69 Paleolimnological Studies of Climate Variability and Environmental Response (Posters)

Tuesday, 21 March 2017
1:30 PM - 5:30 PM
Grand Ballroom, 17th Floor

A LATEGLACIAL AND HOLOCENE LACUSTRINE RECORD OF PALEOENVIRONMENTAL CHANGE FROM LOST LAKE, INTERIOR ALASKA

Paper number: 69-8
Program: Theme Sessions
Time: 1:30 PM – 5:30 PM

Authors

Abstract

Sediment cores collected from Lost Lake, Alaska, are used to reconstruct relative lake-level change and shifting moisture balance conditions from the latest Pleistocene to the present. Sedimentological analysis of core-transects from closed-basin lakes in the interior of Alaska indicate a period of aridity during the Last Glacial Maximum, higher, variable lake-levels during the Lateglacial period, and high, generally stable lake-levels since the early Holocene. However, after lake-levels increased and stabilized during the early Holocene, many lacustrine systems became largely insensitive to subsequent smaller scale fluctuations. Lost Lake is a relatively shallow (~11 m max. depth) closed-basin lake, which we hypothesize makes it sensitive to lower magnitude lake-level changes. Three sediment cores were collected along a transect from the shoreline to the central depocenter in July of 2012 in 10.6 m, 6.8 m, and 3.1 m water depths. The cores were analyzed for bulk density, grain size, organic matter, high-resolution imagery, grayscale, magnetic susceptibility, and are dated using radiocarbon analysis on terrestrial macrofossils. Basal radiocarbon ages for the deep and intermediate water depth core sites indicate the start of fine-grained, banded to laminated (lacustrine) sedimentation at ~12 ka cal BP. A basal radiocarbon age for the shallow water core (D-12 core) indicates that lacustrine sedimentation began at ~8.1 ka cal BP. Combined, these results suggest dry conditions prior to ~ 12 ka, an increase in lake levels ~ 12 ka, and a further increase to high lake levels ~ 8.1 ka. Abrupt changes in grain size and the presence of coarse sandy layers in the D-12 core suggests the presence of several unconformities and fluctuating lake-levels through the mid to late Holocene. Radiocarbon dating and statistical analyses of a high-resolution (0.1 cm) grayscale record will be used to detect shifts in sedimentology to further constrain lake level variability.

Geological Society of America Abstracts with Programs. Vol. 49, No. 2

doi: 10.1130/abs/2017NE-290702

© Copyright 2017 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.