PAST AND PRESENT WEATHERING ENVIRONMENTS IN THE DRY VALLEYS, ANTARCTICA BASED ON SEDIMENT CHEMISTRY
CIA values for the tills, regardless of age, are similar. However, fluvial samples show an age-related difference. Modern stream sediments had an average CIA of 42, ranging from 40 to 44. Holocene alluvial fans, dated using OSL, range from CIA of 36 - 50 (avg = 41). These values suggest a relatively weak weathering environment. Fluvial sediments dated using volcanic ash to before the climate transition have CIA values ranging from 42 to 77, with an average of 69. This suggests a more intense weathering regime at that time. On a CIA plot, samples from the Friis Hills show slight variation from the expected trend toward K.
The very low CIA values observed in select samples may be due to the contribution of mafic volcanic dikes and sills to the sediment matrix (e.g., Ferrar dolerite CIA = 43). Aerial deposit of salts from the nearby ocean may also contribute to low CIA values. The combination of various bedrock contributions and weathering regimes results in distinct geochemical groupings. We are evaluating whether chemical fingerprinting of each sediment type, related to weathering environment, age, and provenance, is possible.