Pliocene-pleistocene evolution of tropical aridity
This research tries to determine the nature and origin of low-latitude terrestrial climate variability prior to and after the rapid expansion of high-latitude ice sheets near 2.4 Myr to understand the interactions between high- and low-latitude climate systems since the late Pliocene (ca. 3.5 Myr). Records of eolian dust variability were reconstructed from wholecore magnetic susceptibility data at Ocean Drilling Project Site 661 in the eastern equatorial Atlantic and Site 721 on the Owen Ridge in the Arabian Sea. Susceptibility is a rapidly-measured and conservative indicator of terrigenous (eolian) variations at both sites and correlations were used to construct well-dated, composite sequences extending to 3.5 Myr. Evolutive spectral analysis of the two susceptibility records demonstrate that prior to 2.4 Myr both eolian records are dominated by variance at the 23-19 kyr precessional periodicities, whereas after 2.4 Myr the records exhibit strong increases in 41 kyr power. Dominant 23- 19 kyr variations at Site 721 extend from 2.4 Myr to at least the late Miocene (ca. 6 Myr). The increase in 41 kyr power after 2.4 Myr and the subsequent increase in 100 kyr power after 0.7 Myr reflect the onset of glacial aridity in African and Arabian dust source areas. We also present a 0.9 Myr record of eolian accumulation from ODP Site 663 in the tropical Atlantic; concentrations of two terrestrial eolian components, opal phytoliths (grass cuticles) and freshwater diatom (Melosira) valves from desiccated lake beds, were also measured. General circulation model sensitivity tests were used to examine physical linkages between high and low latitude climate, demonstrating that the African and Asian monsoon circulations are very responsive to precessional insolation forcing in the absence of significant ice volume variability. However, full glacial ice cover caused significant precipitation and temperature decreases in monsoon dust source areas in Arabia and northeast Africa.
- Research Organization:
- Columbia Univ., Dobbs Ferry, NY (United States). Hudson Labs.
- OSTI ID:
- 6246991
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
Similar Records
Downhole measurement data as paleoclimate indicators: A Plio-Pleistocene record of Asian eolian dust deposition to the Sea of Japan
Plio-pleistocene African climate
Related Subjects
CLIMATIC CHANGE
GENERAL CIRCULATION MODELS
PLEISTOCENE EPOCH
PLIOCENE EPOCH
TROPICAL REGIONS
PALEOCLIMATOLOGY
AFRICA
ARID LANDS
ATMOSPHERIC PRECIPITATIONS
DIATOMS
GLACIERS
MAGNETIC SUSCEPTIBILITY
MONSOONS
ALGAE
CENOZOIC ERA
CHROMOPHYCOTA
DISASTERS
GEOLOGIC AGES
MAGNETIC PROPERTIES
MATHEMATICAL MODELS
PALEONTOLOGY
PHYSICAL PROPERTIES
PLANTS
QUATERNARY PERIOD
STORMS
TERTIARY PERIOD
540110*