Systematics of Early Cambrian Paleomagnetic Directions...

782

ISSN 1069-3513, Izvestiya, Physics of the Solid Earth, 2018, Vol. 54, No. 5, pp. 782–805. © Pleiades Publishing, Ltd., 2018.Original Russian Text © V.E. Pavlov, A.M. Pasenko, A.V. Shatsillo, V.I. Powerman, V.V. Shcherbakova, S.V. Malyshev, 2018, published in Fizika Zemli, 2018, No. 5, pp.00000–00000.

Systematics of Early Cambrian Paleomagnetic Directionsfrom the Northern and Eastern regions of the Siberian Platform

and the Problem of an Anomalous Geomagnetic Field in the Time Vicinity of the Proterozoic–Phanerozoic Boundary

V. E. Pavlova, b, *, A. M. Pasenkoa, A. V. Shatsilloa, V. I. Powermana, b, d,V. V. Shcherbakovae, and S. V. Malysheva, c

aSchmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, 123242 RussiabGeological Faculty, Kazan Federal University, Kazan, Republic of Tatarstan, 420008 Russia

cSt. Petersburg State University, Institute of Earth Sciences, St. Petersburg, 199034 RussiadInstitute of the Earth Crust, Siberian Branch, Russian Academy of Sciences, Irkutsk, 664033 Russia

eBorok Geophysical Observatory, Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Borok, 152742 Russia*e-mail: [email protected]

Received April 9, 2018

Abstract—Representative paleomagnetic collections of Lower Cambrian rocks from the northern and easternregions of the Siberian platform are studied. New evidence demonstrating the anomalous character of thepaleomagnetic record in these rocks is obtained. These data confidently support the hypothesis (Pavlov et al.,2004) that in the substantial part of the Lower Cambrian section of the Siberian platform there are two stablehigh-temperature magnetization components having significantly different directions, each of which is eligi-ble for being a primary component that was formed, at the latest, in the Early Cambrian. The analysis of theworld’s paleomagnetic data for this interval of the geological history shows that the peculiarities observed inSiberia in the paleomagnetic record for the Precambrian–Phanerozoic boundary are global, inconsistentwith the traditional notion of a paleomagnetic record as reflecting the predominant axial dipole componentof the geomagnetic field, and necessitates the assumption that the geomagnetic field at the Proterozoic–Pha-nerozoic boundary (Ediacaran–Lower Cambrian) substantially differed from the field of most of the othergeological epochs. In order to explain the observed paleomagnetic record, we propose a hypothesis suggestingthat the geomagnetic field at the Precambrian–Cambrian boundary had an anomalous character. This fieldwas characterized by the presence of two alternating quasi-stable generation regimes. According to ourhypothesis, the magnetic field at the Precambrian–Cambrian boundary can be described by the alternationof long periods dominated by an axial, mainly monopolar dipole field and relatively short epochs, lasting afew hundred kA, with the prevalence of the near-equatorial or midlatitude dipole. The proposed hypothesisagrees with the data obtained from studies of the transitional fields of Paleozoic reversals (Khramov and Iosi-fidi, 2012) and with the results of geodynamo numerical simulations (Aubert and Wicht, 2004; Glatzmayerand Olson, 2005; Gissinger et al., 2012).

DOI: 10.1134/S1069351318050117

INTRODUCTIONIt is well known (e.g., (Merril et al., 1996)) that the

Earth’s magnetic field during the geological historycould exist in two states:

(1) a stable state (of normal or reversed polarity),with a predominant dipole geometry and wide spec-trum of the lengths of geomagnetic polarity intervalsranging from hundreds of ka to dozens of Ma;

(2) a transitional (reversal) state with the complexgeometry of the field and a duration ranging from afew hundred years to the first few kA.

The recent studies (Pavlov et al., 2004; Abrajevitchand Van de Voo, 2010; Biggin et al., 2012; Bazhenovet al., 2016; Halls, 2015; Gallet and Pavlov, 2016, etc.)indicate that in the history of the Earth there probablywere sufficiently long periods (on the order of a fewMa and longer) when the state of the Earth’s magneticfield differed from the two regimes noted above. Themain distinctive feature of this new fundamental statewas hyperactivity, i.e., extreme variability of the mainparameters of the field (the direction, intensity, ampli-tude of secular variation, etc.) and/or significant devi-ation from the axial dipole geometry.

IZVESTIYA, PHYSICS OF THE SOLID EARTH Vol. 54 No. 5 2018

SYSTEMATICS OF EARLY CAMBRIAN PALEOMAGNETIC DIRECTIONS 783

The epoch of the transition from the Proterozoic tothe Phanerozoic corresponding to the end of the Edi-acaran (Vendian)–beginning of the Cambrian wasperhaps one such period. In this work we consider thepaleomagnetic data for a number of geological objectspredominantly pertaining to the Early Cambrian andlocated in the north, northeast, and east of the Sibe-rian platform, which allows us to test this hypothesis toa certain extent.

THE PROBLEM OF THE PALEOMAGNETISM OF THE LOWER CAMBRIAN

FROM THE SIBERIAN PLATFORMThe Lower Cambrian rocks are widespread across

the platform and are mainly represented by carbonatefacies, which were formed within warm shallow epi-cratonic seas. The Siberian Lower Cambrian sectionsfrequently contain a significant amount of red andgreen beds which, as experience shows, are fairlyfavorable for recording and preserving the paleomag-netic signal.

Except for the formations composing some sec-tions in the platform’s marginal parts, the LowerCambrian rocks of the platform are typically onlybarely metamorphosed and have never subsided tobelow a depth of 1–3 km. The fact that these sectionsare extensively outcropped and have been excellentlyexplored from the biostratigraphic standpoint(Rozanov et al., 1992) makes them even more attrac-tive for paleomagnetologists. The Siberian LowerCambrian sections often contain numerous faunalremains, allowing the researchers to track the evolu-tion of the organic world during that time interval, toconduct a detailed biostratigraphic subdivision of thesections, and to correlate the sections. It would not bean overstatement if we say that the Lower Cambriansections of the Siberian platform rank among the bestones, and in many cases are indeed the best ones ofthis age in the world.

Therefore it is not surprising that the Lower Cam-brian rocks from the Siberian Platform have attractedthe attention of researchers since the very first years ofthe development of paleomagnetology in our country.Perhaps the first published work that presented theresults of these studies was the paper of E.P. Sidorova,the researcher with the Paleomagnetic laboratory atthe All-Russia Petroleum Research Exploration Insti-tute (VNIGRI), where she reported the data obtainedby her by studying the sub-red-bed formations in themiddle reaches of the Lena River and Chara formationof the Olekma River (Sidorova, 1963; Paleomagnit-nye…, 1971). The papers published a year later byDavydov and Kravchinskii (1965) and Sidorova (1965)addressed the paleomagnetism of the Ust-Tagul for-mation of the Biryusa area of the Sayan region andPestrotsvetnaya formation of the Maya River. In 1973,the new paleomagnetic result obtained for the LowerCambrian of the Siberian platform was presented in

the catalog (Paleomagnitnye…, 1973) under the editor-ship of A.N. Khramov. This result was determinedfrom the section in the middle reaches of the OlenekRiver where E.P. Osipova (E.P. Sidorova) studied sev-eral exposures of the Emyaksa Formation. In 1984,V.P. Rodionov presented the paleomagnetic resultsderived by him for the Emyaksa Formation of theUdzha River valley (Rodionov, 1984), and two yearslater the Paleomagnetic catalog (Paleomagnitnye…,1986) was added by the new data on the paleomagne-tism of the Pestrotsvetnaya formation of the Uchur–Maya region studied in the valley of the Iniken River—the left tributary of the Maya River. In (Komissarovaand Osipova, 1986) the authors again touched uponthe question concerning the paleomagnetism of therocks of the Pestrotsvetnaya formation from the MayaRiver section and presented a new paleomagneticresult which fairly well agrees with the previous resultsdetermined from this formation.

The research carried out by S.A. Pisarevskii et al.(Pisarevskii, 1986) at the beginning of the 1980s at theVNIGRI Paleomagnetic Laboratory is perhaps themost comprehensive and detailed study conducted inthat period of studying the Lower Cambrian from theSiberian platform. In the cited work, the authorsexplored more than 300 stratigraphic levels from 12 out-crops exposed over more than 200 km along the lowerreaches of the Olenek River.

As a result of the conducted studies, up to the mid-1980s, the paleomagnetic poles were obtained from anumber of Lower Cambrian objects representing dif-ferent regions of the Siberian Platform. These poleswere located near the southern termination of Austra-lia and fairly closely agreed with each other. They werealso closely consistent with the younger Lower Paleo-zoic paleomagnetic poles suggesting a more or less sta-ble (quiet) drift of the Siberian platform at the begin-ning of the Phanerozoic. The problem of the positionof the Early Cambrian paleomagnetic pole for theSiberian Platform seemed to be close to being com-pletely solved. In his book of 1982 (Khramov et al.,1982), Khramov generalized these data and calculatedthe average pole which is hereinafter referred to asKhramov’s pole.

Against this background, the result published in1984 by J. Kirschvink and A.Yu. Rozanov in Geologi-cal Magazine (Kirschvink and Rozanov, 1984) wasextremely surprising. At the beginning of the 1980s,Kirschvink, with the involvement of A.Yu. Zhuravlevand Rozanov, carried out detailed studies on theLower Cambrian stratotype reference sections in thelower reaches of the Lena River and obtained thepaleomagnetic pole for the Lower Cambrian whichdiffers from the closest (in age) Middle Cambrian poleby an angle of about 70° (Kirschvink and Rozanov,1984). The results were obtained with the use the cryo-genic magnetometer and the new, at the time, methodfor calculating the magnetic components—PCA

784


PAVLOV et al.

(Kirschvink, 1980), which allowed Kirschvink and anumber of other authors to consider this result as moresubstantiated compared to the previous ones.

The primary nature of Kirschvink’s direction wasfairly soundly supported by the fact that the zones ofmagnetic polarity identified in the remote exposuresreasonably well agreed with each other. The obtainedpaleomagnetic data were reliably correlated to theTommotian–Atdabanian biostratigraphic scale whichhad been well developed up to that time, and this wascertainly a strong point of the cited work. In his study,Kirschvink examined about 500 samples from fourexposures of the Variegated Formation spaced a fewkm to a few dozen km apart from each other. Interest-ingly, in his analyses Kirschvink used rather largedemagnetization steps (30°–40°–50°), including inthe high-temperature domain; i.e., the degree of detailin these demagnetization experiments was rather lowfrom the present-day standpoint.

