Gold Run tephra: a Middle Pleistocene stratigraphic and paleoenvironmental marker across west-central Yukon Territory, Canada

2009 ◽  
Vol 46 (6) ◽  
pp. 465-478 ◽  
Author(s):  
J. A. Westgate ◽  
S. J. Preece ◽  
D. G. Froese ◽  
A. M. Telka ◽  
J. E. Storer ◽  
...  
Keyword(s):  
Magnetic Polarity ◽  
Yukon Territory ◽  
Middle Pleistocene ◽  
Long Distance ◽  
West Central ◽  
Shrub Tundra ◽  
Chemical Attributes ◽  
Brunhes Chron ◽  
Tephra Beds ◽  
Study Sites

Gold Run tephra has been found at Thistle Creek, Sixtymile River, and the Klondike goldfields of west-central Yukon, Canada. It is a hornblende-bearing rhyolitic tephra with thicknesses of up to 10 cm at each site, suggesting a widespread distribution across interior Alaska and the Yukon Territory, given the long distance to the nearest volcanic centre. Old Crow, Flat Creek, and TA tephra beds are stratigraphically associated with Gold Run tephra at our study sites and have distinctive compositions. Gold Run tephra is not accommodated by the current classification scheme for late Cenozoic distal tephra beds in Alaska and the Yukon Territory — a scheme based on the physical and chemical attributes — so that its provenance is unknown. An early-Middle Pleistocene age is supported by a glass fission-track age of 0.74 ± 0.06 Ma, a normal remanent magnetic polarity for the enclosing loess, and the presence of a late Irvingtonian faunal assemblage in the associated organic-rich silts at Thistle Creek. Hence, Gold Run tephra was deposited during the very early part of the Brunhes Chron, at which time a shrub tundra environment prevailed across west-central Yukon.

Characterization of Lower and Middle Pleistocene tephra beds in the southern plains of western Canada

2021 ◽  
Author(s):  
John Arthur Westgate ◽  
Nancy D Naeser ◽  
Rene W. Barendregt ◽  
N. J.G. Pearce
Keyword(s):  
Trace Element ◽  
Pacific Northwest ◽  
Magnetic Polarity ◽  
Middle Pleistocene ◽  
Southern Plains ◽  
Matuyama Chron ◽  
Chemical Attributes ◽  
Brunhes Chron ◽  
Fossil Vertebrate ◽  
Tephra Beds

Wellsch Valley tephra, near Swift Current, southwestern Saskatchewan, and Galt Island tephra, near Medicine Hat, southeastern Alberta, have been referenced in the literature since the 1970s, but little is available on their physical and chemical attributes – necessary information if they are to be recognized elsewhere. This study seeks to remedy this situation. Both have a calc-alkaline rhyolitic composition with hornblende, biotite, plagioclase, pyroxene, and Fe-Ti oxides being dominant. They have a similar composition but are not the same. Wellsch Valley tephra has a glass fission-track age of 0.75 ± 0.05 Ma, a reversed magnetic polarity, and was deposited at the close of the Matuyama Chron. Galt Island tephra has an age of 0.49 ± 0.05 Ma, a normal magnetic polarity, and was deposited during the early Brunhes Chron. Rich fossil vertebrate faunas occur in sediments close to them. Major- and trace-element concentrations in their glass shards indicate a source in the Cascade Range of the Pacific Northwest, USA, but differences in trace-element ratios suggest they are not consanguineous.

