skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Last ice sheet recession and landscape emergence above sea level in east-central Sweden, evaluated using in situ cosmogenic 14 C from quartz
Title: Last ice sheet recession and landscape emergence above sea level in east-central Sweden, evaluated using in situ cosmogenic 14 C from quartz
Abstract. In situ cosmogenic 14C (in situ 14C) in quartz provides a recently developed tool to date exposure of bedrock surfaces of up to ∼ 25 000 years. From outcrops located in east-central Sweden, we tested the accuracy of in situ 14C dating against (i) a relative sea level (RSL) curve constructed from radiocarbon dating of organic material in isolation basins and (ii) the timing of local deglaciation constructed from a clay varve chronology complemented with traditional radiocarbon dating. Five samples of granitoid bedrock were taken along an elevation transect extending southwestwards from the coast of the Baltic Sea near Forsmark. Because these samples derive from bedrock outcrops positioned below the highest postglacial shoreline, they target the timing of progressive landscape emergence above sea level. In contrast, in situ 14C concentrations in an additional five samples taken from granitoid outcrops above the highest postglacial shoreline, located 100 km west of Forsmark, should reflect local deglaciation ages. The 10 in situ 14C measurements provide robust age constraints that, within uncertainties, compare favourably with the RSL curve and the local deglaciation chronology. These data demonstrate the utility of in situ 14C to accurately date ice sheet deglaciation, and durations of postglacial exposure, in regions where cosmogenic 10Be and 26Al routinely return complex exposure results.  more » « less
Award ID(s):
2300559
PAR ID:
10575395
Author(s) / Creator(s):
; ; ; ; ; ; ;
Publisher / Repository:
European Geophysical Union
Date Published:
Journal Name:
Geochronology
Volume:
6
Issue:
2
ISSN:
2628-3719
Page Range / eLocation ID:
291 to 302
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; (, Quaternary Research)
    Abstract Postglacial emergence curves are used to infer mantle rheology, delimit ice extent, and test models of the solid Earth response to changing ice and water loads. Such curves are rarely produced by direct dating of land emergence; rather, most rely on the presence of radiocarbon-datable organic material and inferences made between the age of sedimentary deposits and landforms indicative of former sea level. Here, we demonstrate a new approach,10Be dating, to determine rates of postglacial land emergence in two different settings. In southern Greenland (Narsarsuaq/Igaliku), we date directly the exposure, as relative sea level fell, of gravel beaches and rocky outcrops allowing determination of rapid, post–Younger Dryas emergence. In western Greenland (Kangerlussuaq), we constrain Holocene isostatic response by dating the sequential stripping of terrace sediment driven by land-surface uplift, relative sea-level fall, and resulting fluvial incision. The technique we employ provides high temporal and elevation resolution important for quantifying rapid emergence immediately after deglaciation and less rapid uplift during the middle Holocene.10Be-constrained emergence curves can improve knowledge of relative sea-level change by dating land emergence along rocky coasts, at elevations and locations where radiocarbon-datable sediments are not present, and without the lag time needed for organic material to accumulate. 
    more » « less
  2. ; ; ; (, Geochronology)
    Abstract. We report new cosmogenic 21Ne in quartz exposure ages from 18 samples on three distinct moraines deposited in the Lost Creek drainage, approximately 3–7 km down-valley from Lassen Peak in Lassen Volcanic National Park. Although measuring 21Ne in quartz is generally straightforward, accurate 21Ne exposure dating of deposits of late Pleistocene is rarely possible due to the significant quantities of non-cosmogenic 21Ne present in most lithologies. Young quartz-bearing volcanic rocks have been observed to be an exception. We take advantage of moraine boulders sourced from the ∼ 28 ka dacite of Lassen Peak to generate a chronology of alpine deglaciation in Lassen Volcanic National Park. Ages from three distinct moraines are in stratigraphic order at 22.1 ± 3.8, 20.2 ± 2.4, and 15.3 ± 3.8 ka and generally agree with other terminal and some recessional moraine ages across the Cascade Range and Sierra Nevada of the western United States. To date, these are among the youngest surfaces ever dated using cosmogenic 21Ne and provide a cost-effective proof-of-concept approach to dating moraines where applicable. 
