Mesozoic Palaeomagnetic Scale of the USSR

Pechersky, D. M.; Храмов, А. Н.

doi:10.1038/244499a0

Cited by 46 publications

(18 citation statements)

References 1 publication

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“…The quiet zone, probably representing a long interval of almost exclusively normal polarity (Helsley and Steiner, 1969), has been approximately dated by Deep Sea Drilling as Campanian (Sclater et al, 1974) to Barremian (Sclater, personal communication), in fairly good agreement with polarities of continental rocks (Irving, 1973;Pechersky and Khramov, 1973 1969; Pechersky and Khramov, 1973) or dominantly normal polarity with a single reversal (Pechersky and Khramov, 1973). The short middle to lower Albian reversal observed at Site 260 thus may correlate with the reversal assigned by Pechersky and Khramov (1973) to the Albian-Aptian boundary.…”

Section: Reversal Stratigraphysupporting

confidence: 53%

Paleomagnetism of Some Leg Sediment Cores

Jarrard¹

1974

Initial Reports of the Deep Sea Drilling Project

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METHODSCretaceous cores from Site 260 (16°8.67'S, 110°17.92'E); Site 261 (12°56.83'S, 117°53.56'E); and Site 263 (23°19.43'S, 110°57.81'E) were sampled for paleomagnetic measurements. Except for the upper cores from Site 260, which were sampled by pressing the 5.8-cc rectangular sample boxes into the split core face, all samples were cut on a diamond saw. The cores consist of cylindrical pieces of undeformed claystone and siltstone from a few centimeters to tens of centimeters in length. Drilling caused the pieces to rotate horizontally by an unknown amount. Rather than a uniform sampling interval, several adjacent samples from the same piece were often taken to minimize breakup of core material, expedite sampling, and enable comparison of declination data from samples known to have undergone no horizontal rotation relative to each other. Table 1 shows the directions of remanent magnetization and intensities of the samples after 50-oe ac demagnetization. Samples were measured at 5 Hz on a Schonstedt magnetometer. An asterisk in Column 1 indicates that the Schonstedt magnetometer and ac demagnetization apparatus at Massachusetts Institute of Technology were used (see Green and Brecher [this volume] for detailed discussion of these measurements). All other samples were measured using the Schonstedt magnetometer and ac demagnetization apparatus at the University of California at Santa Barbara. Sample Interval in Table 1 is the distance in centimeters from the top of the 2-cm-wide sample to the top of the section. Inclinations (Incl) are given with respect to the present horizontal, positive downward, assuming vertical drill holes; negative inclinations indicate normal polarities for these southern hemisphere cores. Declinations (Decl) are relative only to the split face of the core. RELIABILITY OF MEASUREMENTSMM and A are measures of the consistency of replicate measurements on a single sample (Doell and Cox, 1965). Values of MM greater than about 30% or of A greater than about 5° indicate that the intensity or direction of magnetization, respectively, are probably unreliable, generally because the sample intensity is near the noise level of the magnetometer or because of instability of sample magnetization. Table 2 shows results of ac demagnetization series on four samples. Little change in direction of magnetization upon demagnetization is apparent, indicating that postdepositional viscous components of magnetization are small. Cumulative intensity changes for these samples (Figure 1) show that a majority of the magnetization resides in domains of high coercive force.Fifty oersted was chosen as the minimum demagnetizing field needed to remove viscous components. Histograms of 50-oe inclinations are generally considerably steeper than the geocentric axial dipole inclinations for the present latitudes of the sites. If a significant viscous component is present in these 50-oe measurements,lower average inclinations and higher average intensities should result for normally polarized samples than for reversely magne...

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Section: Reversal Stratigraphysupporting

confidence: 53%

Paleomagnetism of Some Leg Sediment Cores

Jarrard¹

1974

Initial Reports of the Deep Sea Drilling Project

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“…Studies of oceanic magnetic anomalies (Larson and Pitman, 1972) suggest that the Cretaceous normal polarity interval ended during the Coniacian Stage, and volcanic rocks having apparently the same age but mixed polarities (Hanna, 1967) tend to support this idea. However, other studies such as those by Pechersky and Khramov (1973), Shive and Frerichs (1974), and Keating, Helsley, and Pessagno (1975) show predominantly normal polarities at least until some time during the Maestrichtian. The question of why these strata became remagnetized still remains to be answered.…”

Section: Discussionmentioning

confidence: 93%

Journal of Research of the U. S. Geological Survey, 1978, volume 6, issue 3

1978

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“…According to Mc-ELHINNY and BUREK (1971), this normal interval includes two short reversed zones which may become important global time markers. The presence of reversed zones in the Late Cretaceous was also proposed by SASAJIMA andSHIMADA (1966) andPECHERSKY andKHRAMOV (1973). The reversed zone was placed in the Middle Santonian (80m.…”

Section: Discussionmentioning

confidence: 96%

“…+) on the basis of the stratigraphic correlation was called Akoh zone (SASAJIMA and SHIMADA, 1966;HELSLEY and STEINER, 1968;MCELHINNY and BUREK, 1971). PECHERSKY and KHRAMOV (1973) suggested the presence of a reversed zone (Kuldjin zone) in the Jalal normal Interval. The present results also suggest the presence of two reversals 2) The intrusions of monzonite or piclitic dolerite probably occurred at three different times.…”

Section: Discussionmentioning

confidence: 99%

“…The present results also suggest that the transitional field reversals also occurred in the Late Cretaceous and the time required for the field transition was probably short on the basis of the assumption that the field reversal probably occurred during the cooling process of the relatively thin intrusive body. Many authors suggest a long interval of time of predominantly normal geomagnetic field polarity in the Late Cretaceous (SASAJIMA and SHIMADA, 1966;HELSLEY and STEINER, 1968;MCELHINNY and BUREK, 1971;LARSON and PITMAN, 1972;PECHERSKY and KHRAMOV, 1973;IRVING and COUILLARD, 1973). The geologic time ranges of the normal interval suggested by these authors differ to some extent as represented in Fig.…”

Section: Discussionmentioning

confidence: 99%

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Paleomagnetism of Late Cretaceous alkaline rocks in the Nemuro Peninsula, Hokkaido, N.E.Japan.

Fujiwara

Ohtake

1974

J. geomagn. geoelec

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A paleomagnetic study was made on 747 specimens from 57 sites from Late Cretaceous alkaline rocks in the Nemuro Peninsula, Hokkaido, N.E. Japan (43.3N, 145.8E). Direction of magnetization of samples from the marginal parts of some monzonite or piclitic dolerite complex are quite different from those from the central parts. This suggests that the transitional change of geomagnetic field polarity might have occurred during cooling of the rock body. The paleomagnetic results suggest the presence of two short reversed zones in the Upper Cretaceous in which normal polarity was predominant. Recent K-A age determinations suggest that these reversals took place at 88 m.y. and 84 m.y. ago. They should become important time markers in Cretaceous paleomagnetic stratigraphy.

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Mesozoic Palaeomagnetic Scale of the USSR

Cited by 46 publications

References 1 publication

Paleomagnetism of Some Leg Sediment Cores

Paleomagnetism of Some Leg Sediment Cores

Journal of Research of the U. S. Geological Survey, 1978, volume 6, issue 3

Paleomagnetism of Late Cretaceous alkaline rocks in the Nemuro Peninsula, Hokkaido, N.E.Japan.

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