Revision of the tephrostratigraphy of the lower Sixtymile River area, Yukon Territory, Canada

2011 ◽  
Vol 48 (3) ◽  
pp. 695-701 ◽  
Author(s):  
J. A. Westgate ◽  
S. J. Preece ◽  
L. E. Jackson
Keyword(s):  
Glass Phase ◽  
Fission Track ◽  
Yukon Territory ◽  
The Other ◽  
Middle Pleistocene ◽  
Fine Grained ◽  
Tephra Beds ◽  
Age Determinations

Five distinctive tephra beds are preserved in fine-grained sediments on a prominent terrace strath along the lower Sixtymile River of the Yukon Territory. Commencing with the oldest unit, they are TA, SM3, Gold Run, Hollis 2, and Flat Creek tephra beds. The uppermost three tephra beds have rhyolitic compositions, the other two are bimodal with a much more basic glass phase. Three glass fission-track age determinations point to deposition during the early-Middle Pleistocene. We correct an error in an earlier study by clarifying that Flat Creek tephra is younger than Gold Run tephra, TA tephra is older.

Paleomagnetic evidence for multiple late Cenozoic glaciations in the Tintina Trench, west-central Yukon, CanadaThis article is a companion paper to Duk-Rodkin et al., also in this issue.

2010 ◽  
Vol 47 (7) ◽  
pp. 987-1002 ◽  
Author(s):  
René W. Barendregt ◽  
Randolph J. Enkin ◽  
Alejandra Duk-Rodkin ◽  
Judith Baker
Keyword(s):  
Companion Paper ◽  
Opposite Polarity ◽  
Middle Pleistocene ◽  
Late Cenozoic ◽  
West Central ◽  
Matuyama Chron ◽  
Continental Divide ◽  
Normal Polarity ◽  
Brunhes Chron ◽  
Trench Area

The Tintina Trench in west-central Yukon has preserved an extensive record of late Cenozoic preglacial, glacial, and interglacial deposits. These deposits comprise multiple sequences of tills, outwash, loesses, and paleosols. The sediments that were laid down directly by ice (tills) are of both local (montane) and regional (Cordilleran) provenance. The Tintina Trench area was impacted repeatedly by montane ice from the southern Ogilvie Mountains to the northwest (2500 m above sea level (asl)), and also repeatedly along its southern extent by Cordilleran ice from the Selwyn Mountains to the east (2759 m asl), the latter forming the continental divide in this region. We report here the magnetostratigraphy of three sections: Rock Creek (64°13′N, 139°07′W), West Fifteenmile River (64°29′N, 139°55′W), and East Fifteenmile River (64°23′N, 139°48′W). The majority of the units identified at these sections record late Pliocene to mid-Pleistocene glaciations, although relatively thin surficial sequences of late middle Pleistocene to late Pleistocene loesses and tills are present as well. Of the 11 units described in the Tintina Trench, seven have normal polarity, three have reversed polarity, and one has an undefined polarity. These units span about 3.0 million years. It appears that most of the polarity chrons and subchrons of the late Cenozoic are present and that the sequence of six reversals record at least 10 glaciations (three in the Brunhes Chron and seven in the Matuyama Chron), and 11 interglaciations (four in the Brunhes Chron and seven in the Matuyama Chron). The interglacials are recorded as either paleosols or unconformities between glacial or loess units having opposite polarity. While not all Matuyama Chron glacial and interglacial cycles recorded in marine isotopic records are seen on land, the terrestrial records found in the Tintina Trench have thus far proven to be the most complete in terms of the polarity record. While no absolute ages were obtained from the sediments in the trench, the extensive polarity sequence constrains the timing of glaciations to a considerably greater degree than was previously possible for this region. The magnetostratigraphy of the trench sites are compared with the glacial, glaciofluvial, and loessic deposits at the nearby Klondike River valley and Fort Selkirk sites, central Yukon, where tephras and basalts provide absolute ages, and stratigraphic units contain an extensive late Cenozoic climate proxy for northwestern North America (eastern Beringia). In this study, we present new paleomagnetic polarity data and establish a magneto-lithostratigraphy describing preglacial, glacial, and interglacial deposits in the Tintina Trench. These deposits are referred to as the West Tintina Trench Allogroup and provide a broad framework for establishing a paleoclimate record for the northern Canadian Cordillera.

