Late Vendian Unfolded Molasse in the Northeastern, Eastern, and Southwestern Peripheries of the East...

ISSN 0016�7029, Geochemistry International, 2013, Vol. 51, No. 1, pp. 44–64. © Pleiades Publishing, Ltd., 2013.Original Russian Text © A.V. Maslov,V.P. Podkovyrov, 2013, published in Geokhimiya, 2013, Vol. 51, No. 1, pp. 50–71.

44

INTRODUCTION

The Vendian in the East European Platform wasmarked by the widening of sedimentation basins, theactive influx of sedimentary material, and the develop�ment of a number of large depressions, such as Mezen�skaya, Verkhnekamskaya, and Shkapovsko–Shikhin�skaya (Fig. 1) [2–4], which are filled with so�called

unfolded allochthonous molasses [6, 7].1 This termino�

logical expression, which is used in the title of this pub�lication and is widely applied in the text below, has longbeen utilized in the geological literature [7–9] and wascoined in view of the fact that the foredeep north of theAlps is filled with rudaceous molasses consisting of theeroded material from the neighboring growing moun�

1 Sochava [5] referred to this molasse as a teleorogenic formation.

tain structures and composing two zones: southern andnorthern [7]. The former zone is no more than 20 kmwide and is filled by the so�called sub�Alpine or foldedmolasse, whereas the latter zone is much wider andconsists of the so�called unfolded molasse, which iscomprises gently dipping sedimentary rocks made up ofmaterial brought from both neighboring mountainstructures and uplifted platform blocks (such as the Vos�

ges and Schwarzwald). 2 The folded molasse quite often

almost completely consists of material coming from

2 In contrast to the Alpine molasse, such an exhaustively studiedexample of these rocks as the Late Permian molasses in the Ura�lian foredeep was formed predominantly of clastic materialeroded at and transported only from the growing nearby moun�tain structures, and the rocks themselves are dominated bygraywacke and lithic sandstones [10, 11].

Late Vendian Unfolded Molasse in the Northeastern, Eastern, and Southwestern Peripheries of the East European Platform:

Distinctive Lithogeochemical FeaturesV. Maslova and V. P. Podkovyrovb

a Zavaritskii Institute of Geology and Geochemistry, Ural Branch, Russian Academy of Sciences, Pochtovyi per. 7, Yekaterinburg, 620075 Russia

e�mail: [email protected] Institute of Precambrian Geology and Geochronology, Russian Academy of Sciences,

nab. Makarova 2, St. Petersburg, 199034 Russiae�mail: [email protected]

Received October 27, 2010; in final form, August 2, 2011

Abstract—The paper reports data on the lithogeochemistry of sandstones and silty mudstones from UpperVendian sedimentary sequences in the northeastern, eastern, and southwestern peripheries of the East Euro�pean Platform belonging to the so�called unfolded molasse. The sequences are dominated by wackes, arko�ses, subarkoses, litharenites, and sublitharenites, i.e., chemically immature and moderately mature psam�mites, and can be classed with rocks produced by clastic material brought from orogens surrounding the plat�form. The higher TiO2, Al2O3, FeOtot, MgO, Na2O, and K2O concentrations of the psammites than those inthe average cratonic Phanerozoic sandstone (APhSa) testify that the chemical maturing of the rocks was notcompleted. The silty mudstones accompanying the sandstones have a composition closer to those of the aver�age cratonic Phanerozoic shale (APhSh), but this is likely explained by the fact that the rocks were producedof material brought from erosion territories of much greater area. The lithogeochemical data generally indi�cate that these territories were dominated by acid and intermediate magmatic rocks with variable fraction ofsedimentary rocks when the Late Vendian sedimentary associations in question were produced. The distribu�tion of certain indicator trace elements in the sandstones and silty mudstones show that the average compo�sition of the eroded complexes was close to the composition of the post�Archean upper continental crust, butthe erosion areas occasionally (in the Vychegorskii trough and the Shkapovsko–Shikhanskaya depression)contained relatively primitive source rocks. The data points of the great majority of the sandstones and siltymudstones plot in the SiO2–K2O/Na2O and F1–F2 diagrams in the fields of sediments typical of the envi�ronments of active continental margins, which is consistent with the arrangement of the data points of theserocks in the La–Th–Sc, Th–Sc–Zr/10, and Th–Co–Zr/10 diagrams. All of these features confirm that thesedimentary rocks in question affiliate with rock associations produced at an active tectonic regime.

Keywords: Late Vendian; eastern, northeastern, and southwestern peripheries of the East European Platform;lithogeochemistry, unfolded molasse.

DOI: 10.1134/S0016702912110080

GEOCHEMISTRY INTERNATIONAL Vol. 51 No. 1 2013

LATE VENDIAN UNFOLDED MOLASSE IN THE NORTHEASTERN, EASTERN 45

local sources. Along with graywackes, such molassescontain feldspar–quartz, arkose, and sometimes quartzsandstones. The folded molasse differs from theunfolded one in containing more rudaceous rocks andhaving a greater thickness. The folded and unfoldedmolasses are usually separated by an overthrust front.

According to [7] and with regard for certain struc�tural features of Precambrian sections in the East Euro�pean Platform, the following three types of molassescan be recognized. The formations of the first type, towhich the Upper Vendian sedimentary sequences in theBashkirian meganticlinorium and the Shkapovo–Shikhanskaya depression belong, consist of both foldedand unfolded rocks. The formations of the second typeconsist only of folded molasses, whose unfolded ana�logues have never been found so far. The formations ofthe third type, for example, the Late Vendian rocks in

the Timan Range, consist, according to Yu.R. Bekker,only of an unfolded molasse.

One of the sources of the clastic material filling theaforementioned Vendian depression, the Vychegodskiitrough between the Mezenskaya and Verkhnekamskayadepression, and the Dnestrovskii pericratonic depres�sion (which was previously referred to as the Lvov–Kishinev depression) was the neighboring orogenicareas: Uralian, Hyperborean, Caucasian, and Galician[1, 7, 6, 12–14, and others], and the other source wasinternal areas of the East European Platform. The sedi�mentary rocks were produced mainly of clastic materialfrom these two sources, and the variations in the rockassociations at the erosion areas predetermined themostly polymictic and graywacke composition of thesediments [7]. According to [7], this is most clearly pro�nounced in (1) the Late Vendian Ural foredeep, inwhich the inner zone that developed on a folded Riph�

I

II

III

VI

V

IV

Moscow

1

2

3

4

5

6

Fig. 1. Vendian structure of the East European Platform (modified after [1]).(1) Shields, massifs, and anticlyses; (2) observed Riphean graben�shaped troughs; (3) same, inferred; (4) syneclises and depres�sions (I—Moscow, II—Verkhnekamskaya, III—Shkapovsko–Shikhanskaya, Lvov–Kishenev, now referred to as the Dnestro�vskii pericratonic depression, V—Barents Sea, VI—Pricaspian); (5) folded edifices of the Carpathians, Mountainous Crimea,Caucasus, Urals, and Timan; (6) outliers of Precambrian rocks in structures surrounding the platform.

46


MASLOV, PODKOVYROV

ean basement is adjacent to the folded edifice and con�sist of the Ashinskaya Formation (folded Late Vendianmolasse); this zone is separated from the outer zone thatdeveloped on platform structures and consists of rocksof the Bizhbulyakskii Complex (unfolded molasse); (2)Dnestrovskii pericratonic depression, in which the pre�dominant erosion of rocks at the Ukrainian Shield dur�ing the early evolution of the pericraton provided mate�rial for arkose and subarkose sandstones and silty mud�stone of the Mogilev–Podolskaya Group, and the influxof clastic material from the nearby mountainous struc�tures, which occurred in the Vendian where the modernCarpathians are situated now, during the late evolutionproduced much less mature sedimentary sequences ofthe Konilovskaya Group. Sochava et al. [15] believe thatthe molasses include only the lowest three formations ofthe Kanilovskaya Group (see below).

Based on the petrochemistry of terrigenous Vendianrocks in the area, Sochava [5] suggested that the Ven�dian sedimentary sequences were formed in the periph�ery of the East European Platform mostly of the mate�rial provided by the erosion of platform potassic grani�toids. For instance, the mature petrochemicalcomposition of the Mezenskaya and Reshminskaya for�mations in the Mezenskaya depression is, according to[5], inconsistent with orogenic processes that pro�ceeded in the Timan in the Vendian. The petrochemicalsimilarities between rocks in the uppermost Vendiansedimentary sequences in the Southern (Basinskayaand Zinagskaya formations) and Central (Chernoka�menskaya Formation) Urals, on the one hand, and theVaranger–Timan belt, on the other, suggest geneticsimilarities between these rocks and the affiliation of allof them with graywacke turbidite sediments of the con�tinental slope. Their accumulation marked not the col�lision phase in the evolution of the Late Precambrianoceanic basins in the Urals and Timan but the transitionto rifting and spreading. Then the closure of these basinstook place during the Salairian phase of tectonism [5].

