Paleochemistry of Lakes Agassiz and Manitoba based on ostracodes

1997 ◽  
Vol 34 (5) ◽  
pp. 699-708 ◽  
Author(s):  
B. Brandon Curry
Keyword(s):  
Overland Flow ◽  
Ionic Composition ◽  
Late Glacial ◽  
Lake Agassiz ◽  
The Holocene ◽  
The Past ◽  
Evaporative Concentration ◽  
Holocene Record

The ionic composition and salinity of Lake Manitoba and its late-glacial precursor, Lake Agassiz, changed significantly over the past 11 000 years. The paleochemical record reported here is based on modern analog environments of ostracodes identified in a new 14.5 m core from southern Lake Manitoba. The ionic composition of Lake Manitoba today is dominated by Na+, Cl−, and HC03−, with much less Ca2+, Mg2+, and K+. Evaporative concentration of modern Lake Manitoba water would lead to greater salinity and the near depletion of Ca2+ due to continued precipitation of calcite. During periods of highest salinity in the Holocene, however, Lake Manitoba supported Limnocythere staplini. Today this species inhabits waters in which [Ca2+] > [HCO3−], including springs associated with groundwater in Paleozoic bedrock discharging into Lake Winnipegosis (and eventually, after much dilution, into Lake Manitoba). Further complicating the Holocene record are intervals containing Limnocythere friabilis that suggest periodic influxes of dilute water, probably from the Assiniboine River, which bypasses Lake Manitoba today. The variations in Holocene paleochemistry indicated by the ostracode record imply changes in the proportion of overland flow plus precipitation relative to groundwater inputs to Lake Manitoba, independent of changes in evaporation relative to precipitation.

Fluctuations of Outlet and Valley Glaciers in the Southern Andes (Argentina) during the Past 13,000 Years

1999 ◽  
Vol 51 (3) ◽  
pp. 238-247 ◽  
Author(s):  
Gerd Wenzens
Keyword(s):  
Younger Dryas ◽  
Late Glacial ◽  
The South ◽  
Southern Andes ◽  
Outlet Glacier ◽  
The Holocene ◽  
The Past ◽  
Late Glacial And Holocene ◽  
Glacial Time

AbstractIn the southern Argentine Andes, ten advances of valley glaciers were used to reconstruct the late-glacial and Holocene glacier history. The accumulation areas of these glaciers lie in the Precordillera and are thus independent of fluctuations of the South Patagonian Icefield. Like the Viedma outlet glacier, the valley glaciers advanced three times during late-glacial time (14,000–10,000 yr B.P.). The youngest advance correlates with the Younger Dryas Stade, based on two minimum AMS14C dates of 9588 and 9482 yr B.P. The second oldest advance occurred before 11,800 yr B.P. During the first half of the Holocene, (ca. 10,000–5000 yr B.P.), advances culminated about 8500, 8000–7500, and 5800–5500 yr B.P. During the second half of the Holocene, advances occurred between ca. 4500 and 4200 yr B.P., as well as between 3600 and 3300 yr B.P. In the Rı́o Cóndor valley three subsequent advances have been identified.

Dissimilarity Mapping Between Fossil and Contemporary Pollen Spectra in Europe for the Past 13,000 Years

1990 ◽  
Vol 33 (3) ◽  
pp. 360-376 ◽  
Author(s):  
Brian Huntley
Keyword(s):  
Distance Measure ◽  
Threshold Value ◽  
Late Glacial ◽  
The Holocene ◽  
The Past ◽  
Rates Of Change ◽  
Paleoclimatic Changes ◽  
Chord Distance ◽  
Changing Patterns

AbstractThe degree of analogy between fossil and contemporary pollen spectra in Europe has been investigated using the chord-distance dissimilarity measure. No-analog pollen spectra represent vegetation without a modern analog and hence, by inference, represent macroclimatic conditions different from any occurring in the region today. Such spectra have minimum chord distances that exceed a threshold value assessed using contemporary samples from the same and different vegetation u units. Contoured maps of minimum chord distance portray the changing patterns of analogous and no-analog pollen spectra, and hence vegetation units, since 13,000 yr B.P. No-analog vegetation units have been extensive in some regions for much of the Holocene, persisting as recently as 1000 years ago in many areas. The chord-distance measure has also been used to explore the patterns, extent, and rates of change in European pollen spectra since 13,000 yr B.P. Pollen spectra changed rapidly during late-glacial and early Holocene times and during the last millennium. Paleoclimatic changes have brought about the major changes in the Holocene paleovegetation of Europe. Human impact upon European vegetation has obscured neither the contemporary relationship between pollen spectra and vegetation nor the climatically determined long-term changes of vegetation across the continent since 13,000 yr B.P.

