29 Rates, Dates, and Plates: Petrochronological Approaches to Unraveling Tectonometamorphic Histories (Posters)

This session welcomes contributions  applying modern approaches in metamorphic petrology, geochronology, and structural geology to unravel the dynamics of convergent margin processes from the Appalachians and beyond. We encourage submission from Early Career participants.

Monday, 23 March 2026
1:30 PM - 5:30 PM
CCC, Ballroom C

The Provenance and Ages of Glacial Sediments from Long Island, NY

Paper number: 29-7
Program: Technical Sessions
Time: 1:30 PM – 1:30 PM

Authors

Abstract

The Laurentide Ice Sheet (LIS) terminated on Long Island during the last glacial maximum, constructing the Ronkonkoma and Harbor Hill moraines. Despite a century of mapping, debate persists over ice-flow directions and the bedrock sources that fed these deposits. We present a provenance study integrating detrital zircon U–Pb geochronology with heavy-mineral assemblages from four sites spanning ~130 km E–W across Long Island: Huntington and Caumsett State Park in the west, and Greenport (North Fork) and Hither Hills (Montauk) in the east. We dated 939 sand-sized zircons by LA-ICP-MS and characterized heavy-mineral separates by SEM-EDS/EMPA to link age populations and mineralogy to potential source terranes.

Western localities (Huntington; Caumsett) are dominated by Mesoproterozoic age peaks near ~1.0–1.05 Ga, consistent with Grenvillian sources and recycled zircons from Laurentian-margin metasedimentary rocks of the Manhattan Prong. A small peak ~440 Ma matches peak metamorphism during the Taconic orogeny. Eastern sites yield prominent Late Paleozoic–Early Mesozoic peaks: ~275 Ma (regional Permian plutonism/pegmatites) and ~365–409 Ma (Acadian–Neoacadian magmatism and metamorphism). Jurassic ages near ~190 Ma at Caumsett, Greenport, and Hither Hills are difficult to reconcile with local basement but plausibly derive from the White Mountain igneous province to the N–NE. Heavy-mineral suites are dominated by metamorphic minerals: kyanite, staurolite, rutile, pyroxene and amphibole. Magnetite and tourmaline also occur. The geographic partitioning of zircon age modes and heavy-mineral supports dominant ice flow from the N to NE into both moraines.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411096

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