Tephrochronology, magnetostratigraphy and mammalian faunas of Middle and Early Pleistocene sediments at two sites on the Old Crow River, northern Yukon Territory, Canada

2013 ◽  
Vol 79 (1) ◽  
pp. 75-85 ◽  
Author(s):  
John A. Westgate ◽  
G. William Pearce ◽  
Shari J. Preece ◽  
Charles E. Schweger ◽  
Richard E. Morlan ◽  
...  
Keyword(s):  
Age Determination ◽  
Lacustrine Sediments ◽  
Large Error ◽  
Magnetic Polarity ◽  
Yukon Territory ◽  
Early Pleistocene ◽  
East Central ◽  
Mammalian Faunas ◽  
Reversed Polarity ◽  
Tephra Beds

AbstractAlluvial and lacustrine sediments exposed beneath late Pleistocene glaciolacustrine silt and clay at two sites along the Old Crow River, northern Yukon Territory, are rich in fossils and contain tephra beds. Surprise Creek tephra (SZt) occurs in the lower part of the alluvial sequence at CRH47 and Little Timber tephra (LTt) is present near the base of the exposure at CRH94. Surprise Creek tephra has a glass fission-track age of 0.17 ± 0.07 Ma and Little Timber tephra is 1.37 ± 0.12 Ma. All sediments at CRH47 have a normal remanent magnetic polarity and those near LTt at CRH94 have a reversed polarity — in agreement with the geomagnetic time scale. Small mammal remains from sediments near LTt support an Early Pleistocene age but the chronology is not so clear at CRH47 because of the large error associated with the SZt age determination. Tephrochronological and paleomagnetic considerations point to an MIS 7 age for the interglacial beds just below SZt at CRH47 and at Chester Bluffs in east-central Alaska, but mammalian fossils recovered from sediments close to SZt suggest a late Irvingtonian age, therefore older than MIS 7. Further studies are needed to resolve this problem.

Identification and significance of late Holocene tephra from Otter Creek, southern British Columbia, and localities in west-central Alberta

1977 ◽  
Vol 14 (11) ◽  
pp. 2593-2600 ◽  
Author(s):  
J. A. Westgate
Keyword(s):  
British Columbia ◽  
Late Holocene ◽  
Far North ◽  
West Central ◽  
Tephra Beds ◽  
Middle Unit ◽  
Mount St Helens

Three thin, light-coloured, ash-grade tephra beds occur within the uppermost metre of peat at Otter Creek bog in southern British Columbia. The youngest tephra is related to the ~2600 year old Bridge River tephra but is probably the product of a younger and weaker eruption that directed tephra to the southeast of the vent, believed to be located in the Meager Mountain district of southwestern British Columbia. The middle unit is ~2100 years old and is tentatively correlated with one of the upper beds of set P tephra of Mount St. Helens in Washington. The lowermost tephra is equivalent to the Yn bed of set Y, derived from an eruption of Mount St. Helens about 3400 years ago.The Yn tephra has been located as far north as Entwistle in west-central Alberta but mineralogically and chemically similar tephra elsewhere in this region is ~4300 years old and thus represents an older part of the Y set. Significant compositional differences between these two extensive members of the Y set have not yet been recognized.

scholarly journals An Investigation into Marmot Migration in Grand Teton National Park

1996 ◽  
Vol 20 ◽  
pp. 78-82
Author(s):  
George Montopoli ◽  
Nick Visser ◽  
Hank Harlow
Keyword(s):  
National Park ◽  
Movement Patterns ◽  
Snow Melt ◽  
Marmota Flaviventris ◽  
Long Distance ◽  
The North ◽  
North Fork ◽  
Males And Females ◽  
Study Sites ◽  
Long Distance Movement

