A new glacial varve chronology along the southern Laurentide Ice Sheet that spans the Younger Dryas–Holocene boundary

Geology ◽  
2020 ◽  
Author(s):  
A. Breckenridge ◽  
T.V. Lowell ◽  
D. Peteet ◽  
N. Wattrus ◽  
M. Moretto ◽  
...  
Keyword(s):  
North America ◽  
Ice Core ◽  
Younger Dryas ◽  
Laurentide Ice Sheet ◽  
Lake Agassiz ◽  
Red Clay ◽  
Data Set ◽  
The Holocene ◽  
Varve Chronology ◽  
Constant Rate

Glacial varves can detail ice-margin positions and provide a proxy for meltwater discharge at resolutions comparable to those of the Greenland ice core archives, and thus they can be critical paleorecords for assessing the response of both ancient and modern ice sheets to climate change. Here we provide an ~1500 yr varve chronology straddling the Younger Dryas (YD)–Holocene boundary (11.65 cal. kyr B.P.), the first such chronology in North America. The varves are from glacial Lake Agassiz (central North America). The chronology is pinned on accelerator mass spectrometry radiocarbon-dated terrestrial macrofossils at the base of a widespread red-clay bed deposited during flooding from the Lake Superior basin. We illustrate the utility of this record by examining ice-margin retreat and melting through the late Younger Dryas and across the Holocene boundary. The ice margin receded at a constant rate, not only during the late YD, but for at least 300 yr after the onset of the Holocene. In contrast, varve thicknesses increased at the boundary, and a moraine formed over a 50 yr period, perhaps in response to the warming climate. Our expectation is that this time series will continue to be developed, expanded, and refined because it promises to be the longest and most geographically extensive glacial varve data set in North America.

scholarly journals A New 14C Calibration Data Set for the Last Deglaciation Based on Marine Varves

Radiocarbon ◽  
1997 ◽  
Vol 40 (1) ◽  
pp. 483-494 ◽  
Author(s):  
Konrad A. Hughen ◽  
Jonathan T. Overpeck ◽  
Scott J. Lehman ◽  
Michaele Kashgarian ◽  
John R. Southon ◽  
...  
Keyword(s):  
Global Climate ◽  
Ice Core ◽  
Younger Dryas ◽  
Core Layer ◽  
Cariaco Basin ◽  
Calibration Data ◽  
Last Deglaciation ◽  
Data Set ◽  
The Last Deglaciation ◽  
Calibration Data Set

Varved sediments of the tropical Cariaco Basin provide a new 14C calibration data set for the period of deglaciation (10,000 to 14,500 years before present: 10–14.5 cal ka bp). Independent evaluations of the Cariaco Basin calendar and 14C chronologies were based on the agreement of varve ages with the GISP2 ice core layer chronology for similar high-resolution paleoclimate records, in addition to 14C age agreement with terrestrial 14C dates, even during large climatic changes. These assessments indicate that the Cariaco Basin 14C reservoir age remained stable throughout the Younger Dryas and late Allerød climatic events and that the varve and 14C chronologies provide an accurate alternative to existing calibrations based on coral U/Th dates. The Cariaco Basin calibration generally agrees with coral-derived calibrations but is more continuous and resolves century-scale details of 14C change not seen in the coral records. 14C plateaus can be identified at 9.6, 11.4, and 11.7 14C ka bp, in addition to a large, sloping “plateau” during the Younger Dryas (∼10 to 11 14C ka bp). Accounting for features such as these is crucial to determining the relative timing and rates of change during abrupt global climate changes of the last deglaciation.

Changing Patterns in the Holocene Pollen Record of Northeastern North America: A Mapped Summary

1977 ◽  
Vol 8 (1) ◽  
pp. 64-96 ◽  
Author(s):  
J. Christopher Bernabo ◽  
Thompson Webb
Keyword(s):  
North America ◽  
Large Scale ◽  
Deciduous Forest ◽  
Rapid Expansion ◽  
Early Holocene ◽  
Pollen Record ◽  
Data Set ◽  
Northeastern North America ◽  
The Holocene ◽  
Changing Patterns

By mapping the data from 62 radiocarbon-dated pollen diagrams, this paper illustrates the Holocene history of four major vegetational regions in northeastern North America. Isopoll maps, difference maps, and isochrone maps are used in order to examine the changing patterns within the data set and to study broad-scale and long-term vegetational dynamics. Isopoll maps show the distributions of spruce (Picea), pine (Pinus), oak (Quercus), herb (nonarboreal pollen groups excluding Cyperaceae), and birch + maple + beech + hemlock (Betula, Acer, Fagus, Tsuga) pollen at specified times from 11,000 BP to present. Difference maps were constructed by subtracting successive isopoll maps and illustrate the changing patterns of pollen abundances from one time to the next. The isochrone maps portray the movement of ecotones and range limits by showing their positions at a sequence of times during the Holocene. After 11,000 BP, the broad region over which spruce pollen had dominated progressively shrank as the boreal forest zone was compressed between the retreating ice margin and the rapidly westward and northward expanding region where pine was the predominant pollen type. Simultaneously, the oak-pollen-dominated deciduous forest moved up from the south and the prairie expanded eastward. By 7000 BP, the prairie had attained its maximum eastward extent with the period of its most rapid expansion evident between 10,000 and 9000 BP. Many of the trends of the early Holocene were reversed after 7000 BP with the prairie retreating westward and the boreal and other zones edging southward. In the last 500 years, man's impact on the vegetation is clearly visible, especially in the greatly expanded region dominated by herb pollen. The large scale changes before 7000 BP probably reflect shifts in the macroclimatic patterns that were themselves being modified by the retreat and disintegration of the Laurentide ice sheet. Subsequent changes in the pollen and vegetation were less dramatic than those of the early Holocene.

