Abstracts

 

CHARCOAL EVIDENCE FOR INDIAN SET FIRES

Clark and Royall (1995) present a charcoal influx curve for Crawford Lake in southern Ontario and conclude that the Indians were responsible for a succession from beech to oak and pine throughout southern Ontario. We present an alternative hypothesis, that the 'Little Ice Age' caused the forest succession and that domestic fires and burning of stubble in agricultural fields were responsible for the charcoal record.

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PERISHABLE TECHNOLOGY FROM THE HISCOCK SITE

The 1996 excavations at the Hiscock Site yielded a remarkably well preserved impression and, possibly, actual minute pieces of a twined textile or basket. It was recovered from the site's Fibrous Gravelly Clay, within 5 cm of the overlying Older Woody Layer, and may be of late Pleistocene age. The impression represents a segment of a very well made close diagonal twined textile or basket with paired Z-twist wefts, a continuous weft side selvage, and is part of a fully flexible cloth construction of indeterminate configuration. The specimen was in loose stratigraphic association with a concentration of white-tailed deer (Odocoileus virginianus) bones. Whatever its exact chronological ascription, the specimen is potentially one of the earliest examples of textile or basketry technology in the Northeast and is, hence, highly informative of local perishable technology at or near the Pleistocene/Holocene transition. The technology, context, association and possible age(s) of this specimen are discussed in detail and this unique item is placed in the larger framework of perishable developments in the New World.

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BISON EXTIRPATION MAY HAVE CAUSED ASPEN EXPANSION IN WESTERN CANADA

The aspen Populus tremuloides parkland that forms the northern margin of the North American grassland or prairie has been variously attributed either individually or in different combinations to the ecological effects of prairie fire, fire suppression, frequent drought, and grazing. Plains bison Bison bison bison, formerly abundant on the western North American plains, inhibited growth of aspen by browsing, wallowing, trampling and toppling. Historical references show that aspen populations have expanded over the past century, and fossil pollen evidence suggests that the expansion occurred mainly after the near extinction of bison but before European homesteading and subsequent fire suppression in the late 1800s. We suggest that a prehistoric cycle of grassland, fire, aspen suckering, bison activity, and return to grassland was interrupted by the removal of bison, allowing aspen expansion.

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PALEOINDIAN CULTURES IN THE GREAT-LAKES REGION OF NORTH-AMERICA - PALEOCLIMATIC, GEOMORPHIC, AND STRATIGRAPHIC CONTEXT

Paleoindian cultures are the first clearly documented and widespread human occupation in central North America. Early Paleo-indians (EPI) made distinctive fluted points, and lived mainly south of 46-degrees latitude. The location of EPI sites along C-14 dated proglacial Great Lakes strandlines and typological similarities with artifacts from 14C dated sites in adjacent regions, indicates these cultures span ca. 11 500 to 10 000 BP. They were succeeded by Late Paleo-indian (LPI) cultures, who persisted until ca. 7 500 BP in the North. Early Archaic cultures re aced LPI in the southern region after ca. 10 000 BP.

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PALYNOLOGY OF INDIAN AND EUROPEAN FOREST CLEARANCE AND FRAMING IN LAKE SEDIMENT CORES FROM AWENDA PROVINCIAL PARK, ONTARIO.

 

Palynologic analyses of four short cores collected along shallow- to deep-water transects in Second and Gignac lakes indicate two periods of forest clearance for farming. The first deforestation was by Huron Indians between A.D. 1450 and 1650, when a maple (Acer ), beech (Fagus ), and oak (Quercus ) forest was cleared and corn (Zea ) planted. This disturbance is identified by decreased tree pollen and increased Pteridium, Artemisia , and other herbs and is confirmed by Zea pollen in Gignac Lake. From 1650 to 1875 there was a forest succession to oak, birch (Betula ), and pine (Pinus ). Following this recovery European loggers and farmers cleared this forest and attempted farming. Besides a reduction in tree pollen, a product of this deforestation includes the pollen of weedy Ambrosia , Gramineae, and introduced European Rumex and Plantago . During the last 25 years an increase in tree pollen indicates local forest recovery consistent with present land use. By relating upland vegetation successions to lacustrine algal assemblage change, probable ecological controls on algae during the last 600 years are identified. Perdinium willei Huitfeldt-Kaas and Pediastrum respond to changes induced by forest clearance and agriculture.

