Date of Thesis

Spring 2026

Description

Anthropogenic climate change is altering the hydrologic cycle, increasing flood frequency and severity, with associated increased risks in population exposure. This is associated with increasing risks to the population of the Susquehanna River Valley, which supports over 600,000 people today. However, our understanding of the frequencies of large floods is limited by relatively short instrumental records. By studying sediments from an abandoned chute channel in the Robert Allen Natural Area near Williamsport, PA, we can extend the existing flood records using paleoflood slackwater sediments along the West Branch of the Susquehanna River.  Sylvan Dell is an abandoned chute channel that is currently disconnected from high velocity flow from the main channel. A raised railroad track runs horizontally through the area; however, there is low velocity flow during high flooding events. We collected 355 cm of sediment from the Sylvan Dell wetland (41°14’024” N, 076°57’888 W) using a Vibracore, from a location downstream and inside the bend of the abandoned chute (Core 1). The top 69 cm of the core encompasses a modern soil horizon, the remaining 286 cm are made up of 36 storm deposits of very fine - medium sand and silt/clay. These packets ranged in thickness from 4 - 7 cm to 1 - < 1 cm. Sediment size analysis was completed using a Camsizer X2 Particle Analyzer (X-Jet module)  to better understand grain size variation throughout the core, and Loss on Ignition provided insights into the total organic content of collected sandy layers. Initially, a dramatic shift from storm deposits to massive clay was interpreted to be caused by the construction of a railroad (1854) that runs through the wetland. However, radiocarbon dates at 56.5 cm and 280.5 cm depth report dates from 1963 and 1967, drastically changing our inferred timeline of the sediment deposition. Elemental analysis was completed via X-ray Fluorescence of sand and silt layers (n = 127) for potential patterns between grain size and elemental composition. Fine-grained layers had higher Rb, Ca, and Al due to their clay content, while sand layers were found to have the same concentration of Ti and increased levels of Si and Zr. A second core (Core 2) was collected further into the wetland at 41° 14' 0.48" N, 76° 57' 53.16" W. Made up of silt and peat, a radiocarbon date of 9,579 years ago was collected from 34.5 cm depth. A thick peat layer at the bottom of the core is overlain abruptly by clay and a developing soil horizon. Overall, more dates and understanding of the wider wetland sedimentology and stratigraphy are required to make a Holocene paleoflood chronology of the West branch of the Susquehanna.

Keywords

geology, sediment cores, grain size analysis, Holocene

Access Type

Honors Thesis

Degree Type

Bachelor of Science

Major

Geology

Second Major

Women's & Gender Studies

First Advisor

Lorelei Curtin

Second Advisor

Ellen Chamberlin

Third Advisor

Ellen Herman

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