When surveying the banks of the Lena River in1994, T. Torsvik, together with V.M. Moralev andJ. Tait (Torsvik et al., 1995), resampled the outcropsstudied by Kirschvink. The subsequent laboratoryinvestigations conducted by Torsvik have shown that thepaleomagnetic signal in the studied rocks has anextremely low quality and is unsuitable for interpretation.

In 1995, in the outcrops that were explored byKirschvink, we carried out confirmatory sampling ofthe intervals of the section that were described as mostfavorable in Kirschvink’s paper. Overall, 200 sampleswere acquired. Our working hypothesis was that due tothe difference in the Soviet and western systems ofmeasuring the attitude of the samples, an error proba-bly occurred in the orientation of the cores (the sam-ples for Kirschvink were largely acquired by Zhurav-lev) causing the discrepancy of the directions obtainedby Kirschvink from Khramov’s directions. In 1996,32 samples of this collection were investigated at thePaleomagnetic Laboratory of the Institut de Physiquedu Globe de Paris. Kirschvink’s direction was notrevealed in any of the thoroughly examined sampleswhich, by the way, gave very good Zijderveld dia-grams. Moreover, at that time, we did not even observeunambiguous circles tending to concentrate towardsKirschvink’s direction. The single clearly identified com-ponent (the present-day component) coincided within1°–2° with its counterpart obtained by Kirschwink,which indicated that it was all right with the orientation ofthe samples in Kirschvink’s collection.

However, to be fair, we should note that the Zij-derveld projections tended sometimes slightly andseemingly nonsystematically to miss the origin of theZijderveld diagrams, which might have indicated theexistence of a certain extremely weak ancient compo-nent; however, in our works conducted in 1995–1996,we failed to find any other signs of the presence ofKirschvink’s component.

In 1997, Pisarevskii et al. published a paper in theJournal of Geophysical Research (Pisarevsky et al., 1997)where Khramov’s directions were confirmed based onreinvestigating the old Lower Cambrian collection(Kessyusin and Erkeket formations) from the lowerreaches of the Olenek River with the up-to-dateinstruments and techniques. However, followingA.Yu. Kazanskii (2002), we note that the data pre-sented on some stereograms in (Pisarevsky et al., 1997)can also be considered as indicating the probable pres-ence of Kirschvink’s component in the magnetizationof the studied rocks.

Also in 1997, based on analyzing a number of thepaleomagnetic data (including the Lower Cambrianones) for several continents, Kirschvink et al. (1997)proposed the well-known Inertial Interchange TruePolar Wander (IITPW) hypothesis suggesting a huge,on the order of 90°, shift of the Earth’s crust and man-tle relative to the Earth’s rotation axis from the end ofthe Atdabanian to the beginning of the Middle Cam-brian (15–20 Ma).

The data used in the cited work immediately drewsharp criticism (Torsvik et al., 1998). The heateddebate (see also (Evans et al., 1998; Meert, 1999;Meert and van der Voo, 2001; Pisarevsky et al., 2001)),inter alia, has led to the understanding that no com-monly accepted paleomagnetic poles for the Late Ven-dian–Early Cambrian existed for any of the ancientcontinents at that time (this fully applies for the pres-ent as well). We note, however, that some of the dis-cussed poles, mainly the Vendian ones, satisfied thepresent-day reliability criteria quite well. The contro-versies that have become apparent suggested that theway out of the problem should perhaps be soughtbeyond the range of the traditional paleomagneticpostulates (Khramov et al., 1982). However, westarted approaching this conclusion only after study-ing quite a few Lower Cambrian reference sections inthe Siberian platform.

Thus, up to the beginning of the 2000s and mid-2010s, things have come to such a pass that two moreor less reliable strongly different paleomagnetic poleswere suggested for the Lower Cambrian of Siberia,leading to significantly dissimilar conclusions aboutthe geodynamical history of the Siberian Platform andthe Earth overall.

Resolving this contradiction needed a furtherresearch into the Lower Cambrian rocks with theexpansion of the study over the neighboring timeintervals and other rock types that were different fromthe previously studied ones. It was important to obtainan Early Cambrian paleomagnetic record in the igne-ous rocks which acquire magnetization by a differentmechanism compared to the sedimentary formations.This could help avoid the difficulties associated withthe probable duration of the paleomagnetic record’sformation in sedimentary rocks and the ensuing com-plicated superimposition of the magnetic components.



In subsequent years we carried out extensiveresearch of the Lower Cambrian and Vendian (Edi-acaran) rocks from the Siberian platform. The resultsof a part of these studies have been published (Galletet al., 2003; Shatsillo et al., 2005). In this work wepresent the results of the few past years of studying theLower Cambrian sedimentary and igneous rocks fromthe northeast and east of the Siberian platform.

BRIEF OUTLINE OF STUDY OBJECTS

Below we present the results determined from theLower Cambrian rocks of the Emyaksa formation out-cropping in the middle reaches of the Bol’shayaKuonamka river valley on the eastern slope of theAnabar uplift, of the Pestrotsvetnaya formation out-cropping in the valleys of the lower reaches of theBelaya and Maya rivers in the east of the Siberian plat-form, from the Nemakit–Daldyn rocks of the Sardanaformation within the Kyllakh Ridge, and from thebasic sills of the Chekurovka anticline (northeasternSiberian platform, valley in the lower reaches of LenaRiver, Fig. 1).

The Emyaksa Formation of the Bol’shayaKuonamka River is composed of clayey f laglike lime-stones, gray and greenish gray in the bottom part, red

higher in the sequence, and again greenish gray in theuppermost layers. The samples from paleomagneticanalysis were handed over to us by A. Kuchinskii whostudied the Emyaksa sequences of the Bol’shayaKuonamka River at the end of the 1990s. The rocks inthese sections have a subhorizontal bedding; the abun-dant faunal remains found in this formation (Rozanovet al., 1992) date it to the Tommotian–Atdabanian;the upper half of the Emyaksa formation correspond-ing to the upper Tommotian and the Atdabanianstages was sampled with an interval of 1 to 1.5 m. Fifty-four oriented samples were acquired here from a 70-mthick stratigraphic level.

The Pestrotsvetnaya formation is widespread alongthe eastern framing of the Siberian platform. In thestudied exposures of the Belaya and Maya rivers, thisformation is represented by clayey f loglike limestones,sometimes greenish gray, gray, pink, red, and wine-colored marls. In the Maya sections, the Pestrotsvet-naya formation has an almost horizontal bedding, athickness of about 50 m, and is only partially exposedin separate outcrops with a thickness of 2 to 5 m. At thebeginning of the 2000s, we studied four outcrops: twoon the left bank of the Maya River upstream of theInikan River mouth, one on the right bank of theInikan River 3 km upsttream of the river mouth, and

Fig. 1. Geographic positions of studied objects: (1) Bol’shaya Kuonamka river valley; (2) Neleger river valley; (3) Aldan river val-ley, Kyllakh uplift; (4) Belaya river valley; (5) Maya river valley. Dashed line outlines contours of Siberian platform.

AldanLa

ke B

aika

l

Lena

Anabar

Nizhnyaya Tunguska

Yenisei Anabar

Shield

Aldan Shield

60° N

71° N

10

0° E

127° в

.д.

1

2

34

5

Ed

iaca

ran

Nem

ak

it–

Da

ldy

n

Lo

wer

Ca

mb

ria

n

Atd

aban

ian

To

mm

oti

an

Peri

od

Age

~525 Ma

~521 Ma

~541 Ma

1

1

2

3

4 5

N

Siberian

Platform

Olenek

Uplift

Olenek

786


PAVLOV et al.

one on the right bank of the Maya river 5 km upstreamof the Chaya cliff. Overall, more than 130 orientedsamples were acquired from these outcrops.

The Pestrotsvetnaya formation in the valley of theBelaya River has a limited distribution. We have onlyfound a single outcrop located on the left bankapproximately 20 km upstream of the Mutula Rivermouth. The outcrop is exposed in the low coastal cliffscomposed of f lag-like gently dipping (up to 15°–20°)red and green clayey limestones. During the fieldworks of 2014, we acquired about 30 oriented samplesfrom here. The thickness of the studied interval of theformation is at most 10–15 m.

The Sardana Formation corresponds to the upperpart of the Yudoma group (the Yudomian), it is wide-spread in the region of the Kyllakh uplift, and it under-lies the layers of Pestrotsvetnaya formation. The dataprovided by the studies of the small shelly fauna showthat the upper part of the Yudoma group (and, hence, theSardana formation) pertains to the Nemakit–Daldynhorizon (Khomentovskii and Karlova, 1994; 2002).

The Sardana formation was studied by us in 2014 inthe section of the Kyllakh ridge which outcrops in theright bank of the Aldan River 10 km upstream of theBelaya River mouth. We sampled there the Pes-trotsvetnaya (red and green) layers of siliceous silt-stones and limestones in the stratigraphic sequencewith an interval of 1 to 2 m. About 30 oriented samplesoverall were collected from there.

The region of the Chekurovka anticline (the Tuor–Asis Ridge) is marked by a wide distribution of sillsand dike bodies of basic composition which intrudethe Riphean–Vendian sedimentary strata. The intru-sions most frequently occur in the rocks of the UpperRiphean (?)–Early Ediacaran Neleger Formation andUpper Vendian Kharayutech formation (Khabarovand Izokh, 2014). A few dozen large sills are revealed,with many of them tracked for 10–20 km. The thick-ness of the individual sills ranges from 10 to 120 m(Geologicheskaya…, 1983; Oleinikov, 1983), whereasthe total (cumulative) thickness of the sills is morethan 250 m. During the field works of 2016, we sam-pled seven sills which outcrop in the Neleger River val-ley (the right tributary of the Lena River) and alongthe left bank of the Lena River downstream of theChekurovka village. Overall, 138 oriented samplesfrom these sills were taken for paleomagnetic studies,on average 15 to 20 samples from each sill. The sam-pled igneous bodies are typically composed of trachy-dolerites (Oleinikov, 1983; Prokop’ev et al., 2016).

Until recently, there have been only two K-Ar agedeterminations for the sills of the Chekurovka anti-cline which were obtained more than 30 years ago anddated these rocks to 449 ± 13 and 508 ± 13 Ma(Oleinikov et al., 1983). Recently, for one of the sills inthe Lena river valley, A.V. Prokop’ev et al. obtainedthe model age TNd(DM) = 577–648 Ma (Prokop’evet al., 2016).

