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

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.

Download Full-text

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

Canadian Journal of Earth Sciences ◽

10.1139/e98-068 ◽

1998 ◽

Vol 35 (12) ◽

pp. 1347-1361 ◽

Cited By ~ 8

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.

Download Full-text

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

Quaternary Research ◽

10.1016/0033-5894(83)90003-0 ◽

1983 ◽

Vol 19 (2) ◽

pp. 172-187 ◽

Cited By ~ 42

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.

Download Full-text

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

Quaternary Research ◽

10.1016/j.yqres.2005.06.011 ◽

2006 ◽

Vol 65 (1) ◽

pp. 123-135 ◽

Cited By ~ 10

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.

Download Full-text

Digging the history. Absolute chronology of the settlement complex at Czermno-Cherven’ (eastern Poland). Research status and perspectives

Sprawozdania Archeologiczne ◽

10.23858/sa/72.2020.2.2095 ◽

2020 ◽

Vol 72 (2) ◽

Author(s):

Tomasz Dzieńkowski ◽

Marcin Wołoszyn ◽

Iwona Florkiewicz ◽

Radosław Dobrowolski ◽

Jan Rodzik ◽

...

Keyword(s):

Interdisciplinary Research ◽

Qualitative Change ◽

Archaeological Research ◽

Research Status ◽

History Of ◽

Absolute Dating ◽

First Time ◽

Radiocarbon Datings

The article discusses the results of the latest interdisciplinary research of Czermno stronghold and its immediate surroundings. The site is mentioned in chroniclers’ entries referring to the stronghold Cherven’ (Tale of Bygone Years, first mention under the year 981) and the so-called Cherven’ Towns. Given the scarcity of written records regarding the history of today’s Eastern Poland, Ukraine, and Belarus in the 10th and 11th centuries, recent archaeological research, supported by geoenvironmental analyses and absolute dating, brought a significant qualitative change. In 2014 and 2015, the remains of the oldest rampart of the stronghold were uncovered for the first time. A series of radiocarbon datings allows us to refer the erection of the stronghold to the second half/late 10th century. The results of several years’ interdisciplinary research (2012-2020) introduce qualitatively new data to the issue of the Cherven’ Towns, which both change current considerations and confirm the extraordinary research potential in the archeology of the discussed region.

Download Full-text