EPISODIC MELTWATER DISCHARGES INTO THE GULF OF MEXICO DURING THE LAST DEGLACIATION: THE BENTHIC ISOTOPE RECORD
The oxygen isotope data are derived from four, up to 5 m long, cores taken in the northern GOM at water depths ranging from the upper bathyal (401m and 529 m) to the lower bathyal (1030 m and 1112 m). Sediment accumulation functions developed on the basis of AMS-radiocarbon dated control points and correlation of negative d18O events between cores allowed transfer from depth to time domain.
The d18O records of the benthic foraminifera U. peregrina exhibit three large negative excursions (up to 1) preceding the Younger Dryas cold event, and at least two negative excursions (up to 0.4) succeeding the Younger Dryas time. These negative isotope shifts document entrainment of 18O-depleted meltwaters in dense flows that reached the seafloor. Co-occurrence of the negative d18O shifts in the paired planktonic-benthic foraminifera records suggest that the most intense of the meltwater floods at 13.2, 12.4, 11.7, 9.4 and 9.0 ka were discharged as catastrophic hyperpycnal flows into the GOM. Paired planktonic-benthic isotope records thus provide greater insights into LIS deglacial history and links to abrupt climate changes than planktonic based isotope records alone.