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Apatite Geochemistry and Detrital Zircon Application in Provenance Studies of the Modern Mississippi

Abstract

Modern climate regimes, human diversion and trapping of sediment have created dynamic change in modern Mississippi River sediment transport from source to sink. As a result of this, there is renewed interest in the differential contributions of sediment from the Mississippi and its tributaries. In recent years, detrital zircon U-Pb dating has been used to deduce provenance of ancestral Mississippi River sediments, however only a small amount of data exists for the modern river system. While there is a robust history for the use of detrital zircon in provenance studies, low reset sensitivity and recycling can create ambiguities when interpreting catchments that have sources with a variety of overlapping and often poorly defined ages. Detrital apatite geochemistry is a new technique being used to identify provenance and sediment transport in ancient sedimentary environments. Apatite, like zircon, is a stable heavy mineral, however its trace element chemistry is sensitive to both source composition and change by chemical weathering during transport. Because of this, apatite has more variability and can give further information concerning sediment sources from within well studied basins. This study uses apatite geochemistry in conjunction with zircon U-Pb dating to interpret the provenance and transport of sediment within the modern Mississippi River and its tributaries. These apatite and zircon data are preliminary and are used to better understand the variation of sediment supply within the Mississippi providing more accurate geographic constraints than previously possible. Overall this has implications for interpreting provenance and source to sink transport of modern with diverse bedrock catchments, as well as improved interpretation of the subsurface geological record.