Magnetostratigraphic evidence from the Cold Creek bar for onset of ice-age cataclysmic floods in eastern Washington during the early pleistocene

2006 ◽  
Vol 65 (1) ◽  
pp. 123-135 ◽  
Author(s):  
Christopher J. Pluhar ◽  
Bruce N. Bjornstad ◽  
Stephen P. Reidel ◽  
Robert S. Coe ◽  
Paul B. Nelson
Keyword(s):  
Magnetic Polarity ◽  
Ice Age ◽  
Early Pleistocene ◽  
Magnetic Studies ◽  
Normal Polarity ◽  
History Of ◽  
Reversed Polarity ◽  
Brunhes Chron ◽  
Continental Ice Sheets ◽  
Eastern Washington

AbstractThis study provides a detailed magnetostratigraphy of sediments composing the Cold Creek cataclysmic flood bar in the Pasco Basin, Washington. Our interpretation suggests onset of Missoula floods or similar events prior to 1.1 myr, later than previously suggested by Bjornstad et al. [Bjornstad, B.N., Fecht, K.R., Pluhar, C.J., 2001. Long history of pre-Wisconsin, Ice Age cataclysmic floods: evidence from southeastern Washington State. Journal of Geology 109 (6), 695–713]. Nonetheless these data suggest that Channeled Scabland features formed over a much longer timespan than commonly cited, that continental ice sheets of the early Pleistocene reached as far south as those of the late Pleistocene, and that similar physiography existed in eastern Washington and perhaps Montana to both generate and route Missoula-flood-like events. This study adds paleomagnetic polarity results from 213 new samples of silts and sands derived from nine new drill cores penetrating the Cold Creek cataclysmic flood bar to our previous database of 53 samples from four boreholes, resulting in a much more robust and detailed magnetostratigraphy. Rock magnetic studies on these sediments show pure magnetite to be the predominant remanence-carrying magnetic mineral, ruling out widespread remagnetization by secondary mineralization. The magnetostratigraphy at eastern Cold Creek bar is characterized by a normal polarity interval bracketed by reversed polarities. Equating the normal zone with the Jaramillo subchron (0.99–1.07 myr) affords the simplest correlation to the magnetic polarity timescale. Western Cold Creek bar was likely deposited during the Brunhes chron (0–0.78 myr) since it exhibits mainly normal polarities with only two thin reversed-polarity horizons that we interpret as magnetic excursions during the Brunhes.

New 42 Ma cratonic North American paleomagnetic pole from the Yukon underscores another Cordilleran paleomagnetism-geology conundrum

2003 ◽  
Vol 40 (10) ◽  
pp. 1321-1334 ◽  
Author(s):  
David TA Symons ◽  
Philippe Erdmer ◽  
Phil JA McCausland
Keyword(s):  
North American ◽  
Magnetic Polarity ◽  
Eastern Coast ◽  
The North ◽  
Normal Polarity ◽  
Reversed Polarity ◽  
North American Craton ◽  
Host Rocks ◽  
Pacific Plate Subduction ◽  
Plate Subduction

Eocene posttectonic plutons of the Beaver River alkalic complex in southeastern Yukon intruded Devonian–Mississippian and Triassic sandstones in the Foothills of the Canadian Cordillera. A paleomagnetic collection of 27 sites from three separate plutons produced 326 specimens that were analyzed using alternating field and thermal step demagnetization methods. The A component characteristic remanent magnetization (ChRM) resides in magnetite with normal polarity in the 42.6 ± 0.8 Ma Beaver River pluton, reversed polarity in the 42.1 ± 0.7 Ma Larson Creek East pluton, and both polarities in the 41.3 ± 0.4 Ma Larson Creek West pluton, corresponding with magnetic polarity chrons 20n, 19r, and the boundary between chron 19r and 18n, respectively. The ChRMs of the plutons are indistinguishable (2σ) with a mean for the 42.0 ± 0.5 Ma complex of D = 158.8°, I = –73.1° (N = 21 sites, α95 = 3.0°, k = 116.8). A positive paleomagnetic contact test shows the A component to be primary, and the poorly isolated B component suggests the host rocks for Larson Creek West are Early to Middle Devonian. The paleopole for the Beaver River complex at 79.2°N, 145.8°E (N = 21, dp = 4.8°, dm = 5.4°; Q = 7) is concordant with interpolated 42 Ma reference poles for the North American craton. In contrast, paleopoles from the accreted Intermontane and eastern Coast Belt terranes record clockwise rotations of 24° ± 10° (Eocene) and 13° ± 5° (Oligocene–Pliocene), indicating that the allochthonous Intermontane terranes have been progressively driven ~240 ± 120 km eastwards up and over pericratonic and cratonic North American lower crust by Pacific plate subduction since the mid-Eocene.

