m/sec), 4) sediment profiles that extend far upgradient within infeeder conduits that are unrelated to the surrounding hydrologic setting, and 5) doubling of pre-Wisconsinan phreatic discharge along the master conduit resulting from subglacial infeeder inflows (~ 0.18 m3/sec to 0.33 m3/sec as determined by analysis of scallop wavelengths and conduit dimensions).

Geological Society of America Abstracts with Programs. Vol. 51, No. 1

doi: 10.1130/abs/2019NE-328678

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