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PALEOBOTANY OF A WILD RICE LAKE IN MINNESOTA

Four pollen zones present in a 360-cm core from Rice Lake, Becker County, indicate a vegetation succession from mid-postglacial oak savanna to deciduous forest to pine-hardwood forest to an uppermost ragweed zone representing postsettlement forest disturbance. Seeds of wild rice occur in the upper meter with abundant wild rice type pollen, the initial increase of which is C-14 dated 2450+ or -100 years ago. The ragweed pollen rise dating land settlement about 75 years ago is C-14 dated at 590+ or -95 years. The difference is attributed to contamination and when this error is subtracted from the older date, the spread of wild rice across the lake is dated at 1935+ or -100 years. An extensive stand of wild rice predates by 1000 years prehistoric cultures known to have used it. Its spread is probably due to either climatic change with changes in water quality or to shallowing of the lake by sedimentation, or both.
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GEOCHEMICAL INDICATORS IN LAKE SEDIMENT OF UPLAND EROSION CAUSED BY INDIAN AND EUROPEAN FARMING, AWENDA PROVINCIAL PARK, ONTARIO.

 

Neutron-activation analysis, loss on ignition (LOI), and X-ray diffraction of eight cores collected in Second and Gignac lakes are correlated with historic and palynologic records to identify elements linked to erosion from deforestation and farming. Sedimentation patterns relate to basin morphology. In Gignac Lake the basin is steep sided and relatively deep. Clastic detritus entering the lake is carried over the shallow, nearshore carbonate bank into deeper water. In Second Lake the basin is shallow and gently sloping. Minerals eroded from onshore are more equally distributed in this basin. In Second Lake the most repid sedimentation is nearshore where submerged aquatic macrophytes produce and trap carbonate mud. In Gignac Lake the top of the shallow carbonate bank has few aquatic macrophytes; lime mud formed on the bank is washed into deep water offshore, where it dissolves.

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HOLOCENE POLLEN DIAGRAM FROM LAKE ANTOINE, GRENADA

Upland vegetation history of the Lesser Antilles Islands is poorly known because there are few lakes - Grenada with late-Pleistocene volcanism is an exception. Lake Antoine (17 ha, 6 m asl) occupies a circular volcanic explosion crater, which is 500 m from the sea; it may have formed when rising seawater encountered hot magma about 14,000 years ago. There is no inlet or outlet. Around the lake margin is marsh of Montrichardia arborescens, Cladium jamaicense, Acrostichum danaeifolium, Eleocharis flavescens and Nymphaea ampla. On the adjacent slope is pasture, sugar cane fields and plantations of coconut, cocoa and banana; the upper slopes support secondary dry forest including Bursera simaruba, Spondias mombin and Pisonia fragrans. Organic sediment fills the lake to 5 -7 m depth. An 850-cm long core of detritus gyttja bottomed on sand. Five calibrated radiocarbon dates and two historic levels permit modeling of sedimentation rate and chronology. Palynological analysis of 66 levels shows four zones. Zone 1 in basal sand is dominated by the brackish water marsh fern Acrosticum. Zone 2 is dominated by pollen of the palm Roystonea oleracea with shrub Triumfetta and the alga Pediastrum argentiniense. Zone 3 begins at 4,300 years B.P with a peak of the disturbance-indicating Cecropia; it generally lacks palm pollen. The enigmatic monolete fern spore, cf. Nephrolepis rivularis is abundant; Bursera, Spondias, Pisonia and cf. Pouteria indicate upland dry forest; relatively abundant Cladium and Nymphaea indicate freshwater marsh. Beginning 300 years ago historic Zone 4 (0-190 cm) features Poaceae and especially Zea and Cocos.

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ILLINOIAN TO LATE WISCONSINAN STRATIGRAPHY AT WOODBRIDGE, ONTARIO

Near Woodbridge, northwest of Toronto, Ontario, a 15 metre-high railroad cut and associated borrow pit, first excavated in 1962, exposed a multiple till sequence and intervening fossiliferous sediments. Work over the next 35 years revealed that Illinoian York Till, early Wisconsinan Sunnybrook Till, and late Wisconsinan Humber till, Halton Till, and Wildfield Till are interbedded with fossiliferous sediments equivalent to the Sangamonian Don Formation, early Wisconsinan Scarborough Formation (>50 ka BP), and middle Wisconsinan Thorncliffe Formation (45 ka BP). A complex periglacial record displays multistage fossil frost wedges, indicating intervals of severe climate in late Illinoian and early Wisconsinan time. Cored boreholes indicate deep gravel below and a till on Ordovician shale bedrock (Georgian Bay Formation). Vertebrates, molluscs, ostracodes, insects, and plants (diatoms, wood, seeds, pollen) indicate mostly cool conditions (boreal to tundra) for interstadial sediments. Interglacial conditions are represented by vertebrates, molluscs, and plants above York Till. Many taxa are new to the Quaternary of the Toronto area.

