Elick, Jennifer, Earth & Environmental Sciences, Susquehanna University, 514 University Ave., Selinsgrove, PA, 17870-1164, elick@susqu.edu.
Legacy sediments from Middle Creek Lake near Selinsgrove, PA are attributed to upland logging and agriculture and represent a record from 1833 to 1992. During this time interval three dams (1833, 1906, and 1934) formed the mill pond/lake from a multi-thread stream system to generate hydropower. This legacy sediment represents a record of 159 years. The region was mostly forested (hemlock and chestnut) when settlers arrived in the region-1700’s. By the mid 1800’s, most of the forests had been removed for lumber, making way for the growing communities. By the 1900’s, a secondary forest of mixed deciduous and evergreen forests covered headwater areas with farms located in the valley regions. The upstream region of this drainage basin (396 km2) is geologically diverse and contributes to the composition of the legacy sediment. First order, headwater streams flow through and erode the tightly folded bedrock ranging from the Tuscarora Sandstone (Silurian) to the Catskill Formation (Devonian). Middle Creek is a fourth order stream that flows through the eastward plunging Selinsgrove Anticline, a valley region dominated by Silurian-Devonian Wills Creek, Keyser and Tonoloway Formations (limestone and dolostone), Onondaga and Old Port Formations (cherty limestone) and the Clinton Group and Bloomsburg Formation (sandstone and shales). Where Middle Creek Lake was located near its confluence with Penns Creek, it flows over the Trimmers Rock Formation and Marcellus Shale.
The laminated lake sediments were transformed into soils. In this study, they were analyzed for grain size using a gravitational settling technique. This sediment is predominantly sandy clay loam to loam. Elutriated slides of the legacy sediment were analyzed using X-ray diffraction (XRD) and consist of kaolinite, illite, vermiculite, and muscovite clays. The fine silt and sand size sediment are composed of approximately 95-98 % angular to subrounded quartz, with minor amounts of orthoclase, magnetite, and rock fragments (chert, coal, and siltstone). Mussel shell fragments, charcoal, and reddish orange clay balls (part of the legacy sediment matrix) were also present in the sand size faction. These sediments were analyze using X-ray Fluorescence (XRF) for bulk chemistry and contained 50-65% SIO2, 12-13 % Al2O3, 3-5 % Fe, 2 % K2O, and trace amounts of other minor elements. Of note were Zr values- ranged from 300-400 ppm. The lake sediments were laminated, contain iron oxide nodules from soil formation, and some organisms like the mussel Eastern elliptio and diatoms. Stumps, leaves, and seeds from the original lowland forest (pre-1833) are preserved in the lake sediments.
This study provides a description of sediments eroded from the Valley and Ridge Province following deforestation and during a time of agricultural expansion. These sediments washed down from the headwater regions and were stored in the mill pond for up to 159 years. The layers are in geomorphic disequilibrium with the multi-thread stream system model that can be applied to the lower part of Middle Creek. Eventually, storms and floods will erode and transport the sediment to the Susquehanna River and Chesapeake Bay.
legacy sediments , Middle Creek , logging , agriculture