The recent analysis of the architecture and composi�tion of the sedimentary filling of the Central Ural frag�ment of the Late Devonian Mezenskii basin has, how�ever, shown that the accommodation space in which theSylvytskaya Group was formed was prepared by the sub�sidence of the northeastern continental margin underthe load of the Timan orogen [16], and the sedimentarymaterial was brought from eroded source areas in the

Timan–Pechora folded area and from eroded basementrocks of the East European Platform [17, 18].

This publication presents our analysis of the princi�pal lithogeochemical features of the terrigenous rocks(sandstones and silty mudstones) found in variouslithostratigraphic units in the aforementioned struc�tures (Table 1). We also attempted to reproduce theenvironments in which these rocks were produced andto compare these environments. In preparing the sec�tions devoted to the Moscow syneclise and Dnestrovskiipericratonic depression, we used data from thePRECSED geochemical database that was compiled atthe Institute of Precambrian Geology and Geochronol�ogy, Russian Academy of Sciences, in St. Petersburgunder the supervision of A.V. Sochava. Inasmuch as thevolume of our analyzed information is fairly large,Table 2–4 show only certain selected statistical data onthe concentrations of major oxides and trace elementsin Late Vendian sandstones and fine�grained terrige�nous rocks from the northeastern, eastern, and south�western peripheries of the East European Platform.

LITHOGEOCHEMISTRYU OF LATE VENDIAN UNFOLDED MOLASSES IN VARIOUS

TERRITORIES

The vertical sections of molasses in the northwesternportion of the Mezenskaya depression were penetratedby numerous holes drilled in the Belomorian–Kuloiskoe Plateau and are exposed in shores of theWhite Sea (Zimnii Bereg, Letnii Bereg, etc.). TheLyamitskaya Formation consists of cyclically alternat�ing thin siltstone and clay beds and gray sandstone units.The lower part of the Verkhovskaya Formation consistsof patchy thinly bedded clay and units of alternatingsiltstone and greenish gray clay, and the upper part ofthis formation is made up of thinly bedded pale gray,slightly purplish siltstone and greenish gray sandstone.The Zimnegorskaya Formation is dominated bymildly purplish gray siltstone with thin sandstonebeds, which are overlain by units of intercalating var�iegated sandstone, siltstone, and clay of the Ergin�skaya Formation [19].

In the log (SiO2/Al2O3) versus log (Fe2O3/K2O)classification diagram [20], the data points of UpperVendian sandstones from the Belomorian–KuloiskoePlateau plot in the fields of wackes, arkoses, subarcoses,

Table 1. Major lithostratigraphic units (formations) of Upper Vendian unfolded molasse in the northeastern, eastern,and southwestern peripheries of the East European Platform discussed in this publication

Belomorian–Ku�loiskoe Plateau Vechegodskii trough Shkapovsko–Shikhan�

skaya depression Moscow syneclise Dnestrovskii peric�ratonic depression

Erginskaya

Zimnegorskaya Mezenskaya Karlinskaya Lyubimskaya Krushanovskaya

Verkhovskaya Krasavinskaya Salikhovskaya Ust'�Pinezhskaya Zharovskaya

Lyamitskaya Ust'�Pinezhskaya Staropetrovskaya Pletenevskaya Danilovskaya



litharenites, sublitharenites, and Fe�sandstones(Fig. 2a). The composition of the mudstone and siltymudstone alternating with these rocks correspond tofields V and VI in the NKM–FM diagram [21](Fig. 2a), which comprise chlorite–smectite–hydrom�ica and hydromica clays rich in feldspars.

The comparison of the composition of Upper Ven�dian sandstone from the Belomorian–Kuloiskoe Pla�teau with the composition of average Phanerozoicsandstone (APhSa) [22] shows that they are closeenough to each other only in terms ofSiO2concentration (Fig. 3a), whereas the concentra�tions of other major oxides, except only for CaO andsometimes also TiO2 and Na2O, in the Vendian sand�stones are notably higher, which suggests that theserocks were formed in environments other than platformones. The chemical composition of the Upper Vendiansilty mudstones from the Belomorian–Kuloiskoe Pla�teau is somewhat closer to the composition of the aver�age Phanerozoic shale (APhSh) [22], but also signifi�cantly differs from the latter in CaO and Na2O concen�trations (Fig. 3b).

The concentrations of several trace elements in ourmudstone and silty mudstones do not any significantlydiffer from the concentrations in APhSh (Fig. 4a). Therocks are notably richer than the upper continentalcrust (UCC) [23] in Li, and the concentrations of Rb,Y, Nb, some LREE and HREE, and also sometimes Thvary within 1.5–2.0 × UCC (Fig. 4b).

The value of the chemical index of alteration CIA[24] of Upper Vendian sandstones from the Belomo�rian–Kuloiskoe Plateau varies from 46 to 73 at amedian of 57 ± 8. The CIAmedian of the silty mudstonesis 64 ± 5. These values testify that the eroded sourcerocks were relatively insignificantly modified by chemi�cal weathering.

In the SiO2–K2O/Na2O diagram [25], Upper Ven�dian sandstones from the Belomorian–Kuloiskoe Pla�teau plot almost exclusively within the field of composi�tions typical of passive continental margins (Fig. 5a).Conversely, the fine�grained terrigenous rocks areprone to plot in this diagram in the field of active conti�nental margins. In the F1–F2 diagram [29], the datapoints of sandstones, mudstones, and silty mudstonesare not any significantly scattered, many of them plot

Table 2. Median, minimum, and maximum concentrations (wt %) of major oxides in sandstones from the Mezenskaya and Sh�kapovsko–Shikhanskaya depressions, Moscow syneclise, and Dnestrovskii pericratonic depression

Component Belomorian–Kuloiskoe Plateau Shkapovsko–Shikhanskaya depression

Dnestrovskii pericratonic depression Moscow syneclise

SiO2

TiO2

Al2O3

Fe2O3tot

MnO

MgO

CaO

Na2O

K2O

P2O5

n 35 25 26 23

Note: numerators show median values and standard deviations, and the denominators are the minimum and maximum values; n is thenumber of analyzed samples.

78.35 5.09±

69.8–90.97�� 74.00 5.69±

65.03–88.00�� 77.86 4.91±

69.72–84.54�� 83.49 7.86±

64.24–95.13��

0.39 0.19±

0.01–0.80�� 0.43 0.18±

0.15–0.77�� 0.49 0.15±

0.19–0.75�� 0.27 0.16±

0.05–0.68��

8.59 2.14±

4.14–11.70�� 11.58 2.41±

5.87–17.36�� 9.51 2.20±

6.63–13.09�� 6.24 2.88±

0.69–14.24��

3.60 1.89±

1.12–11.45�� 4.30 1.32±

1.88–7.00�� 2.53 0.90±

1.17–4.31�� 2.83 1.36±

0.85–6.11��

0.05 0.06±

0.01–0.21�� 0.09 0.03±

0.04–0.13�� 0.07 0.04±

0.02–0.20�� 0.08 0.24±

0.01–0.78��

1.22 0.78±

0.10–3.04�� 1.60 0.84±

0.26–3.75�� 0.81 0.51±

0.20–1.88�� 0.62 0.85±

0.10–3.78��

0.55 1.36±

0.08–7.12�� 0.76 0.37±

0.40–2.10�� 0.62 1.49±

0.19–6.79�� 0.74 2.41±

0.17–10.71��

0.79 0.55±

0.07–2.41�� 2.40 0.96±

0.90–4.40�� 1.42 0.53±

0.94–2.75�� 1.16 0.59±

0.08–2.28��

2.10 0.63±

1.04–3.96�� 1.89 0.87±

0.62–4.31�� 1.90 0.34±

1.29–2.67�� 1.11 0.83±

0.16–3.62��

0.06 0.03±

0.02–0.14�� 0.08 0.04±

0.03–0.19�� 0.05 0.02±

0.01–0.10�� 0.05 0.04±

0.02–0.16��

48


MASLOV, PODKOVYROV

Table 3. Median, minimum, and maximum concentrations (wt %) of major oxides in silty mudstones from the Mezenskaya andShkapovsko–Shikhanskaya depressions, Moscow syneclise, and Dnestrovskii pericratonic depression

Compo�nent

Mezenskaya depressionShkapovsko–Shikhanskaya

depressionDnestrovskii peric�ratonic depression

Moscow synecliseBelomorian–Kuloiskoe

PlateauVychegodskii

trough

SiO2

TiO2

Al2O3

Fe2O3tot

MnO

MgO

CaO

Na2O

K2O

P2O5

n 60 28 57 53 57

Note: numerators show median values and standard deviations, and the denominators are the minimum and maximum values; n is thenumber of analyzed samples.

