Sedimentology and Palynology of Middle Wisconsinan Deposits in the Pecatonica River Valley, Wisconsin and Illinois

1982 ◽  
Vol 17 (2) ◽  
pp. 228-240 ◽  
Author(s):  
G. Richard Whittecar ◽  
Anthony M. Davis
Keyword(s):  
Pollen Record ◽  
Peat Accumulation ◽  
Climatic Fluctuations ◽  
Radiocarbon Dates ◽  
Forest Tundra ◽  
Valley Fill ◽  
Vegetation Zones ◽  
Zone Ii ◽  
Sediment Data ◽  
Channel Deposits

AbstractThe bedrock valley of the Pecatonica River north of Freeport, Illinois, contains a thick valley-fill complex of alluvium and drift. Within the valley, loess-capped benches surround hills of silty Illinoian drift. Beneath these benches lie thick deposits of poorly sorted stony silt interbedded with thin lenses of silt, sand, and organic-rich loam. Channel deposits and peat cap the diamicton in places. We interpret the stony silts as solifluction debris shed from silty slopes within the valley-fill during the Early or Middle Wisconsinan (Altonian). Top and bottom radiocarbon dates from a 2.5-m section of peat overlying the diamicton are 26,820 ± 200 and 40,500 ± 1700 yr B.P., respectively. We informally refer to the stony silts, channel sediments, and peat as the “Martintown unit.” Geomorphic position, sediment input, and macrofossils suggest that the dated peat was deposited in a floodplain pond (oxbow?). The pollen record from the peat indicates that a boreal forest dominated this area during the Middle Wisconsinan (late Altonian and Farmdalian). Two pollen zones are recognized: a basal Zone I with Pinus slightly more abundant than Picea and with few herbs and shrubs, and an upper Zone II dominated by Picea and with a larger representation of herbaceous and shrub taxa. Little displacement of vegetation zones is indicated, even though ice advanced to within 100 km of the site during the time of peat accumulation. Because of the problems involved in clearly defining Middle Wisconsinan forest-tundra in mid-latitudes by using analogs of Holocene forest-tundra in high latitudes, caution is required in making geomorphic inferences solely from vegetation data. Together, though, pollen and sediment data indicate that during the Middle Wisconsinan, Pecatonica hillslopes progressed through a sequence of instability-stability-instability related to climatic fluctuations.

scholarly journals Palynological evidence from a sub-alpine marsh of enhanced Little Ice Age snowpack in the Marrakech High Atlas, North Africa

2021 ◽  
Author(s):  
Benjamin A. Bell ◽  
William J. Fletcher ◽  
Philip D. Hughes ◽  
Henk L. Cornelissen ◽  
David Fink ◽  
...  
Keyword(s):  
20Th Century ◽  
Little Ice Age ◽  
Management Practices ◽  
Accumulation Point ◽  
Ice Age ◽  
Pollen Record ◽  
Climatic Fluctuations ◽  
Radiocarbon Dates ◽  
High Atlas ◽  
Grazing Impacts

AbstractThe grazing lands of the High Atlas are vulnerable to climate change and the decline of traditional management practices. However, prior to the mid-20th century, there is little information to examine historical environmental change and resilience to past climate variability. Here, we present a new pollen, non-pollen palynomorph (NPP) and microcharcoal record from a sub-alpine marsh (pozzine) at Oukaïmeden, located in the Marrakech High Atlas, Morocco. The record reveals a history of grazing impacts with diverse non-arboreal pollen assemblages dominant throughout the record as well as recurrent shifts between wetter and drier conditions. A large suite of radiocarbon dates (n = 22) constrains the deposit to the last ~ 1,000 years although multiple reversed ages preclude development of a robust age-depth model for all intervals. Between relatively dry conditions during the Medieval period and in the 20th century, intervening wet conditions are observed, which we interpret as a locally enhanced snowpack during the Little Ice Age. Hydrological fluctuations evidenced by wetland pollen and NPPs are possibly associated with centennial-scale precipitation variability evidenced in regional speleothem records. The pollen record reveals an herbaceous grassland flora resilient against climatic fluctuations through the last millennium, possibly supported by sustainable collective management practices (agdal), with grazing indicators suggesting a flourishing pastoral economy. However, during the 20th century, floristic changes and increases in charcoal accumulation point to a decline in management practices, diversification of land-use (including afforestation) and intensification of human activity.

scholarly journals Evidence of Mid-Holocene (Northgrippian Age) Dry Climate Recorded in Organic Soil Profiles in the Central Appalachian Mountains of the Eastern United States

