RESPONSE OF TURBIDITE DEPOSITION TO CLIMATE CHANGE AND ASTRONOMICAL FORCING DURING THE PALEOCENE-EOCENE THERMAL MAXIMUM
Turbidity currents are one of the most important sediment transport processes on the Earth's surface,and the key means by which sediment is moved from continental shelves to the deep ocean.By studying the distribution patterns of turbidite event beds deposited during hyperthermal events,important insights can potentially be gained about how turbidity currents,and marine sediment fluxes generally,behave under global warming scenarios.In a previous study,we found evidence for high-frequency precession-modulated turbidite deposition in the North Sea Basin during the Paleocene-Eocene Thermal Maximum(PETM).In this study,we conducted further time series analysis on Paleocene-Eocene turbidites from the Zumaia section(43° 18′4.5″N,2° 15′31.2″W)in the Basque Basin,Spain.Based on published age models,we converted the 458 beds in turbidite sequence at Zumaia section(from-19.76 m to 37.12 m in depth)from the depth domain to the time domain via linear interpolation.Three independent methods of spectral analysis(circular spectral analysis,Schuster spectrum,and multi-taper method)of the age-constrained turbidite sequence indicate that there is a ca.400 ka cycle in turbidite recurrence time.Considering potential errors in the chronological anchors and depth-time conversion processes,we suggest that the turbidites(and hence sediment flux)responded to 405 ka long eccentricity climate forcing.Analysis of other PETM turbidite records failed to find clear evidence of astronomical cycles.As such,among the available Paleocene-Eocene turbidite records,astronomical forcing signals can be robustly identified only in the North Sea Basin and the Basque Basin.The locations of these records appear to coincide with areas that were likely sensitive to orbital parameter variations based on analysis of simulated annual mean precipitation from climate modeling.This supports the inference that enhanced precipitation,represented by some turbidite deposits during this greenhouse climate period,responded to astronomical cycles.However,it also implies that the formation of most turbidites in the studied Paleocene-Eocene records is not commonly related to astronomical forcing but to other factors.In general,a decrease in turbidity current frequency at most sites during the PETM was likely primarily in response to a global sea level rise.
万方数据
维普
