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

2007 ◽  
Vol 47 (2) ◽  
pp. 193-210 ◽  
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.

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

1989 ◽  
Vol 26 (9) ◽  
pp. 1834-1841 ◽  
Author(s):  
W. F. Rannie ◽  
L. H. Thorleifson ◽  
J. T. Teller
Keyword(s):  
Alluvial Fan ◽  
Red River ◽  
Lake Agassiz ◽  
Radiocarbon Dates ◽  
The Holocene ◽  
Sediment Loads ◽  
History Of ◽  
Western Side

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.

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

2012 ◽  
Vol 12 (6) ◽  
pp. 2051-2064 ◽  
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.

Siliceous microfossils and mineral magnetic characteristics in a sediment core from Lake Manitoba, Canada: a remnant of glacial Lake Agassiz

1999 ◽  
Vol 36 (8) ◽  
pp. 1299-1314 ◽  
Author(s):  
Jan Risberg ◽  
Per Sandgren ◽  
James T Teller ◽  
William M Last
Keyword(s):  
Great Plains ◽  
Late Holocene ◽  
Climatic Conditions ◽  
Glacial Lake ◽  
Magnetic Characteristics ◽  
Northern Great Plains ◽  
Silty Clay ◽  
Lake Agassiz ◽  
Radiocarbon Dates ◽  
Glacial Lake Agassiz

A 14.2 m long core was recovered from the southern Lake Manitoba basin. The sediment, consisting mainly of silty clay, was studied for siliceous microfossil content and mineral magnetics; 14 new accelerator mass spectrometry (AMS) radiocarbon dates provide chronological control of the paleoenvironmental history of the basin. The basal 5 m contains ice-rafted clasts and is largely barren of siliceous microfossils; these sediments were deposited when the lake was part of glacial Lake Agassiz. Sediments immediately overlying the barren part of the sequence contain AMS dates of 7700-7400 BP and reflect a dramatic change in conditions in the basin. Diatom abundances rise abruptly. Magnetic characteristics change substantially. The presence of freshwater taxa such as Stephanodiscus niagarae, together with brackish water diatoms, indicate that shallow, turbid, high-nutrient conditions with variable salinity occurred during the early part of the middle Holocene. Although climatic conditions throughout the northern Great Plains are known to have become drier and warmer during the mid-Holocene, there is a distinct change in diatom taxa in the Lake Manitoba sequence toward less saline conditions at this time. The presence of the riverine diatom Aulacoseira granulata in this interval supports previous conclusions that these freshwater conditions resulted from the northward diversion of the Assiniboine River into the basin. Following this, diatoms indicate an abrupt increase in salinity to >1500 mg·L-1 total dissolved solids between 4000 and 2600 BP, reflecting the diversion of the fresh waters of the Assiniboine River away from Lake Manitoba. Increasingly cooler and wetter conditions during the late Holocene, combined with differential isostatic rebound, caused a freshening of the lake during the late Holocene.

Interpretation of radiocarbon dates from the upper surface of late-Holocene peat layers in coastal lowlands

The Holocene ◽  
2006 ◽  
Vol 16 (1) ◽  
pp. 51-61 ◽  
Author(s):  
M. P. Waller ◽  
A. J. Long ◽  
J. E. Schofield
Keyword(s):  
Plant Communities ◽  
Late Holocene ◽  
A Priori ◽  
Radiocarbon Dates ◽  
Coastal Lowland ◽  
The North ◽  
Clastic Sediments ◽  
The North Sea ◽  
Underlying Processes ◽  
Coastal Lowlands

Marine/brackish clastic sediments replace freshwater peats in the stratigraphic column of many coastal lowland areas bordering the North Sea during the late Holocene. Radiocarbon dates are routinely used to provide a chronology for this shift. We examine the assumptions underpinning this approach. The results of investigations from 13 sites in the Rye area of Romney Marsh, southeast England, are reported. Dates from apparently gradational contacts of a highly humified, laterally persistent, peat layer range from 3170-2840 cal. yr BP to 1290-1050 cal. yr BP. Multiple inundations or prolonged gradual inundation are nevertheless rejected, as discrete post-peat bodies of sediment are absent and because peat growth appears to have slowed-down or ceased at many sites in advance of inundation. Additionally in the Rye area, sharp contacts are widespread and the pollen assemblages rarely indicate the occurrence of transitional plant communities. A review of the dating evidence from other coastal lowland regions reveals that multiple dating of the upper surface of peat beds invariably produces diachronous results. As a consequence time transgressive processes feature prominently as causal mechanisms underlying this shift. However, many of the dating difficulties recognized in the Rye area appear to apply to other regions. We conclude that radiocarbon dates from the upper surface of peat layers should in most instances only be regarded as limiting ages for the deposition of the overlying clastic sediments. New chronologies need to be built without a priori assumptions as to the underlying processes, ideally through the direct dating of the clastic sediments.

scholarly journals Coastal Response to Changes in Sea Level Since the Last 4500 BP On the East Coast of Tamil Nadu, India

Radiocarbon ◽  
2002 ◽  
Vol 44 (1) ◽  
pp. 137-144 ◽  
Author(s):  
Hema Achyuthan ◽  
V R Baker
Keyword(s):  
Sea Level ◽  
Tamil Nadu ◽  
Late Holocene ◽  
East Coast ◽  
Tidal Zone ◽  
Zone Formation ◽  
Coastal Evolution ◽  
Radiocarbon Dates ◽  
The North ◽  
Coastal Sedimentation

