Publication Date:
2017-04-04
Description:
Paleomagnetic and rock magnetic analyses were conducted on
discrete samples from sediments drilled during Integrated Ocean
Drilling Program Expedition 317 in the Canterbury Basin offshore
New Zealand to assess the nature of magnetic remanence and to
evaluate the directional data for a magnetic reversal stratigraphy.
The sediments consist of relatively coarse grained lithologies from
shelf to slope settings. The presence of several hiatuses, together
with very low core recovery in some intervals as well as drillingrelated
magnetic overprints, prevented establishment of a good
shipboard magnetostratigraphy. In an effort to overcome some of
the magnetic shortcomings and to substantiate shipboard measurements
(overprints and partial demagnetization to 20 mT),
natural remanent magnetization and subsequent full stepwise alternating
field or thermal demagnetization measurements were
taken on 765 individual discrete samples from Holes U1351B (131
samples), U1352B/U1352C (485 samples), U1353B (54 samples),
and U1354B/U1354C (95 samples). Some rock magnetic measurements,
including thermomagnetic curves, were taken on a few
representative samples to acquire information on the magnetic
carriers. The remanence intensity of the sediments is relatively
low (usually 10–3 to 10–5 A/m) and often displays unstable behavior
upon demagnetization. Demagnetization data have been separated
into four different classes based on their quality. Classes 1
and 2 are of sufficient quality to be used for magnetostratigraphic
purposes and represent ~40% of the studied samples (although
some of them could still represent a steep magnetic drilling overprint).
Considering the calculated characteristic remanent magnetization
inclination, a number of polarity zones can be defined.
However, the fragmentary nature of the data set, mostly related to
core recovery in addition to detected and undetected sedimentary
hiatuses, makes determination of the precise position of the reversal
boundaries and their correlation to the geomagnetic polarity
timescale a difficult task. Nevertheless, when combined shipboard
and postcruise discrete measurements are placed within biostratigraphic
constraints, some magnetostratigraphic insights can potentially
refine the available age model. These insights include the
identification of the Matuyama/Brunhes boundary (C1r1r/C1n,
0.778 Ma) at all four sites, the Gauss/Matuyama boundary
(C2An.1n/C2r.2r, 2.581 Ma) in Hole U1351B, and also the position
of the Olduvai Subchron (C2n, 1.778–1.945 Ma) in Hole U1351B, which relates to the position of the classical
Pliocene/Pleistocene boundary.
Description:
Published
Description:
1-31
Description:
1A. Geomagnetismo e Paleomagnetismo
Description:
N/A or not JCR
Description:
restricted
Keywords:
Deep Sea
;
magnetostratigraphy
;
rock magnetism
;
Plio-Pleistecene
;
Miocene
;
03. Hydrosphere::03.01. General::03.01.06. Paleoceanography and paleoclimatology
;
04. Solid Earth::04.04. Geology::04.04.08. Sediments: dating, processes, transport
;
04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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