Northeastern Section - 57th Annual Meeting - 2022

Paper No. 7-1
Presentation Time: 8:00 AM-12:00 PM


BIERLY, Aaron, DCNR: Pennsylvania Geological Survey, 3240 Schoolhouse Road, Middletown, PA 17057, ASHWORTH, Allan C., Department of Geosciences, North Dakota State University, Fargo, ND 58102, PETEET, Dorothy M., Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, DAVIS, Margaret A., Institutes of Energy and the Environment, Penn State University, 6 Land and Water Research Bldg, University Park, PA 16802 and CULLETON, Brendan J., Institutes of Energy and the Environment, Penn State University, 6 Land and Water Research Bldg., University Park, PA 16802

During the mining of sand and gravel from glacial deposits at the Three Rivers Aggregate Companies Quarry, Slippery Rock, Pennsylvania (GPS: 41.043369°, -80.150203°), wood, moss, charcoal, fungal sclerotia, Picea (spruce) needles, Salix (willow) buds, Carex (sedge) achenes, a Viola (violet) seed and beetle remains were recovered from a 0.2 -1.0 ft-thick silt and peat bed at a depth of 32.0 ft from the surface. Pollen (n=664) and spores (n=14) compiled from two samples in the silty peat (31.85 ft bls to 31.89 ft bls and 32.03 ft bls) include 53.3% Picea, 38.4% Pinus, 5.3% Cyperaceae, 1.9% Polypodiaceae, 0.6% Asteroideae, 0.3% Poaceae, 0.1% Cichoroideae, and 0.1% Selaginella selaginoides. Beetle remains found in the silty peat include species of Patrobus, Cytilus, Acidota, and either Enochrus or Cymbiodyta.

The biota indicates a wetland environment (bog, fen, or lake shore) in a spruce-dominant forest similar to those found currently in central Canada. Two radiocarbon samples from this horizon have ages of 42,110±1280 BP (41006 cal BC to 45833 cal BC) (PSUAMS-8083) and 42,190±1290 BP (41029 cal BC to 45938 cal BC) (PSUAMS-8082).

Below the silt and peat there is a 12.2 ft-thick sand that bears fine filaments of plant material. Within that sand at 39.2 ft bls, a pollen (n=307) and spore (n=8) assemblage has the composition 57.8% Picea, 32.4% Pinus, 7.0% Cyperaceae, 1.6% Selaginella selaginoides, and 0.9% Huperzia selago, and 0.3% Cichoroideae. Elytra (wing cases) of the ground beetle Blethisa catenaria, a ground beetle which lives exclusively on tundra, was also found at 39.2 ft bls. The sediment at 39.2 ft bls was deposited in a tundra-spruce environment similar to that today on the North Slope of Alaska and the Canadian Arctic.

The faunal and floral changes indicate climatic warming from the lower to the upper organic horizons. The mean July temperature at 39.2 ft bls is estimated to be 11-12°C and at 32.0 ft bls 15-17°C compared to 21°C at Slippery Rock today.

  • NEGSA_2022_Pleistocene_Beetles_PennsylvaniaGSA 2022.FINAL_Reduced_Size.pdf (2.8 MB)
  • Bierly 201008 PSUAMS Results 2022 GSA Poster.pdf (173.9 kB)