Holocene evolution of the Assiniboine River paleochannels and Portage la Prairie alluvial fan

The Portage la Prairie alluvial fan was constructed by numerous successive paleochannels of the Assiniboine River along the western side of the Lake Agassiz basin as the level of the lake rapidly declined beginning 9500 years ago. The history of the paleochannels during the first several thousand years is not known. Paleochannel morphologies and cross-cutting relations, soil maturity, and radiocarbon dates, however, indicate that by 6000–7000 years ago flow was northward into Lake Manitoba. This direction was maintained until about 3000 years ago, when avulsion redirected the Assiniboine eastward to the Red River near Winnipeg. The morphologies of the paleochannels suggest that channel-forming discharges and sediment loads of the ancestral rivers have not differed significantly from the modern values despite palynological evidence that the climate was warmer and drier during much of the Holocene.

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Fluvial Sedimentology and Paleoecology of Holocene Alluvial Deposits, Red River, Manitoba

Géographie physique et Quaternaire ◽

10.7202/032948ar ◽

2007 ◽

Vol 47 (2) ◽

pp. 193-210 ◽

Cited By ~ 8

Author(s):

Erik Nielsen ◽

W. Brian McKillop ◽

Glen G. Conley

Keyword(s):

Late Holocene ◽

Red River ◽

Present Position ◽

Lake Agassiz ◽

Alluvial Deposits ◽

Radiocarbon Dates ◽

The North ◽

Mollusc Species ◽

History Of ◽

Overbank Sedimentation

ABSTRACT Stratigraphie and paleoecological analyses at five sections, together with age determinations based on 19 previously published and 21 new radiocarbon dates, provide a detailed late Holocene history of the Red River, Manitoba. Ecological information, such as age frequency analysis, relative abundance, diversity and association of species was drawn from 19 mollusc species. These data indicate that the Red and Assiniboine rivers cut the valleys they occupy today within a thousand years of the regression of Lake Agassiz. In the south, up to 14 m of alluvium has accumulated during the last 7000 years. A decrease in the sedimentation rate at 1400 BP is coincident with the shift in the position of the Assiniboine from the valley of the La Salle River to its present position. Overbank sedimentation did not start in the northern part of the area until ca. 5200 BP. Initial rapid sedimentation rates in this area are attributed to increased precipitation and a brief eastward excursion of the Assiniboine River into the Red. In spite of increased precipitation, flood frequencies remained low in the north until 1400 BP. Increased overbank sedimentation after 1400 BP is attributed to the northward shift in the position ot the Assiniboine.

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The last glaciation and sea level history of Fosheim Peninsula, Ellesmere Island, Canadian High Arctic

Canadian Journal of Earth Sciences ◽

10.1139/e96-082 ◽

1996 ◽

Vol 33 (7) ◽

pp. 1075-1086 ◽

Cited By ~ 37

Author(s):

Trevor Bell

Keyword(s):

High Arctic ◽

Radiocarbon Dates ◽

The Holocene ◽

Ice Caps ◽

Marine Deposits ◽

Last Glaciation ◽

Maximum Elevation ◽

Glacier Runoff ◽

History Of ◽

Ice Conditions

The last glaciation of Fosheim Peninsula is reconstructed on the basis of landform and sediment mapping and associated radiocarbon dates. Ice growth involved the expansion of cirque glaciers and accumulation on upland surfaces that are now ice free. Limited ice buildup, despite lowering of the paleoglaciation level by 700–800 m, is attributed to the hyperaridity of the region during glacial conditions. Marine deposits in formerly submerged basins beyond the ice margins are interpreted to represent (i) sedimentation caused by local ice buildup and marine transgression by 10.6 ka BP, (ii) increased ablation and glacier runoff [Formula: see text]9.5 ka BP, and (iii) marine regression during the Holocene. Holocene marine limit reaches a maximum elevation of approximately 150 m asl along northern Eureka Sound and Greely Fiord and descends southeastwards to 139–142 m asl near the Sawtooth Mountains. A synchronous marine limit is implied where the last ice limit was inland of the sea. The magnitude and pattern of Holocene emergence cannot be fully explained by the glacioisostatic effects of the small ice load during the last glaciation of the region. Deglaciation of the peninsula was underway by 9.5 ka BP; however, local ice caps may have persisted through the wannest period of the Holocene until 6–5 ka BP. This was likely a function of reduced sea ice conditions and increased moisture availability which benefited low-lying coastal icefields, but had negligible effect on interior highland ice caps.

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Late Holocene landscape change history related to the Alpine Fault determined from drowned forests in Lake Poerua, Westland, New Zealand

Natural Hazards and Earth System Science ◽

10.5194/nhess-12-2051-2012 ◽

2012 ◽

Vol 12 (6) ◽

pp. 2051-2064 ◽

Cited By ~ 8

Author(s):

R. M. Langridge ◽

R. Basili ◽

L. Basher ◽

A. P. Wells

Keyword(s):