    more » « less
  3. ; ; ; ; (, Geosciences)
    Constraining the timing and rate of Laurentide Ice Sheet (LIS) retreat through the northeastern United States is important for understanding the co-evolution of complex climatic and glaciologic events that characterized the end of the Pleistocene epoch. However, no in situ cosmogenic 10Be exposure age estimates for LIS retreat exist through large parts of Connecticut or Massachusetts. Due to the large disagreement between radiocarbon and 10Be ages constraining LIS retreat at the maximum southern margin and the paucity of data in central New England, the timing of LIS retreat through this region is uncertain. Here, we date LIS retreat through south-central New England using 14 new in situ cosmogenic 10Be exposure ages measured in samples collected from bedrock and boulders. Our results suggest ice retreated entirely from Connecticut by 18.3 ± 0.3 ka (n = 3). In Massachusetts, exposure ages from similar latitudes suggest ice may have occupied the Hudson River Valley up to 2 kyr longer (15.2 ± 0.3 ka, average, n = 2) than the Connecticut River Valley (17.4 ± 1.0 ka, average, n = 5). We use these new ages to provide insight about LIS retreat timing during the early deglacial period and to explore the mismatch between radiocarbon and cosmogenic deglacial age chronologies in this region. 
    more » « less
  4. ; ; ; ; ; ; ; ; ; (, The Cryosphere)
    Abstract. Investigating North Pacific climate variability during warmintervals prior to the Common Era can improve our understanding of thebehavior of ocean–atmosphere teleconnections between low latitudes and theArctic under future warming scenarios. However, most of the existing icecore records from the Alaskan and Yukon region only allow access to climateinformation covering the last few centuries. Here we present asurface-to-bedrock age scale for a 210 m long ice core recovered in 2013from the summit plateau of Begguya (Mt. Hunter; Denali National Park,Central Alaska). Combining dating by annual layer counting with absolutedates from micro-radiocarbon dating, a continuous chronology for the entireice core archive was established using an ice flow model. Calibrated14C ages from the deepest section (209.1 m, 7.7 to 9.0 ka cal BP)indicate that basal ice on Begguya is at least of early Holocene origin. Aseries of samples from a shallower depth interval (199.8 to 206.6 m) weredated with near-uniform 14C ages (3 to 5 ka cal BP). Our resultssuggest this may be related to an increase in annual net snow accumulationrates over this period following the Northern Hemisphere Holocene ClimateOptimum (around 8 to 5 kyr BP). With absolute dates constraining thetimescale for the last >8 kyr BP, this paleo-archive will allowfuture investigations of Holocene climate and the regional evolution ofspatial and temporal changes in atmospheric circulation and hydroclimate inthe North Pacific. 
    more » « less
  5. ; ; ; ; ; ; (, EGUsphere, Cyrosphere preprint)
    Abstract. To understand the erosivity of the eastern portion of the Laurentide Ice Sheet and the isotopic characteristics of the sediment it transported, we sampled buried sand from deglacial features (eskers and deltas) across eastern Canada (n = 10), a landscape repeatedly covered by the Quebec-Labrador Ice Dome. We measured concentrations of 10Be and 26Al in quartz isolated from the sediment and, after correcting for sub-surface cosmic-ray exposure after Holocene deglaciation, used these results to determine nuclide concentrations at the time the ice sheet deposited the sediment. To determine what percentage of sediment moving through streams and rivers currently draining the field area was derived from incision of thick glacial deposits as opposed to surface erosion, we used 10Be and 26Al as tracers by collecting and analyzing modern river sand sourced from Holocene-exposed landscapes (n = 11). We find that all ten deglacial sediment samples contain measurable concentrations of 10Be and 26Al equivalent on average to several thousand years of surface exposure – after correction, based on sampling depth, for Holocene nuclide production after deposition. Error-weighted averages (1 standard deviation errors) of measured 26Al/10Be ratios for both corrected deglacial (6.1 ± 1.2) and modern sediment samples (6.6 ± 0.5) are slightly lower than the production ratio at high latitudes (7.3 ± 0.3) implying burial and preferential decay of 26Al, the shorter-lived nuclide. However, five deglacial samples collected closer to the center of the former Quebec-Labrador Ice Dome have much lower corrected 26Al/10Be ratios (5.2 ± 0.8) than five samples collected closer to the former ice margins (7.0 ± 0.7). Modern river sand contains on average about 1.75 times the concentration of both nuclides compared to deglacial sediment corrected for Holocene exposure. The ubiquitous presence of 10Be and 26Al in eastern Quebec deglacial sediment is consistent with many older-than-expected exposure ages, reported here and by others, for bedrock outcrops and boulders once covered by the Quebec-Labrador Ice Dome. Together, these data suggest that glacial erosion and sediment transport in eastern Canada were insufficient to remove material containing cosmogenic nuclides produced during prior interglacial periods both from at least some bedrock outcrops and from all glacially transported sediment we sampled. Near the center of the Quebec-Labrador Ice Dome, ratios of 26Al/10Be are below those characteristic of surface production at high latitude. This suggests burial of the glacially transported sediment for at least many hundreds of thousands of years and the possibility that ice at the center of the Quebec-Labrador Ice Dome survived many interglacials when more distal ice melted away. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email