In 1994 and 1995, a high abundant winter snowfall at higher elevations appeared to result in long distance movement patterns by yellow-bellied marmot (Marmota flaviventris) over snow to lower, snowfree elevations where food was more available. As the snow melted and food became abundant, the marmots return to higher altitudes. In 1996, we continued to investigate the potential for migrational movements, by studying two study sites at different elevations in the North Fork of Cascade Canyon. Four marmots at each site were implanted with intraperitoneal tracking transmitters. Of eight marmots that were equipped with intraperitoneal transmitters, six demonstrated significant movements of greater than 0.5 km, one did not, and one most likely died as a result of predation before any movement could be observed. Of the six that demonstrated significant movements within the canyon, only one moved distances greater than 1 km. Marmots, after emerging from hibernation, migrated down canyon to snowfree areas as they become available. With progressive snow melt, most marmots move upward to higher elevations, but not to the extent originally expected. Instead, they moved to the first available habitat where food was obtainable, and other (dominant) marmots accepted their presence. This movement is exhibited in both males and females, yearlings and adults, and melanistic and normal colored marmots.

scholarly journals Is a spatial investigation possible without long-distance refit/conjoin? Application to the MIS 11 lithic assemblage of levels E and J from La Cansaladeta site (Tarragona, Spain)

2021 ◽  
Vol 13 (9) ◽  
Author(s):  
Görkem Cenk Yeşilova ◽  
Andreu Ollé ◽  
Josep Maria Vergès
Keyword(s):  
Spatial Patterns ◽  
Spatial Information ◽  
Small Dimension ◽  
Middle Pleistocene ◽  
Small Scale ◽  
Spatial Pattern Analysis ◽  
Long Distance ◽  
Great Opportunity ◽  
Density Mapping ◽  
Study Materials

AbstractIn this manuscript, we present the first systematic refitting results of the small-scale Middle Pleistocene (MIS11) rock shelter site of La Cansaladeta. The lithic materials that have been recovered from the archaeological levels E and J were the main study materials. These levels were investigated regarding spatial pattern analysis and analyzed with auxiliary methods such as quantitative density mapping demonstration and technological analysis of the lithic clusters. Thus, the spatial patterns of the two levels were compared and discussed, in terms of connections, clusters, and movement of the lithic elements. Undoubtedly, the well preservation of the archaeological levels offered a great opportunity for the interpretation of the spatial patterns in a high-resolution perspective. La Cansaladeta has not been paid attention adequately so far may be due to the small dimension of the excavation surface or to the scarcity of faunal record. Our results show that small-scale sites without long-distance refit/conjoin connections can provide significant spatial information. Indeed, if the sites have very well-preserved archaeological levels, the absence of long connections can be supported by the auxiliary methods.

The quest for chron E23r at Partridge Island, Bay of Fundy, Canada: CAMP emplacement postdates the end-Triassic extinction event at the North American craton

2011 ◽  
Vol 48 (8) ◽  
pp. 1282-1291 ◽  
Author(s):  
M.H.L. Deenen ◽  
W. Krijgsman ◽  
M. Ruhl
Keyword(s):  
Magnetic Polarity ◽  
Bay Of Fundy ◽  
Long Distance ◽  
The North ◽  
Extinction Event ◽  
Maritime Canada ◽  
North American Craton ◽  
Geomagnetic Polarity ◽  
Central Atlantic ◽  
Geomagnetic Polarity Time Scale

The Partridge Island stratigraphic section at the Bay of Fundy, Maritime Canada, reveals a continental sedimentary succession with the end-Triassic mass extinction level closely followed by basalts of the Central Atlantic Magmatic Province (CAMP). New Paleomagnetic data show that a short reverse magnetic polarity chron, correlative to E23r of the Newark Geomagnetic Polarity Time Scale (GPTS), is present below the extinction event. Organic carbon isotope data and basalt geochemistry further indicate that the onset of CAMP emplacement in the Bay of Fundy was roughly synchronous with emplacement in the Newark basin, but slightly postdates the oldest CAMP volcanism in Morocco by ∼20 ka. These results confirm the potential for long-distance CAMP correlations based on geochemical trace elements, indicate substantiate provincialism of latest Triassic palynoflora, and suggest a very concise period (<<100 ka) of CAMP emplacement in the northern Atlantic region.