Geomorphology, clay mineral composition, and radiocarbon dates from Muttukadu to Marakkanam estuaries and the tidal zone along the east coast of Tamil Nadu, India, have been used to reconstruct coastal evolution between approximately 4500 and 1100 B P. Formation of alternate oyster beds with intervening tidal clay units indicate fluctuation in the sea level may be a consequence of changes in the Mid-Holocene sedimentation pattern and coastal configuration. 14C dates from Muttukadu indicate a rapid relative sea-level rise (RSL) subsequent to 3500 BP and tidal flat sedimentation between 3475 and 3145 BP. Marine conditions along the east coast area returned around 1900 B P. Comparison of dates with other sites, e.g. Muttukadu, Mammallapuram, and Marakkanam, points toward short removal of marine conditions, ample sediment supplies in the tidal zones, and neotectonic activity. Reactivation of the north–south trending fault line occurred not earlier than approximately 1050 B P. Our study indicates that Middle to Late Holocene coastal sedimentation and the chronology of the tidal zone formation have been strongly influenced by local factors. These have provided considerable scope for internal reorganization with changing coastal processes.

scholarly journals Stochastic alluvial fan and terrace formation triggered by a high-magnitude Holocene landslide in the Klados Gorge, Crete

2021 ◽  
Author(s):  
Elena T. Bruni ◽  
Richard F. Ott ◽  
Vincenzo Picotti ◽  
Negar Haghipour ◽  
Karl W. Wegmann ◽  
...  
Keyword(s):  
Late Holocene ◽  
Alluvial Fan ◽  
Tectonic Activity ◽  
Climate Variations ◽  
Alluvial Deposits ◽  
Small Catchment ◽  
Radiocarbon Dates ◽  
Quaternary Climate ◽  
Stochastic Events

Abstract. Alluvial fan and terrace formation is traditionally interpreted as related to Quaternary climate oscillations under the backdrop of slow and steady tectonic activity. However, several recent studies challenge this conventional wisdom, showing that such landforms can evolve rapidly as a geomorphic system responds to catastrophic and stochastic events, like large magnitude mass-wasting. Here, we contribute to this topic through a detailed field and geochronological investigation of alluvial sequences in the Klados catchment in southwestern Crete, Greece. The Klados River catchment is characterised by well-preserved, alluvial terraces and a set of fans at the river mouth, which do not seem to fit the sediment capacity of a small catchment with a drainage area of ~ 11.5 km2. Previous studies interpreted the formation of the deposits and their development to be of Pleistocene age and controlled by climate variations and the region's long-term tectonic activity. We find that the > 20 m thick intermediate fan buries a paleoshoreline uplifted in AD 365 placing the depositional age of this unit firmly into the Late Holocene. This is supported by seven new radiocarbon dates that infer mid to late Holocene ages for the entire fan and terrace sequence. As sediment source, we identify a landslide scar at the head of the catchment. We document landslide deposits 100 m above the modern stream and utilise landslide runout modelling to reconstruct landslide volumes and validate our hypothesis. We find that a landslide volume of 0.0908 km2 matches the observed distribution of landslide deposits and the landslide scar dimensions. We hypothesise that subsequent aggradation and incision cycles of the alluvial deposits are not linked to long-term tectonic uplift and climate variations but rather stochastic events such as mobilisation of sediment in large earthquakes, storm events, or blockage in the valley's narrow reaches. The Klados case study represents a model-environment for how stochastically-driven events can mimic climate-induced sedimentary archives, and how catchments can become ultrasensitive to external perturbations after catastrophic events.

The need for paleoflood investigations on the American reach of the Red River of the North

The Holocene ◽  
2021 ◽  
pp. 095968362110605
Author(s):  
Scott St. George ◽  
Joseph Zeleznik ◽  
Judith Avila ◽  
Matthew Schlauderaff
Keyword(s):  
United States ◽  
The United States ◽  
Flood Frequency ◽  
Red River ◽  
Past Century ◽  
Policy Makers ◽  
The Past ◽  
The North ◽  
Diversion Channel ◽  
History Of

Over the past century, the Red River of the North has been the least stationary river in the continental United States. In Canada, historical and paleoenvironmental evidence indicates severe floods were common during the early 1800s, with the record ce 1826 flood having an estimated peak discharge 50% higher than the second-most severe flood ever observed. Unfortunately, the recorded history of flooding upstream in the United States does not begin until seven decades after this event. If 1826 was an equally exceptional flood on American reach of the river, then current flood-frequency curves for the river underestimate significantly the risks posed by future flooding. Alternatively, if the American stretch did not produce a major flood in 1826, then the recent spate of flooding that has occurred over the past two decades is exceptional within the context of the past 200 years. Communities in the Fargo-Moorhead metropolitan area are building a 58-km long, $2.75 billion (USD) diversion channel that would redirect floodwaters westward around the two cities before returning it to the main channel. Because this and other infrastructure in North Dakota and Minnesota is intended to provide protection against low-probability, high-magnitude floods, new paleoflood investigations in the region would help local, state, and federal policy-makers better understand the true flood threats posed by the Red River of the North.

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