In the absence of direct isotopic age determinationof the sills, their relationship with the trachybasalticlava f low that outcrops at the base of the Cambriansection four km downstream of the Chekurovka villageimmediately downstream of the mouth of the Biskeibitbrook becomes key to their dating. The data of thechemical and isotopic studies obtained in (Prokop’evet al., 2016) quite definitely show that the f low and thesills are comagmatic bodies which are very likely tohave been formed simultaneously. If this is so, the ageconstraints existing for this f low can be applied to thesills of the Chekurovka anticline.

The considered flow has the model age TNd(DM) =532–629 Ma and is located within the TommotianTyuser Formation (Rozanov et al., 1992). The f lowoverlays the conglomerate with occurrences of rhyolitepebbles. The concordant U-Pb age of the youngest ofthe studied pebbles is 525.6±3.9 Ma. Thus, the age ofthe f low (and, naturally, the age of all the Chekurovkasills) is limited by this date from below and should fallwithin the time limits of the Tommotian age which,according to the present-day notions (Geological…,2012) correspond to 525–521 Ma.

An additional argument in favor of this age is pro-vided by the data that were recently obtained byV.I. Powerman et al. (2018). These authors have sepa-rated and dated detrital zircons from the terrigenouslayers of Neleger Formation directly bordering the sillthat outcrops on the right bank of Lena River in theUkta River mouth. These studies have shown thatquite a few of these zircons have a U-Pb age of 520–525 Ma. This age does not reflect the time of zirconcrystallization since the terrigenous layers hosting thezircons are much older; instead, this date probablycorresponds to a certain event that had disturbed theU-Pb system in the clastic zircons of the Neleger For-mation at a significantly later time than the time of itsdeposition. It is logical to hypothesize that the rees-tablishment of the age of the zircons is probably due totheir active hydrothermal alteration during the intru-sion of the sill. These phenomena have been describedin the literature (Pidgeon et al., 1966).

PALEOMAGNETIC ANALYSISAll the described collections were investigated by

the standard paleomagnetic techniques (Khramovet al., 1082; Butler, 1998; Tauxe, 2010). The magneti-zation components were identified based on theresults of the detailed thermal demagnetization; andthe directions of these components were calculatedusing the PCA method (Kirschvink, 1980).

Emyaksa FormationThe natural remanent magnetization (NRM) of

the gray varieties of the Emyaksa Formation varieswithin (4–12) × 10–4 A/m and the magnetization ofred rocks is (1–5) × 10–3 A/m. In the first approxima-



tion, the component content of the magnetization inthe rocks composing this formation can be describedby the superimposition of two components. One is arelatively weakly stable low temperature component(LTC) which is mainly destroyed at 300°–350°. By itsdirection this component is close to the present geo-magnetic field and is likely to have been acquired rela-tively recently (Fig. 2, samples 765, 5215, etc.).Another component is the ancient one, hereinafterreferred to as the A-component. This component issignificantly more stable, has the maximal unblockingtemperatures of 600–680°C, and is characterized by aNNW declination and moderate inclination. Theexample of this component content is presented inFig. 2, samples 765 and 5215.

However, a more thorough examination of the Zij-derveld diagrams shows that component A in the high-temperature area quite frequently misses the origin of

the diagram, suggesting the probable presence ofanother high-temperature magnetization component(Fig. 2, sample 711). The presence of this component(hereinafter, referred to as B) in a number of samplesquite clearly manifests itself in the stereograms by achain of remagnetization circles diverging from theprojection of the A-component (Fig. 2, sample 7275)or from the projection of the present-day LTC compo-nent. In the second case, the NRM is the result of thesuperimposition of the LTC- and B-components.

Almost the entire diversity of the obtained Zij-derveld diagrams and stereograms can be explained bya certain combination of the LTC-, A-, and B-compo-nents. It is important that, firstly, the B-component isnever isolated in a pure form: due to the overlappingspectra of the unblocking temperatures of the magne-tization components, we failed to obtain any end pointcorresponding to this component; and, secondly, the

Fig. 2. Bol’shaya Kuonamka river section. Behavior of NRM vectors during demagnetization. Zijderveld diagrams: filled andopen circles denote vector projections on horizontal and vertical plane, respectively. Stereograms: filled and open circles denotevector projections on lower and upper hemispheres, respectively. data are presented in ancient coordinate system.

Scale = 1 mA/m Scale = 0.5 mA/m

Scale = 0.5 mA/m

Scale = 0.5 mA/m

Scale = 1 mA/m

Scale = 0.2 mA/m

Scale = 0.2 mA/m

Sample 765 Sample 5215

Sample 7275

Sample 711

Sample 7295

Sample 7515

Sample 7485

N N

N N

N N

N N

N

N

N

N

N N

N N

N

N

N

E Up

HTC

HTC

HTC

HTC

A-component

A-component

HTC

HTC

E Up

E Up

E Up

E Up

E Up

E Up

NRM

NRM

NRM

NRM

NRM

NRM

NRM

120°

120°

120°

250°

250°340°

380°

430–560°

600–670°

120°

120°

120°

120°

250°

250°

340°

250°340°

380–670°

340–670°

480–650°

190°250°

300°

380°

250°380°

430°

670°480–650°

520–560°

580–600°

(a) (b)

788


PAVLOV et al.

A- and B-components are likely to be contaminated bythe present-day component. The presence of this con-tamination is demonstrated, e.g., by samples 711,7485, and 7515 (Fig. 2), where the existence of thepresent-day component is perceived up to the highesttemperatures. By analyzing the Zijderveld diagrams, wemanaged to isolate the A-component (although notfully devoid of the admixture of the other components)and calculate its mean direction (Fig. 3, Table 1).

In the case of the B-component, by using theremagnetization circles, we can only constrain theprobable direction of this component. As seen in Fig.4, there is a certain regularity in the distribution of thecircles across the diagram: the circles are predomi-nantly oriented in the NE–SW direction. An import-

ant fact is that practically all the circles diverge fromthe vicinity or interspace between the LTC- andA-components and frequently go in the opposite direc-tions, indicating the bipolar character of the B-compo-nent (Fig. 2, sample 7515; Fig. 3, sample 7435). Here,the projections of the NRM vectors sliding along thecircles during the demagnetization process movetowards the expected Kirschvink direction, which sug-gests that the sought B-component is likely to corre-spond to Kirschvink’s paleomagnetic pole. At thesame time, the A-component, which is separated fairlyreliably, corresponds to Khramov’s paleomagneticdirection (Fig. 4, Table 1). Several observed remagne-tization circles fall out of the described predominanttrend (Fig. 3, sample 735). These circles could proba-

Table 1. Paleomagnetic directions and paleomagnetic poles of Lower Cambrian rocks outcropped along Kuonamka, Maya,Belaya, and Neleger rivers and within Kyllakh uplift

D, I, K, а95 are parameters of Fisher’s distribution; Plat, Plong, A95 are coordinates of paleomagnetic poles and their confidence circles.

Outcrop, component, formation N

Geographic coordinate system Stratigraphic coordinate system

D I K α95 D I K α95

Kuonamka River section (Emyaksa Formation, 70.6° N, 112.8° E)HTC (KHR),A-component

47 342.3 57.6 57.2 3.9 342.3 57.6 57.2 3.9

Plat = –56.3° Plong = 138.3° A95 = 4.9°Maya River section (Pestrotsvetnaya formation, 59.3° N, 135.0° E)

Maya 99, HTC, 9 7.9 52.5 55.3 7.0 7.9 52.5 55.3 7.0Inikan, HTC(KHR) 11 358.7 55.2 35.0 7.8 356.8 51.5 44.3 6.9Outcrop 2,HTC(KHR) 24 0 52.5 59.4 3.9 1 52.4 48.3 4.3Outcrop 4, HTC(KHR) 8 353.8 57.6 42.6 8.6 354.3 56.2 40.7 8.8Average over 4 outcrops 4 0.3 54.4 375.3 4.7 0.1 53.3 388.4 4.7

Plat = –64.6°; Plong = 134.8°; A95 = 5.4

Belaya River section (Pestrotsvetnaya formation, 61.5° N, 136.5° E)HTC (KHR) 27 4.3 48.4 35.4 4.7 3.5 47.7 36.2 4.7

Plat = –57.2; Plong = 130.8°; A95 = 4.9°Kyllakh Ridge section (Sardana Formation, 61.6° N, 135.6° E)

HTC (KHR) 14 342.6 35.3 25.0 8.1 24.0 51.3 28.3 7.6Plat = –56.5°; Plong = 96.8°; A95 = 8.5°

Neleger River Section (71.2° N, 127.7° E)Sill 1, HTC component (KRS)

10 213.9 –18.8 139.7 4.1 218.6 –16.1 139.7 4.1

Sill 2, HTC component (KRS)

9 224.2 –22.6 50.7 7.3 229.0 –16.1 50.7 7.3

Sample average 19 218.6 –22.7 54.2 4.6 223.5 –16.2 54.2 4.6Sample average disre-garding two extremes

17 217.2 –22.2 76.7 4.1 222.1 –16.1 89.5 3.8

Plat = –21.8°; Plong = 82.1°; A95 = 2.8°Kirschvink’s pole: Plat = –17°; Plong = 65°; A95 = 5° (Kirschvink and Rozanov, 1984)Khramov’s pole: Plat = –44°; Plong = 157°; A95 = 8° (Khramov et al., 1982)



Fig. 3. Bol’shaya Kuonamka river section: (a) behavior of NRM vectors during demagnetization. Left: Zijderveld diagrams; right:corresponding stereograms. Designations for Zijderveld diagrams are hereinafter same as in Fig. 2; (b) distribution of normals ofdemagnetization circles (right-hand convention). Filled (open) squares denote projections of normals on lower (upper) hemi-sphere; filled circle and oval around it denote normal of “average” circle and its confidence oval, respectively; asterisks denoteexpected Kirschvink’s directions with allowance for closing of Vilyui rift system (with filled circle) and without it. Black circlewith white cross denotes direction of A- (Khramov’s) component; white circle with black cross denotes direction of low-tempera-ture LTC component.

E UP

E UP

N N

N N

Scale = 0.5 mA/m

Scale = 0.5 mA/m

NRM

NRM

120°

120°300°

380°

250°

480–650°

430–680°

Sample 7435

Sample 735

N

N

0

180

90270

A-componentLTC

HTC

B-component

(а)

(b)

790


PAVLOV et al.

bly be formed by the B-component of a differentpolarity.