Évolution postglaciaire des hauts sommets alpins et subalpins de la Gaspésie

1984 ◽  
Vol 21 (3) ◽  
pp. 319-335 ◽  
Author(s):  
Serge Payette ◽  
Francis Boudreau
Keyword(s):  
Little Ice Age ◽  
Podzolic Soil ◽  
Late Glacial ◽  
Ice Age ◽  
Soil Profiles ◽  
Ecological Situation ◽  
The Holocene ◽  
The Past ◽  
Cooling Trend ◽  
Surficial Deposits

The stratigraphy of surficial deposits located in a snow-patch site, at an altitude of 1200 m in the Mount Jacques-Cartier area, provides evidence of a Late Glacial to mid-Holocene deglaciation. During the Late Glacial, or at the beginning of the Holocene, the diamictons on the high summits of the McGerrigle Mountains were affected by a severe periglacial climate, responsible for the formation of most of the periglacial landforms, such as sorted polygons, sorted stripes, stone-banked lobes, and block fields. During the Holocene, these landforms were fossilized by vegetation, and podzolic soil profiles developed within the stony deposits. After the Hypsithermal, a cooling trend was registered in snow-patch sites, where gelifluction was active after ca. 5200, 3470 – 3340, 2500, 2100, 1860, 1490, and 650 BP. Subalpine meadows followed the opening of the forest, at least since 2200 BP, and were due to neoglacial cooling. Within the alpine belt, the coniferous cover regression is registered at least since 1400 BP. During the so-called Little Ice Age of the past centuries, conifers retracted because of periglacial activity, which was followed by the formation of sorted stripes and gelifluction lobes. The extinction of tree species in the alpine tundra is related to periglacial activity, an ecological situation rather specific to the high summits of Gaspé.

scholarly journals A Late Glacial to Holocene record of environmental change from Lake Dojran (Macedonia, Greece)

2012 ◽  
Vol 8 (6) ◽  
pp. 5743-5785 ◽  
Author(s):  
A. Francke ◽  
B. Wagner ◽  
M. J. Leng ◽  
J. Rethemeyer
Keyword(s):  
Late Glacial ◽  
Ice Age ◽  
Humid Climate ◽  
Climate Conditions ◽  
The Holocene ◽  
Erosion Processes ◽  
Environmental Variations ◽  
Age Model ◽  
Balkan Region ◽  
Holocene Record

Abstract. A Late Glacial to Holocene sediment sequence (Co1260, 717 cm) from Lake Dojran, located at the boarder of the F.Y.R. of Macedonia and Greece, has been investigated to provide information on climate variability in the Balkan region. A robust age-model was established from 13 radiocarbon ages, and indicates that the base of the sequence was deposited at ca. 12 500 cal yr BP, when the lake-level was low. Variations in sedimentological (TOC, CaCO3, TC, N, S, grain-size, XRF, δ18Ocarb, δ13Ccarb, δ13Corg) data were linked to hydro-acoustic data and indicate that warmer and more humid climate conditions characterized the remaining period of the Younger Dryas until the beginning of the Holocene. The Holocene exhibits significant environmental variations, including the 8.2 ka and 4.2 ka cooling events, the Medieval Warm Period, and the Little Ice Age. Human induced erosion processes in the catchment of Lake Dojran intensified after 2800 cal yr BP.

scholarly journals A Late Glacial to Holocene record of environmental change from Lake Dojran (Macedonia, Greece)

2013 ◽  
Vol 9 (1) ◽  
pp. 481-498 ◽  
Author(s):  
A. Francke ◽  
B. Wagner ◽  
M. J. Leng ◽  
J. Rethemeyer
Keyword(s):  
Late Glacial ◽  
Ice Age ◽  
Humid Climate ◽  
Climate Conditions ◽  
The Holocene ◽  
Erosion Processes ◽  
Environmental Variations ◽  
Age Model ◽  
Balkan Region ◽  
Holocene Record

Abstract. A Late Glacial to Holocene sediment sequence (Co1260, 717 cm) from Lake Dojran, located at the boarder of the F.Y.R. of Macedonia and Greece, has been investigated to provide information on climate variability in the Balkan region. A robust age-model was established from 13 radiocarbon ages, and indicates that the base of the sequence was deposited at ca. 12 500 cal yr BP, when the lake-level was low. Variations in sedimentological (H2O, TOC, CaCO3, TS, TOC/TN, TOC/TS, grain-size, XRF, δ18Ocarb, δ13Ccarb, δ13Corg) data were linked to hydro-acoustic data and indicate that warmer and more humid climate conditions characterised the remaining period of the Younger Dryas until the beginning of the Holocene. The Holocene exhibits significant environmental variations, including the 8.2 and 4.2 ka cooling events, the Medieval Warm Period and the Little Ice Age. Human induced erosion processes in the catchment of Lake Dojran intensified after 2800 cal yr BP.

scholarly journals Extension of the Holocene Dendrochronology by the Preboreal Pine Series, 8800 to 10,100 BP

Radiocarbon ◽  
1986 ◽  
Vol 28 (2B) ◽  
pp. 961-967 ◽  
Author(s):  
Bernd Becker ◽  
Bernd Kromer
Keyword(s):  
Tree Ring ◽  
Late Glacial ◽  
Pine Forests ◽  
Oak Forests ◽  
The Holocene ◽  
The Past ◽  
Pine Tree ◽  
South Central ◽  
Pine Trees ◽  
European Oak