Geosciences ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 477
Author(s):  
Mitzy L. Schaney ◽  
James S. Kite ◽  
Christopher R. Schaney ◽  
James A. Thompson
Keyword(s):  
United States ◽  
Appalachian Mountains ◽  
Organic Soil ◽  
Field Investigation ◽  
Soil Profiles ◽  
Eastern United States ◽  
Accumulation Rates ◽  
Peat Accumulation ◽  
Climatic Fluctuations ◽  
Radiocarbon Dates

Peatlands in Canaan Valley National Wildlife Refuge hold a pedomemory of Pleistocene and Holocene climatic fluctuations in the central Appalachian Mountains of the eastern United States. A field investigation profiling 88 organic soil profiles, coupled with 52 radiocarbon dates and peat accumulation rates, revealed a distinct sequence of organic soil horizons throughout five study areas. The dominantly anaerobic lower portions of the organic soil profiles consist of varied thicknesses of hemic and sapric soil materials, typically layered as an upper hemic horizon, underlain by a sapric horizon, underlain by another hemic horizon. Peat deposition began after the Last Glacial Maximum with relatively high Heinrich Stadial 1 accumulation rates to form the lowest hemic horizon. Peat accumulated at significantly slower rates as the climate continued to warm in the early Holocene Greenlandian Age. However, between 10,000 and 4200 cal yr BP peat accumulation decreased further and the decomposition of previously deposited peat prevailed, forming the sapric horizon. This interval of greater decomposition indicates a drier climatic with dates spanning the late Greenlandian Age through the Northgrippian Age. The upper hemic horizon within the anaerobic portion of the soil profile formed from high peat accumulation rates during the wetter late Holocene Meghalayan Age.

Insect faunas of late Devensian and Flandrian age from Church Stretton, Shropshire

1972 ◽  
Vol 263 (852) ◽  
pp. 327-367 ◽  
Keyword(s):  
Pollen Analysis ◽  
Thermal Environment ◽  
Radiocarbon Date ◽  
Radiocarbon Dates ◽  
Number Of Species ◽  
Summer Temperatures ◽  
Zone Ii ◽  
Climatic Optimum ◽  
The Church

Invertebrate faunas consisting mainly of insects, from deposits in the Church Stretton valley, are described and discussed. These deposits fall into two periods: ( a ) Late Devensian, which follows an episode of glaciation and precedes a period of accumulation of frost-shattered gravel fans; and ( b ) Flandrian, which post-dates the gravels and has been placed in the post-Glacial pollen zones VI and VII. The faunas of these two episodes are dealt with separately in Parts I and II respectively. Part I. From two sites in which sequences containing clays, peats and silts were examined five radiocarbon dates are available, the oldest being 13 555 ± 620 years B.P. and the most recent 11 000 ± 200 years B.P. The faunas include a substantial number of species not now found in Shropshire, many not in Britain. Inferences on the changing ecology and thermal environment of the area are drawn from these faunas and are compared with the pollen analytical zones. This comparison shows that, according to the insects, the warmest part of the episode was late zone I, and that zone II (the Allerod), often considered to be the climatic optimum of the period, appears to have been a time of gradually deteriorating summer temperatures. Part II. Deposits from three late Flandrian sites are discussed. Although only one radiocarbon date was obtained, of 8101 ± 138 years B.P., pollen analysis was carried out by Rowlands throughout each sequence and this showed that the earliest deposit, at Little Stretton, dated from zone VI a and at all three localities deposition continued into zone VII b. An examination of the insect assemblages shows that completely different biotopes, from open pasture to dense woodland, were existing side by side in the Church Stretton valley in late Flandrian time. Summer temperatures at least as high as those of today are inferred. The possibility exists that during the period represented here the climate was even warmer than that of the present but until more information is available it is not possible to be more definite on this point.

Subsurface sediment profiles below Point Pelee: indicators of postglacial evolution in western Lake Erie

1998 ◽  
Vol 35 (1) ◽  
pp. 88-99
Author(s):  
John P Coakley ◽  
Allan S Crowe ◽  
Patrice A Huddart
Keyword(s):  
Lake Levels ◽  
Dune Sand ◽  
Radiocarbon Dates ◽  
Subsurface Sediment ◽  
Fine Grained ◽  
Western Lake ◽  
Planar Wave ◽  
Point Pelee ◽  
Sediment Data ◽  
Point Pelee National Park