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QUATERNARY INTERGLACIAL AND ASSOCIATED DEPOSITS IN SOUTHWEST NEWFOUNDLAND CANADA

A coastal cliff section near Codroy, Newfoundland, exposes 5 distinctive lithologic units, which are defined lithologically and structurally as colluvial, lacustrine or glacial in origin. They have been preserved in a gypsum karst depression, but continuing karst evolution has disturbed their original attitudes. The 2 oldest units, 5 and 4, were formed by sidewall slumping of local bedrock and earlier glacial material from the failing rim of a newly formed sinkhole. Unit 3 represents tranquil sedimentation of thin sand and silt-clay laminae, 1st in a freshwater sinkhole pond, then in brackish marine waters that entered after breaching of its seaward wall and finally again in fresh water as sea level fell below the sill of the small embayment. Units 2 and 1 are glacial deposits laid down over older units after a 2nd major sinkhole collapse. Collapse has continued to the present day. Pollen and spores from unit 3 indicate that during its deposition regional vegetation changed from tundra (Zone A) to boreal forest (Zone B), and back to tundra (Zone C), through an interglacial cycle of vegetation change. Balsam fir wood from Zone B is radiocarbon-dated to > 40,000 B.P. Foraminifera from unit 3 indicate that brackish marine conditions prevailed before Zone B times, and that nearshore fully marine conditions briefly prevailed in Zone B times. Zone B is thus assigned full interglacial status, based on pollen and foraminiferal evidence and is tentatively assigned to the Sangamonian for want of indications to the contrary and for economy of interpretation. The overlying glaciogenic units 1 and 2 are thus probably of early Wisconsinan age. Calcite crystals, possibly pseudomorphous, found within Zone B of unit 3, were radiocarbon-dated at 30,000 .+-. 1450 B.P. .delta.18O values of -6.8 to -7.5%.permill. (vs. PDB [Peedee belemnite]) indicate replacement by calcite under conditions similar to present. .delta.13C values of -24.00 to -26.24.permill. (vs. PDB) indicate that carbonate C was supplied by decay of local organic matter. The date is a minimum and supports the contention that the sediments are of at least last interglacial age. Gypsum karst has thus been evolving in this area since before the last interglacial and has preserved a record of environmental change for that period that is unique in the Atlantic Provinces of Canada. Unit 3 is proposed as the stratotype for the Codroy Interglacial Beds (new name).

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PERISHABLE TECHNOLOGY FROM THE HISCOCK SITE

The 1996 excavations at the Hiscock Site yielded a remarkably well preserved impression and, possibly, actual minute pieces of a twined textile or basket. It was recovered from the site's Fibrous Gravelly Clay, within 5 cm of the overlying Older Woody Layer, and may be of late Pleistocene age. The impression represents a segment of a very well made close diagonal twined textile or basket with paired Z-twist wefts, a continuous weft side selvage, and is part of a fully flexible cloth construction of indeterminate configuration. The specimen was in loose stratigraphic association with a concentration of white-tailed deer (Odocoileus virginianus) bones. Whatever its exact chronological ascription, the specimen is potentially one of the earliest examples of textile or basketry technology in the Northeast and is, hence, highly informative of local perishable technology at or near the Pleistocene/Holocene transition. The technology, context, association and possible age(s) of this specimen are discussed in detail and this unique item is placed in the larger framework of perishable developments in the New World.

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GLACIAL LAKE ARKONA - WHITTLESEY TRANSITION NEAR LEAMINGTON, ONTARIO - GEOLOGY, PLANT, AND MUSKOX FOSSILS

Proglacial subaquatic fans between Leamington and Colchester, Essex County, Ontario, were deposited in glacial Lake Maumee at the end of the Port Bruce Stade by ice retreating northward. Some fans were buried by till and glaciolacustrine materials. One fan surface, northwest of Leamington, was only modified by lake current that transgressed and regressed over it. An aggregate excavation (Bondi site) exists within the surface of this fan. We describe the sedimentology of the site that provides evidence for fan and overlying bar deposits.
Lake levels fell to the levels of lakes Arkona (216 m) and Ypsilanti (122 m) following the deposition of the fans. Large terrestrial areas supported plants and animals. Their presence is recorded at the Bondi site by a single bone and several organic mats recovered from the fan and bar sediment contact at two separate exposures. Radiocarbon dates on the bone of 13 410 +/- 100 BP (TO-1803), organic material dates of 13 225 +/- 200 BP (BGS-1404) and 13 150 +/- 100 BP (WE-01-89), the altitude (209 m), and the sedimentological setting indicate deposition during the Lake Arkona (216 m) - Lake Whittlesey (226 m) transition period.