Holocene tree-ring chronologies have been established for south-central Europe covering the past 11,000 years. The Hohenheim absolute oak chronology extends to 4089 bc. The C-calibrated mid-Holocene floating oak master covers a 3181-year period from ca 4045 to 7225 bc. The earliest well-replicated floating oak master (estimated calendar age 7215 to 7825 bc) extends the European oak dendrochronology back to Boreal times.Further extension of the Holocene dendrochronology has been achieved by subfossil oak and pine trees from the Rhine, Main, and Danube Rivers. A 774-year floating series of Preboreal pine has been established. 14C ages range (from younger to older end) from 9200 to 9800 BP. Within this series a major atmospheric 14C variation is indicated, resulting in nearly constant 14C ages (9600 BP) over a period of 370 tree-rings.The European oak and pine tree-ring chronologies cover without major gaps the entire Holocene epoch. Based on the length of the dendro-records, an approximate solar year age of 11,280 years is calculated for the Holocene/Pleistocene boundary.The Preboreal pine forests along the rivers were replaced by mixed oak forests between 9200 and 8800 BP. By linking the earliest oak masters and the Preboreal pine series, the European dendrochronology can be extended up to the end of Late Glacial times.

Development of the mixed conifer forest in northern New Mexico and its relationship to Holocene environmental change

2008 ◽  
Vol 69 (2) ◽  
pp. 263-275 ◽  
Author(s):  
R. Scott Anderson ◽  
Renata B. Jass ◽  
Jaime L. Toney ◽  
Craig D. Allen ◽  
Luz M. Cisneros-Dozal ◽  
...  
Keyword(s):  
New Mexico ◽  
Pinus Ponderosa ◽  
Late Glacial ◽  
Conifer Forest ◽  
Lake Levels ◽  
Mixed Conifer ◽  
The Holocene ◽  
Groundwater Levels ◽  
Mixed Conifer Forest ◽  
Jemez Mountains

Chihuahueños Bog (2925 m) in the Jemez Mountains of northern New Mexico contains one of the few records of late-glacial and postglacial development of the mixed conifer forest in southwestern North America. The Chihuahueños Bog record extends to over 15,000 cal yr BP. AnArtemisiasteppe, then an openPiceawoodland grew around a small pond until ca. 11,700 cal yr BP whenPinus ponderosabecame established. C/N ratios,δ13C andδ15N values indicate both terrestrial and aquatic organic matter was incorporated into the sediment. Higher percentages of aquatic algae and elevated C/N ratios indicate higher lake levels at the opening of the Holocene, but a wetland developed subsequently as climate warmed. From ca. 8500 to 6400 cal yr BP the pond desiccated in what must have been the driest period of the Holocene there. C/N ratios declined to their lowest Holocene levels, indicating intense decomposition in the sediment. Wetter conditions returned after 6400 cal yr BP, with conversion of the site to a sedge bog as groundwater levels rose. Higher charcoal influx rates after 6400 cal yr BP probably result from greater biomass production rates. Only minor shifts in the overstory species occurred during the Holocene, suggesting that mixed conifer forest dominated throughout the record.

scholarly journals Global sea-level control on local parasequence architecture from the Holocene record of the Po Plain, Italy

2017 ◽  
Vol 87 ◽  
pp. 99-111 ◽  
Author(s):  
Alessandro Amorosi ◽  
Luigi Bruno ◽  
Bruno Campo ◽  
Agnese Morelli ◽  
Veronica Rossi ◽  
...  
Keyword(s):  
Sea Level ◽  
Level Control ◽  
Po Plain ◽  
The Holocene ◽  
Holocene Record ◽  
Global Sea Level

scholarly journals Holocene Records of Nebraska Mammals

2021 ◽  
Author(s):  
Hugh Genoways
Keyword(s):  
Native Americans ◽  
Fossil Record ◽  
The State ◽  
Additional Species ◽  
The Holocene ◽  
Sand Hills ◽  
Food Species ◽  
Main Portion ◽  
Holocene Record ◽  
Harlan County

A survey of the archeological and paleontological literature allowed a compilation of Holocene records of mammals in Nebraska. This survey identified Holocene records from 338 sites in 62 of the 93 Nebraska counties. These counties were located throughout state, but there was a concentration of sites in southwestern Nebraska where there were 27 fossil sites in Frontier County and 22 in Harlan County. Fossils sites were underrepresented in the Sand Hills region. Records of fossil mammals covered the entire Holocene period from 13,000 years ago until AD 1850. A minimum of 57 species (with eight additional species potentially present) representing six orders of mammals were represented in the compilation—four species of Lagomorpha, four species of Soricomorpha, 17 species of Carnivora (with three additional species potentially present), one species of Perissodactyla, six species of Artiodactyla, and 25 species of Rodentia (with five additional species potentially present). The remains of bison were found at 276 sites, which was more than for any other species in the state. Additional species that formed the main portion of the diet of Native Americans were the next most abundant in the fossil record—deer, pronghorn, and wapiti. That these food species dominated in the Holocene record was to be expected because fossils were recovered primarily from archeological sites.

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