Paleomagnetic evidence for multiple Late Pliocene - Early Pleistocene glaciations in the Klondike area, Yukon Territory

2000 ◽  
Vol 37 (6) ◽  
pp. 863-877 ◽  
Author(s):  
D G Froese ◽  
R W Barendregt ◽  
R J Enkin ◽  
J Baker
Keyword(s):  
Yukon Territory ◽  
Early Pleistocene ◽  
Pleistocene Glaciations ◽  
Glacial Sediments ◽  
Late Pliocene ◽  
Matuyama Chron ◽  
Normal Polarity ◽  
Ice Wedge ◽  
Brunhes Chron ◽  
Cordilleran Ice Sheet

The Late Pliocene - Early Pleistocene terraces of the Klondike area provide a conformal record of sedimentation which marks the transition from preglacial to glacial conditions, and is one of the most complete records of glaciation and interglaciation in the northern Cordillera. Preglacial sedimentation is recorded in the Lower White Channel gravel that contains a reverse-normal polarity sequence. A re-aggradation of the nonglaciated valleys of the goldfields in response to Late Pliocene cooling is recorded by the Upper White Channel gravel, which is characterized by a dominant normal polarity with a lower reversal likely associated with the first ice-wedge casts. Klondike gravel interfingers with Upper White Channel and is normally magnetized, indicating an equivalent magnetostratigraphic unit. This glaciofluvial gravel provides evidence of extra-basinal clasts, marking a major reorganization of drainage associated with the first advance of the Cordilleran Ice Sheet in western Yukon Territory correlated with the Gauss chron (>2.58 Ma). An intermediate terrace in Klondike valley is overlain by 8 m of fluvial and glaciofluvial gravel named the Midnight Dome gravel. This gravel is mantled by 15 m of loess and hillslope deposits, named the Midnight Dome loess, which preserve at least three interglacial pollen assemblages, and a reverse-normal-reverse-normal polarity sequence assigned to the late Matuyama chron, including Jaramillo subchron (1.07-0.99 Ma), and early Brunhes chron (<0.78 Ma). The oldest glaciations here, based on the preferred interpretation, extend well into the Pliocene (>2.58 Ma) making these among the oldest glacial sediments in North America.

Paleomagnetism of tills and associated paleosols in southwestern Alberta and northern Montana: evidence for Late Pliocene–Early Pleistocene glaciations

1995 ◽  
Vol 32 (5) ◽  
pp. 555-564 ◽  
Author(s):  
M. T. Cioppa ◽  
E. T. Karlstrom ◽  
E. Irving ◽  
R. W. Barendregt
Keyword(s):  
North America ◽  
Early Pleistocene ◽  
Pleistocene Glaciations ◽  
Glacial Deposits ◽  
Late Pliocene ◽  
Carbonate Cement ◽  
Paleomagnetic Study ◽  
Normal Polarity ◽  
Reversed Polarity ◽  
Initial Deposition

Sequences of pre-Wisconsinan till and intercalated paleosols were sampled for paleomagnetic study. The tills were deposited during successive glaciations and the paleosols formed during interglacial intervals. Paleoargillic horizons of the paleosols and the carbonate cement (calcrete) found in some till–paleosol units generally yielded excellent data. Magnetizations of paleosols probably were acquired during the formation of the paleosols rather than during initial deposition of the tills in which they were developed. At Mokowan Butte (Alberta), the lowest paleosol has normal polarity, two of the middle tills have reversed polarity, and the uppermost till–paleosol unit has normal polarity. At Saint Mary Ridge (Montana), three of the lower tills have reversed polarity, and the upper two till–paleosol units have normal polarity. At Two Medicine Ridge (Montana), the lowest three tills are reversed, but the paleoargillic horizon on the uppermost (fourth) till is normal. Magnetostratigraphic correlation indicates that at least six glacial and six interglacial episodes are represented in the Kennedy Drift. The upper normal polarity units are interpreted as having been developed during the Brunhes Normal Chron, the underlying reversed polarity sediments during the Matuyama Reversed Chron, and the lowest normal polarity unit at Mokowan Butte during the Gauss Normal Chron. The oldest glaciations here extend into the Pliocene (2600 ka), making these sediments among the oldest glacial deposits in North America. Alternatively, the lowest normally magnetized paleosol at Mokowan Butte may have formed during either the Jaramillo or the Olduvai subchrons, although this is considered less likely.

