Mono Lake

Mono Lake is a special place with something for every earth scientist: the striking granitic peaks of the Sierra Nevada separated from the lake by the Sierra Nevada Fault, glacial moraines pouring forth from them, the line of young volcanos marching into the lake in the Mono-Inyo Craters, the stack of associated ashes interbedded with thick deposits of lake sediments, abundant geomorphological evidence for changes in lake level associated with past climate variability, and the extreme chemistry and biology of the lake itself. Lamont scientists have worked at the lake since Wally Broecker in 1955. The involvement of the AGES lab extends back to the 1990s, and the group has worked on both the geochemistry of the lake and the chronology of the sediments and other geomorphological features around it.

The Wilson Creek Formation has been a particular focus of the group. This stack of late Pleistocene lake sediments sits high above the modern lake, indicating that the lake was much higher during glacial times. There are nineteen distinct ash layers (most of which actually comprise multiple eruptive events) throughout the section, which spans about 67,000 years from approximately the transition for the last major interglacial (MIS 5a/MIS4 boundary) until just before the start of the Holocene. Dating these ashes is a challenge due to their young age, but is imperative because of their significance for the climate system. Lab members including Sidney Hemming, Stephen Cox, and alum Guleed Ali, along with many collaborators and other alumni, have employed novel techniques including allanite (U-Th)/He (Cox et al., 2012) and carbonate U-Th disequilibrium (Ali et al., 2020) dating of associated deposits along with pushing the boundaries of 40Ar/39Ar dating to address this challenge.

Columbia Affiliations