STRATIGRAPHIC CORRELATION AND SIGNAL PROPAGATION ACROSS SEDIMENTARY SYSTEM SEGMENTS USING U-PB DETRITAL ZIRCON GEOCHRONOLOGY: INSIGHTS FROM THE LATE PLEISTOCENE MISSISSIPPI RIVER AND DEEP-SEA FAN

The Mississippi River fluvial network has undergone significant modifications during the Pleistocene that are attributed to fluctuations in northern hemisphere ice sheets. Terrigenous sediments in the Mississippi deep-sea fan, Gulf of Mexico, preserve stratigraphic changes in U-Pb detrital zircon (DZ) provenance that are interpreted to result from up-system changes in sediment supply and source area, largely driven by ice sheet dynamics and the sedimentary system response. Here, we build on existing work focused on sediment composition, geochemistry, and DZ provenance of the Mississippi deep-sea fan, by measuring U-Pb ages of DZs from deposits in upstream (and time correlative) ancient Mississippi River deposits, which would have fed submarine fans in the Gulf of Mexico.

We performed reconnaissance level sampling of full glacial to early deglacial age deposits in the Western Lowlands and central Mississippi Valley (depositional ages of ~25 ka and ~15 ka, respectively). We hypothesize that measured DZ age patterns from ancient river sediments in the Mississippi Valley should be similar to those found in the upper most, time-correlative deep-sea fan deposits. If this hypothesis is verified by new DZ provenance results, it would demonstrate (1) the utility of relatively high resolution stratigraphic correlation using DZ geochronology across source to sink system segments, and (2) further improve our understanding of the effects of ice sheets on functioning of continent-scale source to sink systems. Furthermore, this result would suggest rapid system response timescales to external forcing, and rapid signal propagation from source to sink. However, if fluvial deposits contain DZ age patterns with significant departures from those of correlative deep-sea fan deposits, interpretations of rapid signal propagation or preservation from source to sink, and inversion of stratigraphic records from the Mississippi deep-sea fan may need to be reevaluated. This phase of our study targets some of the youngest late Pleistocene deposits in the Mississippi Valley and Mississippi fan, and future work will analyze older fluvial deposits (ca. 70 – 40 ka) to further test the applicability of U-Pb DZ methods to stratigraphic correlation across sedimentary system segments.