A multi-proxy study of changing environmental conditions in a Younger Dryas sequence in southwestern Manitoba, Canada, and evidence for an extraterrestrial event

2019 ◽  
Vol 93 ◽  
pp. 60-87 ◽  
Author(s):  
James Teller ◽  
Matthew Boyd ◽  
Malcolm LeCompte ◽  
James Kennett ◽  
Allen West ◽  
...  
Keyword(s):  
Younger Dryas ◽  
Water Levels ◽  
Laurentide Ice Sheet ◽  
Lake Agassiz ◽  
Canadian Prairies ◽  
Rivers And Lakes ◽  
Sudden Appearance ◽  
River Valleys ◽  
Dry Woodland ◽  
Insight Into

AbstractMulti-proxy analyses of a sequence spanning the Younger Dryas (YD) in the Glacial Lake Hind basin of Manitoba provides insight into regional paleohydrology and paleovegetation of meltwater rivers and lakes spanning >4000 yr; the sequence is controlled by 25 new accelerator mass spectrometry ages. This lake, dammed by the Laurentide Ice Sheet, overflowed into Lake Agassiz. The pre-YD interval records rapid sedimentation from meltwaters that headed in proglacial lakes in the Canadian Prairies that are known to have been catastrophically released when ice or sediment barriers were breached. Pollen in this phase is dominated by pre-Quaternary forms eroded from Paleocene bedrock. At the onset of the YD at ~12.8 cal ka, the sudden appearance of concentrations of nanodiamonds, high-temperature magnetic spherules, platinum, and iridium provide evidence of an extraterrestrial (ET) event that others have identified at more than 40 sites in North America. Major changes in oceans and climate, and the catastrophic outflow of nearby Lake Agassiz at the onset of the YD, may be related. Lower water levels and a reduction of Souris River inflow to Lake Hind followed, which are reflected by more clayey and organic-rich sediments and a decrease in pre-Quaternary palynomorphs. This may have resulted from the deepening of river valleys caused by the release of meltwater triggered by the ET event. Wetlands then began to develop, leading to peat deposition from 12.3 to 11 cal ka. This was followed by a fluvial episode depositing sand and then by increased Holocene aridity that resulted in accumulation of a thick sequence of dune sands. A dry woodland environment with a mix of conifers (especially Picea and Larix) and deciduous trees (especially Populus and Quercus) covered the uplands from ~13 to 10 cal ka.

scholarly journals Direct land/sea correlation of the Eemian, and its comparison with the Holocene: a high-resolution palynological record off the Iberian margin

2000 ◽  
Vol 79 (2-3) ◽  
pp. 345-354 ◽  
Author(s):  
M.F. Sánchez Goñi ◽  
J.-L. Turon ◽  
F. Eynaud ◽  
N.J. Shackleton ◽  
O. Cayre
Keyword(s):  
High Resolution ◽  
Ice Core ◽  
Younger Dryas ◽  
Warming Trend ◽  
Climatic Changes ◽  
The Holocene ◽  
Ice Core Record ◽  
Marine Isotope Stage 5 ◽  
Climatic Pattern ◽  
Mis 5

AbstractHigh-resolution pollen, dinocyst and isotopie profiles covering the marine isotope stage 5 (MIS 5) are presented from core MD952042 (Tagus abyssal plain, 37°47'N, 10°09'W). Both marine and terrestrial proxies indicate the occurrence of a Bølling-Allerød-Younger Dryas-like event at the beginning of MI substage 5e. The terrestrial Eemian stage coincides with both the lightest oxygen isotope values of substage 5e and the heavier ones approaching the 5e/5d transition. Accordingly, the Eemian is not equivalent to MI substage 5e, as the Holocene is not equivalent to MIS 1.Remarkably, both pollen and dinocyst data reflect the same climatic pattern on land and ocean, and they evidence a succession of climatic events that the isotope signal does not identify. The Eemian began with a Mediterranean vegetation that was gradually replaced by Eurosiberian formations indicating a change from Mediterranean to oceanic climates. In the middle of the Eemian, warming conditions were interrupted by an event corresponding to a slight cooling resulting from an increase in precipitation over land and ocean. Finally, a warming trend characterised the last phase of the Eemian. The occurrence of small climatic changes during this interglacial is inconsistent with the dramatic variability suggested by the GRIP ice-core record.

scholarly journals A detailed radiostratigraphic data set for the central East Antarctic Plateau spanning from the Holocene to the mid-Pleistocene