The pollen and plant macrofossil assemblages recovered from the organic material indicate a forest-tundra environment, with a mean July temperature of 14-degrees-C. This interpretation fits well with the bone identified as cf. Euceratherium sp., a shrubox. The discovery of cf. Euceratherium sp. is surprising, as its previous range was south and west of this site. The organic material was subsequently buried by the formation of a bar as water levels rose within the Lake Erie basin and transgressed the site.

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PALEOINDIAN CULTURES IN THE GREAT-LAKES REGION OF NORTH-AMERICA - PALEOCLIMATIC, GEOMORPHIC, AND STRATIGRAPHIC CONTEXT

Paleoindian cultures are the first clearly documented and widespread human occupation in central North America. Early Paleo-indians (EPI) made distinctive fluted points, and lived mainly south of 46-degrees latitude. The location of EPI sites along C-14 dated proglacial Great Lakes strandlines and typological similarities with artifacts from 14C dated sites in adjacent regions, indicates these cultures span ca. 11 500 to 10 000 BP. They were succeeded by Late Paleo-indian (LPI) cultures, who persisted until ca. 7 500 BP in the North. Early Archaic cultures re aced LPI in the southern region after ca. 10 000 BP.

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IDENTIFYING FOSSIL WILD RICE (ZIZANIA) POLLEN FROM COOTES PARADISE, ONTARIO: A NEW APPROACH USING SCANNING ELECTRON MICROSCOPY

Although prehistoric native peoples probably used wild rice for food and ceremony, evidence is sparse. Macrofossil remains of wild rice are uncommon on archaeological sites even where the plant is still common nearby. The association between documented human habitation and wild rice is explored with pollen records from associated wild rice wetlands. For this, reliable identification of wild rice pollen is essential. Three approaches are examined: (1) the pollen spectral signature (percentage and density of grass pollen), (2) coeval community pollen types, and (3) the pollen morphology (size and sculpturing) of wild rice versus other stand-forming wetland grasses. We report pollen spectra from a contemporary wild rice marsh and compare it with fossil pollen from Cootes Paradise, a wetland at the western end of Lake Ontario. The pollen signature from the modern wild rice wetlands was similar to that of the fossil site, but this correspondence does not confirm that the fossil grass pollen is wild rice. Wild rice pollen is separable by size from that of all the stand-forming wetland grasses examined, but the fossil pollen from Bull's Point is not the same size as that of modern wild rice. Scanning electron microscopy (SEM), however, indicates that wild rice pollen is identifiable by its sculpturing and that the fossil pollen has an identical micromorphology. (C) 2003 Published by Elsevier Ltd.

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INFLUENCES OF HOLOCENE CLIMATE AND WATER LEVELS ON VEGETATION DYNAMICS OF A LAKESIDE WETLAND

Sediment lithology, pollen, and plant-macrofossil data from the Paynter Site, southern Ontario, revealed three wetland developmental stages during the past 11 000 years: (i) a Carex, Eupatorium, and Eleocharis dominated marsh with some Larix, Abies, and Picea (ca. 11 000-8300 cal years BP); (ii) a Verbena hastata and Mentha arvensis marsh (ca. 8300-7460 cal years BP); and (iii) a white cedar (Thuja occidentalis) swamp (7460 cal years BP to present). There were no significant successional changes in the initial diverse marsh (stage 1) for about 2700 years; its high taxon richness was maintained by fluctuating water levels. The succession from marsh to swamp at 7460 cal years BP was caused by mid-Holocene warm and dry climate, which corresponded with cedar expansion elsewhere in Ontario. The swamp peat record was interrupted at ca. 6400 cal years BP by declining water levels, culminating in a dry period, as indicated by a sandy layer, rare macrofossils, and a low sediment-accumulation rate (0.012 cm/year). The reappearance of cedar swamp macrofossils since 3200 cal years BP corresponded with the recovery of water levels owing to a more humid late Holocene climate and flooding from isostatic tilt. Human disturbance such as damming and logging caused the development of historical cedar and thicket swamps with abundant Alnus rugosa and weedy taxa. This sequence of wetland development did not match the present vegetational gradients from Carex-Typha herb marsh, through Myrica-Decodon shrub marsh and Alnus-Fraxinus thicket, to Thuja swamp. At this site, the wetland development was mainly influenced by allogenic factors such as water levels and climate rather than autogenic factors.