Lithostratigraphy and paleomagnetism of pre-Fraser glacial deposits in south-central British Columbia

1999 ◽  
Vol 36 (8) ◽  
pp. 1357-1370 ◽  
Author(s):  
Olav B Lian ◽  
R W Barendregt ◽  
R J Enkin
Keyword(s):  
British Columbia ◽  
Early Pleistocene ◽  
Fluvial Sediments ◽  
Optical Dating ◽  
Late Pliocene ◽  
South Central ◽  
Last Glaciation ◽  
Matuyama Chron ◽  
Sedimentary Succession ◽  
Cordilleran Ice Sheet

Lithostratigraphic records spanning considerable parts of the Pleistocene were studied at three sites in south-central British Columbia. A sedimentary succession near Pavilion includes three distinctly different till units. While the surface till can be associated with the last glaciation (the Fraser Glaciation δ18O stage 2), the ages of the two older till units are presently unknown. However, optical dating of outwash silt resting on the oldest till indicates that this outwash unit and all the overlying units are younger than ~160 ka. In Big Bar Creek valley, about 50 km north of Pavilion, an aggradational sequence of indurated glaciofluvial sand, gravel, and till is exposed. A silt unit and a sand lens within an overlying till bed near the top of the section have reversed magnetization, indicating deposition prior to 780 ka, probably during the Matuyama chron. The Big Bar Creek sequence also includes glacio(?)fluvial sediments near the base that are normally magnetized, suggesting that they were deposited, at the latest, during the Jaramillo subchron (~1.0 Ma), but probably during the Gauss chron, before 2.6 Ma. Reversely magnetized glacio(?)fluvial gravel and sand also occur along Jesmond Road between the Marble Range and Edge Hills. These units give support for the development of at least one Cordilleran ice sheet in the Early Pleistocene or Late Pliocene.

scholarly journals Late Pliocene Cordilleran Ice Sheet development with warm northeast Pacific sea surface temperatures

2020 ◽  
Vol 16 (1) ◽  
pp. 299-313 ◽  
Author(s):  
Maria Luisa Sánchez-Montes ◽  
Erin L. McClymont ◽  
Jeremy M. Lloyd ◽  
Juliane Müller ◽  
Ellen A. Cowan ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Ice Sheet ◽  
Gulf Of Alaska ◽  
Sea Surface ◽  
Early Pleistocene ◽  
Late Pliocene ◽  
Subarctic Pacific ◽  
Cordilleran Ice Sheet ◽  
Forcing Mechanisms ◽  
Atmospheric Co2 Concentrations

Abstract. The initiation and evolution of the Cordilleran Ice Sheet are relatively poorly constrained. International Ocean Discovery Program (IODP) Expedition 341 recovered marine sediments at Site U1417 in the Gulf of Alaska (GOA). Here we present alkenone-derived sea surface temperature (SST) analyses alongside ice-rafted debris (IRD), terrigenous, and marine organic matter inputs to the GOA through the late Pliocene and early Pleistocene. The first IRD contribution from tidewater glaciers in southwest Alaska is recorded at 2.9 Ma, indicating that the Cordilleran Ice Sheet extent increased in the late Pliocene. A higher occurrence of IRD and higher sedimentation rates in the GOA during the early Pleistocene, at 2.5 Ma, occur in synchrony with SSTs warming on the order of 1 ∘C relative to the Pliocene. All records show a high degree of variability in the early Pleistocene, indicating highly efficient ocean–climate–ice interactions through warm SST–ocean evaporation–orographic precipitation–ice growth mechanisms. A climatic shift towards ocean circulation in the subarctic Pacific similar to the pattern observed during negative Pacific Decadal Oscillation (PDO) conditions today occurs with the development of more extensive Cordilleran glaciation and may have played a role through increased moisture supply to the subarctic Pacific. The drop in atmospheric CO2 concentrations since 2.8 Ma is suggested as one of the main forcing mechanisms driving the Cordilleran glaciation.

Stratigraphy and paleomagnetism of Late Pliocene and Pleistocene sediments in the Wellsch Valley and Swift Current Creek areas, southwestern Saskatchewan, Canada

1998 ◽  
Vol 35 (12) ◽  
pp. 1347-1361 ◽  
Author(s):  
R W Barendregt ◽  
E Irving ◽  
E A Christiansen ◽  
E K Sauer ◽  
B T Schreiner
Keyword(s):  
Late Pleistocene ◽  
Magnetic Polarity ◽  
Early Pleistocene ◽  
Western Canada ◽  
Marked Contrast ◽  
Glacial Deposits ◽  
Late Pliocene ◽  
Matuyama Chron ◽  
Reversed Polarity

