Chronology of Laurentide glaciation in New Jersey and the New York City area, United States

Abstract

Deposits of at least three glaciations are present in New Jersey and the New York City area. The oldest deposits are magnetically reversed. Pollen and stratigraphic relations suggest that they are from the earliest Laurentide advance at ~2.4 Ma. Deposits of a second advance are overlain by peat dated to 41 ka and so are pre-Marine Isotope Stage (pre-MIS) 2. Their relation to marine deposits indicates that they predate MIS 5 but postdate MIS 11 and may postdate MIS 7 or 9, suggesting an MIS 6 age. The most recent deposits are of MIS 2 (last glacial maximum [LGM]) age. Radiocarbon dates and varve counts tied to glacial-lake events indicate that LGM ice arrived at its terminus at 25 ka, stood at the terminus until ~24 ka, retreated at a rate of 80 m/yr until 23.5 ka, and then retreated at a rate of 12 m/yr to 18 ka. At 18 ka the retreat record connects to the base of the North American Varve Chronology at Newburgh, New York. The 25–24 ka age for the LGM is slightly younger than, but within the uncertainty of, cosmogenic ages; it is significantly older than the oldest dated macrofossils in postglacial deposits in the region.

A critical re‐analysis of constraints on the timing and rate of Laurentide Ice Sheet recession in the northeastern United States

“…A new LGM and deglacial varve chronology from the Hudson River valley in southern New York and northern New Jersey (Stanford et al, 2020;Fig. 3) supports maximum ice extent between 25 and 24 ka followed by rapid recession (80 m a −1 ) from 24 and 23.5 ka and then slowing to ~12 m a −1 from 23.5 to 22.5 ka.…”

“…Glacial varve chronologies provide the highest resolution record of ice recession through the northeastern US and serve as important benchmarks against which to compare the pace of ice recession implied by 14 C and 10 Be ages, but uncertainties remain about the timing of deglaciation according to varve records near the terminal moraine zone. Although the varve chronologies considered here Stanford et al, 2020) are continuous and thought to have minimal counting errors, they, like all varve chronologies, are floating. To use varve chronologies for dating ice margin recession they must be tied to the calendar timescale, typically by 14 C dating of organic material, preferably plant macrofossils identified to species level, within the varve sequence (see 'Varve chronologies', above).…”

“…Calibration of the varve chronology in the central and northern part of our study area is based on macrofossil 14 C ages from specific varves (Ridge and Larsen, 1990; Ridge et al, 2012), while the calibration of the varve chronology near the terminal moraine zone is based on bulk‐sediment samples and inorganic concretions (Stanford et al, 2020). The macrofossils used for dating were in excellent condition (mostly Dryas leaves) and showed little evidence of decay or erosion during transport.…”

“…Over the past 70 years, the development of new dating techniques and collection of geochronologic data have produced over 200 organic 14 C and cosmogenic 10 Be ages (e.g. Dalton et al, 2020; Halsted et al, 2022, and references therein) and two calibrated glacial varve chronologies (Ridge et al, 2012; Stanford et al, 2020) that together constrain recession of the Laurentide Ice Sheet (LIS) margin in the region following the LGM (Fig. 1).…”

“…Location map showing deglacial chronology samples, varve chronologies (Ridge et al, 2012; Stanford et al, 2020), place names and study area location relative to the whole Laurentide Ice Sheet (red box). State names are abbreviated for Pennsylvania (PA), New Jersey (NJ), Connecticut (CT) and Rhode Island (RI).…”