Characterizing large river history with shallow geophysics: Middle Yukon River, Yukon Territory and Alaska

Froese, Duane G.; Smith, Derald G.; Clement, David Thomas

doi:10.1016/j.geomorph.2004.11.011

Cited by 64 publications

(49 citation statements)

References 23 publications

(22 reference statements)

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“…1). The floodplain is 4-6 km wide and capped by locally derived aeolian sediments deposited in the late Pleistocene and early Holocene (23). The site consists of 2 m of fluvial sand overlain by 12 m of calcareous loess, interbedded with at least seven buried soils (paleosols), each in the early stages of soil development (Inceptisols).…”

Section: Resultsmentioning

confidence: 99%

Ancient DNA reveals late survival of mammoth and horse in interior Alaska

Haile

Froese

MacPhee

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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181

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Causes of late Quaternary extinctions of large mammals (''megafauna'') continue to be debated, especially for continental losses, because spatial and temporal patterns of extinction are poorly known. Accurate latest appearance dates (LADs) for such taxa are critical for interpreting the process of extinction. The extinction of woolly mammoth and horse in northwestern North America is currently placed at 15,000 -13,000 calendar years before present (yr BP), based on LADs from dating surveys of macrofossils (bones and teeth). Advantages of using macrofossils to estimate when a species became extinct are offset, however, by the improbability of finding and dating the remains of the last-surviving members of populations that were restricted in numbers or confined to refugia. Here we report an alternative approach to detect 'ghost ranges' of dwindling populations, based on recovery of ancient DNA from perennially frozen and securely dated sediments (sedaDNA). In such contexts, sedaDNA can reveal the molecular presence of species that appear absent in the macrofossil record. We show that woolly mammoth and horse persisted in interior Alaska until at least 10,500 yr BP, several thousands of years later than indicated from macrofossil surveys. These results contradict claims that Holocene survival of mammoths in Beringia was restricted to ecologically isolated high-latitude islands. More importantly, our finding that mammoth and horse overlapped with humans for several millennia in the region where people initially entered the Americas challenges theories that megafaunal extinction occurred within centuries of human arrival or were due to an extraterrestrial impact in the late Pleistocene.extinction ͉ permafrost ͉ megafauna ͉ Beringia

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Section: Resultsmentioning

confidence: 99%

Ancient DNA reveals late survival of mammoth and horse in interior Alaska

Haile

Froese

MacPhee

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

247

181

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“…In the case of alluvial deposits, the diffractions caused by a lateral truncation of various heterogeneities can disturb the image of alluvial structures (Vanderberghe and van Overmeeren 1999). It should be noted that silt or clay deposits cause attenuation of the radar signal which limits the depth range of measurement but can also be useful to determine the thickness of the alluvial fill as was done by Leclerc and Hickin (1997) and Froese et al (2005). Basal till significantly limits the depth range of the GPR measurements.…”

mentioning

confidence: 99%

Reconstructing migration phases of meandering channels by means of ground-penetrating radar (GPR): the case of the Obra River, Poland

Słowik

2011

J Soils Sediments

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Purpose The main goal of the study was to compare the potential of conventional and geophysical methods (ground-penetrating radar; GPR) to reconstruct the migration phases of a meandering lowland riverbed: the Obra River in western Poland. The purpose was to verify that the migration phases can be distinguished using the GPR measurement providing near-continuous imaging of alluvial structures and to discuss differences between the spatial extent of the migration phases distinguished using geologic data and GPR surveys. Materials and methods Historical maps from the eighteenth and the nineteenth century were analyzed to study transformations of the Obra River bed pattern. One hundred twenty tube sample borings were undertaken along five profiles to recognize the floodplain lithology. Granulation coefficients were determined using the method of moments to distinguish lithofacies of the alluvial deposits. The GPR measurement was performed using a georadar MALA ProEx equipped with shielded 100 and 250 MHz antennae. The GPR images were compared to geologic profiles to determine the depth scale and accuracy of the measurements. The depth scale of the GPR images was determined on the basis of the correlation of the radar reflections with the geologic profiles. Ten organic sediment samples were collected to determine the age of the migration phases.Results and discussion Point bars with layering of sand deposits, organic sediment fills, erosion surfaces, and gravel beds were distinguished using the 250 MHz antenna. However, some of sedimentary structures (e.g., inserts of fine sands in the organic deposits) were beyond the detection range of the antennae. The glacial/alluvial sediment interface was detected using the 100 MHz antenna which enabled the determination of the thickness of the alluvial fill. Traces of a period of early development of the Obra valley and three migration phases of the Obra River bed were distinguished. The research indicated that the Obra was a meandering river at least 7,000 years before present and that during the last 3,000 years, channel islands were formed within the studied section of the valley. Conclusions The GPR method allowed for the analysis of the spatial variability of alluvial deposits and helped to describe how meander bends were formed. The presented GPR images illustrate the spatial extent of the migration phases in a more detailed way than using only sedimentary information. However, geologic data are necessary for interpretation of the GPR images. It was shown that the GPR method gives useful results in spite of rough land surface and dense vegetation.

