Vegetation history in central Kentucky and Tennessee (USA) during the last glacial and deglacial periods

2012 ◽  
Vol 79 (2) ◽  
pp. 189-198 ◽  
Author(s):  
Yao Liu ◽  
Jennifer J. Andersen ◽  
John W. Williams ◽  
Stephen T. Jackson
Keyword(s):  
Vegetation Dynamics ◽  
Vegetation History ◽  
Deciduous Tree ◽  
Climatic Warming ◽  
Last Glacial ◽  
The North ◽  
Site Density ◽  
Heinrich Event ◽  
Pollen Records ◽  
The Last Glacial

AbstractKnowledge about vegetation dynamics during the last glacial and deglacial periods in southeastern North America is under-constrained owing to low site density and problematic chronologies. New pollen records from two classic sites, Anderson Pond, TN, and Jackson Pond, KY, supported by AMS 14C age models, span 25.2–13.7 ka and 31.0–15.4 ka, respectively. A transition from Pinus dominance to Picea dominance is recorded at Jackson Pond ca. 26.2 ka, ~ coincident with Heinrich Event H2. Anderson and Jackson Ponds record a transition from conifer to deciduous-tree dominance ~ 15.9 and 15.4 ka, respectively, marking the development of no-analog vegetation characterized by moderate to high abundances of Picea, Quercus, Carya, Ulmus, Fraxinus, Ostrya/Carpinus, Cyperaceae, and Poaceae, and preceding by ~ 2000 yr the advent of similar no-analog vegetation in glaciated terrain to the north. No-analog vegetation developed as a time-transgressive, south-to-north pattern, mediated by climatic warming. Sporormiella abundances are consistently low throughout the Jackson and Anderson Pond records, suggesting that megafaunal abundances and effects on vegetation varied regionally or possibly that the Sporormiella signal was not well-expressed at these sites. Additional records with well-constrained chronologies are necessary to assess patterns and mechanisms of vegetation dynamics during the last glacial and deglacial periods.

scholarly journals Evidence for strong relations between the upper Tagus loess formation (central Iberia) and the marine atmosphere off the Iberian margin during the last glacial period

2021 ◽  
pp. 1-30
Author(s):  
Daniel Wolf ◽  
Thomas Kolb ◽  
Karolin Ryborz ◽  
Susann Heinrich ◽  
Imke Schäfer ◽  
...  
Keyword(s):  
North Atlantic ◽  
Moisture Transfer ◽  
Sea Temperature ◽  
Last Glacial ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Terrestrial Environments ◽  
The North Atlantic ◽  
Iberian Margin ◽  
The Last Glacial

Abstract During glacial times, the North Atlantic region was affected by serious climate changes corresponding to Dansgaard-Oeschger cycles that were linked to dramatic shifts in sea temperature and moisture transfer to the continents. However, considerable efforts are still needed to understand the effects of these shifts on terrestrial environments. In this context, the Iberian Peninsula is particularly interesting because of its close proximity to the North Atlantic, although the Iberian interior lacks paleoenvironmental information so far because suitable archives are rare. Here we provide an accurate impression of the last glacial environmental developments in central Iberia based on comprehensive investigations using the upper Tagus loess record. A multi-proxy approach revealed that phases of loess formation during Marine Isotope Stage (MIS) 2 (and upper MIS 3) were linked to utmost aridity, coldness, and highest wind strengths in line with the most intense Greenland stadials also including Heinrich Events 3–1. Lack of loess deposition during the global last glacial maximum (LGM) suggests milder conditions, which agrees with less-cold sea surface temperatures (SST) off the Iberian margin. Our results demonstrate that geomorphological system behavior in central Iberia is highly sensitive to North Atlantic SST fluctuations, thus enabling us to reconstruct a detailed hydrological model in relation to marine–atmospheric circulation patterns.

Absence of Last Glacial Maximum Records in Lowland Tropical Forests

1998 ◽  
Vol 49 (2) ◽  
pp. 233-237 ◽  
Author(s):  
Marie-Pierre Ledru ◽  
Jacques Bertaux ◽  
Abdelfettah Sifeddine ◽  
Kenitiro Suguio
Keyword(s):  
South America ◽  
Tropical Forests ◽  
Last Glacial Maximum ◽  
Sedimentation Rate ◽  
Glacial Maximum ◽  
Radiocarbon Dates ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
Pollen Records ◽  
The Last Glacial

Environmental conditions of the lowland tropical forests during the last glacial maximum (LGM) between ca 20,000 and 18,000 14C yr B.P., are reevaluated in terms of dating control and lithology analyzed in seven pollen records from South America. The reevaluation shows that probably in none of the published records are LGM sediments present or abundant. This conclusion is based on the occurrence of abrupt lithologic changes coupled with changes in sedimentation rate interpolated from radiocarbon dates. These findings suggest that the LGM was represented probably by a hiatus of several thousand years, indicative of drier climates than before or after.

scholarly journals The Last Glacial Maximum and Heinrich Event 1 in terms of climate and vegetation around the Alboran Sea: a preliminary model-data comparison

2005 ◽  
Vol 337 (10-11) ◽  
pp. 983-992 ◽  
Author(s):  
Masa Kageyama ◽  
Nathalie Combourieu Nebout ◽  
Pierre Sepulchre ◽  
Odile Peyron ◽  
Gerhard Krinner ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Model Data ◽  
Last Glacial ◽  
Data Comparison ◽  
Heinrich Event ◽  
Preliminary Model ◽  
The Last Glacial Maximum ◽  
Heinrich Event 1 ◽  
The Last Glacial

scholarly journals Reconstruction of North American drainage basins and river discharge since the Last Glacial Maximum

