16-43 Analysis of Dutchess County, New York’s Classic Metamorphic Barrovian Sequence

Session: From Thin Section to Outcrop: Exploration of Undergraduate Research (Posters)

Presenting Author:

Authors:

Abstract:

Dutchess County, New York, has long been a region of interest for geologists due to its classic Barrovian sequence. Despite the importance of the area as an undergraduate petrology teaching example, relatively limited geochronologic work has been integrated into current petrological and structural studies. A potential consequence of this workflow is the missed opportunity for further studies to link past and current research. We collected new samples along a transect parallel to the regional metamorphic gradient crossing previously mapped isograds, from relatively unmetamorphosed protolith to high-grade, sillimanite-K-feldspar schists. Samples were placed in a broader structural context by digitizing existing geologic maps of the area, including historic geologic maps from a time with greater access to outcrops. Approximately 2,000 structural measurements were digitized, including measurements of the Paleozoic foliation and mylonitic fabric. We then performed spatial interpolation (kriging) to represent fabric orientation across the entire field area. The kriged map shows predicted localities of high strain and allows us to compare the geometry of structures across the sample transect. Thin sections from 41 collected samples show increasing metamorphic grade from West to East, consistent with previous publications. In the kyanite zone, samples from the Walloomsac Formation contain rutile, titanite, and zircon. In the sillimanite zone and sillimanite k-feldspar zone, Manhattan Formation samples contain zircon and rutile. A sample from Precambrian gneiss mapped along strike of the kyanite zone contains titanite. Kyanite zone and Precambrian gneiss sample collection sites coincide with areas of interpolated high-strain fabrics, making samples from these areas good candidates for future geochronology work. U-Pb dating of zircon, rutile, and titanite from high-strain zones, in conjunction with previously published structural data, will help to generate a more detailed metamorphic history. The collection and characterization of new samples paired with the digitization and analysis of previously created maps furthers the knowledge of Dutchess County’s Classic Barrovian sequence.

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.