Hollander, D. J. Northwestern University, david@earth.nwu.edu
Werne, J. J. Northwestern University, josef@earth.nwu.edu

 
UNPREDICTED CARBON AND NITROGEN ISOTOPIC CYCLING IN THE CARIACO BASIN FROM THE YOUNGER DRYAS TO PRESENT: IMPLICATIONS FOR INTERPRETATION OF ISOTOPIC VARIABILITY IN UPWELLING SYSTEMS
 
Upwelling intensity in the Cariaco Basin varies annually as a result of the seasonal migration of the intertropical convergence zone. During periods of high upwelling (winter) enhanced nutrient supply promotes productivity blooms. During the Younger Dryas cold period - Preboreal (YD/PB; ~12.6 - 10 ka), upwelling and productivity in the basin were more intense than today as evidenced by the five-fold increases in organic carbon accumulation rates (OCacc). Under normal conditions of enhanced productivity it is expected that the isotopic composition of the reservoir [13C(CaCO3) ] and that of organic matter (13C and 15N) would increase as a result of reservoir effects, growth rates, and nutrient utilization. Despite the enhanced productivity (OCacc) during the YD/PB, C-isotopic composition of bulk carbonate remains depleted throughout this period suggesting that upwelling supplies an overwhelming amount of 12C-enriched CO2 relative to its utilization through productivity. Isotopic values of organic carbon and nitrogen are also unable to track productivity variations indicating that enhanced growth rates and nutrient utilization are unable to keep pace with the supply of 12C-enriched CO2 and 14N-enriched NO3- from upwelling. These findings bear significantly on interpretations of isotopic compositions of organic and inorganic materials deposited under upwelling regimes.
 
Day: Monday, Feb. 1
Time: 04:45 - 05:00pm
Location: Eldorado Hotel
 
Code: SS32MO0445E