Reconstructing the depositional history of the Eel River paleo meltwater channel, northeastern Indiana using sediment provenance techniques

Abstract

The outwash deposits of the Eel River paleo meltwater channel in DeKalb and Allen Counties, Indiana predominantly originated from the Erie Lobe of the Laurentide Ice Sheet, but do contain some sediment from the Saginaw Lobe. This determination helps clarify the ice dynamics and Last Glacial Maximum sediment depostional history in northeastern Indiana, which is complicated because of the interactions between the Erie and Saginaw Lobes. Outwash deposits were analyzed from IGS core SC0802 in the Eel River paleo meltwater channel, which intersects the previously identified Huntertown Formation. The core includes 29.2 m of deposits underlain by the hard glacial till of the Trafalgar formation. Mean grain size, sediment skewness, lithology, magnetic susceptibility, and quantitative X-ray diffraction were used to evaluate the provenance of the outwash deposits. Representative samples of Erie Lobe and Saginaw Lobe deposits were analyzed to develop end member provenance signatures. A weight of evidence approach was developed and revealed that deposits from 8.0-13.8 m are of mixed origin from the Erie and Saginaw Lobes, whereas the 0-8.0 and 13.8-29.2 m deposits are Erie Lobe in origin. Cluster analysis and discriminant function analysis supported the findings of this approach. These findings suggests that the Eel River paleo meltwater channel was formed as an outwash channel, and that the adjacent Huntertown Formation does not appear to have been directly deposited by the Saginaw Lobe. The sediments of Saginaw origin from ~8-14 m in the Eel River paleo meltwater channel were likely transported from an upgradient source. The sediments from this zone have a larger mean grain size indicating deposition occurred during higher meltwater discharge, such as the release of meltwater from the drainage of proglacial or subglacial lake(s) associated with the disintegration of the Saginaw Lobe, thus resulting in the mixing of Saginaw Lobe deposits with Erie Lobe deposits. However, the majority of the sediment in the Eel River paleo channel near SC0802 is Erie Lobe in origin. Based on the provenance and depositional sequence at SC0802, the Saginaw Lobe disintegrated prior to the Erie Lobe retreat from the Wabash moraine around 16-17 cal ka.