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A COMPARISON OF POSTGLACIAL ARCELLACEANS ("THECAMOEBIAN") AND POLLEN SUCCESSION IN ATLANTIC CANADA, ILLUSTRATING THE POTENTIAL OF ARCELLACEANS FOR PALEOCLIMATIC RECONSTRUCTION.

 

Cores dating back to deglaciation were taken from three lakes in Atlantic Canada and analyzed for arcellaceans and pollen. Paleotemperatures and paleo-precipitation were calculated from the pollen data using transfer functions. A sudden warming is recorded by the pollen around 10,000 years B.P., followed by a general warming to the mid Holocene Hypsithermal, then by a decrease in temperature and increase in effective precipitation to the present. The three lakes, two in western Newfoundland and one in eastern Nova Scotia, contain similar late glacial (13-10 ka), early Holocene (10-8 ka), mid Holocene (8-4 ka), and late Holocene (4-0 ka) arcellacean assemblages. Immediately following retreat of the ice sheets, Centropyxis aculeata, Centropyxis constricta, Difflugia oblonga, Difflugia urceolata, and Difflugia corona were common. The latter part of the late glacial is characterized by sparse assemblages dominated by C. aculeata. The arcellacean record thus suggests a climatic reversal in Atlantic Canada between 11,500 and 10,000 years B.P., analogous to the Younger Dryas, although this is not recorded by the pollen. Species diversity increased sharply at the beginning of the Holocene, and D. oblonga is the dominant taxon in early Holocene sediments. Difflugia oblonga remained common through the mid Holocene, but percentages of C. aculeata were very low, and Pontigulasia compressa and Difflugia bacillifera peaked in abundance during the Hypsithermal. The late Holocene is characterized by a resurgence in C. aculeata at the expense of other taxa. The increase in Heleopera sphagni and Nebella collaris since 5,000 years B.P. at the two sites in southwestern Newfoundland reflects paludification in response to increased precipitation since the Hypsithermal. Because the changes in arcellacean assemblages are regionally synchronous in all three lakes and coincide with climatically driven vegetational successions indicated by the pollen record, arcellaceans appear to respond to climatic change, and thus may be useful paleoecological and paleolimnological indicators. With their quicker generation time, these protists may be better suited than pollen to recording short-lived phenomena, like the mid-Holocene Hypsithermal and the Younger Dryas reversal.

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HOLOCENE WATER LEVELS AT RICE LAKE, ONTARIO, CANADA: SEDIMENT, POLLEN AND PLANT-MACROFOSSIL EVIDENCE

Four cores taken along a transect from the western basin and four cores from the middle basin of Rice Lake, Ontario, provide evidence for shoreline transgression during the early Holocene, for low water levels during the mid-Holocene, and for abrupt rise of the lake levels due to dam building in AD 1838. The transition from detritus mud to the overlying marl, spanning from ca. 10 000 to 8600 BP, indicates flooding of a wetland by a lake; this flooding is supported by plant-macrofossil succession from Larix, Scirpus, and Carex to Najas flexilis. The transgression was due to isostatic tilt after deglaciation, which raised the eastern outlet sill of the lake and caused the lake water to rise and flood westward. A sediment hiatus between the marl and the overlying gyttja (between 6000 and 4000-3000 BP) across the lake basin, supported by the bracketing radiocarbon dates and missing regional pollen zones, indicates low water level caused by a dry/warm climate. Subsequent rise of the lake level after the hiatus was a combination of cooling climate and continued isostatic tilt.

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LATE HOLOCENE AGGRADATION IN THE LOWER HUMBER RIVER VALLEY TORONTO ONTARIO CANADA

Alluvial fills are common in the lower reaches of rivers along the western shore of Lake Ontario. The Humber River floodplain at Toronto is underlain by a 2.5 km long wedge of alluvium that thins upstream from Lake Ontario. Floodplain sediments were studied for their lithology, 14C age, and fossil pollen. On the levees, grey clay is overlain by oxidized silt and sand. Sediment cores from two flood ponds grade upward from gravel, sand, and silt, to silty marl, mineral peat, and clay, to heterogeneous silt and sand. Base-level (Lake Ontario) rise directly controlled aggradation between 6500 and 1800 years ago, after which time base level no longer directly controlled aggradation because levees had emerged alongside the channel and reduced the supply of sediment to the floodplain. For the past 150 years, upstream forest clearance and urbanization increased sediment input to the floodplain, broadened the levees, and filled the flood ponds. Average flood-pond aggradation rates were estimated from seven 14C dates; these rates declined from 65 cm/100 years between 6500 and 3800 years ago, to 47 cm/100 years between 3800 and 3400 years ago, to 26 cm/100 years between 3400 and 1800 years ago. These rates reflect contemporaneous lake-level rise. Between 1800 and 150 years ago, the average aggradation rate declined below the estimated rate of lake-level rise to 14 cm/100 years. Since then, the average aggradation rate has increased tenfold to 140 cm/100 years, surpassing the historic rate of lake-level rise of 23 cm/100 years. Fossil pollen from the flood ponds reflects local flood plain and regional upland vegetation during the past 4000 years.