Section Summary(1) The A-component with the direction corre-

sponding to the expected Khramov direction is reli-ably established in the studied rocks of the Bol’shayaKuonamka River section.

(2) During the demagnetization, a significant partof the samples shows the trends that can be consideredas indicating the presence of a bipolar component withthe Kirschvink direction. This component in a pureform is not separated.

Pestrotsvetnaya Formation of the Maya RiverMost samples have NRM in the interval from (4–

5) × 10–4 to (2–3) × 10–3 A/m and magnetic suscepti-bility varying from a few to a few dozen 10–6 SI units,which is typical of this type of rock. As a rule, twomagnetization components are revealed during thedemagnetization (the samples not yielding a regularsignal, which are predominant in some outcrops, arethe exception). The low-temperature component has

the maximal unblocking temperatures of 400° andhigher; its direction highly accurately coincides withthat of the present dipole field. The high-temperaturecharacteristic component (HTC) has a northern dec-lination and the inclinations of ~50° (Fig. 5, samples974, 944, etc.). Considering the closeness of this com-ponent to the expected Khramov direction, we willrefer to it as the KHR-component. In some cases, sep-arating the components is challenged by the evidentoverlapping of their spectra and relative closeness oftheir directions. The directions of the high-tempera-ture component were only calculated in the caseswhen the Zijderveld diagrams had a distinct bend indi-cating the destruction of the main part of the low-tem-perature component. Clearly, with this approach, thevectors pertaining to that part of the sought distribu-tion where inclinations are relatively high can be lost.However, this separation procedure is unlikely to drawthe calculated mean direction significantly away fromthe true direction because the separated vectors of thehigh-temperature component are probably contami-nated, to some extent, by the present-day component.

Fig. 4. Bol’shaya Kuonamka river section: (a), (d) remagnetization circles; (b), (c), vector distributions. Data are presented inancient coordinate system. Stereograms with remagnetization circles show relationship between orientations of circles and direc-tions of A- (a) and B-components (d).

0

180

90270

0

180

90270

0

180

90270

0

180

90270

A-component

and remagnetization circles

B-component Kirschvink’s direction

and remagnetization circles

LTC component

(a) (b)

(c) (d)



In the studied collection there is a significant set ofsamples where the evidently present high-temperaturecomponent differs from the described one. In practi-cally none of the samples can this component be sep-arated in a pure form; however, its presence is defi-nitely suggested by the respective Zijderveld diagramsand the stereograms. In a number of cases this compo-nent is present in the samples that, besides it, onlycontain a fairly stable present-day component (Fig. 6,sample 945). However, as a rule, this component par-ticipates in a three-component system made up, inaddition to this one, by the relatively low-temperaturepresent-day magnetization component and the KHR-component (Fig. 6, samples 912, 924, and 987).

Examining the respective remagnetization circles(Fig. 7), we do not find any clear regularity whichwould allow us to anyhow constrain the direction ofthe sought component. In our opinion, the existingdata at least do not conflict with the hypothesis thatthis component is actually the KHR one but having anopposite (direct) polarity.

However, we cannot but note that in some samples(Fig. 6, samples 924 and 945) the direction of rema-nent magnetization is shifted towards the presumedKirschvink direction during the demagnetization.

Section Summary(1) The studied Lower Cambrian Pestrotsvetnaya

Formation rocks from the Maya River valley containthe ancient magnetization component KHR that isclose to the expected Khramov direction.

(2) During the detailed demagnetization, somesamples demonstrate peculiarities that can be under-stood as indicating the presence of the Kirschvinkcomponent in these samples. However, these pecu-liarities can also be interpreted as the result of thesuperimposition of the KHR components having adifferent polarity.

PestrotsvetnayaFormation of the Belaya River and Sardana Formation of the Kyllakh Ridge

The samples of the Pestrotsvetnaya formation fromthe outcrop studied in the valley of the Belaya River havemagnetization varying from 1–2 to 10–15 mA/m, whichis by many orders higher than the magnetization of therocks of this formation from the Maya River valley. Thesamples of the Sardana Formation are magnetized, onaverage, weaker than the samples of the Pestrotsvetnayaformation from the Belaya River valley and stronger thanthe samples of this formation from the Maya River valley.Their magnetization is 3–8 mA/m.

The behavior of the NRM of the samples of theSardana Formation is similar to that of the samples ofthe Pestrotsvetnaya formation from the valley of theBelaya River (Figs. 8, 9): in both cases, two magneti-zation components are clearly detected. The first,low- to medium-temperature (LTC) component isrelatively less stable and destroyed to 350–400°C.

The direction of this component is close to thedirection of the present geomagnetic field. This leadsus to suggest a recent origin of this component and,hence, exclude it from the further analysis. The morestable high-temperature characteristic magnetizationcomponent (HTC) is typically destroyed to 640–670°C. We note however that there are some samplesin which the characteristic component is almost com-pletely destroyed to 580°C. This component has amoderate inclination and northern declination, andthis is close to the expected Khramov direction.Therefore, hereinafter we refer to this component asKHR. The mean direction of the KHR-componentfor the Sardana Formation is slightly rotated towardsthe east relative to the mean direction of the KHR-component of the Pestrotsvetnaya formation from theBelaya river valley, which is quite natural to attribute toa certain difference in the age of the respective rocks.

No signs of the Kirschvink component were foundduring the demagnetization of the samples of the Pes-trotsvetnaya formation from the Belaya River and theSardana Formation from the Kyllakh Ridge.

Section Summary(1) The studied Lower Cambrian rocks of the Pes-

trotsvetnaya formation from the Belaya River valleyand the rocks of the Sardana Formation from the Kyl-lakh Ridge contain only one ancient KHR-compo-nent of magnetization which is close to the expectedKhramov direction.

Sills of the Chekurovka AnticlineOverall, we have studied seven sills in the valley of

the Neleger River and lower reaches of the Lena River.In five of them the paleomagnetic record is either cha-otic or demonstrates, more or less explicitly, the pres-ence of the magnetization component with a steeppositive inclination and northeastern–eastern decli-nation (Fig. 10). By its direction this component isclose to the direction of the Mesozoic remagnetiza-tion, which is widespread within the Chekurovka anti-cline (Pavlov et al., 2004). Based on this we assumethat this component is metachronous and reflects theMesozoic magnetic field.

The two remaining sills, both sampled by us in thevalley of the Neleger River, contain a distinct paleo-magnetic record. This record is carried by titanomag-netite with the Curie points in the interval from 480 to520°C, as suggested by the values of the maximalunblocking temperatures of the NRM (Fig. 10).

The same also follows from the temperature depen-dence of the saturation remanent magnetization illus-trated in Fig. 11. We reject the possibility that the dropin the saturation remanent magnetization in the inter-val of 480 to 520°C is due to the disintegration ofmaghemite because in this case the value of saturationremanent magnetization should be expected to dropafter heating rather than to increase by a factor of 14.5

792


PAVLOV et al.

Fig. 5. Demagnetization results for samples of Pestrotsvetnaya formation from Maya River’s lower reaches, KHR component.Data are presented in ancient coordinate system.

Sample 974

Sample 575

Sample 922

Sample 904

Sample 944

E UP E UP

E UPE UP

E UP

N N N N

N NN N

N N

Scale = 0.5 mA/m Scale = .5 mA/m

Scale = .5 mA/m

Scale = 0.5 mA/m

Scale = 0.2 mA/m

N

110°

150°

655°

530°

350°

110°110°

310°

450°

590°

HTC

HTC

410°

560°

680° 660°

550°

470°

340°

110°

340°

440°

670°HTC

KHR



Fig. 6. Demagnetization results for samples of Pestrotsvetnaya formation from Maya River’s lower reaches, KRS component.Data are presented in ancient coordinate system.

Sample 912

Sample 945

Sample 987

Sample 924

E UP

E UP

E UP

E UP

N N

N N

N N

N N

Scale = 0.5 mA/m

Scale = 0.5 mA/m

Scale = 0.5 mA/m

Scale = 0.1 mA/m

110°

340°470°

690°

110°

120°

110°

340°500°

615–690°

390°

390°470–690°

430–680°

LTC

LTC

LTC

KHR

KHR

N

N

N

N

Variegated formation, Maya River

794


PAVLOV et al.

Fig. 7. Vector directions of characteristic (high-temperature, HTC) magnetization component and remagnetization circles in fouroutcrops of Pestrotsvetnaya formation in Maya River’s lower reaches. Lower stereogram shows that revealed remagnetization cir-cles have no predominant orientation. Data are presented in ancient coordinate system.

N

N N

N

N

Variegated formation,

Maya River

Inikan

Outcrop 2Maya 99

Outcrop 4



Fig. 8. Demagnetization results for samples of Pestrotsvetnaya formation from Belaya River. Zijderveld diagrams: filled and opencircles denote vector projections on horizontal and vertical plane, respectively. Stereograms: filled and open circles denote vectorprojections on lower and upper hemisphere, respectively. Data are presented in ancient coordinate system.

E

E

W

W

S, Down

N, Up

N, Up

S, Down

NRM

Sample BEL332

Sample BEL333

270

0

180

0

0

90

180NRM

400°

480°

480°

670°

400°

640°

0

180

0

0

0

90

180

270

270

0

90

180

HTC

A-component

“КНR”

HTC

A-component

“КНR”

NRM = 1.44e–02 A/m

NRM = 8.31e–03 A/m

796


PAVLOV et al.

Fig. 9. Demagnetization results for samples of Sardana formation from Aldan River. Zijderveld diagrams: filled and open circlesdenote vector projections on horizontal and vertical plane, respectively. Stereograms: filled and open circles denote vector pro-jections on lower and upper hemisphere, respectively. Data are presented in ancient coordinate system.

0

NRM

NRM

400°480°

580°

400°470°

650°

400°

490°

640°

NRM

0

Sample 406

Sample 398

Sample 391

270

270

270

0

0

0

90

90

90

180

180

180

E

E

E

W

W

W

S, Down

S, Down

S, Down

N, Up

N, Up

N, Up

0

0

90

180

270

HTC

NRM = 5.42e–03 A/m

NRM = 6.01e–03 A/m

NRM = 4.88e–03 A/m



as is actually observed in the results of the performedexperiment.

The samples of these sills have two clearly distinctmagnetization components. The less stable one, thelow- to medium-temperature LTC-component isremoved by heating up to 350–400°C and, judging byits direction (Table 1), has either the Mesozoic orpresent age. The second, high-temperature compo-nent (JHTC) is mainly destroyed in the temperatureinterval from 400 to 520°C and is the most stable in thestudied samples.

