STRATIGRAPHY OF A LATE WISCONSIN-HOLOCENE AGE FLUVIAL TERRACE NEAR LOCK HAVEN, PENNSYLVANIA

A soil probe was used to take core samples along the Susquehanna River near Lock Haven, Pennsylvania on a Binghamton age fluvial terrace (Late Wisconsin-Holocene age). The cores were cut into centimeter sections and analyzed for color, presence of organics, magnetic susceptibility and chemical composition. The magnetic susceptibility of each core showed a distinct pattern that corresponded well with the color and presence of organics. The magnetic susceptibility between ~1-25cm was relatively high (~7X10^-7). At ~25cm a transition in magnetic susceptibility begins. The transition occurs over a ~5-10cm interval in each core. After the transition the magnetic susceptibility (MS) drops too much lower levels (~4X10^-8 - 6X10^-8). The MS values are thought to be controlled by the amount of iron that is found in the clays, which are deposited by flooding of the Susquehanna River. Further analysis of the cores revealed the presence of magnetic spherules in the upper sections of each core, above the transition zone. Spherules, when present, have much higher MS values but are not thought to be the cause for the transition zone. Spherules were removed from select intervals throughout one core and analyzed using a scanning electron microscope. Energy-dispersive x-ray spectroscopy (EDX) was also performed on each spherule and showed that they were composed mostly of iron with small amounts of titanium. EDX analysis was also performed at select intervals to determine if the distinct MS pattern was caused by soil processes. Using the chemical composition data from the EDX analysis a Chemical Alteration Index (CIA) was calculated for the core. The CIA shows little correlation with the MS pattern seen in the cores. The change from higher MS values to lower MS values is thought to be due to climatic changes at the Late Wisconsin-Holocene boundary. During glacial times winds blew away the fine clays due to the lack of vegetation. During the Holocene the clays were less likely to be blown away, thus providing a finer sediment supply for the Susquehanna River.