THE PROVENANCE OF GLACIAL TILL FROM THE HARBOR HILL MORAINE ON LONG ISLAND, NY DETERMINED BY LA-ICP-MS OF DETRITAL ZIRCON

The provenance of glacial till deposited on Long Island can be used to more accurately characterize the previous extent and flow of the Laurentide Ice Sheet (LIS). In this study, we analyzed detrital zircon from glacial till deposited as part of the Harbor Hill Moraine in Roslyn, NY (40.80°N, -73.65°W). Detrital zircon is particularly useful in this study because it can record age information of crustal units that contributed to the sediment load due to its low solubility in almost all melt and fluid compositions and durability during transport. The U/Pb age of zircon is the chemical signature we will use to determine the source.

To date, over 200 zircon grains have been extracted from bulk sedimentary samples. LA–ICP–MS data is being reduced using Glitter software for U/Pb analysis, and preliminary results indicate that the range of U/Pb ages stretch from 393 Ma to 3,601 Ma. The population of detrital zircon have U/Pb ages that are clustered in two primary groups, one from ~400-600 Ma, and another from ~950-1,350 Ma. Initial analyses using the unmix function in Isoplot 4.15 suggests that there are three main peaks at 501 Ma, 1,113 Ma and 1,172 Ma.

The analysis of detrital zircon from the Harbor Hill Moraine has not been completed before and offers us an opportunity to share unique information that will substantiate the findings of other geologists and glaciologists. Our analyses will provide us with preliminary data that can be paired with cosmogenic nuclide exposure ages in order to determine if the extent and flow of the Laurentide Ice Sheet has changed over time. This synthesis will allow us to compare previous periods of glacial fluctuations, supporting the international effort strongly focused on understanding the environmental change we are experiencing today.