59.8 3.27±

54.97–69.72�� 62.65 1.64±

59.30–66.24�� 61.11 3.86±

51.67–67.63�� 60.54 2.74±

56.34–66.55�� 57.35 3.27±

52.35–66.48��

0.87 0.18±

0.56–2.08�� 0.84 0.07±

0.62–0.94�� 0.75 0.11±

0.43–1.06�� 0.86 0.19±

0.31–1.07�� 0.80 0.11±

0.60–1.06��

16.46 1.60±

10.76–20.82�� 15.28 0.94±

14.02–17.35�� 15.49 1.79±

10.02–20.10�� 17.63 1.08±

15.39–21.18�� 18.79 1.15±

16.04–21.14��

8.62 1.16±

3.44–11.47�� 7.56 0.87±

4.76–8.74�� 6.88 1.16±

3.58–9.91�� 7.04 1.73±

4.73–12.93�� 7.80 1.89±

4.82–13.23��

0.07 0.06±

0.01–0.30�� 0.10 0.03±

0.07–0.18�� 0.10 0.09±

0.05–0.66�� 0.06 0.04±

0.01–0.16�� 2.90 0.04±

0.03–��

3.04 0.63±

1.88–4.11�� 2.93 0.20±

2.33–3.19�� 2.71 0.44±

2.02–4.89�� 2.59 0.54±

1.44–3.65�� 2.07 0.41±

1.25–3.29��

0.59 0.61±

0.21–4.33�� 0.89 0.33±

0.33–1.63�� 0.53 1.79±

0.19–13.09�� 0.80 0.51±

0.18–3.05�� 0.39 0.16±

0.21–1.39��

1.48 0.68±

0.11–2.96�� 1.20 0.41±

0.70–2.60�� 2.25 0.46±

1.10–3.08�� 1.29 0.36±

0.41–2.48�� 1.13 0.17±

0.95–1.68��

4.02 0.79±

1.70–5.32�� 3.40 0.53±

2.53–4.66��

3.68 0.80±

2.10–5.63�� 3.18 0.72±

1.56–5.01�� 3.74 0.33±

2.59–4.26��

0.13 0.08±

0.02–0.56�� 0.18 0.15±

0.12–0.97�� 0.13 0.25±

0.08–1.37�� 0.16 0.28±

0.04–2.00�� 0.04 0.10±

0.02–0.70��

within the field typical of the environment of continen�tal volcanic arcs, and some data points fall within thefield of oceanic (young) volcanic arcs (Fig. 5a).

The proportions of La, Th, Cs, Co, and Zr of themudstones and silty mudstones also suggest, accordingto data in [30], that these rocks were accumulated on anactive continental margin and a continental volcanicarc (Fig. 6).

Judging from the arrangement of the data points ofthe sandstones and silty mudstones in the F3–F4 [31]and La/Sc–Th/Co [32] diagrams (Figs. 5c, 5d), theeroded source rocks of the Upper Vendian sedimentarysequence in the northwestern part of the Mezenskayadepression were dominated by rocks of intermediateand acid composition. This conclusion is also corrobo�rated by the Ce, Cr, Co, and Hf ratios of in the mud�stones and silty mudstones in the Co/Hf–Ce/Cr dia�gram [33], in which the data points of the rocks arelocalized near PAAS (Fig. 5e). Finally, the data pointsof Upper Vendian fine�grained rocks from the Belomo�rian–Kuloiskoe Plateau plot in the Hf–La/Th diagram

[27] mostly close to the composition of mature conti�nental crust (Fig. 5f).

In the Vychegodskii trough in the southern portionof the Mezenskaya depression, Upper Vendian fine�grained terrigenous rocks of the Ust’�Pinezhskaya,Krasavinskaya, and Mezenskaya formations were sam�pled in the core material of Borehole Kel’tma 1. TheUst’�Penzhinskaya Formation comprises dark siltymudstones and mudstones with rare siltstone and siltysandstone beds. The Krasavinskaya Formation consistsof mudstones and silty mudstones with beds of greenishgray siltstones and sandstones. The Mezenskaya For�mation consists of units of alternating greenish gray andvariegated mudstones, siltstones, and more rare sand�stones.

As follows from the arrangement of the data pointsof the fine�grained terrigenous rocks of the three afore�mentioned formations in the NKM–FM diagram(Fig. 2B), the chemistries of these rocks are practicallyindistinguishable from those of Upper Vendian siltymudstones from the Belomorian–Kuloiskoe Plateau.



At the same time, the major�oxide compositions ofthese rocks normalized to AphSh show that the rocksare quite similar, and the CaO deficit so typical of theUpper Vendian fine�grained terrigenous rocks in theBelomorian–Kuloiskoe Plateau is pronounced not asapparently in these rocks (0.7 and 0.4, respectively).

The comparison of the concentrations of certaintrace elements in the Upper Vendian silty mudstonesfrom the Vychegodskii trough with the concentrationsin APhSh indicates that these values do not exhibit anystatistically significant differences (Fig. 4c). Signifi�cantly uneven distributions are typical of the concentra�

1.5

1.0

0.5

0

–0.52.52.01.51.00.50

1

0.1

0.010.60.40.20

log(SiO2/Al2O3)

log(

Fe 2

O3/

K2O

)

Fe�shales

shales

wackes

arkoses subarkoses

Fe�sandstones

sub�arenites

quartz arenites

15

3 4

(a)

NKM

(b)

1

234

5

I

II

III

VI

V

IV

FM

Fig. 2. Composition of sandstones and silty mudstones from Upper Vendian unfolded molasse in (a) the log(SiO2/Al2O3)–log(Fe2O3tot/K2O) and (b) NKM–FM diagrams.Fields in the NKM–FM diagram: I—clays of predominantly kaolinite composition; II—clays of predominantly montmorillo�nite composition with minor amounts of kaolinite and hydromica, III—clays of predominantly chlorite composition with minoramounts of Fe�hydromica, IV—chlorite–hydromica clays, V—chlorite–smectite—hydromica clays, VI—hydromica clays withhigh concentrations of finely divided feldspars. NKM is the normalized alkalinity modulus: (Na2O + K2O)/Al2O3, FM is themafic modulus: (Fe2O3tot + MgO)/SiO2 [21].

10

1

0.1

0.01

P2O

5

Na 2

O

MgO

Al 2

O3

TiO

2

SiO

2

K2O

CaO

FeO

общ

(b)

P2O

5

Na 2

O

MgO

Al 2

O3

TiO

2

SiO

2

K2O

CaO

FeO

общ

(d)

10

1

0.1

0.01

(a) (c)

Fig. 3. APhSa� and APhSh�normalized major�oxide compositions of (a, c) sandstones and (b, d) silty mudstones of Late Vendianage from, respectively, (a, b) the Belomorian–Kuloiskoe Plateau and (c, d) Shkapovsko–Shikhanskaya depression.

50


MASLOV, PODKOVYROV

Table 4. Median, minimum, and maximum concentrations (ppm) of trace elements in Upper Vendian sandstones and silty mud�stones from the Belomorian–Kuloiskoe Plateau, Vychegodskii trough, and Shkapovsko–Shikhanskaya depressions

Element Mezenskaya depression (silty mudstones) Shkapovsko–Shikhanskaya depression