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PALEOHYDROLOGY OF A CANADIAN SHIELD LAKE INFERRED FROM OXYGEN-18 SEDIMENT CELLULOSE

Oxygen- and carbon-isotope analyses on cellulose in the postglacial sediment of Weslemkoon Lake, southern Ontario, show that the cellulose came mainly from aquatic plants or algae, rather than from terrestrial sources. If a wholly aquatic source is assumed, the oxygen-isotope content permits inferences of lake-water .delta.18O values over the past 10,000 years by accounting for the isotopic fractionation that occurs during cellulose synthesis. Chronological control is provided by pollen analysis and six 14C dates. Our reconstruction shows lake-water .delta.18O fluctuated from about 5.permill. lower than present in the early postglacial to 5.permill. or more above present values during the mid-postglacial. These broad, secular shifts reflect a combination of fluctuating mean annual .delta.18O of local precipitation, evaporative isotopic enrichment of surface waters, and snowmelt-bypass effects. The first two factors reflect the changing paleotemperature and paleohydrology, respectively, whereas the third factor is a more speculative interpretation of isotope effects during snowmelt delivery to the lake. The snowmelt-bypass mechanism is supported by parallel changes in the overall abundance and seasonal distribution of precipitation. This effect is probably responsible for pronounced isotopic enrichment of the water throughout the moist climate of the past 6000 years.

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WATER LEVELS IN LAKE ONTARIO 4230-2000 YEARS BP: EVIDENCE FROM GRENADIER POND, TORONTO, CANADA

The transgression of a Grenadier Pond was studied from cores along a transect from the bar that separates the pond from Lake Ontario to the marsh on the north shore. Radiocarbon dates of the transition from swamp peat to pond marl in five cores provide estimates of the rate of water level rise since 4230 yr BP. There were three short intervals of accelerated water level rise in Grenadier Pond, around 4200, 3000, and 2000 yr BP, when water levels rose up to 2 m instantaneously, within the resolution of radiocarbon dating. The intervals of accelerated water level rise in Lake Ontario broadly coincide with periods of cool, wet climate, suggesting that increased moisture may have caused the short term fluctuations in water level.

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SEDIMENTATION RATES AND SEDIMENT CORE PROFILES OF URANIUM-238 AND THORIUM-232 DECAY CHAIN RADIONUCLIDES IN A LAKE AFFECTED BY URANIUM MINING AND MILLING

Radionuclide concentration profiles in sediment cores for three deep basins of Quirke Lake, Ontario [Canada], showed enrichment in the surficial layers related to the period of uranium mining in the watershed, based on sedimentation rates determined from a milling-related pH decline indicated by fossil diatoms. Recent sedimentation rates are 96 .+-. 7 to 185 .+-. 14 g .cntdot. m-2 .cntdot. yr-1. 210Pb profiles could not be used to determine sedimentation rates due to loadings of 226Ra and 210Pb from mining and milling activities. Profiles of 238U and 232Th decay chain radionuclides showed an enrichment of 1-3 orders of magnitude in surficial sediments relative to background in deeper sediments. Radionuclide levels in surficial sediments exceeded those reported in lake sediments in uncontaminated systems and, for some radionuclides, approached or equalled levels in sediments contaminated with uranium and radium refining residues. Radionuclide activity ratios in the surficial layers of the Quirke Lake cores and in downstream sediments demonstrated the relative mobilities of the elements in the watershed. Net sediment loading rates for radionuclides in the three basins were 130-230 mg .cntdot. m-2 .cntdot. yr-1 for U, 340-4000 Bq .cntdot. m-2 .cntdot. yr-1 for other members of the 238U decay chain, and 210-530 Bq .cntdot. m-2 .cntdot. yr-1 for 232Th and 228Th.