2016 ◽  
Vol 4 (4) ◽  
pp. 831-869 ◽  
Author(s):  
Andrew D. Wickert
Keyword(s):  
North American ◽  
Drainage Basin ◽  
Ice Sheets ◽  
Glacial Isostatic Adjustment ◽  
Drainage Basins ◽  
Last Glacial ◽  
Isostatic Adjustment ◽  
The North ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Over the last glacial cycle, ice sheets and the resultant glacial isostatic adjustment (GIA) rearranged river systems. As these riverine threads that tied the ice sheets to the sea were stretched, severed, and restructured, they also shrank and swelled with the pulse of meltwater inputs and time-varying drainage basin areas, and sometimes delivered enough meltwater to the oceans in the right places to influence global climate. Here I present a general method to compute past river flow paths, drainage basin geometries, and river discharges, by combining models of past ice sheets, glacial isostatic adjustment, and climate. The result is a time series of synthetic paleohydrographs and drainage basin maps from the Last Glacial Maximum to present for nine major drainage basins – the Mississippi, Rio Grande, Colorado, Columbia, Mackenzie, Hudson Bay, Saint Lawrence, Hudson, and Susquehanna/Chesapeake Bay. These are based on five published reconstructions of the North American ice sheets. I compare these maps with drainage reconstructions and discharge histories based on a review of observational evidence, including river deposits and terraces, isotopic records, mineral provenance markers, glacial moraine histories, and evidence of ice stream and tunnel valley flow directions. The sharp boundaries of the reconstructed past drainage basins complement the flexurally smoothed GIA signal that is more often used to validate ice-sheet reconstructions, and provide a complementary framework to reduce nonuniqueness in model reconstructions of the North American ice-sheet complex.

scholarly journals A high-resolution model of the 100 ka ice-age cycle

1997 ◽  
Vol 25 ◽  
pp. 58-65 ◽  
Author(s):  
L. Tarasov ◽  
W. R. Peltier
Keyword(s):  
Large Scale ◽  
Climate Model ◽  
Relaxation Times ◽  
Ice Age ◽  
Adjustment Process ◽  
Glacial Cycle ◽  
Ice Dynamics ◽  
Last Glacial ◽  
The North ◽  
The Last Glacial

Significant improvements to the representation of climate forcing and mass-balance response in a coupled two-dimensional global energy balance climate model (EBM) and vertically integrated ice-sheet model (ISM) have led to the prediction of an ice-volume chronology for the most recent ice-age cycle of the Northern Hemisphere that is close to that inferred from the geological record. Most significant is that full glacial termination is delivered by the model without the need for new physical ingredients. In addition, a relatively close match is achieved between the Last Glacial Maximum (LGM) model ice topography and that of the recently-described ICE-4G reconstruction. These results suggest that large-scale climate system reorganization is not required to explain the main variations of the North American (NA) ice sheets over the last glacial cycle. Lack of sea-ice and marine-ice dynamics in the model leaves the situation over the Eurasian (EA) sector much more uncertain.The incorporation of a gravitationally self-consistent description of the glacial isostatic adjustment process demonstrates that the NA and EA bedrock responses can be adequately represented by simpler damped-relaxation models with characteristic time-scales of 3–5ka and 5 ka, respectively. These relaxation times agree with those independently inferred on the basis of postglacial relative sea-level histories.

Rapid climatic warming at the end of the last glacial: new perspectives

2001 ◽  
Vol 30 (1-2) ◽  
pp. 155-165 ◽  
Author(s):  
H Renssen ◽  
R.F.B Isarin ◽  
J Vandenberghe
Keyword(s):  
Climatic Warming ◽  
Last Glacial ◽  
The Last Glacial

Grassland Vegetation in the Southern Great Plains during the Last Glacial Maximum

1995 ◽  
Vol 44 (2) ◽  
pp. 237-245 ◽  
Author(s):  
Stephen A. Hall ◽  
Salvatore Valastro
Keyword(s):  
Last Glacial Maximum ◽  
Great Plains ◽  
Glacial Maximum ◽  
High Plains ◽  
Edwards Plateau ◽  
Southern Great Plains ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
Pollen Records ◽  
The Last Glacial

AbstractNew pollen records from White Lake in the Southern High Plains and from Friesenhahn Cave on the southeastern Edwards Plateau of Texas indicate that the glacial-age vegetation of the southern Great Plains was a grassland. The High Plains was a treeless Artemisia grassland and the Edwards Plateau, at the south edge of the Great Plains, was a grassland with pinyon pines and deciduous trees in canyons and riparian habitats. The glacial-age grasslands differ from modern shortgrass and tallgrass prairies and may have no modern analog. The dominance of prairie vegetation during the last glacial maximum is compatible with late Pleistocene mammalian faunas and late-glacial grassland pollen records from the region. Earlier interpretations of a pine-spruce forest on the High Plains were based on pollen assemblages that are here shown to have been altered by postdepositional deterioration, resulting in differential preservation of conifer pollen grains. Accordingly, the "Tahoka Pluvial" and other "climatic episodes" defined by High Plains pollen records are abandoned.

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