Belomorian–Kuloiskoe Plateau Vychegodskii trough silty mudstones sandstones

Li

Be

Sc

V

Cr

Co

Ni

Cu

Zn

Ga

Ge – –

Rb

Sr

Y

Zr

Nb

Mo

Ag – –

Cd – –

Sn – –

Sb – –

Te – –

Cs

Ba

63.26 15.24±

31.33–100.13�� 40.33 13.84±

32.05–86.27�� 52.46 42.18±

10.19–155.55�� 24.19 10.68±

12.46–69.33��

2.79 0.43±

2.28–3.72�� 1.65 0.75±

0.83–5.27�� 2.48 1.32±

0.54–5.52�� 1.15 0.61±

0.35–3.38��

16.61 2.66±

12.28–20.83�� 11.41 2.80±

5.28–18.07�� 15.63 5.41±

3.33–19.21�� 5.68 2.81±

1.65–13.13��

116.15 18.69±

79.40–154.06�� 106.38 22.40±

52.15–163.93�� 103.31 33.57±

24.10–136.37�� 47.70 20.28±

12.75–122.97��

105.01 17.65±

89.71–137.46�� 59.32 19.98±

29.92–125.11�� 103.72 50.27±

33.41–214.41�� 189.38 82.86±

98.49–422.57��

19.32 4.93±

10.92–28.75�� 15.67 3.36±

8.44–24.29�� 16.25 6.07±

6.37–27.62�� 7.84 2.94±

3.15–15.20��

51.66 13.34±

18.00–66.9�� 25.94 6.53±

16.76–47.91�� 27.30 11.13±

4.44–54.04�� 17.76 5.65±

8.26–38.48��

20.75 21.01±

4.04–94.23�� 33.72 9.01±

15.09–52.97�� 18.27 11.69±

3.25–43.02�� 47.27 24.87±

17.29–111.22��

65.90 10.02±

46.81–83.25�� 69.69 42.28±

46.65–265.78�� 73.24 38.51±

20.69–178.39�� 46.83 19.24±

14.41–120.32��

19.89 2.06±

15.84–23.43�� 17.95 4.13±

9.73–32.74�� 22.40 8.17±

5.82–36.58�� 11.02 3.84±

3.54–19.63��

1.14 0.45±

0.84–2.81�� 1.07 0.19±

0.74–1.58��

143.25 29.59±

61.56–185.87�� 90.74 24.95±

27.82–147.54�� 145.01 61.20±

27.72–249.09�� 51.03 21.19±

21.49–111.16��

105.84 35.22±

75.49–253.05�� 107.16 32.30±

72.47–211.08�� 79.08 34.88±

24.20–141.02�� 88.20 29.55±

24.74–155.18��

31.90 4.76±

25.82–42.04�� 16.31 6.26±

10.35–40.17�� 28.08 27.48±

5.16–120.83�� 11.14 7.36±

3.34–31.87��

211.62 31.06±

154.49–294.43�� 120.26 66.47±

76.16–377.11�� 169.70 107.06±

46.63–465.83�� 97.44 64.97±

28.30–387.45��

19.84 2.78±

15.03–26.04�� 10.28 24.74±

4.78–143.46�� 19.50 11.41±

3.20–52.10�� 9.28 5.58±

2.27–25.14��

0.99 0.90±�� 0.28 0.16±

0.17–0.79�� 0.56 0.92±

0.15–3.83�� 0.52 0.20±

0.28–1.14��

0.18 0.33±

0.08–1.95�� 0.58 0.77±

0.05–4.55��

0.08 0.06±

0.01–0.24�� 0.07 0.06±

0.01–0.26��

1.55 0.55±

0.76–3.72�� 1.33 1.06±

0.49–7.15��

0.23 0.09±

0.16–0.52�� 0.31 0.13±

0.05–0.65��

0.04 0.02±

0.01–0.12�� 0.02 0.02±

0.01–0.08��

3.83 1.54±

3.46–8.43�� 3.74 1.50±

1.03–8.90�� 6.00 3.25±

0.99–12.62�� 1.79 1.71±

0.29–7.69��

310.20 59.55±

266.00–501.20�� 237.47 1402.80±

172.08–8185.19�� 404.41 160.90±

95.57–630.64�� 390.61 467.28±

98.02–2226.21��



Table 4. (Contd.)

Element Mezenskaya depression (silty mudstones) Shkapovsko–Shikhanskaya depression

Belomorian–Kuloiskoe Plateau Vychegodskii trough silty mudstones sandstones

La

Ce

Pr

Nd

Sm

Eu

Gd

Tb

Dy

Ho

Er

Tm

Yb

Lu

Hf

Ta –

W

Tl –

Pb

Bi

Th

U

n 22 32 22 43Note: numerators show median values and standard deviations, and the denominators are the minimum and maximum values; n is the

number of analyzed samples. Dashes mean that no data are available.

49.46 7.11±

28.66–57.80�� 21.88 8.43±

11.19–51.17�� 39.01 28.38±

7.60–125.72�� 12.67 12.34±

3.42–74.49��

97.47 15.08±

60.68–115.02�� 44.37 16.98±

21.65–102.58�� 81.16 59.66±

17.28–255.15�� 25.15 25.31±

6.72–154.78��

11.25 1.58±

7.54–13.49�� 5.59 2.44±

3.22–14.83�� 9.28 7.24±

2.23–30.75�� 3.16 3.68±

0.74–23.20��

41.46 6.83±

27.95–54.22�� 21.75 10.26±

12.86–63.62�� 34.86 27.74±

9.46–113.79�� 13.28 13.92±

2.98–87.70��

7.24 1.72±

4.93–12.46�� 4.10 2.25±

2.57–14.28�� 6.12 5.79±

1.76–24.26�� 2.58 2.43±

0.67–15.10��

1.29 0.37±

0.92–2.69�� 0.86 0.43±

0.56–2.72�� 1.26 1.02±

0.36–4.59�� 0.54 0.49±

0.15–3.13��

5.99 1.54±

4.20–11.21�� 3.56 2.13±

2.36–12.62�� 5.36 5.19±

1.61–23.33�� 2.38 1.93±

0.66–11.09��

0.90 0.22±

0.68–1.65�� 0.49 0.23±

0.33–1.48�� 0.84 0.76±

0.24–3.48�� 0.33 0.26±

0.09–1.30��

5.51 0.99±

4.44–8.48�� 3.28 1.29±

2.17–8.20�� 5.03 4.15±

1.31–18.74�� 2.31 1.54±

0.63–6.59��

1.17 0.16±

0.96–1.48�� 0.65 0.23±

0.43–1.43�� 1.04 0.81±

0.26–3.48�� 0.49 0.31±

0.14–1.31��

3.28 0.36±

2.72–3.76�� 1.85 0.62±

1.20–3.68�� 2.87 2.01±

0.68–8.42�� 1.32 0.88±

0.41–3.88��

0.49 0.05±

0.40–0.59�� 0.27 0.09±

0.17–0.54�� 0.43 0.28±

0.09–1.16�� 0.20 0.13±

0.07–0.64��

3.20 0.37±

2.62–3.94�� 1.82 0.62±

1.13–3.75�� 2.82 1.78±

0.57–6.93�� 1.31 0.88±

0.48–4.34��

0.49 0.07±

0.39–0.64�� 0.27 0.09±

0.16–0.57�� 0.44 0.27±

0.08–1.01�� 0.20 0.13±

0.07–0.64��

5.41 1.34±

3.00–7.77�� 3.18 2.07±

1.93–11.26�� 4.57 2.97±

0.89–13.85�� 2.76 1.79±

0.87–10.16��

1.23 0.18±

0.92–1.55�� 0.62 0.99±

0.29–5.17�� 0.75 0.57±

0.22–3.12��

1.18 0.24±

0.58–1.57�� 0.76 0.36±

0.38–2.40�� 1.37 0.75±

0.29–2.72�� 1.14 0.36±

0.58–2.11��

0.78 0.16±

0.55–1.15�� 0.39 0.17±

0.19–1.10�� 0.45 0.18±

0.16–0.96��

9.09 4.34±

4.83–20.03�� 11.89 9.10±

5.02–51.01�� 15.93 9.07±

2.41–41.65�� 7.90 6.55±

2.01–37.20��

0.17 0.10±

0.05–0.42�� 0.16 0.07±

0.10–0.40�� 0.23 0.17±

0.04–0.76�� 0.09 0.10±

0.02–0.52��

15.36 2.70±

8.94–19.97�� 6.12 2.98±

3.85–16.75�� 14.26 6.36±

2.69–29.39�� 4.69 3.66±

1.78–21.20��

2.22 2.65±

1.27–11.38�� 1.48 1.24±

1.05–6.76�� 2.07 2.80±

0.56–12.87�� 1.30 0.82±

0.39–3.96��

52


MASLOV, PODKOVYROV

tions of Zr, Hf, Nb, and some REE. Compared toUCC, the fine�grained terrigenous rocks in the Vyche�godskii trough are much richer in Li but poorer in Zn,Nb, LREE, Ta, Pb, Bi, and U (Fig. 4d).

The median CIA value of the Upper Vendian siltymudstones in the Vychegodskii trough is 64 ± 3, whichsuggests that the rocks were produced in a climate closeto arid or niveal (snow climate).