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PALYNOLOGY OF INDIAN AND EUROPEAN FOREST CLEARANCE AND FARMING IN LAKE SEDIMENT CORES FROM AWENDA PROVINCIAL PARK ONTARIO CANADA

Palynologic analyses of four short cores collected along shallow- to deep-water transects in Second and Gignac lakes indicate two periods of forest clearance for farming. The first deforestation was by Huron Indians between A.D. 1450 and 1650, when a maple (Acer), beech (Fagus), and oak (Quercus) forest was cleared and corn (Zea) planted. This disturbance is identified by decreased tree pollen and increased Pteridium, Artemisia, and other herbs and is confirmed by Zea pollen in Gignac Lake. From 1650 to 1875 there was a forest succession to oak, birch (Betula), and pine (Pinus). Following this recovery European loggers and farmers cleared this forest and attempted farming. Besides a reduction in tree pollen, a product of this deforestration includes the pollen of weedy Ambrosia, Gramineae, and introduced European Rumex and Plantago. During the last 25 years an increase in tree pollen indicates local forest recovery consistent with present land use By relating upland vegtation successions to lacustrine algal assemblage changes, probable ecological control on algae during the last 600 years are identified. Peridinium willei Huitfeldt-Kaas and Pediastrum respond to changes induced by forest clearance and agriculture. Aquadulcum awendae n. sp. and Peridinium wisconsinense Eddy prefer less alkaline water. Variations in palynomorph influx are related to basin morphology and water circulation. Gignac Lake, a steep sided and relatively deep lake, directs palynomorphs from shallow marginal banks to the deeper basin, whereas Second Lake, with a gently sloping shallow lake bottom, preferentially accumulates palynormorphs close to shore.

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GEOCHEMICAL INDICATORS IN LAKE SEDIMENT OF UPLAND EROSION CAUSED BY INDIAN AND EUROPEAN FARMING AWENDA PROVINCIAL PARK ONTARIO CANADA

Neutron-activation analysis, loss on ignition (LOI), and X-ray diffraction of eight cores collected in Second and Gignac lakes are correlated with historic and palynologic records to identify elements linked to erosion from deforestation and farming. Forest disturbance and farming are identified in cores of organic detritus sediment (gyttja) by decreased LOI and increased Na, Mg, Ba, Al, Ti, and Dy. LOI is not suitable for identifying forest disturbances in carbonate sediments. From neutron-activation analysis of carbonate mud only Na, Al, and Dy indicate erosion. Elements linked to the quantity of organic matter in sediments include U, V, and Cl, whereas Mn and I in surface sediments presumably correspond with variations in the oxidation potential and plant productivity, respectively. Sedimentation patterns relate to basin morphology. In Gignac Lake the basin is steep sides and relatively deep. Clastic detritus entering the lake is carried over the shallow, nearshore carbonate bank into deeper water. In Second Lake the basin is shallow and gently sloping. Minerals eroded from onshore are more equally distributed in this basin. In Second Lake the most rapid sedimentation is nearshore where submerged aquatic macrophytes produce and trap carbonate mud. In Gignac Lake the top of the shallow carbonate bank has few aquatic macrophytes; lime mud formed on the bank is washed into deep water offshore, where it dissolves.

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POSTGLACIAL RELATIVE SEA-LEVEL CHANGE PORT-AU-PORT AREA WEST NEWFOUNDLAND CANADA

We first report pollen and foraminifera analyses and radiocarbon dates from two cores taken from salt-marsh deposits bordering Port au Port Bay, southwestern Newfoundland. Results show that relative sea level (RSL) stood at 2.8 m below present higher high-water level (HHWL) at 2770 .+-. 300 years BP and at 1.8 m at 2365 .+-. 175 years BP at the core sites. They permit calculation of a rate of late Holocene RSL change from western Newfoundland. We then report other available dates bearing on the earlier RSL record of this area. A date of 5800 .+-. 200 years BP fixes the age of minimum RSL in Port au Port Bay at 11-14 m below present. A date of 9350 .+-. 120 years BP from St. George's provides a minimum age for the passage of sea level below present there. A date of 12,600 .+-. 140 years BP from Stephenville fixes a sea level at 29 m above present, whereas one of 13,600 .+-. 110 years BP from Abrahams Cove dates the marine limit at 44 m. These geographically restricted data closely constrain a curve of postglacial RSL change in the Port au Port Bay - northern St. George's Bay area. The form of the curve supports a recent model predicting sea-level response to wastage of a limited late Wisconsinan ice load in the wider region.