The direction of this high-temperature componentsignificantly differs from the expected Khramov direc-tion (i.e., the one recalculated from the Khramov poleto the coordinates of the sampling sites) and has a verylow negative inclination and southwestern declination.However, the direction of this component is very closeto the expected Kirschvink direction, and, in theunderstanding defined above, this component shouldbe considered as the Kirschvink component (KRS).The virtual geomagnetic pole calculated from thecharacteristic magnetization of the sills from the Nele-ger River is close to the geographical position of theEarly Cambrian pole determined by Kirschvink andRozanov (Kirschvink and Rozanov, 1984), Table 1,Fig. 12).

We also note that any signs indicating the presenceof the Kramov component in the studied sills have notbeen found.

Section Summary(1) The characteristic component separated in the

Lower Cambrian sills of the Neleger River valley cor-responds to the expected Kirschvink direction.

(2) No other stable components besides the Meso-zoic of the present-age low- to medium-temperaturecomponent were found in the studied objects.

DISCUSSIONAnomalous Character of the Paleomagnetic Record

in the Lower Cambrian Rocks of the Siberian PlatformLet us summarize some results. Extensive studies

were carried out with the analysis of quite a few sam-ples from different outcrops of the Lower Cambrianrocks in the northern and eastern regions of the Sibe-rian Platform.

In the outcrops of the Emyaksa Formation, thepresence of two high-temperature magnetizationcomponents was detected. One component is clearlyidentified in many samples by the linear segment inthe Zijderveld diagrams and has the direction corre-sponding to the Khramov direction (KHR). The pres-ence of the second high-temperature component issuggested by the distinctly pronounced circles in thestereograms. During the demagnetization, the projec-tions of the NRM vectors migrate along these circlestowards the expected Kirschvink direction (KRS).

This manifestly qualifies the second high-temperaturecomponent as the Kirschvink component.

A similar component content (combination ofKHR and KRS with a relatively smaller contributionof KRS) is also observed in the rocks of the Pes-trotsvetnaya formation exposed in the valley of theMaya River, more than 1500 km away from the out-crops of the Emyaksa Formation in the valley of theKuonamka River.

The magnetization component corresponding tothe Kirschvink’s direction was identified by us in anexplicit form in the sills of the Neleger River. The pres-ence of this component in both the sedimentary andigneous rocks is a strong argument in favor of its realexistence.

For completeness we recall that the KRS compo-nent was detected in the Lower Cambrian rocks of theTyuser Formation in the Chekurovka reference section(the lower reaches of the Lena River) (Pavlov et al.,2004) and Erkeket formation along the KhorbusuonkaRiver (Gallet et al., 2003). The presence of this compo-nent in the Late Vendian–Early Cambrian rocks fromthe southern region of the Siberian Platform was alsoreported in (Kravchinsky et al., 2001; Rodionov, 2014).

Thus, there is a fairly large body of data supportingthe existence of the Kirschvink component (KRS) inthe Late Vendian–Early Cambrian rocks of Siberia.The existence of the Khramov component (KHR)which was repeatedly described in a series of previousworks (e.g., (Pisarevskii et al., 1998)) also does notraise any doubt. The data obtained in our present workvalidate its reality once again.

The results of these studies suggest the followingconclusions.

(1) The magnetization of the Lower Cambrianrocks from the Siberian platform typically has twoancient highly stable components: the Khramov(KHR) component and the Kirschvink (KRS) com-ponent, significantly different by their directions.

(2) The KHR component is predominantly monopo-lar and is fairly confidently identified in a significant partof the studied objects by the linear segments trendingtowards or going past the origin of the Zijderveld dia-grams. The second component typically manifestsitself by the remagnetization circles (frequently ratherweakly pronounced) in the stereograms and by somepeculiarities in the behavior of the vector projectionson the Zijderveld diagrams. During the present workwe have for the first time found the Lower Cambrianobjects (the sills of the Neleger River) carrying theKRS component in the direct form.

(3) Each of these components exists objectively andis not an artifact of data processing.

(4) Both components are frequently present in thesections spaced by a thousand or many hundred kilo-meters from each other and representing differentregions of the Siberian Platform with a different geo-

798


PAVLOV et al.

Fig. 10. Demagnetization results for samples from sills of Neleger River. Zijderveld diagrams: filled and open circles denote vectorprojections on horizontal and vertical plane, respectively. Stereograms: filled and open circles denote vector projections on lowerand upper hemisphere, respectively. Data are presented in ancient coordinate system.

Sample 6666

Sample 6664

Sample 6655

N, Up

S, Down

S, Down

S, Down

EW

NRM

EW

NRM

N, Up

N, Up

EW

NRM

270 90

0

180

270 90

0

180

270 90

0

180

0

90

180

270

(a)

(b)

(c)

(d)

LTC

HTCKRS

570°520°500°

480°

400°

570°520°500°

480°

400°

520°500°

480°

540°

NRM = 47.7e–03 A/m

NRM = 245.7e–03 A/m

NRM = 63.6e–03 A/m

Average direction

over two sills



logical history, e.g., the area of the Anabar block,Uchur–Maya region, and Cis-Sayan south of theSiberian Platform (Kravchinsky et al., 2001).

(5) In a part of the samples, these components arepresent in the form of a single high-temperature char-acteristic component. In another part of the samples,these components are present jointly, in the form oftwo high-temperature components with relativelystrongly overlapping spectra of their unblocking tem-peratures. In these cases, KRS is, as a rule, the high-est-temperature (end) component.

(6) The studied sections are largely composed ofsedimentary, mainly carbonate rocks. However, in thisstudy, one of the discussed components was isolated inthe igneous rocks.

We note that the results of this work completelyrule out the interpretation of the Kirschvink compo-nents as an artifact caused by the superimposition ofthe Khramov components with the normal andreversed polarities by the superposition of theKhramov and younger remagnetizing componentsbecause the Kirschvink component is identified in thesills of the Neleger River clearly and unambiguously,without any relation to the Khramov component. Nor

can Kirschvink’s component be the result of subse-quent remagnetization since the respective pole isquite distant from the Phanerozoic segment of Sibe-ria’s apparent polar wander path (Torsvik et al., 2012),Fig. 12.

However, the hypothesis of the metachronousnature of Khramov’s component implying its Middle-or Late Cambrian age also faces a very serious chal-lenge. This is because the KHR component is fre-quently present in the Vendian–Cambrian sectionslocated in different segments of the Siberian Platform,having different geological histories and composed ofdissimilar rocks. The discussed magnetization compo-nent occurs in the Cambrian rocks which are distrib-uted across vast territories and, being a secondarycomponent, it should have been formed as a result of acertain large-scale tectonic or magmatic event that hitthe Siberian platform in the last half of the Cambrian.However, we find no signs of this event in the geolog-ical history of the Siberian Platform. Moreover, if suchan event had really occurred, why hasn’t it affected themore ancient rocks?. Indeed, we do not see the signsof Khramov’s component the Riphean rocks of theUchur–Maya region (Pavlov et al., 2000), in the Sibe-

Fig. 11. Sills of Neleger River. Sample NEL666. Temperature dependence of saturation remanent magnetization. Top: first heat-ing; bottom: second heating. After first heating, magnetization increases by a factor of 14.5.

0 100 200 300 400 500 600 700

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700

0.2

0.4

0.6

0.8

1.0

1.2

Ma

gn

eti

c m

om

en

t, a

rb.

un

its

Ma

gn

eti

c m

om

en

t, a

rb.

un

its

Temperature, °C

Temperature, °C

Irs(t)/Irs0(t) – Sample’s first heating

Nel666

Irs(t)/Irs0(t) – Sample’s second heating

Nel666

800


PAVLOV et al.

rian platform’s northwest (Gallet et al., 2000), north(Ernst et al., 2000; Veselovskii et al., 2006; 2009), north-east (Rodionov, 1984), and south (Komisarova, 1983).

The statistically significant difference of therespective paleomagnetic poles (Fig. 12) is anotherstrong argument disproving the Middle–Late Paleo-zoic remagnetization as a source of origin of the KHRcomponent.

Thus, the obtained data strongly point to the valid-ity of our previous conclusion (Pavlov et al., 2004) thatin a significant part of the transitional Vendian–Cam-brian layers in the Siberian Platform there are two

objectively existing stable high-temperature magneti-zation components, each of which can be consideredas the primary one that had not been formed later thanthe Early Cambrian.

However, the presence of two different primarycomponents evidently contradicts the traditionalnotion of the paleomagnetic record as mainly reflect-ing the axial dipole character of the geomagnetic field.This leads us to seek an alternative interpretation of theobserved facts.

We suggest the following hypothesis as a probableexplanation. Both the considered components in the

Fig. 12. Comparison of obtained poles corresponding to KHR and KRS components with Paleozoic poles (squares) of Siberianplatform (Smethurst et al., 1998). Dashed line marks curve of = apparent wander path of paleomagnetic poles for Siberian plat-form. Black asterisk indicates pole from (Kirschvink and Rozanov, 1984). Ages of Paleozoic poles: Cm2, Middle Cambrian;Cm3-O3, Late Cambrian–Early Ordovician; O2-O3, Middle to Late Ordovician; D3-C1, Late Devonian–Early Carboniferous;P-T, Permian–Triassic. Pole numbers: (1) Usatovskaya Formation (Rodionov, 2014); (2) Shamanskaya Formation (Kravchinskiiet al., 2001); (3) Sardana Formation; (4) Pestrotsvetnaya formation of Belaya River; (5) Pestrotsvetnaya formation of Maya River;(6) Emyaksa Formation of Kuonamka River; (7) sills of Tuor-Asis Ridge (poles 3–7 are obtained in this work).

P-T

D3-C1

O2-O3

Cm3-O1

Cm2

1

2

3 4

5

6

7Khramov’s pole

Kirschvink’s pole

Equator 90° E 150° E

60° S

30° S

30° E



sedimentary rocks are primary in the sense that theyhave been acquired either during the deposition of thestudied sediments or shortly after this. These compo-nents can have both syndepositional and early diage-netic origin. The difference of their directions is due tothe fact that the geomagnetic field at the end of LateVendian and at the beginning of the Cambrian had ananomalous character with relatively long periods of thepredominant axial molopolar dipole field recorded inthe KHR component alternating with the relativelyshort epochs dominated by the reverting subequatorialdipole recorded in the KRS component.

The data obtained in this work substantially expandthe body of evidence supporting this hypothesis.

