On the nature and origin of "muck" deposits in the Klondike area, Yukon Territory

1997 ◽  
Vol 34 (10) ◽  
pp. 1333-1344 ◽  
Author(s):  
T. A. Fraser ◽  
C. R. Burn
Keyword(s):  
Organic Matter ◽  
Fine Sand ◽  
Yukon Territory ◽  
Low Flow ◽  
Radiocarbon Dates ◽  
The Holocene ◽  
Yukon River ◽  
Laboratory Investigations ◽  
Late Wisconsinan ◽  
Kluane Lake

Organic-rich "muck" deposits, which blanket auriferous gravels in the Klondike area, Yukon Territory, comprise two principal stratigraphic units: (i) a silty Late Pleistocene deposit, and (ii) Holocene organics lying unconformably on the silt. The deposits are found predominantly in valley bottoms and, if undisturbed, are normally perennially frozen. Field and laboratory investigations of particle size, mineralogy, and morphology, as well as organic matter and sedimentary structures, indicate that the silt is both primary (massive) and redeposited (bedded) loess (by weight 87% medium and coarse silt and fine sand). Radiocarbon dates indicate that the loess was deposited during Late Wisconsinan McConnell glaciation, beginning after 27 000 14C years BP. The loess was likely derived from the floodplain of the Yukon River during periods of low flow. Turf in growth position and organic matter in the silt similar to that of loessal grasslands near Kluane Lake suggest a grassland environment for the area during McConnell glaciation. A mummified carcass in the silts indicates that some of these sediments have been frozen since shortly after deposition. Ice wedges are commonly found in the upper portion of the silt, but these wedges rarely extend into the overlying organic material. Separate, smaller ice wedges are found in the Holocene unit. Radiocarbon dates indicate that peat growth began at the start of the Holocene, as in other unglaciated portions of Yukon, when the climate became abruptly wetter.

Chronology of Late Wisconsinan glaciation, Emerald Basin, Scotian Shelf

1989 ◽  
Vol 26 (2) ◽  
pp. 333-335 ◽  
Author(s):  
Michael R. Gipp ◽  
David J. W. Piper
Keyword(s):  
Mass Spectrometry ◽  
Organic Matter ◽  
Accelerator Mass Spectrometry ◽  
Total Organic Matter ◽  
Scotian Shelf ◽  
Radiocarbon Dates ◽  
Late Wisconsinan

Eight new accelerator mass spectrometry (AMS) radiocarbon dates from proglacial sediments in Emerald Basin indicate that the previously proposed chronology, based on dates of total organic matter, is much too old. The new chronology indicates that grounded ice occupied Emerald Basin in the Late Wisconsinan.

scholarly journals Shape Analysis of Cumulative Probability Density Function of Radiocarbon Dates Set in the Study of Climate Change in the Late Glacial and Holocene

Radiocarbon ◽  
2004 ◽  
Vol 46 (2) ◽  
pp. 733-744 ◽  
Author(s):  
Danuta J Michczyńska ◽  
Anna Pazdur
Keyword(s):  
Organic Matter ◽  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Late Glacial ◽  
Cumulative Probability ◽  
Large Set ◽  
Radiocarbon Dates ◽  
Frequency Distributions ◽  
The Holocene

We report on a statistical analysis of a large set of radiocarbon dates for reconstruction of paleoclimate. Probability density functions were constructed by summing the probability distributions of individual 14C dates. Our analysis was based on 2 assumptions: 1) The amount of organic matter in sediments depends on paleogeographical conditions; 2) The number of 14C-dated samples is proportional to the amount of organic matter deposited in sediments in the examined time intervals. We quantified how many dates are required to give statistically reliable results. As an example, 785 peat dates from Poland were selected. The dates encompassed the Holocene and Late Glacial period. All dates came from the Gliwice Radiocarbon Laboratory. Results were compared with other paleoenvironmental records. Detailed analysis of the frequency distributions showed that preferential sampling plays an important part in the shape determination. The general rule to take samples from locations where visible changes of sedimentation are apparent (e.g. from the top and the bottom of the peat layer) results in narrow peaks in the probability density function near the limits of the Holocene subdivision.

