TY - JOUR
T1 - Shell we date? ESR dating Sangamon Interglacial Episode deposits At Hopwood Farm, IL
AU - Blackwell, Bonnie A B
AU - Kim, Danny M K
AU - Curry, B. Brandon
AU - Grimley, David A.
AU - Blickstein, Joel I B
AU - Skinner, Anne R.
N1 - Funding Information:
US National Science Foundation (ILI 9151111 to ARS), grants to B.B.C. and D.A.G., Illinois State Geological Survey, McMaster Nuclear Reactor, Williams College, and the RFK Science Research Institute supported this work. We thank Israt Ahmed, Jon Florentin, Alex Lee, and the 2012-2013 RFK crew for their assistance. Alice Pidruczny, McMaster University Nuclear Reactor, performed the NAA analyses. Jon Florentin designed some figures. The reviewers provided excellent suggestions to improve this work.
Publisher Copyright:
© The Author 2016.
PY - 2016/12
Y1 - 2016/12
N2 - During the Sangamon Episode, North America occasionally experienced warm climates. At Hopwood Farm, IL, a small kettle lake filled with sediment after the Illinois Episode glaciers retreated from southern Illinois. To date those deposits, 14 mollusc samples newly collected with associated sediment from three depths at Hopwood Farm were dated by standard electron spin resonance (ESR) dating. ESR can date molluscs from ~0.5 ka to > 2Ma in age with 5-10% precision, by comparing the accumulated radiation dose with the total radiation dose rate from the mollusc and its environment. Because all molluscs contained ≤0.6 ppm U, their ages do not depend on the assumed U uptake model. Using five different species, ESR analyses for 14 mollusc subsamples from Hopwood Farm showed that Unit 3, a layer rich in lacustrine molluscs, dates at 102 ± 7 ka to 90 ± 6 ka, which correlates with Marine (Oxygen) Isotope Stage 5c-b. Thus, the period with the highest non-arboreal pollen at Hopwood also correlates with the European Brørup, Dansgaard-Oeschger Event DO 23, a time period when climates were cooling and drying somewhat over the same period.
AB - During the Sangamon Episode, North America occasionally experienced warm climates. At Hopwood Farm, IL, a small kettle lake filled with sediment after the Illinois Episode glaciers retreated from southern Illinois. To date those deposits, 14 mollusc samples newly collected with associated sediment from three depths at Hopwood Farm were dated by standard electron spin resonance (ESR) dating. ESR can date molluscs from ~0.5 ka to > 2Ma in age with 5-10% precision, by comparing the accumulated radiation dose with the total radiation dose rate from the mollusc and its environment. Because all molluscs contained ≤0.6 ppm U, their ages do not depend on the assumed U uptake model. Using five different species, ESR analyses for 14 mollusc subsamples from Hopwood Farm showed that Unit 3, a layer rich in lacustrine molluscs, dates at 102 ± 7 ka to 90 ± 6 ka, which correlates with Marine (Oxygen) Isotope Stage 5c-b. Thus, the period with the highest non-arboreal pollen at Hopwood also correlates with the European Brørup, Dansgaard-Oeschger Event DO 23, a time period when climates were cooling and drying somewhat over the same period.
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U2 - 10.1093/rpd/ncw213
DO - 10.1093/rpd/ncw213
M3 - Article
C2 - 27683396
AN - SCOPUS:85014068342
VL - 172
SP - 283
EP - 295
JO - Radiation Protection Dosimetry
JF - Radiation Protection Dosimetry
SN - 0144-8420
IS - 1-3
ER -