In our opinion, this behavior of the magnetic fieldcould explain most of the peculiarities of the paleo-magnetic record that we observe in the studied sec-tions and to reconcile the seemingly antagonisticresults obtained by the different researchers.

In the case the magnetization in the sediments wasformed virtually simultaneously with the sediment,the deposited sequences will record the alternation ofthe KHR and KRS components. This character of thepaleomagnetic record is observed in that part of theChekurovka section which has not been remagnetizedby the Mesozoic field (Pavlov et al., 2004).

In the case the magnetization was formed rapidlybut still with a certain delay commensurate with theduration of the KRS epochs, the KHR-component onsome levels of the section will be observed alone,whereas on the other levels this component will besuperimposed on the relatively weaker KRS-compo-nent. The presence of the latter can probably be onlyperceived through the trends of the Zijderveld dia-grams and through the remagnetization circles tendingtowards Kirschvink’s component. Clearly, the KHR-component in this case will frequently be present inthe samples as an intermediate component. This char-acter of the record is observed, e.g., in the LowerCambrian sections of the Bol’shaya Kuonamka andMaya rivers. In the case when the present-day compo-nent significantly contributes to the magnetization,these trends will be masked and blurred; and the rela-tively close positions of the present-day and Kramov’scomponents will impede their separation.

If the recording of the paleomagnetic signal in therocks lasted significantly longer than the duration ofKRS epochs, it should be expected that during thedemagnetization these rocks will show the presence ofonly one magnetization component. This is observedin the Lower Cambrian rocks of the Pestrotsvetnayaformation from the Belaya River and Sardana Forma-tion of the Kyllakh Ridge.

However, if the paleomagnetic record was formedvery fast (as typically occurs in the sills after theirintrusion) and the direction of the field correspondedto Kirschvink’s pole, we should see the record of the

KRS component alone—the case observed in the sillsof the Neleger River.

Analysis of the Global DataIf the anomalous field actually existed during the

considered time interval, this phenomenon should beon a global scale and should manifest itself on theother continents. In (Shatsillo et al., 2005), we carriedout a detailed analysis of the Vendian–Cambriandetermination contained in the Global PaleomagneticDatabase (Pisarevsky and McElhinny, 2003). In thecited work, we have shown that the presence of twononidentical directions during the Vendian–LowerCambrian can indeed be considered as a global-scaleevent apparently ref lecting the anomalous behavior ofthe Earth’s magnetic field. In this case, the character-istic angular distance between the corresponding polesis typically close to 50°, which is also the case for theSiberian KHR and KRS poles.

A conceptually similar study was recently con-ducted by A. Abrajevitch and R. Van der Voo (2009).These authors analyzed the entire existing data for theEdiacaran of Laurentia and Baltica to come to practi-cally the same conclusions as we obtained a few yearsearlier mainly based on the Siberian data (e.g., (Pavlovet al., 2004; Shatsillo et al., 2005)). Abrajevitch andVan der Voo have shown that the paleomagneticresults determined from different Ediacaran objects ofBaltica and Laurentia definitely point to the coexis-tence of two magnetization components, one shallowand the other steeply inclined. Besides, there aresound arguments (including positive field tests) indi-cating that both components are primary and veryclose in age. The traditional interpretation of thesedata in the scope of the geocentric axial dipolehypothesis requires implausibly high velocities of con-tinental migration which are neither attained by theplate tectonics nor by the true polar wander hypothe-sis. The authors assert that the observed data can onlybe accounted for by the extremely irregular, anoma-lous behavior of the geomagnetic field at that time,which can probably be described by the alternation ofthe co-axial and quasi-equatorial dipole. This behav-ior of the geomagnetic field can emerge under certainspecific conditions in the core and/or at thecore/mantle boundary which, in turn, strongly con-strains the thermal evolution of the inner shells of theEarth.

In the recent work of Halls et al. (2015), based onthe Grenville dikes dated to ~585 Ma, it was shownthat the studied dike swarms that are scattered in ageby at most 4 Ma (perhaps even by a much shorterperiod) carry the primary magnetization with sharplydifferent (by ~90°) directions. The latter cannot beexplained by the ordinary geomagnetic variations, andthe obtained paleomagnetic data cannot be inter-preted as reflecting the tectonic motions. The authorspropose that one of the two directions obtained by

802


PAVLOV et al.

them corresponds to some quasi-stable state of thesubequatorial dipole, which substantially determinesthe geometry of the field during the change of itspolarity. The role of this subequatorial dipole signifi-cantly increases during the periods when the geomag-netic field is in an hyperactive state with extremely fre-quent reversals. It is the combination of highly fre-quent reversals and the presence of a relatively stablesubequatorial dipole that is suggested by the authors toexplain the two sharply different paleomagnetic direc-tions in the Ediacaran rocks of a similar age.

The possibility of the existence of epochs with ahyperactive geomagnetic field characterized by anextremely low intensity and very high variability in thedirections is substantiated in the recent work (Scher-bakova et al., 2017).

Thus, the world data fairly well agree with ourresults for the Siberian Platform and definitely supportour conclusion about the anomalous character of thegeomagnetic field in the Ediacaran–Lower Cambrian.

Anomalous Field at the Precambrian/Cambrian Boundary

In order to explain the observed paleomagneticrecord, we suggest the hypothesis that the geomag-netic field at the Precambrian/Cambrian boundaryhad an anomalous character induced by two alternat-ing quasi-stable generation regimes. In the prelimi-nary form this hypothesis was formulated in our work(Pavlov et al., 2004). According to this hypothesis, themagnetic field of the Earth at the Precambrian/Cam-brian boundary can be described by the alternation oflong periods of predominance of the axial, mainlymonopolar dipole field, which is recorded in the KHRcomponent and the relatively short epochs when themagnetic field was mainly determined by the reversingsubequatorial or midlatitude dipole and recorded inthe form of the KRS component.

A conceptually similar two-dipole model was pro-posed by L. Pesonen and H. Nevanlinna (Nevanlinnaand Pesonen, 1983) to explain the asymmetric rever-sals detected by these authors in the Keweenawan sec-tions (1100–1000 Ma).

Importantly, we do not insist that the observedpaleomagnetic record necessarily needs the imple-mentation of a two-dipole model. The observed phe-nomenon can be alternatively explained, e.g., by thehypothesis of the significant (at times) contribution ofnondipole components in the geomagnetic field at thePrecambrian/Phanerozoic boundary. In any case, theperformed analysis of the Siberian and global paleo-magnetic data indicates that the geomagnetic field inthe latest Vendian and Early Cambrian was signifi-cantly different from the geomagnetic field of most ofthe subsequent epochs.

A very interesting and, perhaps, not coincidentalfact is that the model suggested by has surprisingly

many points in common with the model of the geo-magnetic reversals developed by Khramov and his col-leagues based on the studies of these reversals in theEarly Paleozoic (Khramov and Iosifidi, 2012).According to their model, the field of the geocentricaxial dipole diminishes, up to completely vanishing,during the geomagnetic reversals. However, the geo-magnetic field does not disappear altogether but isdetermined by the superimposition of the equatorialdipole and nondipole components. In this case,according to (Khramov and Iosifidi, 2012), the contri-bution of the nondipole components can make up 15–20% of the dipole axial field. Actually, this modelcould fully describe the peculiarities of the Late Ven-dian–Early Cambrian paleomagnetic record observedby us if we assume the reversals of the nonaxial dipole.In this case, the axial dipole field which is recorded inthe KHR-type components would be the normal,ordinary stable field, whereas the KRS-type compo-nents would reflect a certain transitional state resem-bling the one described in the literature as the excur-sions of the geomagnetic field. In this approach, itshould also be assumed that these excursions (let usrefer to them as superexcursions) have the followingimportant feature: certain predominant approximatelyantipodal positions of the magnetic poles associatedwith the reversals of the nonaxial dipole would beobserved during these events.

The possibility of the existence of this dipole is val-idated by the results of analyzing the set of bipolarpaleomagnetic determinations contained in the Inter-national Paleomagnetic Database (Khramov and Iosi-fidi, 2012). The considered data support the model ofthe paleomagnetic field according to which the fieldincludes a long-surviving component correspondingto the equatorial dipole. This dipole is responsible forthe nonantipodality of the paleomagnetic directions inthe zones of direct and reversed polarity in the sedi-mentary and volcanic sequences. During the intervalfrom 359 to 207 Ma, the equatorial dipole preserved itsintensity at a level of 5 to 8% of the geocentric axialdipole but f lipped its polarity several times. The posi-tions of its northern poles on the surface of the Earthformed two antipodal groups located within or close tothe subduction zones in the periphery of the Pangaeasupercontinent. It is assumed that this localization ofthe equatorial dipole is associated with the descendingbranches of the mantle convection and with thetopography of both boundaries of the Earth’s coreouter part.

Superexcursions should have another importantfeature: in order to leave a sufficiently distinct imprinton the paleomagnetic record, they should last notice-ably longer than the ordinary excursions.

In this case, the hypothesis of the anomalous LateVendian–Early Cambrian geomagnetic field can beformulated in a somewhat different form: the Earth’smagnetic field at the Precambrian/Cambrian bound-



ary was far less stable than in the Cenozoic, and thenormal state of the field corresponding to the axialdipole was frequently interrupted by the geomagneticexcursions. The latter had the following distinctivefeatures: (a) the virtual poles associated with theexcursions were predominantly concentrated in twocoarsely antipodal regions of the globe, which werelocated in the middle-to-low latitudes; (b) the geo-magnetic excursions were more frequent and lastedlonger than in the Cenozoic.

An important point to note is that according to thenumerical simulation carried out by Gissinger et al.(2012), the field during the reversals can be in the statethat is described, in the first approximation, by a tilteddipole. Thus, our model is also fairly consistent withthe results of the numerical simulations if we assume,as in the case of Khramov’s model, that the magneticpoles during the excursions/reversals are localized incertain preferred areas and that these excur-sions/reversals have a relatively longer duration.

The existence of the preferred areas of localizationof the magnetic poles during the reversals was pro-posed by a number of researchers, explained by theexistence of certain heterogeneities at the core/mantleboundary, and is the subject of lively debate (Clement,1991; Tric et al., 1991a; 1991b; Laj et al., 1991a; 1991b;Prevot and Camp, 1993; Hofman, 1991; 1992; Quidel-leur and Valet, 1994).