Cryostratigraphy of the Klondike "muck" deposits, west-central Yukon Territory

2000 ◽  
Vol 37 (6) ◽  
pp. 849-861 ◽  
Author(s):  
E Kotler ◽  
C R Burn
Keyword(s):  
Abrupt Change ◽  
Late Quaternary ◽  
Yukon Territory ◽  
Valley Bottom ◽  
Glacial Sediments ◽  
The Holocene ◽  
Oxygen Isotope Ratios ◽  
Bottom Deposits ◽  
Late Wisconsinan ◽  
Lower Contact

Four late Quaternary cryostratigraphic units are recognized in the unconsolidated valley-bottom deposits of the Klondike area, Yukon Territory. Three of the units, in ice-rich, loessal sediments of pre-Wisconsinan or Wisconsinan age, collectively compose the King Solomon Formation. They are overlain by a Holocene organic unit. The units are distinguished by their cryostratigraphic characteristics and oxygen-isotope ratios of included ground ice. The basal unit is the Last Chance Creek Member, a pre-Late Wisconsinan deposit, containing preserved ice wedges δ18O ~ -28 to -26‰; δD ~ -225 to -209‰). The overlying Quartz Creek Member, a Late Wisconsinan unit, is dominated by organic-rich loess. Massive ice is noticeably absent, although the sediments are ice rich. The isotopic composition of ice in this unit is characteristic of full-glacial conditions (δ18O ~ -32 to -29‰; δD ~ -234 to -257‰). An abrupt change to warmer and wetter conditions at the end of glaciation, prior to the Holocene, is recorded by the ice-rich, colluviated Dago Hill Member (δ18O ~ -28 to -21‰; δD ~ -164 to -225‰), which began accumulating by 11.62 14C ka BP. Large ice wedges originate in this unit, and, in places, penetrate the underlying full-glacial sediments. Even higher δ18O and δD values occur for ice in the Holocene organic unit (δ18O ~ -25 to -20‰; δD ~ -164 to -189‰). The majority of the massive icy bodies in the King Solomon Formation are ice wedges, but pool ice and aggradational ice are also exposed, especially in the Dago Hill Member. Massive icy beds formed by groundwater intrusion into permafrost occur at the lower contact of the Quartz Creek Member.

scholarly journals Soils in Karst Sinkholes Record the Holocene History of Local Forest Fires at the North of European Russia

Forests ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1268
Author(s):  
Nikita Mergelov ◽  
Dmitry Petrov ◽  
Elya Zazovskaya ◽  
Andrey Dolgikh ◽  
Alexandra Golyeva ◽  
...  
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Forest Fires ◽  
Soil Formation ◽  
Soil Morphology ◽  
Deep Soil ◽  
Radiocarbon Dates ◽  
The Holocene ◽  
The North ◽  
Peat Deposits

Despite the abundance of charcoal material entrapped in soils, they remain relatively less studied pyrogenic archives in comparison to the sedimentary paleofire records (e.g., lacustrine and peat deposits), and that is especially the case in most of Russia’s territory. We report here on the deep soil archives of the Holocene forest fires from the Pinega District of the Arkhangelsk region (64.747° N, 43.387° E). Series of buried soil profiles separated by charcoal layers and clusters were revealed in specific geomorphological traps represented by the active and paleokarst subsidence sinkholes on sulfate rocks overlaid by glacial and fluvial deposits. We combine the study of soil morphology and stratigraphy with a set of radiocarbon data on charcoal and soil organic matter, as well as the anthracomass analysis, to extract a set of paleoenvironmental data. A total of 45 radiocarbon dates were obtained for the macrocharcoal material and the soil organic matter. The maximum temporal “depth” of archives estimated from the radiocarbon dating of macrocharcoal reached 10,260 ± 35 cal yr BP. Soil formation with Podzols established at the inter-pyrogenic stages repeatedly reproduced within the period of ten thousand years, while the dominant tree species was Pinus sp. According to the macrocharcoal data, the intervals between fires have shortened in the last thousand years. Dendrochronological estimates suggest the occurrence of fires in almost every decade of the 20th and early 21st centuries. This is the first study of the millennia-scale soil record of forest fires in this particular region of Russia.