In the SiO2–K2O/Na2O and F1–F2 diagrams, thecompositional data points of the Upper Vendian fine�grained terrigenous rocks from the Vychegodskii troughfall within the field of an active continental margin(Figs. 7a, 7b), as the data point of these rocks also do inthe La–Th–Sc and Th–Co–Zr/10 diagrams (Figs. 6c,

6d). Judging from the localization of the compositionpoints of the silty mudstones in the F3–F4 (Fig. 7c) andLa/Sc–Th/Co (Fig. 7d) diagrams, their eroded sourcerocks were, similar to those of the fine�grained terrige�nous rocks in the Belomorian–Kuloiskoe Plateau,mostly acid rocks. At the same time, some of our sam�ples show Th/Co < 2, which suggests that the ancienterosion areas contained certain amounts of mafic mag�matic rocks. The Co/Hf and Ce/Cr ratios of most of ouranalyzed samples are close to those of PAAS, but someof our samples have these ratios close to those in theaverage Archean mudstone [26] (Fig. 7e). The La/Thratio of all of our samples correspond to those of rocksmade up of erosion products of the mature continental

5

4

3

2

1

0

Li

Be

Sc V Cr

Co

Ni

Cu

Zn

Ga

Rb Sr Y Zr

Nb

Mo

Cs

Ba

La

Ce Pr

Nd

Sm Eu

Gd

Tb

Dy

Ho Er

Tm Yb

Lu

Hf

Ta Ti

Pb Bi

Th U

(d)

5

4

3

2

1

0

Li

Be

Sc V Cr

Co

Ni

Cu

Zn

Ga

Rb Sr Y Zr

Nb

Mo

Cs

Ba

La

Ce Pr

Nd

Sm Eu

Gd

Tb

Dy

Ho Er

Tm Yb

Lu

Hf

Ta Ti

Pb Bi

Th U

(b)

5

4

3

2

1

0

(c)

Rb Sr

Ba

Pb

Th U Zr

Hf

Nb

Ta Y La

Ce

Nd

Sm Eu

Gd

Tb

Yb

Lu Sc V Cr

Co

Ni

5

4

3

2

1

0

(а)

Rb Sr

Ba

Pb

Th U Zr

Hf

Nb

Ta Y La

Ce

Nd

Sm Eu

Gd

Tb

Yb

Lu Sc V Cr

Co

Ni

Fig. 4. APhSa� and APhSh�normalized trace�element compositions of Upper Vendian silty mudstones from (a, b) the Belomo�rian–Kuloiskoe Plateau and (c, d) the Vychegodskii trough.



crust, but the Hf concentrations of these rocks indicatethat they can be subdivided into two distinctly differentgroups: one of them does correspond to a “felsicsource”, whereas the other one corresponds to fine�grained aluminosilicate terrigenous rocks produced bythe erosion of less mature rocks (Fig. 7e).

In the Shkapovsko–Shikhanskaya depression, theUpper Vendian rocks (Bizhbulyakskii Complex) com�pose the Baikibashevskaya, Staropetrovskaya

(Kairovskaya Group), Salikhovskaya, and Karlinskaya(Shkapovskaya Group) formations [34, 35], which con�tain much quartz–feldspar, feldspar–quartz, and lithicsandstones. According to [7], the Kairovskaya Sub�group corresponds to the lower molassoid formation,and the Shkapovskaya Group is the upper molassoidformation. However, below we do not consider theBaikibashevskaya Formation in the unfolded molassebecause this formation is, like the Uryuk Formation in

12

7

–3

–830–3

F2

F1

(b)

activecontinentalmargins

oceanicisland/

arcs

6

2

volcanic

continentalvolcanic arc

10

1

0.1

0.011010.1

Th

/Co

La/Sc

(d)values typical of erosionproducts ofacid rocks

values typical oferosionproducts ofmafic rocks

100

10

1

0.1807060

K2O

/Na 2

O

SiO2

(a)passivecontinentalmargins

activecontinentalmarginsoceanic

island arcs

10

–5

–10 0–5

F4

F3

(c)

5

0

12

quartz�richsedimentary

rocks

acid magmatic

rocks

3

1

20100

Ce/

Cr

Сo/Hf

(e)

2

14

2

0 5

La/

Th

Hf

(f)

10

12

PAAS

ApApr

10

8

6

4

tholeiites in oceanicislands

maturecontinental crust (felsic source)

passivecontinentalmargins

maficmagmatic rocks

andesiteisland�arc

source

magmaticintermediate

rocks

Fig. 5. Discriminant diagrams for Upper Vendian sandstones and silty mudstones from the Belomorian–Kuloiskoe Plateau.(1) Sandstones; (2) silty mudstones.F1 = 30.638 × TiO2/Al2O3 – 12.541 × Fe2O3 tot./Al2O3 + 7.329 × MgO/Al2O3 + 12.031 × Na2O/Al2O3 + 35.402 × K2O/Al2O3 –6.382;F2 = 56.5 × TiO2/Al2O3 – 10.879 × Fe2O3 tot/Al2O3 + 30.875 × MgO/Al2O3 – 5.404 × Na2O/Al2O3 + 11.112 × K2O/Al2O3 –3.89;F3 = 0.303 – 0.0447 × SiO2 – 0.972 × TiO2 + 0.008 × Al2O3 – 0.267 × Fe2O3 + 0.208 × FeO – 3.082 × MnO + 0.14 × MgO +0.195 × CaO + 0.719 × Na2O – 0.032 × K2O + 7.51 × P2O5;

F4 = 43.57 – 0.421 × SiO2 + 1.988 × TiO2 – 0.526 × Al2O3 – 0.551 × Fe2O3 – 1.61 × FeO + 2.72 × MnO + 0.881 × MgO – 0.907 ×CaO – 0.177 × Na2O – 1.84 × K2O + 7.244 × P2O5.

54


MASLOV, PODKOVYROV

La

Th

OIA

+C

IA

AC

M PM

Sc

Zr/

10C

oS

c

OIA

CIA

Th

La

Th

La

Th

AC

M

Sc

Zr/

10Z

r/10

PMT

h

OIA

+C

IAA

CM

PM

Sc

OIA

CIA

PMT

h

PM

OIA

CIA

AC

M

PM

(a)

(b)

(c)

(d)

(e)

(f)

Sc

AC

MA

CM

OIA

+C

IA

Fig

. 6. L

a–T

h–

Sc,

Th

–S

c–Z

r/10

, an

d T

h–

Co–

Zr/

10 d

iagr

ams

for

san

dsto

nes

an

d si

lty

mud

ston

es f

rom

(a,

b)

the

Bel

omor

ian

–K

uloi

skoe

Pla

teau

an

d (c

, d)

Sh

kapo

vsko

–S

hik

han

skay

a de

pres

sion

.O

IA m

ean

s oc

ean

ic is

lan

d ar

cs,

CIA

mea

ns

con

tin

enta

l an

d n

ear�

con

tin

ent

isla

nd

arcs

, A

CM

mea

ns

acti

ve c

onti

nen

tal m

argi

ns,

PM

are

pas

sive

con

tin

enta

l mar

gin

s. S

ee F

ig.

5 fo

r ot

her

sym

bol e

xpla

nat

ion

s.



the Bashkirskii meganticlinorium, with which theformer formation is traditionally paralleled [35], madeup exclusively of erosion products of the crystallinebasement of the East European Platform [2].

In the log(SiO2/Al2O3)–log(Fe2O3/K2O) diagram,the data points of Upper Vendian psammites in theShkapovsko–Shikhanskaya depression are constrainedmostly to the fields of wackes, litharenites, and sublith�arenites (Fig. 2a). The fine�grained terrigenous rocks ofthe Staropetrovskaya, Salikhovskaya, and Karlinskayaformations plot in the NKM–FM diagram in fields Vand VI, as also do rocks of granulometrically similarcomposition from the Belomorian–Kuloiskoe Plateauand Vychegodskii trough (Fig. 2b).

The SiO2 concentration in Upper Vendian sand�stones in the Shkapovsko–Shikhanskaya depression is

close to that in APhSa (Fig. 3c), and the rocks have alower CaO concentration and higher concentrations ofother major oxides. The situation with the silty mud�stones is somewhat different: the SiO2, TiO2, Al2O3,FeO, Fe2O3, K2O, and P2O5 concentrations are largelycomparable with those in APhSh, the CaO concentra�tions are usually lower, and the Na2O concentrationsare higher in APhSh (Fig. 3d).