The Late Pliocene and Pleistocene are represented in southern Saskatchewan by sequences of preglacial, glacial, and nonglacial deposits. These have been studied in surface exposures and bore cores and have been subdivided and correlated on the basis of their lithologies. In this study, new observations of magnetic polarity are presented. They reveal a lower preglacial sequence (Empress Group) with reversed polarity, and an upper normally magnetized sequence which contains glacial deposits of pre-Illinoian, Illinoian, and Wisconsinan age and which are correlative with the Saskatoon and Sutherland groups of central Saskatchewan. The reversed preglacial sequence is referred to the Matuyama Zone (Late Pliocene to Early Pleistocene: 2.58-0.78 Ma) and the normal glacial sequence to the Brunhes Zone (Middle to Late Pleistocene and Holocene: 0.78 Ma to present). In southern Saskatchewan there is no evidence of glaciation during the Late Pliocene and Early Pleistocene (Matuyama Chron) which is in marked contrast with parts of the Cordilleran region of western Canada where glaciations occur throughout this time.

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.

Paleomagnetism of Quaternary and late Tertiary sediments on Mokowan Butte, southwestern Alberta

1991 ◽  
Vol 28 (12) ◽  
pp. 1956-1964 ◽  
Author(s):  
R. W. Barendregt ◽  
E. Irving ◽  
E. T. Karlstrom
Keyword(s):  
British Columbia ◽  
Geomagnetic Field ◽  
Early Pleistocene ◽  
Glacial Sediments ◽  
Banks Island ◽  
Quaternary Sequences ◽  
Matuyama Chron ◽  
Late Tertiary ◽  
Unconsolidated Sediment ◽  
Accurate Record

Mokowan Butte in southwestern Alberta is capped by 32 m of unconsolidated sediment comprising five tills and their associated paleosols. Previous stratigraphic work has indicated that the older tills are probably Early Pleistocene to late Tertiary in age. Paleomagnetic studies, based on 125 samples, show that the uppermost till–paleosol unit and the modern subsoil are normally magnetized, whereas the till–paleosol units from the middle of the sequence have reversed magnetization. We argue that these belong to the Brunhes and Matuyama polarity zones, respectively. The lowest part of the sequence has not been studied in detail and is generally too coarse for paleomagnetic sampling, and samples that have been obtained contain no accurate record of the paleofield. These new data, together with those from Wellsch Valley in Saskatchewan, Banks Island in the Northwest Territories, Fort Selkirk in the Yukon, and Merritt in British Columbia, bring to five the number of early Quaternary sequences in Canada that have yielded a record of glacial sediments deposited during the Matuyama chron, and hence record glacial events prior to the last reversal of the geomagnetic field (720 ka).

Early Pleistocene volcanism and glaciation in central Yukon: a new chronology from field studies and paleomagnetism

1996 ◽  
Vol 33 (6) ◽  
pp. 904-916 ◽  
Author(s):  
L. E. Jackson Jr ◽  
R.W. Barendregt ◽  
J. Baker ◽  
E. Irving
Keyword(s):  
Secular Variation ◽  
Field Studies ◽  
Early Pleistocene ◽  
Pleistocene Glaciations ◽  
Matuyama Chron ◽  
Filling Phase ◽  
Pleistocene Volcanism ◽  
Low K ◽  
Radiometric Dates

The paleomagnetism of the Selkirk Volcanics and nearby stratified Pleistocene sediments was investigated to resolve the chronology of Early Pleistocene glaciations in central Yukon. Radiometric dates on these low-K basalts have proven to be erroneously old. Most sampled sediments and all basalts accurately record the paleofield and true reversals. The valley-filling phase of the Selkirk Volcanics was in part coeval with the younger pre-Reid glaciation. It was erupted during the Matuyama Chron, either post-Cobb Mountain Subchron or post-Jaramillo Subchron, over a period too brief to average secular variation. The older pre-Reid glaciation occurred after ca. 1.60 Ma and prior to the eruption of the Fort Selkirk tephra (pre-Jaramillo or pre-Cobb Mountain). Sediments investigated at Revenue Creek and Braden's Canyon are normally magnetized. The assigned Brunhes age is compatible with their occurrence in valleys that were cut or deepened sometime after the pre-Reid glaciations.

scholarly journals Snapshots of the Greenland ice sheet configuration in the Pliocene to early Pleistocene