Genesis of Turbic Cryosols on north-facing slopes in a dissected, unglaciated landscape, west-central Yukon Territory

2009 ◽  
Vol 89 (5) ◽  
pp. 611-622 ◽  
Author(s):  
C A.S. Smith ◽  
P T Sanborn ◽  
J D Bond ◽  
G Frank
Keyword(s):  
Organic Matter ◽  
Active Layer ◽  
Forest Fires ◽  
Mass Movement ◽  
Clay Mineralogy ◽  
Yukon Territory ◽  
Element Geochemistry ◽  
Radiocarbon Dates ◽  
Carbon Mass ◽  
Dawson City

The characteristics and landscape distribution of Histic Dystric Turbic Cryosols were examined on a steep (>30%) northerly slope in the unglaciated Klondike Plateau, near Dawson City, Yukon Territory. Based on texture, major element geochemistry, and clay mineralogy, the mineral parent materials were crudely stratified, with a silty material of likely aeolian origin overlying sandy gravelly colluvium. Discontinuous organic matter-enriched horizons occurred 50 cm or more below the active layer, and contained abundant partially decomposed plant detritus. Eight accelerator radiocarbon dates, ranging from 350 ± 40 to 3680 ± 40 14C years BP, suggested that incorporation of organic materials within and below the active layer was geologically recent, and had likely occurred by a combination of cryoturbation and slope processes. The widespread and rapid initiation of mass movements on slopes containing permafrost that followed forest fires in 2004 on the Klondike Plateau may be an analogue for the processes that contributed to organic matter burial in these Cryosols. These soils may represent a significant reservoir of C, as similar sites occupy at least 15% of a representative portion of the Plateau. This reservoir may be vulnerable to mobilization if future climatic warming increases the frequency of forest fires and resulting slope instability.Key words: Tyrbic Cryosol, Yukon Territory, cryoturbation, soil organic carbon, mass movement

scholarly journals DOM degradation by light and microbes along the Yukon River-coastal ocean continuum

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Brice K. Grunert ◽  
Maria Tzortziou ◽  
Patrick Neale ◽  
Alana Menendez ◽  
Peter Hernes
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Salinity Gradient ◽  
Coastal Ocean ◽  
Interactive Effects ◽  
The Arctic ◽  
Yukon River ◽  
Spring Freshet ◽  
Dom Composition

AbstractThe Arctic is experiencing rapid warming, resulting in fundamental shifts in hydrologic connectivity and carbon cycling. Dissolved organic matter (DOM) is a significant component of the Arctic and global carbon cycle, and significant perturbations to DOM cycling are expected with Arctic warming. The impact of photochemical and microbial degradation, and their interactive effects, on DOM composition and remineralization have been documented in Arctic soils and rivers. However, the role of microbes, sunlight and their interactions on Arctic DOM alteration and remineralization in the coastal ocean has not been considered, particularly during the spring freshet when DOM loads are high, photoexposure can be quite limited and residence time within river networks is low. Here, we collected DOM samples along a salinity gradient in the Yukon River delta, plume and coastal ocean during peak river discharge immediately after spring freshet and explored the role of UV exposure, microbial transformations and interactive effects on DOM quantity and composition. Our results show: (1) photochemical alteration of DOM significantly shifts processing pathways of terrestrial DOM, including increasing relative humification of DOM by microbes by > 10%; (2) microbes produce humic-like material that is not optically distinguishable from terrestrial humics; and (3) size-fractionation of the microbial community indicates a size-dependent role for DOM remineralization and humification of DOM observed through modeled PARAFAC components of fluorescent DOM, either through direct or community effects. Field observations indicate apparent conservative mixing along the salinity gradient; however, changing photochemical and microbial alteration of DOM with increasing salinity indicate changing DOM composition likely due to microbial activity. Finally, our findings show potential for rapid transformation of DOM in the coastal ocean from photochemical and microbial alteration, with microbes responsible for the majority of dissolved organic matter remineralization.

Ice-free conditions in southwestern British Columbia at 16000 years BP

1988 ◽  
Vol 25 (6) ◽  
pp. 938-941 ◽  
Author(s):  
John J. Clague ◽  
Ian R. Saunders ◽  
Michael C. Roberts
Keyword(s):  
British Columbia ◽  
Ice Sheet ◽  
Radiocarbon Dates ◽  
Maximum Extent ◽  
Late Wisconsinan ◽  
Cordilleran Ice Sheet

New radiocarbon dates on wood from two exposures in Chilliwack valley, southwestern British Columbia, indicate that this area was ice free and locally forested 16 000 radiocarbon years ago. This suggests that the Late Wisconsinan Cordilleran Ice Sheet reached its maximum extent in this region after 16 000 years BP. The Chilliwack valley dates are the youngest in British Columbia that bear on the growth of the Cordilleran Ice Sheet.

The Metazoan Meiofauna in Its Biogeochemical Environment: The Case of an Antarctic Coastal Sediment

1998 ◽  
Vol 78 (2) ◽  
pp. 411-434 ◽  
Author(s):  
S. Vanhove ◽  
H.J. Lee ◽  
M. Beghyn ◽  
D. Van Gansbeke ◽  
S. Brockington ◽  
...  
Keyword(s):  
Organic Matter ◽  
Standing Stock ◽  
Austral Summer ◽  
Fine Sand ◽  
Coastal Sediment ◽  
Feeding Guild ◽  
Fresh Organic Matter ◽  
Benthic Environment ◽  
Metazoan Meiofauna ◽  
Deposit Feeding

The metazoan meiobenthos was investigated in an Antarctic coastal sediment (Factory Cove, Signy Island, Antarctica). The fine sands contained much higher abundances compared to major sublittoral sediments worldwide. Classified second after Narrangansett Bay (North Atlantic) they reached numbers of 13 × 106ind m-2. The meiofauna was highly abundant in the surface layers, but densities decreased sharply below 2 cm. Vertical profiles mirrored steep gradients of microbiota, chloropigments and organic matter and were coincident with chemical stratification. Spatial patchiness manifested especially in the surface layer. Nematodes dominated (up to 90%), andAponema, Chromctdorita, Diplolaimella, Daptonema, MicrolaimusandNeochromadoraconstituted almost the entire community. Overall, the nematode fauna showed a strong similarity with fine sand communities elsewhere. The dominant trophic strategies were epistrarum and non-selective deposit feeding, but the applied classification for feeding guild structure of the nematodes of Factory Cove is discussed. High standing stock, low diversity and shallow depth distribution may have occurred because of the high nutritive (chlorophyll exceeded lOOOmgm-2and constituted almost 50% of the organic pool) and reductive character of the benthic environment. These observations must have originated from the substantial input of fresh organic matter from phytoplankton and microphytobenthic production, typical for an Antarctic coastal ecosystem during the austral summer.

Pleistocene Mammals from Gold Run Creek, Yukon Territory

1973 ◽  
Vol 10 (5) ◽  
pp. 697-759 ◽  
Author(s):  
C. R. Harington ◽  
F. V. Clulow
Keyword(s):  
Yukon Territory ◽  
Radiocarbon Date ◽  
Common Elements ◽  
Radiocarbon Dates ◽  
Equus Asinus ◽  
Wild Ass ◽  
Pleistocene Mammals ◽  
First Time

Remains of thirteen species of mammals are reported from Pleistocene deposits at Gold Run Creek near Dawson, Yukon Territory. Eight of the thirteen species are extinct and two are no longer living in the Yukon. The most common elements of the fauna are Equus (Asinus) lambei (Yukon wild ass), and Bison crassicornis (large-horned bison). Taxidea (badger) and Bison alaskensis (Alaskan bison) are reported for the first time from the Yukon Pleistocene. A kiang-like horse is also reported from deposits at Gold Run Creek.These mammals may have inhabited a cool grassland or open parkland during late Wisconsin time. Bison crassicornis and mammoth bone from deposits at Gold Run Creek have yielded radiocarbon dates of 22 200 ± 1400 yr B.P. and 32 250 ± 1750 yr B.P. respectively. Bison alaskensis is evidently older than the remainder of the fauna as bone from the specimen yielded a radiocarbon date of over 39 900 yr B.P.

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