New advances on the magnetic chronostratigraphy of cave sediments in Atapuerca Gran Dolina, Spain

2021 ◽  
Author(s):  
Josep M Pares ◽  
Mathieu Duval ◽  
Isidoro Campaña ◽  
José M. Bermúdez de Castro ◽  
Eudald Carbonell
Keyword(s):  
Magnetic Polarity ◽  
Age Dating ◽  
Middle Pleistocene ◽  
Geologic History ◽  
Cave Sediments ◽  
Normal Polarity ◽  
Gran Dolina ◽  
Geomagnetic Polarity ◽  
Quartz Grains ◽  
Numerical Dating

&lt;p&gt;Magnetostratigraphy has proven to be a powerful and versatile method as well the first line of defence for dating sediments. When properly anchored to the Geomagnetic Polarity Time Scale (GPTS), chron boundaries provide a basis for numerical dating by correlating the local magnetostratigraphy to the GPTS. A caveat and intrinsic limitation when anchoring magnetic stratigraphy to the GPTS is that we deal with essentially a binary code, a sequence of normal and reverse polarity zones. To overcome such limitation biostratigraphy or (ideally) numerical (absolute) age dating is required. Unfortunately, numerical dating of sediments is typically hampered by the lack of amenable minerals for the application of standard methods such as Ar-Ar, requiring thus the use of less conventional methods. Burial dating is possible using methods such as Electron Spin Resonance (ESR) on optically bleached quartz grains. Similar to luminescence, ESR is a paleodosimetric method that provides the time elapsed since the last exposure of quartz grains to natural sun light. Cave sediments are particularly amenable for paleodosimetric methods, as sediments are preserved in the dark and the ESR signal should survive over the geologic history of the deposits. On the down side, we date the moment when the quartz grain enters the karst system, not its deposition. If the transit time is too long, this might be an issue and we would be significantly overestimating the true burial age. Caves at Atapuerca (N Spain) hold the richest Quaternary paleontological record in Eurasia, including fossils and lithic tools. Sediments in these caves have been traditionally dated via magnetostratigraphy by identifying the Matuyama-Brunhes reversal (0.78 Ma) thus providing the Lower to Middle Pleistocene boundary. Nevertheless, the appearance of older sediments in the caves required the combination of paleomagnetism with methods such as ESR to interpret older intra-Matuyama Subchrons. In the deepest levels of the Gran Dolina cave, close to the floor of the cavity, a number of short intervals of normal polarity have been identified in the fluviatile sediments belonging to TD1 unit, which we interpret in terms of Subchrons using ESR ages of quartz grains. We will discuss both paleomagnetic data and interpret the magnetic polarity stratigraphy in the view of the ESR ages obtained from the Multiple Centre (MC) approach.&amp;#160;&lt;/p&gt;

A re-examination of pseudoleucite from Spotted Fawn Creek, west-central Yukon

1969 ◽  
Vol 6 (1) ◽  
pp. 55-62 ◽  
Author(s):  
Dirk J. Tempelman-Kluit
Keyword(s):  
Experimental Data ◽  
Experimental Evidence ◽  
Water Pressure ◽  
Fluid Phase ◽  
Yukon Territory ◽  
Chemical Data ◽  
Partial Removal ◽  
West Central

New petrographic and chemical data for pseudoleucite from Spotted Fawn Creek and two new nearby localities in central Yukon Territory are presented and discussed in the light of recent experimental evidence on the origin of pseudoleucite. The petrologic, chemical, and experimental data suggest that natural pseudoleucite results from subsolidus breakdown of leucite under water pressure and that the space provided by this breakdown results in influx of the fluid phase that accomplishes partial removal of potash, enrichment in soda, and addition of water.

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