Upper Vendian sandstones in the Shkapovsko–Shikhanskaya depression differ from APhSa in concen�trations of several trace elements (Fig. 8a). The medianSr, Ba, Ta, Sc, V, Cr, and Co concentrations of theserocks are higher than 2.5 × APhSa, and their maximumconcentrations can reach 14 × APhSa. Silty mudstonesfrom Upper Vendian sedimentary sequences in the

10

1

0.1

0.011010.1

Th

/Co

La/Sc

(d)

values typical of erosionproducts ofacid rocks

valuestypical of erosion products of mafic rocks

100

10

1

0.1706050

K2O

/Na 2

O

SiO2



oceanicisland arc

12

–3

–830–3

F2

F1

(b)

activecontinental margins

oceanicisland/

arcs

6

2

volcanic

continental volcanicarcs

–5

–100–5

F4

F3

(c)

5

0

quartz�rich sedimentary

rocks

acid magmaticrocks

3

1

20100

Ce/

Cr

Сo/Hf

(e)

2

14

2

0 5

La/

Th

Hf

(f)

10

12

PAAS

Archean

10

8

6

4

tholeiites inoceanicislands

maturecontinentalcrust(felsic source)

mudstone

andesite island�arc

source

maficmagmaticrocks


intermediatemagmaticrocks

Fig. 7. Discriminant diagrams for sandstones and silty mudstones from the Vychegodskii trough. See Fig. 5 for symbol explana�tions.

56


MASLOV, PODKOVYROV

Shkapovsko–Shikhanskaya depression have medianconcentrations of trace elements fairly close to those inAPhSa (Fig. 8b), and only their Sr and Ni concentra�tions are notably lower than in APhSa.

The median concentrations of several trace elementsin sandstones of the Kairovskaya and Shkapovskayagroups are much lower than in UCC (Fig. 9a), althoughthe maximum concentrations of a number of elementsare only two to four times higher than in the upper crust.Cr is the only element whose median concentration isapproximately 2.0 × UCC. The median concentration

of most trace elements in the silty mudstones are, con�versely, roughly the same as in UCC (Fig. 9b). None ofthe elements is contained in a concentration Cmedian >2.5, and the Ni, Sr, and Mo median concentrations areroughly 0.5–0.6 × UCC or lower.

The median CIA values of Upper Vendian sand�stones and silty mudstones in the Shkapovsko–Shikhanskaya depression are statistically indistinguish�able (re, respectively, 53 ± 6 and 57 ± 4). These valuesled us to provisionally suggest that the ancient erosionareas of the sedimentary rocks of the Kairovskaya and

5

4

3

2

1

0

(b)

Rb Sr

Ba

Pb

Th U Zr

Hf

Nb

Ta Y La

Ce

Nd

Sm Eu

Gd

Tb

Yb

Lu Sc V Cr

Co

Ni

5

4

3

2

1

0

(a)

Fig. 8. (a) APhSa� and (b) APhSh�normalized trace�element patterns of sandstones and silty mudstones from the BizhbulyakskiiComplex (without the Baikibashevskaya Formation) in the Shkapovsko–Shikhanskaya depression.

5

4

3

2

1

0

Li

Be

Sc V Cr

Co

Ni

Cu

Zn

Ga

Rb Sr Y Zr

Nb

Mo

Cs

Ba

La

Ce Pr

Nd

Sm Eu

Gd

Tb

Dy

Ho Er

Tm Yb

Lu

Hf

Ta Ti

Pb Bi

Th U

(b)

5

4

3

2

1

0

(а)

Fig. 9. UCC�normalized trace�element patterns of (a) sandstones and silty mudstones from the Bizhbulyak Complex (withoutthe Baikibashevskaya Formation) in the Shkapovsko–Shikhanskaya depression.



Shkapovskaya groups were practically not affected bychemical weathering.

In the SiO2–K2O/Na2O diagram, the data points ofUpper Vendian sandstones and silty mudstones fromthe Shkapovsko–Shikhanskaya depression plot almostexclusively within the field of active continental margins(Fig. 10a). The same pertains to the data points of therocks in the F1–F2 diagram (Fig. 10b). In the La–Th–Sc diagram, practically all data points of terrigenousrocks of the Kairovskaya and Shkapovskaya groups clus�ter within the ACM field (Fig. 6e), although the Th, Sc,and Zr proportions of these rocks suggest a somewhatdifferent geodynamic provenance of these rocks(Fig. 6f). The F3 and F4 values of sandstones and siltymudstones of these groups (Fig. 10c) indicate that their

eroded source rocks were both sedimentary and igneousacid and intermediate. This is generally consistent withthe distribution of the data points of these rocks in theLa/Sc–Th/Co and Hf–La/Th diagrams (Figs. 10d,10f), although in the latter instance several samples haveHf concentrations close to those in source rocks petro�chemically less mature than the standard “felsicsource”. This is also pronounced in the arrangement ofthe data points of the sandstones and silty mudstones inthe Co/Hf–Ce/Cr diagram (Fig. 10e), in which severalof the data points cluster not far from the averageArchean mudstone.

The unfolded Upper Vendian molasse in the Moscowsyneclise consists of the Pleenevskaya, Ust’�Pinezhs�kaya, and Lyubimskaya (Mezenskaya) formations of the

10

1

0.1

0.011010.1

Th

/Co

La/Sc

(d)valuestypical of erosionproducts ofacid rocks

valuestypical oferosionproducts of mafic rocks

100

10

1

0.1706050

K2O

/Na 2

O

SiO2



oceanicislandarc

12

7

–3

–830–3

F2

F1

(b)passivecontinentalmargins

activecontinental

oceanic island/volcanic

2

arcs

5

–5

–100–5

F4

F3

(c)

5

0

intermediatemagmaticrocks

acidmagmaticrocks

3

1

20100

Ce/

Cr

Сo/Hf

(e)

2

14

2

0 5

La/

Th

Hf

(f)

10

12

PAAS

Archean

10

8

6

4

tholeiites in oceanicislands

maturecontinentalcrust(felsic source)

80

mudstone

margins

mafic magmatic rocks

andesiteisland�arc

source

Fig. 10. Discriminant diagrams for sandstones and silty mudstones from Bizhbulyak Complex (without the Baikibashevskaya For�mation) in the Shkapovsko–Shikhanskaya depression. See Fig. 5 for symbol explanations.

58


MASLOV, PODKOVYROV

Valdaiskaya Group [6]. 3 The Upper Vendian rocks in

the central part of the Moscow syneclise are finergrained than in the Mezenskaya depression; theserocks cease to exhibit typical features of Alpine�typemolasse and rather resemble terrigenous platformformations [7].

The lithochemistry of sandstones and silty mud�stones form this structure are described below based ondata obtained by examining core material from Bore�holes Gavrilov Yam 1, 2, and 5 and BoreholeKrasavino 2 (materials are compiled from thePRECSED database).

In the log(SiO2/Al2O3)–log(Fe2O3/K2O) diagram(Fig. 2a), the data points of Upper Vendian sandstonesfrom the Moscow syneclise fall mostly into the field ofwackes, litharenites, sublitharenites, arkoses, subarko�

3 In analyzing stratigraphic sections of the Upper Vendian in theMoscow syneclise and Dnestovskii pericratonic depression, werely on their stratigraphic subdivision in [3, 15]. According tolater publications, for instance, [35], the Upper Vendian rockson the southern flank of the Yaroslavskaya depression in theMoscow syneclise are subdivided into the Pletnevskaya,Gavrilov�Yamskaya, Nepeitsinskaya, Makar’evskaya, Lyubim�skaya, Reshminskaya (Padunskaya), and Nekrasovskaya forma�tions. At the same time, rocks of the Padunskaya Formation insoutheastern Belomorie were found out to contain traces of theactivity of Diplocraterion parallelum Torell, 1980, whichappeared in the Early Cambrian [36].

ses, Fe�sandstones, and even quartz arenites (Fig. 2a).Much narrower compositional variations are typical ofthe fine�grained terrigenous rocks. In the NKM–FMdiagram, the data points of almost all of our analyzedsamples cluster within field V (Fig. 2b), which corre�sponds to chlorite–smectite–hydromica clays.

The Upper Devonian sandstones from the Moscowsyneclise have notably higher (by factors of approxi�mately 1.4 to 2.9) median concentrations of Al2O3,FeO, Fe2O3, MgO, Na2O, K2O, and P2O5, whereas theCaOmedian content is as low as 0.6 × APhSa. At the sametime, the SiO2 and TiO2 concentrations of the psam�mites are roughly the same as in the average Phanero�zoic cratonic sandstone according to K. Condie (Fig.11a). The differences between the compositions of thefine�grained terrigenous rocks and APhSh are not assignificant. The median concentrations of SiO2, TiO2,Al2O3, MgO, Na2O, and K2O are from 0.9 to 1.07 ×APhSh and are much lower for CaO (~0.3 × APhSh),whereas the median concentration of FeO reaches 1.2 ×

APhSh (Fig. 11b).The median values of CIA for sandstones and silty

mudstones from this structure are remarkably different.The CIAmedian is 55 ± 4 for the former and 71 ± 2 for thelatter. This suggests that the silty mudstones are domi�nated by fine�grained aluminosilicate clastic material

10

1

0.1

0.01

P2O

5

Na 2

O

MgO

Al 2

O3

TiO

2

SiO

2

K2O

CaO

FeO

общ

(b)

(c)10

1

0.1

0.01

(а)

P2O

5

Na 2

O

MgO

Al 2

O3

TiO

2

SiO

2

K2O

CaO

FeO

общ

(d)

Fig. 11. APhSa� and APhSh�normalized concentrations of major oxides of (a, c) sandstones and (b, d) silty mudstones from (a,b) the Valdaiskii Group in the Moscow syneclise and (c, d) the Kanilovskii Complex (three lowermost formations) in the Dnestro�vskii pericratonic depression.



that was produced in a semiarid–semihumid climateat ancient source erosion areas, whereas the sand�stones are made up of highly lithochemically imma�ture material.

The field of the silty mudstones in the SiO2–K2O/Na2O diagram is parallel to the boundaries of theclassification fields and almost completely coincideswith the ACM field (Fig. 12a). The data points of thesandstones fall within both this field and the fields ofpassive continental margins. This is corroborated by thearrangement of the data points in the F1–F2 diagram(Fig. 12b). The distribution of the compositional datapoints of the silty mudstones and sandstones in the F3–F4 diagram suggests that the ancient erosion areas con�sisted of a broad spectrum of sedimentary and mag�

matic rocks when the Valdaiskaya Group was formed(Fig. 12c).

In the territory of the Dnestrovskii pericratonicdepression, which bounds the Ukraininan Shield in thesouth and is adjacent with the Dobruja Baikalides in thesouthwest, the unfolded molasse (continuation of theVendian molasse of the Dobruja foredeep in the terri�tory of the platform) includes the Mogilev�Podol’skayaand Kanilovskaya groups [7]. At the same time, pro�ceeding from geological and petrographic lines of evi�dence, Sochava et al. [15] believe that this genesis likelypertains only to the Danilovskaya, Zharnovskaya, andKrushanovskaya formations of the KanilovskayaGroup; these formations show the least differentiatedSiO2 and Al2O3 concentrations and the highest MgO

100

10

1

0.1807060

K2O

/Na 2

O

SiO2

(d)

100

10

1

0.1806050

K2O

/Na 2

O

SiO2



oceanicisland arcs

12

7

–3

–830–3

F2

F1

(b)passivecontinentalmargins

oceanic

volcanic

2

arcs

10

–5

–10 0–5

F4

F3

(c)

5

0


rocks

70



oceanicislandarcs

12

7

–3

–830–3

F2

F1

(e)

oceanic island/volcanic

2

arcs

–5

–10 0–5

F4

F3

(f)

5

0


rocks

continentalvolcanic arc

acidmagmaticrocks

intermediate magmaticrocks

maficmagmatic rocks

mafic magmaticrocks

continentaяmargins

active


island/


Fig. 12. Discriminant diagrams for sandstones and silty mudstones from (a, b, c) the Valdaiskii Group in the Moscow synecliseand (d, e, f) the Kanilovskii Complex (three lowermost formations) in the Dnestrovskii pericratonic depression. See Fig. 5 forsymbol explanations.

60


MASLOV, PODKOVYROV

and Na2O concentrations in the group. We also adhereto this viewpoint on the strength of the fact that the datapoints of the great majority of sandstones and severalsilty mudstones of the Mogilev�Podol’skaya Groupcluster in the SiO2–K2O/Na2O diagram in the field ofpassive continental margins (Fig. 13).

Along with quartz–feldspar varieties, the sand–silt�stone rocks of the Kanilovskaya Group include wide�spread polymictic/graywacke varieties with fragmentsof acid and mafic volcanics, metamorphic schists, andsiliceous rocks [15, 37]. The chemical composition ofthe sandstones and silty mudstones of the three forma�tions of the Kanilovskaya Group have several parame�ters close to those of clastic rocks in other Upper Ven�dian unfolded molasses filling large depressions in thenortheastern and eastern peripheries of the East Euro�pean Platform (Tables 2, 3). In the log(SiO2 /Al2O3)–log(Fe2O3/K2O) diagram (Fig. 2a), the data points ofsandstones of the Kanolowskaya Group swarm in thefields of wackes, arkoses, and litharenites. The datapoints of litharenites of this group plot in the NKM–FM diagram in fields II (clays of predominantly smec�tite composition with minor amounts of kaolinite andhydromica), V, and VI (Fig. 2b).

The median SiO2 concentration of the sandstones isclose to 0.85 × APhSa, and the maximum SiO2 concen�tration in the psammites is only 1.2 times higher thanthe minimum concentration. The median CaO con�centration is approximately 0.5 × APhSa (the minimumand maximum ones are 0.15 × APhSa and ~5.2 ×APhSa, respectively). The median concentrations ofother major oxides are much higher than in APhSa (byfactors from 1.9 for TiO2 to 3.4 for Na2O). The mini�mum Csample/CAPhSa ratio for Na2O is 2.2, and the maxi�mum one is 6.6, and the analogous values for P2O5 differby almost one order of magnitude (Fig. 11c).

The median SiO2, TiO2, and Al2O3 concentrationsof the silty mudstones generally do not principally differfrom the analogous concentrations of APhSh(Fig. 11d). The median concentrations of MgO, Na2O,and P2O5 are somewhat higher than in APhSh (from1.13 × APhSh to 1.17 × APhSh). The CaOmedian in all ofthe instances discussed above is remarkably lower thanthat in the average cratonic Phanerozoic shale accord�ing to K. Condie, and the FeOtot concentration is 1.3 ×APhSh.

Compared to APhSh, sandstones in theKanilovskaya Group have notably higher median con�centrations of Rb, Ba, Y, V, and Co. The rocks bearslightly elevated median Ni concentrations, whereastheir Pb and Cr concentrations are close to those inAPhSa (Fig. 14a). The median concentrations of prac�tically all trace elements discussed herein are in the siltymudstones lower than in APhSh, and most of these ele�ments are unevenly distributed: the maximum Ba, Pb,Zr, Y, and V concentrations are more than one order ofmagnitude higher than their minimum concentrations,and these coefficients are lower than ten only for themaximum concentrations of Rb, Sr, Cr, Co, and Ni(Fig. 14b).

Sandstones in the three lowermost formations of theKanilovskaya Group show relatively low median valuesof CIA (58 × 4), and this parameter for the silty mud�stones is 68 × 4. Considered together with the issues dis�

100

10

1

0.1907060

K2O

/Na 2

O

SiO2

(b)passivecontinental margins

active continental margins

oceanicislandarc

80

100

10

1

0.1806050

K2O

/Na 2

O(a)

passivecontinental margins

active continental margins

oceanicislandarc

70

1

2

Fig. 13. SiO2–K2O/Na2O diagram for (a) silty mud�stones and (b) sandstones from (1) the Mogilev�Podol’skiiand (b) Kanilovskii Late Vendian groups in the Dnestro�vskii pericratonic depression.



cussed above, these values testify to the relatively weaktransformation of the clastic material by chemicalweathering at the ancient erosion areas. This couldresult either from an arid/niveal climate and/or someclimatic environments close to them or from a signifi�cant effect of tectonism on the processes that producedthe terrigenous material at the erosion areas.

In the SiO2–K2O/Na2O diagram, practically alldata points of the silty mudstones swarm within the fieldof active continental margins (Fig. 12d). The composi�tional data points of the sandstones fall within this fieldand the field of compositions produced at passive con�tinental margins. A roughly analogous arrangement isalso typical of the data points of these rocks in the F1–F2 diagram (Fig. 12e). Based on the distribution of thedata points of the sandstones and silty mudstones in theF3–F4 diagram (Fig. 12f), it is reasonable to suggestthat the erosion regions during the accumulation of theKanilovskaya Group were dominated by intermediateand acid magmatic rocks and sedimentary rocks. Thedata points of the Upper Vendian terrigenous rocksfrom the Dnestrovskii epricratonic depression andMoscow syneclise are generally closely similarly distrib�uted in the aforementioned diagrams.

DISCUSSION AND CONCLUSIONS

It is known that Upper Vendian sedimentarysequences in the northeastern and eastern parts of theEast European Platform are dominated by polymicticand feldspar–quartz sandstones and siltstones [2, 38–40], i.e., rocks produced at sluggish/moderately activetectonic processes (so�called tectono–polymictic levelII, according to V.D. Shutov, which is recognized based

on the proportions of quartz, feldspar, and rock frag�ments in sandstones [41]). As follows from our data (seeabove) on the chemical composition of sandstones fromUpper Vendian sedimentary sequences in the north�eastern, eastern, and southwestern peripheries of theEast European Platform, these sedimentary sequencesare composed of a broad spectrum of psammites:wackes, arkoses, subarkoses, litharenites, sublithareni�tes, and their Fe�rich varieties. This diversity of thechemically immature or mildly mature psammites inthe sedimentary sequences and the absence of anyappreciable amounts of quartz sandstones in thesesequences seems to suggest that that these sedimentarysequences should not be classed with the platform coverbut with the unfolded molasse, i.e., sedimentary depos�its produced when clastic material was brought fromorogenic areas that surrounded the platform. Our datasets do not show any significant differences from oneanother.

The hypothesis that the Upper Vendian sandstonesin the northeastern, eastern, and southwestern periph�eries of the East European Platform cannot be ascribedto typical platform cover is corroborated by the compar�ison of their chemical composition with the composi�tion of the average cratonic sandstone according to K.Condie. The higher TiO2, Al2O3, FeOtot, MgO, Na2O,and K2O concentrations in the psammites than inAPhSa directly testify to the incompleteness of thechemical maturation of the former rocks.

The siltstones accompanying the sandstones in vari�ous structures filled with the Upper Vendian unfoldedmolasse have a composition closer to the average Phan�erozoic cratonic shale, but this can be explained by theproduction of the fine�grained terrigenous rocks of

5

4

3

2

1

0

(b)

Rb Sr

Ba

Pb

Th U Zr

Hf

Nb

Ta Y La

Ce

Nd

Sm Eu

Gd

Tb

Yb

Lu Sc V Cr

Co

Ni

5

4

3

2

1

0

(а)

Fig. 14. APhSa� and APhSh�normalized trace�element patterns of (a) sandstones and (b) silty mudstones in the KanilovskiiComplex (three lowermost formations) in the Dnestrovskii pericratonic depression.

62


MASLOV, PODKOVYROV

material collected from much greater erosion areas.Similar to the sandstones, these rocks are also similar incomposition in various structures and plot mostlywithin fields V and VI in the NKM–FM classificationdiagram, i.e., are normal chlorite–smectite–hydrom�ica and hydromica clays rich in feldspars. Only theUpper Vendian silty mudstones of the KanilovskayaGroup in the Dnestrovskii pericratonic depression beara certain admixture of smectite and kaolinite. Accord�ing to [42], such rocks are typical mostly of environ�ments with an arid climate.

This conclusion is consistent with the chemicalindexes of alteration typical of the silty mudstones andsandstones. The lowest median values of 57 × 4 weredetected in the silty mudstones of the BizhbulyakskiiComplex in the Shkapovsko–Shikhanskaya depression.Sandstones in this structure also show a minimum CIAvalue in our dataset: 53 × 6. The low CIA values typicalof terrigenous rocks from the Shkapovsko–Shikhan�skaya depression can likely be explained by various rea�sons. These are, first, climatic environments similar toarid ones and, second, relatively active tectonism,which precluded the maturation of the clastic materialin the erosion region (modern Southern Urals). LowCIA values of sandstones in unfolded molasse can gen�erally be explained by that the composition of the rockswas formed at a leading role of tectonism, which dimin�ished the effect of chemical transformations at theancient erosion areas.

The minimum median value of CIA (71 × 2) is typi�cal of silty mudstones in the Moscow syneclise. Aclosely similar CIA value was also determined in fine�grained terrigenous rocks in the Dnestrovskii pericra�tonic depression. These rocks were formed at relativelysignificant distances from their source erosion regions,at the minimum effect of tectonism on the sedimenta�tion processes, and this obviously facilitated the chem�ical maturation of the rocks.

Compared to the average Phanerozoic cratonicsandstone, the psammites of the unfolded molasseexhibit relatively narrow ranges of their concentrationsof most trace elements (0.5–1.0, occasionally 2.0 ×APhSa). At the same time, psammites in the Bizhbu�lyak Complex have notably higher (3.0–4.0 × APhSa)concentrations of Sr, Ba, Pb, Nb, Ta, Yb, Sc, V, Cr, andCo than in APhSa, and sandstones from theKanilovskaya Group in the Dnestrovskii pericratonicdepression have median concentrations of Co and Vclose to 3.0 × APhSa.

The concentrations of the great majority of trace ele�ments in silty mudstones in the Upper Vendianunfolded molasse varies from 0.5 × APhSh to 1.5 ×APhSh, and these concentrations are sometimesunevenly distributed. This can also be inferred from thecomparison of the concentration of trace elements insilty mudstones with the analogous concentrations inthe upper continental crust. Most of our silty mudstonesbear average concentrations of trace elements of 0.5–

2.0 × UCC, sometimes as low as 0.5–1.0 (or 1.2) ×UCC.

Both litho� and geochemical data suggest that theancient source erosion areas were dominated by acidand intermediate magmatic rocks with variableamounts of sedimentary rocks when the Upper Vendiansedimentary associations were produced. The distribu�tions of certain indicator trace elements in the sand�stones and silty mudstones indicates that the averagecomposition of the eroded complexes was close to theaverage composition of the post�Archean upper conti�nental crust, as follows from the fact that several datapoints of the rocks cluster near the PAAS point. In cer�tain instances, the erosion areas contained relativelymuch primitive rocks, including those of Archean age.It is reasonable to think that this exactly clastic materialwas brought to the sedimentation basins from the EastEuropean Platform. The fact that the Upper Vendiansedimentary sequences in the Shkapovsko–Shikhan�skaya depression include sandstones and silty mud�stones containing <5 ppm Hf, as is typical of the erosionproducts of arc rock associations (i.e., not completelymature crustal material), seems to be consistent withthis hypothesis.

The overwhelming majority of the data points ofsandstones and silty mudstones from all of the afore�mentioned Upper Vendian sedimentary sequences inthe northeastern, eastern, and southwestern peripheriesof the East European Platform plot in the SiO2–K2O/Na2O and F1–F2 diagrams in the compositionfields of active continental margins, and this is consis�tent with the distribution of the data points in the La–Th–Sc, Th–Sc–Zr/10, and Th–Co–Zr/10 diagrams.Similar to the aforementioned bulk�rock compositionfeatures of the sandstones, this also highlights the pro�nounced paleogeodynamic specifics of the Upper Ven�dian sedimentary sequences in the Mezenskaya andShkapovsko–Shikhanskaya depressions, Vychegodskiitrough, Dnestrovskii pericratonic depression, and eventhe Moscow syneclise and confirms that the rocks affil�iate with sedimentary associations produced in a fairlyactive tectonic regime. This led us to conclude that theUpper Vendian sedimentary sequences in the peripher�ies of the East European Platform cannot be regarded asplate/platform rocks, although they fill major platestructures, such as syneclyses and marginal depressions,whose modern contours were shaped in the Late Ven�dian [6, 43].

Some researchers [44–50 and others] are latelyprone to regard the Late Vendian–Cambrian as anepoch of collision between the Timan–Pechora terrane/peri�Gondwana/Antarctica and the eastern margin ofthe Baltic (Timan–Ural passive margin). The westernperiphery of the Baltic is thereby thought to be markedby the opening of the Yapetus and Tornquist oceans.The Timan–Ural foredeep is treated in these recon�structions as a typical marginal basin in front of theTiman–Pechora–Ural orogen. We believe that an anal�ogous scenario cannot be ruled out for the Dnestrovskii



pericratonic depression, whereas the Moskovskii andMezenskii basins are distal portions of the fore�Timan–Fore�Ural (proto?)foreland system.

ACKNOWLEDGMENTS

The authors thank N.P. Gorbunova, L.A. Tatar�inova, V.P. Vlasov, G.S. Neupokoeva, and G.M. Yatluk(Zavaritskii Institute of Geology and Geochemistry,Ural Branch, Russian Academy of Sciences) for theanalysis of Upper Vendian rocks from the Shkapovsko–Shikhanskaya depression and Vychegodskii trough formajor oxides by XRF on a VRA�30 spectrometer.N.S. Glushkova is thanked for preparing illustrativematerial for this publication. This study was financiallysupported by the Integration Project “Estimating theSources of Material for Sedimentary Basins in North�ern Eurasia: Sedimentation Environments and OrePotential” under the Ural, Siberian, and Far Easternbranches of the Russian Academy of Sciences (projectURO RAS 09�T�5�1019) and the Russian Foundationfor Basic Research (project no. 09�05�00279).

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