The probable existence of the dynamo that pre-dominantly generates the equatorial dipole field orcoexistence of the alternating equatorial and axialdipoles was theoretically demonstrated in (Ishiharaand Kida, 2002; Aubert and Wicht, 2004; Gissingeret al., 2012). Both configurations of the field areimplementable in a certain space of parameters deter-mined by the combination of the electrical conductiv-ity and viscosity of the conductive f luid, as well as thethickness of the conductive layer. As noted in (Abraje-vitch and Van der Voo, 2009), the question of whetherthis combination of parameters has ever occurred inthe Earth’s history remains open. It should be born inmind that these parameters significantly depend onthe heat f low intensities in the core and at thecore/mantle boundary; on the composition, the size,and the age of the inner core; and on the thermal prop-erties of the mantle, i.e., on the characteristics whichare still insufficiently well constrained for the geologi-cal history of the Earth.

Our data suggest that the answer to this question isprobably affirmative.

ACKNOWLEDGMENTSThis work was supported by the Russian Science

Foundation (project no. 161710097). Part of the researchconcerning the systematization and interpretation ofthe published and new isotope data was carried outwith the use of the funds provided by the Russian

Foundation for Basic Research under project nos. 17-35-50068 and 17-05-00021. We are grateful toA.G. Iosifidi and V.G. Bakhmutov for their carefulreview of our manuscript. The thermomagnetic analy-sis was carried out using the instruments developed atthe Borok Geophysical observatory by a team led byYu.K. Vinogradov.

REFERENCESAbrajevitch, A. and Van der Voo, R., Incompatible Ediaca-ran paleomagnetic directions suggest an equatorial geomag-netic dipole hypothesis, Earth Planet. Sci. Lett., 2010,vol. 293, nos. 1–2, pp. 164–170.Aubert, J. and Wicht, J., Axial vs equatorial dipolar dynamomodels with implications for planetary magnetic fields,Earth Planet. Sci. Lett., 2004, vol. 221, pp. 409–419.Bazhenov, M.L., Levashova, N.M., Meert, J.G., Golova-nova, I.V., Danukalov, K.N., and Fedorova, N.M., LateEdiacaran magnetostratigraphy of Baltica: evidence formagnetic field hyperactivity? Earth Planet. Sci. Lett., 2016,vol. 435, pp. 124–135. doi 10.1016/j.epsl.2015.12.015Biggin, A.J., Steinberger, B., Aubert, J., Suttie, N., Holme, R.,and Torsvik, T.H., Possible links between long-term geo-magnetic variations and whole-mantle convection pro-cesses, Nature Geosci., 2012, vol. 5, no. 8, pp. 526–533.Butler, R.F., Paleomagnetism: Magnetic Domains to Geolog-ical Terranes. 1998. Electronic edition. http://www.earth.rochester.edu/butlerbook/Clement, B.M., Geographical distribution of transitionalVGPs: evidence for nonzonal equatorial symmetry during theMatuyama–Brunhes geomagnetic reversal. Earth Planet. Sci.Lett., 1991, vol. 104, pp. 48–58.Davydov, V.F. and Kravchinskii, A.Ya., Paleomagnitnyeissledovaniya gornykh porod Vostochnoi Sibiri. Paleomag-netic studies of the rocks of East Siberia, in Nastoyashchee iproshloe magnitnogo polya Zemli (The Present and the Pastof the Magnetic Field of the Earth), Moscow: Nauka, 1965,pp. 294–302.Ernst, R.E., Buchan, K.L., Hamilton, M.A., Okrugin, A.V.,and Tomshin, M.D., Integrated paleomagnetism and U-Pbgeochronology of mafic dikes of the eastern Anabar shieldregion: implication for Mezoproterozoic paleolatitude ofSiberia and comparison with Laurentia, J. Geol., 2000,vol. 108, pp. 381–401.Evans, D.A., Ripperdan, R.L., and Kirschvink, J.L.,Response: Polar wander and the Cambrian. Science, 1998,vol. 279, p. 9a. Technical comment. www.sciencemag.org.Gallet, Y. and Pavlov, V.E., Three distinct reversing modesin the geodynamo, Izv., Phys. Solid Earth, 2016, vol. 52,no. 2, pp. 291–296.Gallet, Y., Pavlov, V.E., Semikhatov, M.A., and Petrov, P.Ju.,Late Mesoproterozoic magnetostratigraphic results from Sibe-ria: paleogeographic implications and magnetic field behavior,J. Geophys. Res., 2000, vol. 105, no. B7, pp. 16481–16499.Gallet, Y., Pavlov, V., and Courtillot, V., Magnetic reversalfrequency and apparent polar path of the Siberian platformin the earliest Paleozoic, inferred from the Khorbusuonkariver section (northeastern Siberia), Geophys. J. Int., 2003,vol. 154, pp. 829–840.Geologicheskaya karta SSSR masshtaba 1 : 1000000 (novayaseriya). Ob”yasnitel’naya zapiska. List R-(50)-52. Tiksi(Geological Map of the USSR, scale 1:1000000, new series.

804


PAVLOV et al.

Explanatory Note. Sheet R-(50)-52. Tiksi), Mezhvilk, A.A.and Markov, F.G., Eds., Leningrad: Ministerstvo geologiiSSSR, VSEGEI, 1983.The Geologic Time Scale 2012, vol. 1, Gradstein, F.M.,Ogg, J.G., Schmitz, M.D., and Ogg, G.M., Eds., Amster-dam: Elsevier, 2012.Gissinger, C., Petitdemange, L., Schrinner, M., andDormy, E., Bistability between equatorial and axial dipolesduring magnetic field reversals. 2012. arXiv:1203.4144[physics.f lu-dyn].Halls, H.C., Lovette, A., Hamilton, M.A., and Soderlund, U.,A paleomagnetic and U–Pb geochronology study of thewestern end of the Grenville dyke swarm: rapid changes inpaleomagnetic field direction at ca. 585 Ma related to polarityreversals?, Precambrian Res., 2015, vol. 257, pp. 137–166.Hofman, K.A., Long-lived states of the geomagnetic fieldand two dynamo families, Nature, 1991, vol. 354, pp. 273–277.Hofman, K.A., Dipolar reversals state of the geomagneticfield and core-mantle dynamics, Nature, 1992, vol. 359,pp. 789–794.Ishihara, N. and Kida, S., Equatorial magnetic dipole feldintensifcation by convection vortices in a rotating sphericalshell, Fluid Dyn. Res., 2002, vol. 31, pp. 253–274.Kazanskii, A.Yu., Evolution of the structures of westernframing of the Siberian platform from paleomagnetic data,Extended Abstract of Doctoral (Geol.-Miner. Sci.) Disserta-tion, Novosibirsk: Institute of Geology of the SiberianBranch of the Russian Academy of Sciences, 2002.Khabarov, E.M. and Izokh, O.P., Sedimentology and iso-tope geochemistry of Riphean carbonates in the Kharau-lakh Range of northern East Siberia, Russ. Geol. Geophys.,2014, vol. 55, pp. 629–648.Khomentovskii, V.V. and Karlova, G.A., Specifics of theecology of Vendian–Cambrian small shelly fossil biota fromSiberian platform, Stratigr. Geol. Korrel., 1994, vol. 2, no. 3,pp. 8–17.Khomentovskii, V.V. and Karlova, G.A., The boundarybetween the Nemakit–Daldynian and the Tommotian(Vendian–Cambrian) of Siberia, Stratigr. Geol. Korrel.,2002, vol. 10, no. 3, pp. 13–34.Khramov, A.N., Geomagnetic Reversals in the Paleozoic:A transitional field, polarity bias, and mantle convection,Izv., Phys. Solid Earth, 2007, vol. 43, no. 10, pp. 800–810.Khramov, A.N. and Iosifidi, A.G., Asymmetry of geomag-netic polarity: equatorial dipole, Pangaea, and the Earth’score, Izv., Phys. Solid Earth, 2012, vol. 48, no. 1, pp. 28–41.Khramov, A.N., Goncharov, G.I., Komissarova, R.A.,et al., Paleomagnitologiya (Paleomagnetology), Leningrad:Nedra, 1982.Kirschvink, J.L., The least-square line and plane and theanalysis of palemagnetic data, Geophys. J. R. Astron. Soc.,1980, vol. 62, pp. 699–718.Kirschvink, J.L. and Rozanov, A.Ju., Magnetostratigraphyof Lower Cambrian strata from the Siberian Platform:palaeomagnetic pole and preliminary polarity time-scale,Geol. Mag., 1984, vol. 121, no. 3, pp. 189–203.Kirschvink, J.L., Ripperdan, R.L., and Evans, D.A., Evi-dence for a large-scale reorganization of Early Cambriancontinental masses by inertial interchange true polar wan-der, Science, 1997, vol. 277, pp. 541–545.Komissarova, R.A., Paleomagnetism of the Riphean andVendian sediments of Western Baikal region, in Paleomag-

netizm verkhnego dokembriya (Paleomagnetism of UpperPrecambrian), Leningrad: Izd. VNIGRI, 1983, pp. 52–66.Komissarova, R.A. and Osipova, E.P., Results of paleo-magnetic investigation of Middle Riphean–Cambrianrocks of the Maya River, in Magnitostratigrafiya i paleomag-netizm osadochnykh i vulkanogennykh formatsii SSSR (Mag-netostratigraphy and Paleomagnetism of Sedimentary andVolcanic Formations of the USSR), Khramov, A.N., Ed.,Leningrad: VNIGRI, 1986, pp. 5–13.Kravchinsky, V.A., Konstantinov, K.M., and Cogne, J.P.,Paleomagnetic study of Vendian and Early Cambrian rocksof South Ssiberia and Central Mongolia: was the Siberianplatform assembled at that time?, Precambrian Res., 2001,vol. 110, pp. 61–92.Laj, C., Mazaud, A., Weeks, R., Fuller, M., and Herrero-Bervera, E., Geomagnetic reversal paths, Nature, 1991a,vol. 351, p. 447.Laj, C., Mazaud, A., Weeks, R., Fuller, M., and Herrero-Bervera, E., Geomagnetic reversal paths (discussion),Nature, 1991b, vol. 359, pp. 111–112.Meert, J., A paleomagnetic analysis of Cambrian true polarwander, Earth Planet. Sci. Lett., 1999, vol. 168, pp. 131–144.Meert, J. and Van der Voo, R., Comment on 'New palaeo-magnetic result from Vendian red sediments in Cisbaikaliaand the problem of the relationship of Siberia and Laurentiain the Vendian’ by Pisarevsky S.A., Komissarova R.A. andKhramov A.N, Geophys. J. Int., 2001, vol. 146, no. 3, p. 867.Merrill, R., McElhinny, M., and McFadden, P., The Mag-netic Field of the Earth: Paleomagnetism, the Core, and theDeep Mantle, San Diego, CA: Academic, 1996.Nevanlinna, H. and Pesonen, L., Late PrecambrianKeweenawan asymmetric polarities as analyzed by axial off-set dipole geomagnetic models, J. Geophys. Res., 1983,vol. 88, pp. 645–658.Oleinikov, B.V., Mashchak, M.S., Kolodeznikov, I.I.,Kopylova, A.G., Savvinov, V.T., Tomshin, M.D., andTulasynov, B.N., Petrologiya i geokhimiya pozdnedokembri-iskikh intruzivnykh bazitov Sibirskoi platformy (Petrologyand Geochemistry of Late Precambrian Intrisive Basites ofthe Siberian Platform), Novosibirsk: Nauka, 1983.Osipova, E.P., Paleomagnetism of the Middle CambrianDeposits within the Western Limb of the Chekurovka Anti-cline, in Paleomagnetizm i akkretsionnaya tektonika (Paleo-magnetism and Accretionary Tectonics), Khramov, A.N.,Ed., Leningrad: VNIGRI, 1988, pp. 93–100.Paleomagnitnye napravleniya i paleomagnitnye polyusa(PNiP). Dannye po SSSR (Paleomagnetic Directions andPaleomagnetic Poles (PNiP). Data for the USSR),Khramov, A.N., Ed., vol. 1., Leningrad, 1971.Paleomagnitnye napravleniya i paleomagnitnye polyusa(PNiP). Dannye po SSSR (Paleomagnetic Directions andPaleomagnetic Poles (PNiP). Data for the USSR),Khramov, A.N., Ed., vol. 2, Moscow, 1973.Paleomagnitnye napravleniya i paleomagnitnye polyusa(PNiP). Dannye po SSSR (Paleomagnetic Directions andPaleomagnetic Poles (PNiP). Data for the USSR),Khramov, A.N., Ed., vol. 6., Moscow, 1986.Powerman, V.I., Pasenko, A.V., and Shatsillo, A.V., TheKazan Center for Petrochronology: first results of datingthe zircons from the Neoproterozoic formations of thenortheastern and western regions of the Siberian platform,in Problemy tektoniki i geodinamiki zemnoi kory i mantii.Materialy L (50-go) yubileinogo Tektonicheskogo sovesh-



chaniya (Problems of Tectonics and Geodynamics of theCrust and Mantle: Proc. L (50th) Jubilee Tectonic Confer-ence), Moscow: GEOS, 2018, vol. 2, p. 61.Pavlov, V.E., Gallet, Y., and Shatsillo, A.V., Paleomagne-tism of the Upper Riphean Lakhandinskaya group in theUchuro-Maiskii area and the hypothesis of the Late Pro-terozoic supercontinent, Izv., Phys. Solid Earth, 2000,vol. 36, no. 8, pp. 638–648.Pavlov, V.E, Gallet, Y., Shatsillo, A.V., and Vodovozov, V.Yu.,Paleomagnetism of the Lower Cambrian from the Lower LenaRiver valley: constraints on the apparent polar wander pathfrom the Siberian Platform and the anomalous behavior of thegeomagnetic field at the beginning of the Phanerozoic, Izv.,Phys. Solid Earth, 2004, vol. 40, no. 2, pp. 114–133.Pidgeon, R.T., O’Neil, J.R., and Silver L.T., Uranium andlead isotopic stability in a metamict zircon under experi-mental hydrothermal conditions, Science, 1966, vol. 154,pp. 1538–1540. doi 10.1126/science.154.3756.1538Pisarevskii, S.A., Paleomagnetism of Cambrian sedimentsfrom the Olenek River section, in Magnitostratigrafiya ipaleomagnetizm osadochnykh i vulkanogennykh formatsii SSSR(Magnetostratigraphy and Paleomagnetism of Sedimentaryand Volcanic Formations of the USSR), Khramov, A.N., Ed.,Leningrad: VNIGRI., 1986, pp. 14–23.Pisarevsky, S.A. and McElhinny, M.E., Global paleomag-netic visual data base developed into its visual form, EOSTransact., 2003b, vol. 84, no. 20, p. 45.Pisarevsky, S.A., Gurevich, E.L., and Khramov, A.N.,Paleomagnetism of Lower Cambrian sediments from theOlenek river section (northern Siberia): paleopoles and theproblem of magnetic polarity in the Early Cambrian, Geo-phys. J. Int., 1997, no. 130, pp. 746–756.Pisarevsky, S.A., Komissarova, R.A., and Khramov, A.N.,Reply to comment by J.G. Meert, R. Van Der Voo on 'Newpalaeomagnetic result from Vendian red sediments in Cis-baikalia and the problem of the relationship of Siberia andLaurentia in the Vendian’, Geophys. J. Int., 2001, vol. 146,no. 3, p. 871.Prevot, M. and Camps, P., Absence of preferred longitudi-nal sectors for poles from volcanic records of geomagneticreversals, Nature, 1993, vol. 366, pp. 53–57.Prokopiev, A.V., Khudoley, A.K., Koroleva, O.V., Kaza-kova, G.G., Lokhov, D.K., Malyshev, S.V., Zaitsev, A.I.,Roev, S.P., Sergeev, S.A., Berezhnaya, N.G., andVasiliev, D.A., The Early Cambrian bimodal magmatismin the northeastern Siberian craton, Rus. Geol. Geophys.,2016, vol. 57, no. 1, pp. 155–175.Quidelleur, X. and Valet, J.P., Paleomagnetic records ofexcursions and reversals: possible biases caused by magne-tization artifacts, Phys. Earth Planet. Inter., 1994, vol. 82,pp. 27–48.Rodionov, V.P., Paleomagnetism of the Upper Precam-brian and Lower Paleozoic in the region of the UdzhaRiver, in Paleomagnitnye metody v stratigrafii (Paleomag-netic Methods in Stratigraphy), Leningrad: VNIGRI, 1984,pp. 18–28.Rodionov, V.P., Paleomagnetic characteristic of the Ven-dian/Cambrian boundary section (Chaya River, northernCisbaikalia), Materialy mezhdunarodnoi shkoly-seminara“Problemy paleomagnetizma i magnetizma gornykh porod”(Proc. Int. Workshop “Problems of Paleomagnetism andRock Magnetism), Shcherbakov, V.P., Ed., St. Petersburg:SOLO, 2014, pp. 147–152.

Rozanov, A.Yu., Repina, L.N., Apollonov, M.K.,Shabanov, Yu.Ya., et al., Kembrii Sibiri (The Cambrian ofSiberia), Transact. Inst. Geol. Geophys. SB RAS, vol. 788,Novosibirsk: Nauka, 1992.Shatsillo, A.V., Didenko, A.N., and Pavlov, V.E., Twocompeting paleomagnetic directions in the Late Vendian:new data for the SW region of the Siberian platform, Russ.J. Earth Sci., 2005, vol. 7, no. 4.Shcherbakova, V.V., Biggin, A.J., Veselovskiy, R., Shatsillo, A.,Hawkins, L., Shcherbakov, V., and Zhidkov, G., Was theDevonian geomagnetic field dipolar or multipolar?Paleointensity studies of Devonian igneous rocks from theMinusa Basin (Siberia) and the Kola Peninsula dykes, Rus-sia, Geophys. J. Int., 2017, vol. 209, pp. 1265–1286.Sidorova, E.P., Results of paleomagnetic studying theLower and Middle Cambrian sediments from Lena andOlekma rivers, in Magnetizm gornykh porod i paleomagne-tizm (Rock Magnetism and Paleomagnetism), Krasnoyarsk:SO AN SSSR, 1963, 403–408.Sidorova, E.P., Paleomagnetic studies of Sinian and Cam-brian sediments in the region of Maya River, in Nastoyash-chee i proshloe magnitnogo polya Zemli (The Present and thePast of the Earth’s Magnetic Field), Moscow: Nauka, 1965,pp. 304–309.Tauxe, L., Essentials of Paleomagnetism, Berkeley: Univ. ofCalifornia, 2010.Torsvik, T.N., Tait, J., Moralev, V.M., McKerrow, W.S.,Sturt, B.A., and Roberts, D., Ordovician paleogeography ofSiberia and adjacent continents, J. Geol. Soc. London, 1995,vol. 152, pp. 279–287.Torsvik, T.H., Meert, J.G., and Smethurst M.A. Polar wan-der and the Cambrian, Science, 1998, vol. 279, p. 9a. Tech-nical comment. www.sciencemag.org.Torsvik, T.H., Van der Voo, R., Preeden, U., Mac Niocaill, C.,Steinberger, B., Doubrovine, P.V., Van Hinsbergen, D.J.J.,Domeier, M., Gaina, C., Tohver, E., Meert, J.G.,McCausland, J.A., and Cocks L.R.M., Phanerozoic polarwander, palaeogeography and dynamics, Earth Sci. Rev.,2012, vol. 114, pp. 325–368.Tric, E., Laj, C., Jehanno, C., Valet, J.-P., Kissel, C.,Mazaud, A., and Iaccorino, S., High-resolution record ofthe upper Ollduvai transition from Po valley (Italy) sedi-ments; supports for dipolar transition geometry?, Phys.Earth Planet. Inter., 1991a, vol. 65, pp. 319–336.Tric, E., Laj, C., Valet, J.-P., Tucholka, P., Paterne, M.,and Guichard, F., The Blake geomagnetic event: transitionalgeometry, dynamical characteristics and geomagnetic signifi-cance, Earth Planet. Sci. Lett., 1991b, vol. 102, pp. 1–13.Veselovsky, R.V., Petrov, P.Yu., Karpenko, S.F., Kosti-tsyn, Yu.A., and Pavlov, V.E., New paleomagnetic and iso-topic data on the mesoproterozoic igneous complex on thenorthern slope of the Anabar massif, Dokl. Earth Sci., 2006,vol. 411, no. 8, pp. 1190–1194.Veselovskiy, R.V., Pavlov, V.E., and Petrov, P.Yu., Newpaleomagnetic data on the Anabar uplift and the Uchur–Maya region and their implications for the paleogeographyand geological correlation of the Riphean of the Siberianplatform, Izv., Phys. Solid Earth, 2009, vol. 45, no. 7,pp. 545–566.

Translated by M. Nazarenko

SPELL: 1. OK

Systematics of Early Cambrian Paleomagnetic Directions...

Documents

Transcript of Systematics of Early Cambrian Paleomagnetic Directions...