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.

Magnetic polarity dating of tectonic events at passive continental margins

1980 ◽  
Vol 294 (1409) ◽  
pp. 189-208 ◽  
Keyword(s):  
Magnetic Anomaly ◽  
Continental Margin ◽  
Time Scale ◽  
General Pattern ◽  
Magnetic Polarity ◽  
Early Pleistocene ◽  
Continental Margins ◽  
Geological Time Scale ◽  
Late Neogene ◽  
Normal Polarity

Palaeomagnetic studies of continental margin sediments drilled during IPOD Legs 47a (NW African margin), 47b (NW Portugal margin) and 48 (NE Bay of Biscay and SW Rockall margins) have provided magnetic polarity records for the late Neogene, early Palaeogene and Cretaceous periods. The general pattern of geomagnetic field polarity reversals during late Neogene times is now well established, and the absolute age of major polarity transitions during the past 5 Ma or so has been determined from palaeomagnetic studies of radiometrically dated igneous rocks (see, for example, McDougall et al. 1977). Consequently, a comparison of the late Neogene polarity sequences identified in the sediments of NE Biscay and the NW African margins, with this ‘standard’ polarity reversal time scale, allows the precise determination of sediment accumulation rates, and the times at which significant changes in these rates occurred. These comparisons have led to the recognition of a short but significant hiatus in early Pleistocene times in both areas. Such information has importance in evaluating the recent geological evolution of these margins. For earlier geological periods the correlation between the magnetic polarity time scale and the geological time scale is less well established but studies of the type described here can still provide important information on the timing of certain geological events recorded in the magnetic anomaly patterns of the oceanic lithosphere. For example, in the early Palaeogene sediments cored at Sites 403-405, off the SW Rockall continental margin, a sequence of magnetic reversals has been identified, which shows a good correlation with marine magnetic anomalies 22-24. Since anomaly 24 is the oldest recognizable anomaly in the Atlantic, and lies immediately adjacent to the continental margins, the biostratigraphic age of this anomaly, determined from the nannofossil and dinocyst zonal determinations at Site 404, provides important information on the date of initial rifting of Rockall (together with the rest of NW Europe) from Greenland. The Site 404 results indicate that this important tectonic event occurred in early Eocene times, at about 52 Ma B.P., rather than at 60 Ma B.P. as was originally proposed by Heirtzler et al .(1968). A further example of the potential value of this type of study is provided by the Cretaceous sediments cored at Sites 397, 398, 400A and 402A. A long section of predominantly normal polarity sediments at the latter three sites appears to correlate with the long Cretaceous interval of dominantly normal polarity identified in marine magnetic anomaly patterns. The combination of palaeomagnetic and biostratigraphic studies allows useful constraints to be placed on the maximum duration of this interval, and on the age of short reversals within and below it. This information has direct relevance to the interpretation of Mesozoic marine magnetic anomaly patterns in terms of the history of seafloor spreading and evolution of continental margins during the early stages of opening of the South Atlantic in Cretaceous times.

Magnetic Polarity Stratigraphy of the Pleistocene Section at Portland (Victoria), Australia

1987 ◽  
Vol 28 (3) ◽  
pp. 364-373 ◽  
Author(s):  
Bruce J. MacFadden ◽  
Michael J. Whitelaw ◽  
Phil McFadden ◽  
Thomas H. V. Rich
Keyword(s):  
Magnetic Polarity ◽  
Beach Sand ◽  
Mammalian Fauna ◽  
Local Fauna ◽  
Depositional History ◽  
Matuyama Chron ◽  
History Of ◽  
Globorotalia Truncatulinoides ◽  
Absolute Dating ◽  
Reversed Polarity

AbstractThree to seven oriented paleomagnetic samples were collected from 16 sites in the Nelson Bay and Bridgewater formations at Portland, Victoria, which contains the recently discovered Nelson Bay local fauna (L.F.). The entire section has reversed polarity. These results, along with Globorotalia truncatulinoides within the section, and the presence of underlying middle Pliocene-dated basalts, indicate that the Portland section, and the included Nelson Bay L.F., was deposited within the late Matuyama Chron between 1.66 and 0.73 myr ago. This represents the first well-documented pre-14C Pleistocene mammalian fauna in Australia calibrated in direct stratigraphic context with absolute dating methods. In addition, the reversed polarity for the Bridgewater Formation confirms the previous hypothesis that the depositional history of this beach-sand deposit is time-transgressive across the Brunhes-Matuyama boundary.

