NORTH AMERICA MAJOR RIVER DRAINAGES MODIFIED AT LATE PLEISTOCENE GLACIAL TRANSITIONS: A TALE FROM DEEP-SEA SEDIMENT

Deep-sea fans are revealing new and fascinating insights into important topics such as climate and earth surface processes. Recent data demonstrates that the sedimentary records of deep-sea fans are a ‘hidden trove’ to unravel the intricacies of tectonics and climate on the continents. Sediment eroded from continents during ice ages can be rapidly (<10⁴ years) transferred via rivers to the deep-sea and preserved in submarine fans, becoming a viable record of landscape evolution.

We applied chemical weathering proxies and zircon geo-thermochronometry to late Pleistocene sediment recovered from the deep-sea Mississippi Fan, revealing interactions between the Laurentide ice sheet and broader Mississippi–Missouri catchment between ca. 70,000 and 10,000 years ago (70 to 10 ka). Sediment contribution from the Missouri catchment to the Mississippi Fan was relatively low between 70 and 30 ka and doubled after the Last Glacial Maximum. We hypothesize that glacial advance altered the vast Missouri drainage through ice dams and/or diverting of the river. The paucity of western U.S. sourced sediment in the Mississippi deep-sea fan also precludes the rerouting of upper-Missouri sediment through the Arkansas or Red River drainages to the southeast, requiring an alternative sediment pathway (Colorado or Snake-Columbia River basins?) during glacial advance. The dramatic shift in sediment sourcing over a brief geologic time span (<70 ka) demonstrates the impact of climate on landscapes and highlights the importance of considering climatic and tectonic events in geochronology provenance studies.