An extensive drilling program, undertaken along the western barrier bar at Point Pelee National Park, Ontario, Canada, yielded considerable subsurface sediment data relevant to the nature and lateral geometry of sedimentary units below the Point Pelee foreland. Four major sedimentary units were identified: a basal clay-rich till, a fine-grained glaciolacustrine sand, a medium-grained sand unit (subdivided into a poorly sorted shoreface sand and an aeolian (dune) sand derived from the shoreface sand), and an organic marsh (gyttja) deposit. The present study confirms the existence of a planar, wave-eroded till surface below the southern portion of Point Pelee at an elevation of approximately 164 m asl. Following this low-water period in the basin, lake levels rose abruptly to an elevation several metres above 172 m asl. This resulted in erosion of the upper part of the glaciolacustrine sand during a later period of stable higher lake levels, perhaps coinciding with the Nipissing flood event (about 4000 BP). This resulted in a planar surface at approximately 169.5 m asl. Several radiocarbon dates on basal gyttja from the marsh (averaging 3200 BP) reflect a subsequent drop in levels to about 2-3 m below present levels. Though undated, the initiation of shoreface and dune sand deposition is roughly coeval with the basal marsh deposits.

scholarly journals Rapid climatic variability in the west Mediterranean during the last 25 000 years from high resolution pollen data

2009 ◽  
Vol 5 (3) ◽  
pp. 503-521 ◽  
Author(s):  
N. Combourieu Nebout ◽  
O. Peyron ◽  
I. Dormoy ◽  
S. Desprat ◽  
C. Beaudouin ◽  
...  
Keyword(s):  
High Resolution ◽  
North Atlantic ◽  
Climate Reconstruction ◽  
Mediterranean Vegetation ◽  
Pollen Record ◽  
Alboran Sea ◽  
Climatic Fluctuations ◽  
The Holocene ◽  
The Mediterranean ◽  
Alborán Sea

Abstract. High-temporal resolution pollen record from the Alboran Sea ODP Site 976, pollen-based quantitative climate reconstruction and biomisation show that changes of Mediterranean vegetation have been clearly modulated by short and long term variability during the last 25 000 years. The reliability of the quantitative climate reconstruction from marine pollen spectra has been tested using 22 marine core-top samples from the Mediterranean. The ODP Site 976 pollen record and climatic reconstruction confirm that Mediterranean environments have a rapid response to the climatic fluctuations during the last Termination. The western Mediterranean vegetation response appears nearly synchronous with North Atlantic variability during the last deglaciation as well as during the Holocene. High-resolution analyses of the ODP Site 976 pollen record show a cooling trend during the Bölling/Allerød period. In addition, this period is marked by two warm episodes bracketing a cooling event that represent the Bölling-Older Dryas-Allerød succession. During the Holocene, recurrent declines of the forest cover over the Alboran Sea borderlands indicate climate events that correlate well with several events of increased Mediterranean dryness observed on the continent and with Mediterranean Sea cooling episodes detected by alkenone-based sea surface temperature reconstructions. These events clearly reflect the response of the Mediterranean vegetation to the North Atlantic Holocene cold events.

Holocene Vegetation Change at Treeline North of Yellowknife, Northwest Territories, Canada

1990 ◽  
Vol 34 (2) ◽  
pp. 227-239 ◽  
Author(s):  
K. A. Moser ◽  
G. M. MacDonald
Keyword(s):  
Picea Mariana ◽  
Vegetation Change ◽  
Geographic Location ◽  
The Arctic ◽  
Small Lakes ◽  
Radiocarbon Dates ◽  
Glacial Ice ◽  
Forest Tundra ◽  
Long Wave ◽  
History Of

AbstractTwo radiocarbon-dated cores from small lakes located approximately 25 km north of the mapped boundary between forest-tundra and tundra provide records of postglacial vegetation change at the treeline near Yellowknife, NWT, Canada. Basal radiocarbon dates of 6180 and 7470 yr B.P. were obtained from the cores. The fossil pollen evidence suggests that the initial vegetation wasBetulatundra with a peatland component.Alnusbecame an important constituent of the pollen assemblages between 6900 and 5500 yr B.P. Both lakes record sharp increases inPiceacf.marianapollen at approximately 5000 yr B.P., suggesting the establishment of forest-tundra. By 3500 yr B.P.Picea marianaforest-tundra had withdrawn. The proportion of organic to inorganic sediment in the cores was at a maximum between 5000 and 3500 yr B.P. Tundra has dominated the region since 3500 yr B.P. In northwestern Canada, the maximum northward advance of treeline occurred between 9000 and 5000 yr B.P. The asynchrony in treeline advance in central and northwestern Canada may reflect that glacial ice persisted in the interior NWT longer than previously believed. Alternatively, the asynchronous history of the treeline may be a result of the geometric properties of the long-wave westerly disturbance that is manifest in the median summer position of the arctic front and ultimately controls the geographic location of the treeline.