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“…Conductivity depends closely on the grain size and porosity of the sediment, making electromagnetic prospecting highly suitable for distinguishing coarse deposits (sand and gravel), generally characterized by low conductivity values, from finer ones (silt, clay and peat) (Archie, 1942;[Gourry et al, 2003] and [Froese et al, 2005]). Thus, in the case of resistive bedrock, such as chalk or limestone in the Choisille catchment, low conductivities are usually associated with coarse deposits or thin sedimentary filling, whereas high conductivities indicate a thick layer of fine deposits .…”

Section: Geophysical Datasetmentioning

confidence: 99%

Spatio-temporal evolution of the Choisille River (southern Parisian Basin, France) during the Weichselian and the Holocene as a record of climate trend and human activity in north-western Europe

Morin

Macaire

Hinschberger

et al. 2011

Quaternary Science Reviews

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drigues, et al.. Spatio-temporal evolution of the Choisille River (southern Parisian Basin, France) during the Weichselian and the Holocene as a record of climate trend and human activity in north-western Europe. Quaternary Science Reviews, Elsevier, 2011, 30 (3-4) AbstractThe morpho-sedimentary evolution of the Choisille floodplain (lowland river, catchment: 288 km 2 ), a tributary of the River Loire in the south-western Parisian Basin, was studied through 61 core drillings along eight transects and a geophysical survey located in four stretches of the river: stretches A and B correspond to two sub-catchments, and stretches C and D are in the main valley. Sixty 14 C and four OSL datings were obtained, and sediments were analysed on seven reference cores. Eight phases of evolution differing markedly from the evolution of more northern areas in the Parisian Basin and north-western Europe were identified from spatio-temporal distribution of nine lithological facies. The deepest incision phase (1) occurred during the first part of the Weichselian, followed by the deposition of a gravelly-sandy unit (phase 2) during the Middle Pleniglacial, which was deeply incised (phase 3), probably during the Bölling. From the Allerød up to the last third of the Boreal (phase 4), sedimentation was continuously dominated by peaty deposits, with no evidence of either increased hydraulic energy during the Younger Dryas, or of incision during the LateGlacialHolocene transition. This trend seems to reflect the specificity of the south-western Parisian Basin climate from the Late Weichselian up to the end of the Boreal, due to the influence of the Atlantic Ocean, compared to more northern areas where the climate was more continental. The downstream incision trend during the last third of the Boreal up to the Subatlantic (phases 5 and 6) indicates a sharp increase in precipitation and vegetation cover; the lack of peaty sediments, widespread in north-western Europe, and also of precipitated carbonates frequent in the Parisian Basin, seems to be due to local physiographic characteristics. The main part of the sediment filling, which is principally silty and retrograde, began during the Subatlantic (phase 7 and 8) as a result of deforestation of the plateaux for crop farming. High humaninduced sediment yield and storage concealed the possible impacts of climate change on fluvial dynamics: lithological facies change from phase 7 to 8 can only indicate the autogenic morphological evolution of the floodplain in accretion. The non-univocal upstreamdownstream variation in the start of phase 7 shows that sediment yield varied in space and time in the catchment, particularly in relation to the agricultural potential of the different areas; this observation could be used to testify human-induced sedimentation in other catchments.

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Characterizing large river history with shallow geophysics: Middle Yukon River, Yukon Territory and Alaska

Cited by 64 publications

References 23 publications

Ancient DNA reveals late survival of mammoth and horse in interior Alaska

Ancient DNA reveals late survival of mammoth and horse in interior Alaska

Reconstructing migration phases of meandering channels by means of ground-penetrating radar (GPR): the case of the Obra River, Poland

Spatio-temporal evolution of the Choisille River (southern Parisian Basin, France) during the Weichselian and the Holocene as a record of climate trend and human activity in north-western Europe

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