Lake Level ◽

Late Holocene ◽

Alluvial Fan ◽

Time Of Death ◽

Fault Rupture ◽

Radiocarbon Dates ◽

Living Tree ◽

Alpine Fault ◽

History Of ◽

Lowland Forests

Abstract. Lake Poerua is a small, shallow lake that abuts the scarp of the Alpine Fault on the West Coast of New Zealand's South Island. Radiocarbon dates from drowned podocarp trees on the lake floor, a sediment core from a rangefront alluvial fan, and living tree ring ages have been used to deduce the late Holocene history of the lake. Remnant drowned stumps of kahikatea (Dacrycarpus dacrydioides) at 1.7–1.9 m water depth yield a preferred time-of-death age at 1766–1807 AD, while a dryland podocarp and kahikatea stumps at 2.4–2.6 m yield preferred time-of-death ages of ca. 1459–1626 AD. These age ranges are matched to, but offset from, the timings of Alpine Fault rupture events at ca. 1717 AD, and either ca. 1615 or 1430 AD. Alluvial fan detritus dated from a core into the toe of a rangefront alluvial fan, at an equivalent depth to the maximum depth of the modern lake (6.7 m), yields a calibrated age of AD 1223–1413. This age is similar to the timing of an earlier Alpine Fault rupture event at ca. 1230 AD ± 50 yr. Kahikatea trees growing on rangefront fans give ages of up to 270 yr, which is consistent with alluvial fan aggradation following the 1717 AD earthquake. The elevation levels of the lake and fan imply a causal and chronological link between lake-level rise and Alpine Fault rupture. The results of this study suggest that the growth of large, coalescing alluvial fans (Dry and Evans Creek fans) originating from landslides within the rangefront of the Alpine Fault and the rise in the level of Lake Poerua may occur within a decade or so of large Alpine Fault earthquakes that rupture adjacent to this area. These rises have in turn drowned lowland forests that fringed the lake. Radiocarbon chronologies built using OxCal show that a series of massive landscape changes beginning with fault rupture, followed by landsliding, fan sedimentation and lake expansion. However, drowned Kahikatea trees may be poor candidates for intimately dating these events, as they may be able to tolerate water for several decades after metre-scale lake level rises have occurred.

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Dating Climatic Episodes of the Holocene

Quaternary Research ◽

10.1016/0033-5894(74)90060-x ◽

1974 ◽

Vol 4 (1) ◽

pp. 9-24 ◽

Cited By ~ 92

Author(s):

Wayne M. Wendland ◽

Reid A. Bryson

Keyword(s):

Cultural History ◽

Sea Level ◽

Cultural Change ◽

Climatic Impact ◽

Radiocarbon Dates ◽

The Holocene ◽

Independent Analysis ◽

The World ◽

History Of ◽

Cultural Discontinuities

Monitoring evidence indicates that the Holocene embraced a sequence of rather discrete climatic episodes. The transitions between these environmental episodes apparently were abrupt and globally synchronous. This paper reports on statistical analyses of radiocarbon dates associated with environmental change and cultural change.Over 800 14C dates associated with pollen maxima and minima, sea level maxima and minima, and top and bottom surfaces of peat beds were simultaneously analyzed to identify times of globally synchronous environmental discontinuities.Some 3700 14C dates associated with 155 cultural continua of the world were collectively analyzed to identify worldwide synchroneities in appearance and termination of the cultures.Significant globally synchronous discontinuities were identified in each independent analysis. The dates of environmental and cultural discontinuities are rather similar, particularly during the recent half of the Holocene. The fact that the cultural discontinuities mostly follow rather closely those of the paleobotanical record suggests that there has been a distinct climatic impact on the cultural history of man.

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Quaternary geology of the Grand Rapids area, Manitoba

Canadian Journal of Earth Sciences ◽

10.1139/e70-081 ◽

1970 ◽

Vol 7 (3) ◽

pp. 853-857 ◽

Cited By ~ 2

Author(s):

R. H. Grice

Keyword(s):

Quaternary Geology ◽

Stream Channels ◽

Drainage Pattern ◽

Lake Agassiz ◽

Quaternary Deposits ◽

Lake Winnipeg ◽

Grand Rapids ◽

Central Canada ◽

History Of ◽

Western Side

Grand Rapids is at the mouth of the Saskatchewan River on the western side of Lake Winnipeg in central Canada and is in the western part of the region formerly covered by Glacial Lake Agassiz.Relict beaches and cliffs, and abandoned spillway and stream channels have been observed in the area. Much of the Paleozoic bedrock is covered by Quaternary deposits consisting of three or four Wisconsin tills interspersed and covered by glacio–lacustrine silts and clays.The events are correlated with the final four episodes in the general history of Lake Agassiz and it appears that after substantial changes in the drainage pattern, the recent course of the lower reaches of the Saskatchewan River developed during the last 8 000 ± 250 y.

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Tartu Radiocarbon Dates IX

Radiocarbon ◽

10.1017/s0033822200004586 ◽

1979 ◽

Vol 21 (3) ◽

pp. 465-471 ◽

Cited By ~ 1

Author(s):

A Liiva ◽

G Elina ◽

V Tchatchkhiani ◽

T Rinne

Keyword(s):

Peat Bogs ◽

Radiocarbon Dates ◽

The Holocene ◽

History Of ◽

Made In

The following list contains dates of organogenous sediments (peat and sapropel from the Karelian ASSR) made in 1972 to 1977 with the aim of studying the history of the development of peat bogs in the Holocene (Elina, 1969; 1971a,b; Pyavchenko et al, 1976). Samples were collected with Hiller or Instorf samplers. Borings were made in the deepest parts of the peat bogs.

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