Small sub-alpine glacial lakes are often targeted as Holocene paleoclimate archives, but their evolution as landforms and depositional basins is understudied. At June Lake in the eastern Sierra Nevada of California (USA), bathymetry, surface sediment composition, and seismic stratigraphy are studied to assess the modern sedimentary system and gain insight into the basin’s origins. A basin-wide seismic survey reveals sublacustrine morphological features that attest to the role of ice in scouring the June Lake basin, including a prominent abraded bedrock shoal and an adjacent overdeepened depression. The seismic survey reveals four acoustically distinct stratigraphic units that reflect the history of sedimentation following glacial scouring. The youngest of these is represented in the recovered lacustrine core records as hemipelagically deposited, organic-rich, laminated diatomaceous oozes alternating with coarse tephra beds. The organic-rich oozes are characterized by low carbon and nitrogen stable-isotope values and occur in profundal areas of the modern lake floor. These sediments suggest an algae-dominated productivity regime and preservation of organic matter at depth. With no perennial streams entering June Lake, surface-sediment grain-size distribution and geochemistry are controlled by water depth and basin morphology. Additional modern facies types include poorly sorted coarse detrital landslide deposits below steep basin walls and volcaniclastic sandy gravel in windward littoral areas. These data provide a modern facies model for sedimentation in ice-scoured, hydrologically closed sub-alpine lakes and a baseline for future paleoclimate studies using June Lake sediment cores.
Bibliographical noteFunding Information:
Work at June Lake was permitted through the Inyo National Forest (USFS). We are grateful for field work support from the Overcash Fund for Field Research and alumni donors to the University of Kentucky Field Geology Fund. Partial funding was also provided by Lawrence Livermore National Laboratories grant 17-ERD-052 to SZ; this is LLNL-JRNL-764279. We thank Casey Shannon from the Inyo NF and Jon Simmons from the June Lake Public Utility District for information on June Lake’s hydrology and water chemistry. We also thank John and Mickey Frederickson at the June Lake Marina for generously allowing us to use their facilities and equipment. We are grateful for laboratory and field assistance from UK students, especially J. Lucas, B. Hodelka, and the EES Quaternary Geology class, and STEAM Academy interns Nell Adkins, Zach Eichner, and Ava Hutt. We appreciate the staff of LacCore for their assistance with core preparation and sampling. Finally, we thank associate editor Dan LeHeron and two anonymous reviewers for comments that greatly improved the manuscript.
Copyright © 2019, SEPM (Society for Sedimentary Geology).
Copyright 2019 Elsevier B.V., All rights reserved.
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