Millennial-Scale Rhythms in Peatlands in the Western Interior of Canada and in the Global Carbon Cycle

2000 ◽  
Vol 54 (1) ◽  
pp. 155-158 ◽  
Author(s):  
Ian D. Campbell ◽  
Celina Campbell ◽  
Zicheng Yu ◽  
Dale H. Vitt ◽  
Michael J. Apps
Keyword(s):  
Feedback Loop ◽  
Carbon Budget ◽  
Warming Trend ◽  
Carbon Budgets ◽  
Climatic Fluctuations ◽  
Radiocarbon Dates ◽  
Greenhouse Gasses ◽  
Global Carbon Budget ◽  
Natural Carbon ◽  
Global Carbon

A natural ∼1450-yr global Holocene climate periodicity underlies a portion of the present global warming trend. Calibrated basal radiocarbon dates from 71 paludified peatlands across the western interior of Canada demonstrate that this periodicity regulated western Canadian peatland initiation. Peatlands, the largest terrestrial carbon pool, and their carbon-budgets are sensitive to hydrological fluctuations. The global atmospheric carbon-budget experienced corresponding fluctuations, as recorded in the Holocene atmospheric CO2 record from Taylor Dome, Antarctica. While the climate changes following this ∼1450-yr periodicity were sufficient to affect the global carbon-budget, the resultant atmospheric CO2 fluctuations did not cause a runaway climate–CO2 feedback loop. This demonstrates that global carbon-budgets are sensitive to small climatic fluctuations; thus international agreements on greenhouse gasses need to take into account the natural carbon-budget imbalance of regions with large climatically sensitive carbon pools.

A High-Resolution 11,400-Yr Diatom Record from Lake Victoria, East Africa

1997 ◽  
Vol 47 (1) ◽  
pp. 81-89 ◽  
Author(s):  
J.Curt Stager ◽  
Brian Cumming ◽  
Loren Meeker
Keyword(s):  
Little Ice Age ◽  
Lake Victoria ◽  
Ice Age ◽  
Pollen Record ◽  
Diatom Assemblages ◽  
Climatic Fluctuations ◽  
The Past ◽  
Phytoplankton Communities ◽  
Abrupt Changes ◽  
Globally Distributed

AbstractFine-interval (∼30–45 yr) sampling of a core from Lake Victoria's Damba Channel shows that numerous abrupt changes in the lake's diatom assemblages have occurred in response to climatic fluctuations over the past 11,40014C yr. Four distinct climatic phases bounded by sudden transitions are inferred: (1) variably dry ∼11,400–10,000 yr B.P., (2) humid ∼10,000–7200 yr B.P., (3) more seasonal ∼7200–2200 yr B.P., and (4) more arid ∼2200–0 yr B.P., with a dry “Little Ice Age” event ∼600–200 yr B.P. The diatom-inferred paleoclimatic history for northern Lake Victoria closely resembles that inferred from a well-dated pollen record from Pilkington Bay. Spectral analysis of the diatom record reveals strong periodicities including globally distributed ∼2360–2550, ∼1400, ∼1030–1130, and ∼500 cal-yr cycles. Repeated, rapid shifts betweenAulacoseira- andNitzschia-dominated diatom assemblages suggest that post-1960 changes in the lake's phytoplankton communities have had earlier, climate-driven analogs.

A Study of Paleosols in the Saskatoon Area of Saskatchewan

1974 ◽  
Vol 11 (7) ◽  
pp. 905-915 ◽  
Author(s):  
L. W. Turchenek ◽  
R. J. St. Arnaud ◽  
E. A. Christiansen
Keyword(s):  
Classification Criteria ◽  
Soil Profiles ◽  
Climatic Fluctuations ◽  
Radiocarbon Dates ◽  
Dune Sands ◽  
Aeolian Sediments ◽  
Alteration Processes ◽  
Buried Soil ◽  
Aeolian Sands

Postglacial paleosols developed in lacustrine and aeolian sediments occur on terraces and in banks of the South Saskatchewan River near Saskatoon. At each of three sites a sequence of two paleosols was studied: a lower soil of immediate postglacial age as indicated by radiocarbon dates, that is buried by aeolian sands, and an upper one, located within the dune sands, that marks a period of stability of the dunes. Climatic fluctuations are inferred to be the cause of aeolian activity.One paleosol met the classification criteria for an Orthic Black Chernozemic soil. The other soils, particularly those developed in the dune sands, were weakly developed, Regosolic types of soils.Pedogenic interpretations were based on macro- and micromorphological observations as well as chemical characteristics. Micromorphology and the determination of calcite and dolomite distribution were particularly useful in differentiating sedimentary, pedogenic, and postburial alteration processes in the buried soil profiles. Studies of the organic matter suggest that it had changed markedly after burial.

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