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POLLEN ANALYSIS OF THE 1973 ICE CORE FROM DEVON ISLAND GLACIER CANADA

Meltwater from a 299-m-long ice core was filtered and analyzed for fossil pollen and spores. Pollen concentration was higher in the late Holocene and interglacial intervals (.apprx. 7 l-1) than in the early Holocene and Wisconsinian (.apprx. 1-2 l-1) ones. The late Holocene and interglacial assemblages were dominated by Alnus (alder); the early Holocene and Wisconsinian ones were dominated by Betula (birch) and Artemisia (sage). During the Holocene and probably the last interglaciation, most of the pollen and spores were blown a minimum of 1000 km from low arctic shrub tundra and adjacent subarctic Picea (spruce) forest; these areas were dominated by the arctic air mass during the summer pollinating season. During the Wisconsinian-early Holocene, glacier ice and arctic air were more widespread and pollen sources were more distant; thus, at this time relatively little pollen was incorporated into the ice. The Devon ice-core data suggest that there should have been pollen in the continental ice sheet of Wisconsin time. When the ice sheet retreated this pollen would be carried by meltwater and redeposited with silt and clay together with contemporary pollen, producing an ecologically anamalous assemblage.

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VEGETATION HISTORY OF THE HUDSON BAY LOWLAND: A POSTGLACIAL POLLEN DIAGRAM FROM THE SUTTON RIDGE.

A sedimentation rate based on two radiocarbon dates and the modern sediment surface provide an estimate of 8200 yr BP for lake emergence from the sea in response to isostatic rebound. Fossil pollen and macrofossils show a succession from sparse coastal tundra to shrub tundra to the modern spruce woodland between 8200 and 6500 yr BP, a response to the decreasing influence of marine climate as Hudson Bay retreated.

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LATE QUATERNARY CLIMATE OF ONTARIO: TEMPERATURE TRENDS FROM THE FOSSIL POLLEN RECORD.

In eastern Ontario zonal vegetation boundaries parallel isotherms of mean annual temperatures. Because modern pollen rain reflects zonal vegetation one can trace zonal vegetation and temperature trends with critical pollen diagrams from the time of deglaciation (14 000 BP). There is no indication of a mid-Holocene Hypsithermal in southern Ontario.

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POSTGLACIAL HISTORY OF PRAIRIE, SAVANNA, AND FOREST IN NORTHWESTERN MINNESOTA

Vegetation of a west-east transect of 11 townships, including Itasca State Park, was mapped as a west-east succession of Prairie, Oak Savanna, Mesic Deciduous Forest, and Pine-Hardwood Forest formations, corresponding with gradients of climate, soil texture, and fire frequency. The mapped vegetation was compared with pollen spectra of short cores from 11 ponds. The postglacial history of the vegetation formations is reconstructed with the aid of pollen diagrams of long cores from four ponds, diagrams representing the past 12,000 years. Absolute dating of the chronosequence is aided by five radiocarbon dates. The vegetation succession is thought to have been basically caused by climatic change acting on the available flora. The period 8,500-4,000 years ago was a time of higher temperature and greater aridity than the preceding and succeeding periods

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A LATE-WISCONSIN BURIED SOIL NEAR AITKIN, MINNESOTA, AND ITS PALEOBOTANICAL SETTING

A podzolic paleosol formed on sand during the Two Creeks interval and buried below marl of Glacial Lake Aitkin is exposed in a diversion canal near Aitkin. The stratigraphic section and results of detailed pollen and plant macrofossil analysis of the soil, as well as the overlying sediments, are reported. The data indicate that during the Valders advance in the area, the vegetation consisted mainly of spruce

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CLUSTER-ANALYSIS OF LATE HOLOCENE POLLEN TRENDS IN ONTARIO

Cluster analysis of Ontario pollen stratigraphies demonstrates similar regional successions during the past 1000 years. Seven character states qualitatively describe the behaviour of the pollen percentage trends for each taxon: 0, absent; 1, present with no visible trend but high noise; 2, rising through time; 3, falling through time; 4, rise-fall; 5, fall-rise; and 6, stable through time. The three similarity indices (S) used were of the form S equals the number of characters in agreement divided by the number of informative characters. The three clustering techniques used are single linkage, complete linkage, and unpaired weighted geometric mean analysis. Single linkage and unpaired weighted geometric mean analysis showed a north-south division with all three indices; complete linkage showed only rare local groupings with all three indices. The division between the two clusters falls just south of Lake Nipissing. All successions indicate climatic cooling; the clusters reflect southward movement of the centres of species abundances, particularly white pine. The method identifies regions of similar vegetation dynamics.

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HONEY BEE, APIS MELLIFERA, POLLEN FORAGING IN SOUTHERN ONTARIO

Honey Bee, Apis mellifera, pollen pellets were collected for five days each week for 16 weeks at the University of Guelph. They were sorted by color, the dispersed pollen cleaned by acetolysis and identified under a light microscope. Over 99% of pollen in each pellet was of one pollen type. Twenty-five pollen types were identified. Over 75% of the pellets were pollen from introduced taxa. The pattern of pollen collection by the bees reflected the blooming period of the plants.

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