Stratigraphy and Magnetic Polarity of the High Terrace Remnants in the Upper Ohio and Monongahela Rivers in West Virginia, Pennsylvania, and Ohio

1988 ◽  
Vol 29 (3) ◽  
pp. 216-232 ◽  
Author(s):  
Robert B. Jacobson ◽  
Donald P. Elston ◽  
John W. Heaton
Keyword(s):  
West Virginia ◽  
Magnetic Polarity ◽  
Early Pleistocene ◽  
Ohio River ◽  
Pleistocene Glaciation ◽  
Drainage Basins ◽  
High Terrace ◽  
Reversed Polarity ◽  
Monongahela River ◽  
Stratigraphic Succession

A synthesis of previous work and new data on the stratigraphy of high terraces of the Ohio and Monongahela Rivers upstream from Parkersburg, West Virginia, indicates a correspondence between terrace histories in the ancient Teays and Pittsburgh drainage basins. Four terraces are identified in each. Sediments of the lower three alluvial and slackwater terraces, correlated with Illinoian, early Wisconsin, and late Wisconsin glacial deposits, have been traced along the modern Ohio River through the former divide between the Teays and Pittsburgh basins. Sediments in the fourth terrace, the highest well-defined terrace in each basin, were deposited in two ice-dammed lakes, separated by a divide near New Martinsville, West Virginia. Some deposits of the highest slackwater terrace in both the Teays and Pittsburgh basins have reversed remanent magnetic polarity. This, and the stratigraphic succession in the two basins, suggests that both were ponded during the same glaciation. Reversed polarity in these terrace sediments restricts the age of the first ice-damming event for which stratigraphic evidence is well-preserved to a pre-Illinoian, early Pleistocene glaciation prior to 788,000 yr ago. In contrast, slackwater sediments in the Monongahela River valley, upstream from an outwash gravel dam at the Allegheny-Monongahela confluence, have normal remanent magnetic polarity, corroborating correlation with an Illinoian ponding event.

Magnetic Polarity Stratigraphy of the Middle Pleistocene (Ensenadan) Tarija Formation of Southern Bolivia

1983 ◽  
Vol 19 (2) ◽  
pp. 172-187 ◽  
Author(s):  
Bruce J. MacFadden ◽  
Oscar Siles ◽  
Peter Zeitler ◽  
Noye M. Johnson ◽  
Kenneth E. Campbell
Keyword(s):  
Fission Track ◽  
Magnetic Polarity ◽  
Middle Pleistocene ◽  
Time Interval ◽  
Zircon Age ◽  
Matuyama Chron ◽  
Composite Section ◽  
Normal Polarity ◽  
Reversed Polarity ◽  
Land Mammal

AbstractThe Tarija Formation of southern Bolivia, which is well known for its classic vertebrate faunas, is of prime importance in understanding of the chronology of the Ensenadan Land Mammal Age. This formation consists of well-exposed and relatively fossiliferous sections of clays, clayey silts, sands, gravels, and tuffs which were deposited in a predominately fluviatile regime in a Pleistocene structural basin. Four stratigraphic sections, each measuring 110 m or less, were studied to establish a magnetic polarity stratigraphy. Paleomagnetic samples were collected from the finer-grained sediments at 100 sites spaced at stratigraphic intervals of 5 m or less. All paleomagnetic specimens were demagnetized in alternating fields of least 250 oersteds (oe). Some specimens were also thermally demagnetized at 200°C or more. Of the 100 sites, 77 were ultimately used to determine the magnetic polarity zonation. Based on the four sections sampled, the Tarija Formation spans a time interval from about 1 my to about 0.7 my B.P. or perhaps younger. The lower half of the composite section is of reversed polarity punctuated by a short normal event. This sequence probably represents the late Matuyama chron with the Jaramillo subchron. The upper part of the section is of normal polarity and represents early Brunhes time. A tuffaceous unit 43 m above the Brunhes-Matuyama boundary yielded a fission track (zircon) age of 0.7 ± 0.2 by B.P. These data indicate that the classic Tarija fauna is middle Pleistocene Ensendan in age.

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.

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.

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.

Long History of Pre‐Wisconsin, Ice Age Cataclysmic Floods: Evidence from Southeastern Washington State

2001 ◽  
Vol 109 (6) ◽  
pp. 695-713 ◽  
Author(s):  
Bruce N. Bjornstad ◽  
Karl R. Fecht ◽  
Christopher J. Pluhar
Keyword(s):  
Washington State ◽  
Ice Age ◽  
History Of
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