Title: Application of the Helium isotopic system to accretion of terrestrial and extraterrestrial dust through the Cenozoic
Description: isotopic system provides novel tools to probe the sedimentary record of the earth over the last few hundred million years. Radiogeneically derived 4He and solar wind implanted 3He is delivered to sediments by weathered continental material and interplanetary dust particles, respectively. The purpose of research presented in this thesis is to use 4He of terrestrial and 3He of extraterrestrial origins as tools to investigate the relationship between global climate and surface processes on earth. I measured 4He in annual growth bands in a Porites coral from the northern Red sea, lacustrine carbonate sediments from the Bahamas and marine sediments in the North Atlantic (Ocean Drilling Program site 1313). Terrestrially derived fraction of the measured 4He in the Red Sea Porites coral and carbonates of the Bahamas together provide accurate information about changes in dust export rates from North Africa over the last millennium; dust fluxes are intimately tied to droughts in North Africa at decadal to centennial time scales over the last millennium that in turn, appears to be modulated by sea surface temperatures (SSTs) in the Indian and the Atlantic Ocean. On the other hand, 4He content in marine sediments in the North Atlantic provide information about changes in sources of detrital over the last six million years that in turn appears to reflect changes in ocean circulation in the sub-polar north Atlantic.