Sediment cores from Burial Lake located in the western Brooks Range in Arctic Alaska record paleoenvironmental changes that span the last 37,000 calendar years before present (cal yr BP). We identified four distinct lithologic subunits based on physical properties (dry bulk density, magnetic susceptibility), sediment composition, and geochemical proxies (organic matter, biogenic silica, C/N, organic matter δ13C and δ15N, and elemental data from scanning X-ray fluorescence). The multi-proxy approach and relatively high temporal resolution (at multi-decadal to centennial time scales) of our proxy analysis, compared with previous studies of intermediate water depth cores from Burial Lake, provide new insights into the paleoenvironmental history of the region spanning the period prior to the Last Glacial Maximum. Relatively high lake-levels and gradually decreasing in-lake and terrestrial productivity occur during the mid-Wisconsin interstadial from 37,200 to 29,600 cal yr BP. The subsequent period is defined by falling and lower lake-levels with decreasing effective-moisture, windier conditions, and sustained low aquatic productivity throughout the LGM between 29,600 and 19,600 cal yr BP. The last deglaciation that commenced by 19,600 cal yr BP is characterized by gradual changes in several sediment physical and geochemical proxies, including increasing C/N ratios and terrestrial productivity, decreasing magnetic susceptibility and clastic sediment flux, along with rising and relatively higher lake-levels. A decrease in aeolian activity after 16,500 cal yr BP is inferred from the appearance of fine (very fine sandy silt) sediment, compared to coarse sediments through the LGM and last deglaciation. The highest levels of terrestrial inputs along with increasing and variable aquatic productivity occur during the Lateglacial to early Holocene interval between 16,500 and 8800 cal yr BP. The absence of multi-proxy evidence for a strong climatic reversal during the Younger Dryas from Burial Lake sediments contrasts with some paleorecords showing cooler temperatures and/or dry conditions in northern Alaska at this time. Peak levels of sediment organic content and terrestrial productivity at Burial Lake between 10,500 and 9900 cal yr BP coincide with the early Holocene summer insolation maxima, which likely represents summertime warming and an enhanced flux of watershed derived organic matter from permafrost degradation. The remainder of the Holocene (since 8800 cal yr BP) at Burial Lake is characterized by relatively high and stable lake levels, landscape stabilization, and relatively high and variable levels of aquatic productivity.
Bibliographical noteFunding Information:
Funding for this project was provided by the National Science Foundation ( NSF-ARC 0909545 ) to Abbott and Stoner. Finkenbinder recognizes support from the University of Pittsburgh Mellon Predoctoral Fellowship during the writing of this manuscript. We would like to thank Dr. Nathan Stansell for his help with fieldwork at Burial Lake in the summer of 2010; John Southon, Guaciarra dos Santos and prep-lab personnel (Chanda Bertrand, Hector Martinez, and Shari Bush) at the Keck Carbon Cycle Accelerator Mass Spectrometry Laboratory at the University of California, Irvine for assistance in preparing graphite targets and radiocarbon measurement; Dr. Emily Elliot for her assistance and use of the UV-VIS spectrophotometer for biogenic silica measurement; Aubrey Hillman and David Pompeani for helpful ideas and discussion with the research; and Darren Larsen for review of an early version of the manuscript. We also thank the editor and comments from two anonymous reviewers that greatly improved the manuscript.
© 2015 Elsevier Ltd.
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- Biogenic silica
- Carbon and nitrogen isotopes
- Climate change
- Eastern Beringia
- Last Glacial Maximum
- Magnetic susceptibility
- Scanning X-ray fluorescence