2021 ◽  
Vol 13 (10) ◽  
pp. 4759-4777
Author(s):  
Marie G. P. Cavitte ◽  
Duncan A. Young ◽  
Robert Mulvaney ◽  
Catherine Ritz ◽  
Jamin S. Greenbaum ◽  
...  
Keyword(s):  
Ice Core ◽  
Radar Data ◽  
Glacial Cycles ◽  
Data Set ◽  
Ice Flow ◽  
The Holocene ◽  
Antarctic Plateau ◽  
The Us ◽  
Core Site ◽  
Program Data

Abstract. We present an ice-penetrating radar data set which consists of 26 internal reflecting horizons (IRHs) that cover the entire Dome C area of the East Antarctic plateau, the most extensive to date in the region. This data set uses radar surveys collected over the space of 10 years, starting with an airborne international collaboration in 2008 to explore the region, up to the detailed ground-based surveys in support of the Beyond EPICA – Oldest Ice (BE-OI) European Consortium. Through direct correlation with the EPICA-DC ice core, we date 19 IRHs that span the past four glacial cycles, from 10 ka, beginning of the Holocene, to over 350 ka, ranging from 10 % to 83 % of the ice thickness at the EPICA-DC ice core site. We indirectly date and provide stratigraphic information for seven older IRHs using a 1D ice flow inverse model, going back to an estimated 700 ka. Depth and age uncertainties are quantified for all IRHs and provided as part of the data set. The IRH data set presented in this study is available at the US Antarctic Program Data Center (USAP-DC) (https://doi.org/10.15784/601411, Cavitte et al., 2020) and represents a contribution to the SCAR AntArchitecture action group (AntArchitecture, 2017).

Importance of the Rossendale Site in Establishing a Deglacial Chronology Along the Southwestern Margin of the Laurentide Ice Sheet

1989 ◽  
Vol 32 (1) ◽  
pp. 12-23 ◽  
Author(s):  
James T. Teller
Keyword(s):  
Organic Matter ◽  
North America ◽  
Radiocarbon Dating ◽  
Ice Sheet ◽  
Water Phase ◽  
Laurentide Ice Sheet ◽  
Lake Agassiz ◽  
Southwestern Margin

AbstractThe timing of deglaciation in the Lake Agassiz basin is critical in establishing the routing of meltwater and precipitation runoff from a 2,000,000-km2 region of central North America and in evaluating the influence this water had on rivers and oceans into which it drained. Dates of 12,400 ± 420 and 12,100 ± 160 yr B.P. for moss at the Rossendale site in Manitoba have long been a key for those advocating an “early” deglacial chronology in this region. However, new dates for wood from this site and paleoecological interpretations of ostracods, molluscs, and the dated moss all support a “young” deglacial scenario. Of particular significance is the fact that the dated moss, Scorpidium scorpioides, is a subaquatic type subject to contamination by old carbon dissolved from bedrock. In fact, most subaquatic moss may be unreliable for radiocarbon dating. For these reasons, the 12,400 and 12,100 yr B.P. dates are rejected. New dates of 9600 ± 70 and 9510 ± 90 yr B.P. for wood from the same organic-rich unit containing the dated moss, ostracods, and molluscs fit well with the “young” deglacial chronology of the southwestern Laurentide ice margin advocated by many. In short, the ice margin appears to have retreated into the southern Lake Agassiz basin after 12,000 yr B.P. and north of the Rossendale site by 11,000 yr B.P. About 10,000 yr B.P., following the Moorhead low-water phase, Lake Agassiz rose to the Campbell level. The dated organic matter at Rossendale was deposited in a lagoon behind the Campbell beach.

Earliest Evidence for Geophyte Use in North America: 11,500-Year-Old Archaeobotanical Remains from California's Santarosae Island

2021 ◽  
pp. 1-13
Author(s):  
Kristina M. Gill ◽  
Todd J. Braje ◽  
Kevin Smith ◽  
Jon M. Erlandson
Keyword(s):  
North America ◽  
Coastal Areas ◽  
Channel Islands ◽  
Plant Resources ◽  
The Holocene ◽  
Return Rates ◽  
Archaeobotanical Remains ◽  
Human Use ◽  
Santa Rosa Island ◽  
Protein Rich

There is growing evidence for human use of geophytes long before the advent of agriculture. Rich in carbohydrates, geophytes were important in many coastal areas where protein-rich marine foods are abundant. On California's Channel Islands, scholars have long questioned how maritime peoples sustained themselves for millennia with limited plant resources. Recent research demonstrates that geophytes were heavily used on the islands for 10,000 years, and here we describe geophyte and other archaeobotanical remains from an approximately 11,500-year-old site on Santa Rosa Island. Currently the earliest evidence for geophyte consumption in North America, our data extend geophyte use on the Channel Islands by roughly 1,500 years and document a diverse and balanced economy for early Paleocoastal peoples. Experimental return rates for a key island geophyte support archaeological evidence that the corms of blue dicks (Dipterostemon capitatus) were a high-ranked staple resource throughout the Holocene.

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