2011 ◽  
Vol 57 (205) ◽  
pp. 871-880 ◽  
Author(s):  
Anne M. Solgaard ◽  
Niels Reeh ◽  
Peter Japsen ◽  
Tove Nielsen
Keyword(s):  
Flow Model ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early Pleistocene ◽  
Pleistocene Glaciations ◽  
Ice Flow ◽  
Late Pliocene ◽  
Ice Caps ◽  
Climate Reconstructions

AbstractThe geometry of the ice sheets during the Pliocene to early Pleistocene is not well constrained. Here we apply an ice-flow model in the study of the Greenland ice sheet (GIS) during three extreme intervals of this period constrained by geological observations and climate reconstructions. We study the extent of the GIS during the Mid-Pliocene Warmth (3.3–3.0 Ma), its advance across the continental shelf during the late Pliocene to early Pleistocene glaciations (3.0–2.4 Ma) as implied by offshore geological studies, and the transition from glacial to interglacial conditions around 2.4 Ma as deduced from the deposits of the Kap København Formation, North Greenland. Our experiments show that no coherent ice sheet is likely to have existed in Greenland during the Mid-Pliocene Warmth and that only local ice caps may have been present in the coastal mountains of East Greenland. Our results illustrate the variability of the GIS during the Pliocene to early Pleistocene and underline the importance of including independent estimates of the GIS in studies of climate during this period. We conclude that the GIS did not exist throughout the Pliocene to early Pleistocene, and that it melted during interglacials even during the late Pliocene climate deterioration.

Evidence for an Early Pleistocene glaciation in the Okanagan Valley, southern British Columbia

2014 ◽  
Vol 51 (2) ◽  
pp. 125-141 ◽  
Author(s):  
Murray A. Roed ◽  
René W. Barendregt ◽  
Jeff A. Benowitz ◽  
C.A.S. Smith ◽  
P.T. Sanborn ◽  
...  
Keyword(s):  
British Columbia ◽  
First Nation ◽  
Early Pleistocene ◽  
Pleistocene Glaciation ◽  
Pleistocene Glaciations ◽  
The West ◽  
Glacial Sediments ◽  
Fabric Analysis ◽  
Minimum Age ◽  
Okanagan Valley

Depositional evidence of Early Pleistocene glaciations in British Columbia are documented at only a few sites. Near Kelowna, in southern British Columbia, a construction project exposed glacial sediments beneath Lambly Creek Basalt, providing a minimum age for this glaciation. The basalt is composed of a number of flows yielding ages that range from 0.76 ± 0.11 to 1.5 ± 0.1 Ma. The sediments consist of a diamicton, interpreted to be till, up to 3 m thick mantled by a weakly developed paleosol. The diamicton is underlain by fluvial sands up to 5 m thick, in places revealing injection features, and minor faulting. A unit of stratified gravel underlain by grey clay is inferred to underlie the exposed sediments, based on nearby outcrops and excavations. Sediments and overlying basalts are normally magnetized and are assigned to the Jaramillo normal subchron (1.069–0.987 Ma). The till is here referred to as the Westbank First Nation Till. It is Early Pleistocene in age and represents the earliest evidence of glaciation in the Okanagan Valley. Stone fabric analysis and clast lithologies suggest that ice movement was from northwest to southeast, and is here referred to as the West Kelowna Advance; we infer that this advance was part of a larger regional glaciation. Other Early Pleistocene glaciations in the Cordillera are briefly reviewed.

The Eastern Beringian vole Microtus deceitensis (Rodentia, Muridae, Arvicolinae) in Late Pliocene and Early Pleistocene faunas of Alaska and Yukon

2003 ◽  
Vol 60 (1) ◽  
pp. 84-93 ◽  
Author(s):  
John E. Storer
Keyword(s):  
Fission Track ◽  
Tooth Enamel ◽  
Magnetic Polarity ◽  
Yukon Territory ◽  
Type Locality ◽  
Early Pleistocene ◽  
Late Pliocene ◽  
Radiometric Dates

AbstractThe fossil vole Microtus deceitensis occurs in Early Pleistocene deposits at Fort Selkirk, Yukon Territory, and Late Pliocene beds at the type locality, Cape Deceit, Alaska. Analyses of simple vs complex morphotypes in the cheek teeth, and of differentiation of tooth enamel, show that the Cape Deceit sample of M. deceitensis is less derived, and thus appears to be older, than the Fort Selkirk sample. The fossiliferous deposits at Fort Selkirk are well constrained by fission-track and radiometric dates and are 1.5 to 1.7 myr. Sediments at Cape Deceit bear a normal magnetic polarity, are correlated with the Olduvai subchron, and probably are latest Pliocene.

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