The Cretaceous superchron geodynamo: Observations near the tangent cylinder

Tarduno, J. A.; Cottrell, R. D.; Смирнов, А. В.

doi:10.1073/pnas.222373499

Cited by 129 publications

(130 citation statements)

References 45 publications

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“…microwave) method with pTRM checks. Eight out of twelve data are obtained from subaerial lava flows, two are based on single plagioclase crystal paleointensity (Cottrel andTarduno, 1999, 2000;Tarduno et al, 2001Tarduno et al, , 2002 while remained two VADMs are obtained using submarine basaltic glasses (SBG, see Staudidel, 2004 andRiisager et al, 2004). Our results are in agreement with SBG data but substantially lower with respect to plagioclase data.…”

Section: Resultssupporting

confidence: 77%

Early cretaceous absolute geomagnetic paleointensities from Córdoba Province (Argentina)

et al. 2006

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We present here new paleointensity and geochronology results from Early Cretaceous volcanic rocks of Sierra Chica de Cordoba (Argentina). The new K-Ar isotopic ages of 5 samples range from 136 to 122 Ma. Twenty five samples from 7 individual flows yielded acceptable paleointensity estimates. The mean paleointensity values per flow are ranging from 53.0 ± 1.9 to 25.4 ± 2.6 μT and the corresponding Virtual Dipole Moments (VDMs) are ranging from 9.3±1.3 to 4.6±0.5 (10 22 Am 2 ). This corresponds to the mean value of 7.3±1.7×10 22 Am 2 , which is compatible to the present geomagnetic axial dipole. Currently available selected paleointensity data from 80 to 130 Ma suggest that geomagnetic field strength frequently fluctuated before and during the Cretaceous Normal Superchron while the magnetic polarity maintained stable. The mean paleointensities derived from Córdoba lavas agree remarkably well with those obtained from the Paraná Magmatic Province (133-132 Ma). This reinforces the hypothesis about the unreliability of 'Mesozoic Dipole Low'.

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Section: Resultssupporting

confidence: 77%

Early cretaceous absolute geomagnetic paleointensities from Córdoba Province (Argentina)

et al. 2006

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“…8). With the exception of the high latitude data (dominated by data from the Cretaceous Normal Superchron, Tarduno et al, 2002), the means of the binned data fit this relationship extraordinarily well. This suggests that our 10-301 Ma dataset is a reasonable first-order description of the time-averaged intensity of the field for this period which is not strongly biased by over-representation of extremes of either secular variation or mantle-forced variations (except at high latitudes).…”

Section: Long Term Trends In Geomagnetic Intensitymentioning

confidence: 88%

The intensity of the geomagnetic field in the late-Archaean: new measurements and an analysis of the updated IAGA palaeointensity database

2009

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We firstly present the results of a detailed palaeointensity study performed on 54 samples from 9 volcanic units of late Archaean age (2724-2772 Ma) from the Pilbara Craton, Western Australia. These results were severely affected by magnetomineralogical alteration occurring during the laboratory heating process necessitating the application of a correction procedure. The correction allowed results from three lavas to pass strict selection criteria but we deem that only one of these exhibits sufficient internal consistency to be considered moderately reliable. It yields a virtual dipole moment of 47±6 ZAm 2 which is 60% of the present-day value. We combine this determination with a filtered dataset from the updated IAGA (International Association of Geomagnetism and Aeronomy) palaeointensity database, PINT08. Directional secular variation has recently been shown to have changed fundamentally since the Archaean, probably as a consequence of inner core growth since that time. However, here we argue that it is still unclear whether this evolution was accompanied by a single long timescale change in average poloidal field intensity. While the distribution of Precambrian palaeointensity determinations as a whole is significantly lower than that for the last 300 Myr, we show that this finding largely reflects data from the Proterozoic aeon. The distribution of more ancient measurements from the late Archaean-earliest Proterozoic is indistinguishable from that of the last 300 Myr which might suggest that a 'Proterozoic dipole low' period existed between two periods of higher field intensity. Were this pattern of long-term geomagnetic intensity variation to be supported by the addition of new data in the future, then it could indicate a related three-stage evolution in core dynamics, namely: vigorous thermal convection caused by high core-mantle heat flux early in the Earth's history, weaker thermal convection later as the heat flux fell, and finally, strong compositional convection since the inner core nucleated.

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“…To quantify the eruption frequency, we have to make an assumption about the PSV speed at ~290 Ma, which is in the PCRS. In terms of PSV magnitude, the Cretaceous normal Superchron has been characterized by a slightly smaller variation at low latitudes compared to the previous 5 Myr (Tarduno et al 2002;Biggin et al 2008). A similar tendency was reported for the PCRS (Halden et al 2009).…”

Section: Psv Speed During Pcrs and Timescale For The Tlip Basalt Actimentioning

confidence: 82%

Paleomagnetic directional groups and paleointensity from the flood basalt in the Tarim large igneous province: implications for eruption frequency

Usui

Tian

2017

Earth Planets Space

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We present paleomagnetic secular variation and paleointensity from the Early Permian Tarim large igneous province, NW China. The studied sections comprise a total of ~400 m of basaltic flows. Paleomagnetic directions were determined for 11 flows. Four successive flows with a cumulative thickness of ~150 m showed a statistically identical paleomagnetic direction. Assuming a paleosecular variation speed similar to that of the present day, the ~150-m-thick basalt was estimated to have erupted within the past few centuries. Paleointensity experiments were performed on both whole-rock and single plagioclase samples. Although alterations during the experiment and/or weak remanence degraded the data quality, the flows with the same paleomagnetic direction revealed similar paleointensity estimates, supporting the hypothesis that the eruption of these flows was rapid. More generally, flows from the Lower Kupukuziman Formation seem to record lower paleointensity compared to flows from the overlying Kaipaizileike Formation.

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The Cretaceous superchron geodynamo: Observations near the tangent cylinder

Cited by 129 publications

References 45 publications

Early cretaceous absolute geomagnetic paleointensities from Córdoba Province (Argentina)

Early cretaceous absolute geomagnetic paleointensities from Córdoba Province (Argentina)

The intensity of the geomagnetic field in the late-Archaean: new measurements and an analysis of the updated IAGA palaeointensity database

Paleomagnetic directional groups and paleointensity from the flood basalt in the Tarim large igneous province: implications for eruption frequency

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