Xiangwei Guo / Earth & Environmental Sciences / Faculty Mentor: Majie Fan
The temporospatial pattern of eolian (wind-transported) loess deposition is crucial for understanding ancient precipitation and atmospheric circulation patterns and atmospheric dust loading that influences Earth’s radiative forcing budget. Late Paleogene (~36-30 Ma) loess in the western USA has abundant volcaniclastic materials and has been viewed as recycled volcanic ashes by some scholars. Additionally, the onset of loess deposition may be earlier than the apparent change of rocks from stratified to massive units. Here I present new mineralogy and grain size data collected from the Flagstaff Rim in central Wyoming and Toadstool Geologic Park in western Nebraska to show that the loess differs in mineralogical composition from the volcanic ashes, and bimodal grain size spectra typical to loess present in the stratified unit interpreted to be floodplain deposits of rivers. Based on the existing chronology, the eolian deposition at the Flagstaff Rim section initiated at ~36 Ma, 2 Myr earlier than previously thought. This initiation was synchronous with that in the Wagon Spring section to the west, suggesting a more extensive loess deposition in the western USA at ~36 Ma. Uplift in the western USA may have triggered aridification in the sediment source, yielding enhanced erosion and loose sediment for wind transport.
mmm2637
Great poster and presentation Xiangwei!
Xiangwei Guo
Thank you!