EOLIAN DEPOSITION PATTERNS IN THE EASTERN EQUATORIAL PACIFIC OCEAN AND THE PALEOCLIMATE OF THE LATE CENOZOIC

Dust records from deep sea sediments help us understand ancient wind patterns during important climate transitions during the Cenozoic. We have isolated and analyzed the eolian fraction of bulk sediments recovered during Integrated Ocean Drilling Program (IODP) Expedition 320/321 in the eastern tropical Pacific. Temporal and spatial patterns of grain size and mass accumulation rate reveal past changes in atmospheric circulation. During the middle to late Miocene (~15 – 5.3 Ma), the Earth’s climate transitioned from a single-pole style glaciation (only Antarctica) to bi-polar glacial conditions (both Antarctica and glacial cycles in the Northern Hemisphere). We will use the dust records transported by ancient trade winds to identify their intensity and to mark the latitudinal location of the intertropical convergence zone (ITCZ). The ITCZ is where the trade winds meet and is characterized by a reduction in the size of eolian dust and increases in their rate of mass accumulation. The paleolocation of the ITCZ reveals where past winds were blowing, providing insight to surface ocean currents and their impact on sea surface temperatures (SST) and productivity levels. Past studies suggest a more northerly latitudinal position of the ITCZ during the middle to late Miocene and a southerly shift as the Northern Tradewinds grew increasingly when northern hemisphere ice ages began in the late Cenozoic (Hovan, 1995). In our study we have produced a higher resolution time series to enable a better comparison between past changes in wind intensity, global ice volume, and other records of global climate.