A Quaternary geomagnetic instability time scale

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doi: 10.1016/j.quageo.2013.10.003
Author(s): Singer, Brad S.
Author Affiliation(s): Primary:
University Wisconsin-Madison, Department of Geoscience, Madison, WI, United States
Volume Title: Advance in <sup>40</sup>Ar/<sup>39</sup>Ar dating of Quaternary events and processes
Volume Author(s): Singer, Brad S., editor; Renne, Paul R.
Source: Advance in >40`Ar/>39`Ar dating of Quaternary events and processes, edited by Brad S. Singer and Paul R. Renne. Quaternary Geochronology, Vol.21, p.29-52. Publisher: Elsevier, Amsterdam, International. ISSN: 1871-1014
Note: In English. 177 refs.; illus., incl. strat. cols., 3 tables, sketch map
Summary: Reversals and excursions of Earth's geomagnetic field create marker horizons that are readily detected in sedimentary and volcanic rocks worldwide. An accurate and precise chronology of these geomagnetic field instabilities is fundamental to understanding several aspects of Quaternary climate, dynamo processes, and surface processes. For example, stratigraphic correlation between marine sediment and polar ice records of climate change across the cryospheres benefits from a highly resolved record of reversals and excursions. The temporal patterns of dynamo behavior may reflect physical interactions between the molten outer core and the solid inner core or lowermost mantle. These interactions may control reversal frequency and shape the weak magnetic fields that arise during successive dynamo instabilities. Moreover, weakening of the axial dipole during reversals and excursions enhances the production of cosmogenic isotopes that are used in sediment and ice core stratigraphy and surface exposure dating. The Geomagnetic Instability Time Scale (GITS) is based on the direct dating of transitional polarity states in lava flows using the 40Ar/39Ar method, in parallel with astrochronologic age models of marine sediments in which oxygen isotope and magnetic records have been obtained. A review of data from Quaternary lava flows and sediments gives rise to a GITS that comprises 10 polarity reversals and 27 excursions that occurred during the past 2.6 million years. Nine of the ten reversals bounding chrons and subchrons are associated with 40Ar/39Ar ages of transitionally-magnetized lava flows. The tenth, the Gauss-Matuyama chron boundary, is tightly bracketed by 40Ar/39Ar dated ash deposits. Of the 27 well-documented geomagnetic field instabilities manifest as short-lived excursions, 14 occurred during the Matuyama chron and 13 during the Brunhes chron. Nineteen excursions have been dated directly using the 40Ar/39Ar method on transitionally-magnetized volcanic rocks and these form the backbone of the GITS. Excursions are clearly not the rare phenomena once thought. Rather, during the Quaternary period, they occur nearly three times as often as full polarity reversals.
Year of Publication: 2014
Research Program: ODP Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; Absolute age; Ar/Ar; Ash; Atlantic Ocean; Brunhes Chron; Cenozoic; Climate change; Correlation; Dates; Geochronology; Geomagnetic Instability Time Scale; Global; Igneous rocks; Leg 162; Magnetic excursions; Matuyama Chron; Models; North Atlantic; ODP Site 980; ODP Site 981; ODP Site 982; ODP Site 983; ODP Site 984; Ocean Drilling Program; Paleomagnetism; Pleistocene; Quaternary; Reversals; Reykjanes Ridge; Rockall Bank; Sedimentary rocks; Stability; Upper Quaternary; Volcanic rocks
Coordinates: N552906 N552906 W0144208 W0144208
N612532 N612532 W0240457 W0240457
Record ID: 2019054904
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands