Upper and lower Jaramillo polarity transitions recorded in IODP Expedition 303 North Atlantic sediments; implications for transitional field geometry

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doi: 10.1016/j.pepi.2008.08.012
Author(s): Mazaud, A.; Channell, J. E. T.; Xuan, C.; Stoner, J. S.
Author Affiliation(s): Primary:
Commissariat a l'Energie Atomique, Laboratoire des Sciences du Climat et de l'Environnement, Gif sur Yvette, France
Other:
University of Florida, United States
Oregon State University, United States
Volume Title: Physics of the Earth and Planetary Interiors
Source: Physics of the Earth and Planetary Interiors, 172(3-4), p.131-140. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0031-9201 CODEN: PEPIAM
Note: In English. 31 refs.; illus., incl. sketch map
Summary: Sediments collected during the Integrated Ocean Drilling Program (IODP) Expedition 303 in the North Atlantic provide records of polarity transitions and geomagnetic excursions at a high resolution. Here we investigate polarity transitions at the upper and lower boundaries of the Jaramillo subchronozone at Sites U1305, U1304, and U1306. The sediments carry strong natural remanent magnetizations (NRM) with median destructive fields consistent with magnetite as the dominant magnetic carrier. Both polarity transitions are characterized by low values of relative paleointensity. The U1305 record of the lower Jaramillo reversal exhibits a marked cluster of virtual geomagnetic poles (VGPs) over southern South America, and a secondary accumulation in the region of NE Asia/North Pacific. The main South American VGP cluster is also visible at Site U1304, which documents a less complex pattern, possibly because of a higher degree of smoothing. Records of the upper Jaramillo polarity transition document a VGP loop over the Americas, followed by north to south motion including a secondary VGP accumulation near India. The similarity between several records of the upper Jaramillo transition obtained at various sites in the North Atlantic is a strong indication that geomagnetic field changes have been faithfully captured. Results suggest that a transverse, possibly dipolar, field component has fluctuated during these polarity reversals, and that these fluctuations combined with a reduced axial dipole component yielded the observed field at the Earth's surface during the polarity transitions. The lower Jaramillo transition also exhibits VGP clusters in the vicinity of South America and eastern Asia but these clusters are shifted relative to the upper Jaramillo VGP clusters, implying a memory exerted by the upper mantle on polarity transition geometry. Abstract Copyright (2009) Elsevier, B.V.
Year of Publication: 2009
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; Asia; Atlantic Ocean; Cenozoic; Demagnetization; Expeditions 303/306; Geometry; IODP Site U1304; IODP Site U1305; IODP Site U1306; India; Indian Peninsula; Integrated Ocean Drilling Program; Jaramillo Subchron; Lower Pleistocene; Magnetic field; Magnetization; Marine sediments; Natural remanent magnetization; North Atlantic; Northeast Atlantic; Northwest Atlantic; Paleomagnetism; Pleistocene; Quaternary; Remanent magnetization; Sediments; South America
Coordinates: N581400 N581400 W0453800 W0453900
N530300 N530300 W0333200 W0333200
N572800 N572900 W0483200 W0483200
Record ID: 2009087557
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands