INTEGRATED HIGH-RESOLUTION GEOLOGICAL AND GEOPHYSICAL EVALUATION OF SEDIMENTARY ARCHITECTURE AT JUNE LAKE, MONO COUNTY, CA

June Lake in the Eastern Sierra Nevada region of California is a small glacial lake that has escaped detailed limnogeological study. The only surface hydrological inputs are seasonal - the lake is fed primarily by underwater springs, with no surface outlets. Its maximum depth is ~40 m, and the surface area is ~1.23 km². Its size and limited recharge make June Lake susceptible to short-term hydrological changes, particularly in light of California’s recent drought.

The objective of this project was to characterize the shallow sedimentary architecture of June Lake, which will help us determine if this basin is a viable archive of Holocene climate change in the Eastern Sierra. CHIRP seismic reflection profiles and a suite of surface sediments and short cores were the primary data sets used; they allowed us to map bathymetry, recent lacustrine sedimentary facies, and the acoustic packages that define the uppermost ~15 meters of the subsurface. Together, these data reveal novel insights into modern sedimentary processes and sublacustrine geomorphology, which provide context for interpretation of the paleoclimate record and guidance for identifying long coring sites. Initial analysis of these cores reveals that recent lacustrine sedimentation varies between authigenic production of biogenic oozes and carbonate with minor clastic contributions, and volcaniclastic deposition of tephra layers, likely sourced from the nearby Mono or Inyo craters. Though not directly observed in cores, more ancient glacial processes are indicated by low amplitude, hummocky acoustic facies in the CHIRP profiles; these are tentatively interpreted as moraine and outwash features.