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Silurian bentonites in Lithuania: correlations based on sanidine phenocryst composition and graptolite biozonation--interpretation of volcanic source regions/Siluri bentoniidid Leedus: korrelatsioonid sanidiini fenokristallide koostise ja graptoliitide biotsonaalsuse jargi--vulkaanipursete piirkondade interpretatsioon.

INTRODUCTION

Volcanic ashes occurring in palaeontologically well-characterized sedimentary sections offer a unique possibility of detailed correlations between different environments (Kiipli & Kallaste 2002; Kiipli et al. 2006, 2008a, 2009, 2010b, 2011, 2012a, 2012b). The mentioned studies used magmatic sanidine composition of bentonites (altered volcanic ashes) analysed by X-ray diffractometry as a correlation criterion. The good precision of that method, up to [+ or -] 1% in favourable cases (Kiipli et al. 2011), enables discrimination of bentonites of quite similar composition. This is an important property, because successive eruptions from the same volcanic source can be characterized by very similar geochemical and mineralogical signatures (Kiipli et al. 2010a). Other methods, e.g. palaeontological, used in combination with sanidine composition of bentonites, provide the most reliable correlation. A negative aspect of using sanidine composition for fingerprinting bentonites is that magmatic sanidine is unstable at Earth's surface temperatures. Elevated diagenetic or metamorphic temperatures accelerate recrystallization significantly and Early Palaeozoic sanidine is often not preserved in some other regions. Sanidine may also be absent in source magma. To avoid these shortcomings, researchers have used the composition of apatite phenocrysts (Batchelor 2009; Carey et al. 2009; Ray et al. 2011) or trace elements for proving correlations (Huff et al. 1998; Kiipli et al. 2008b, 2013a); Inanli et al. 2009; Hetherington et al. 2011. Up to now we have studied mostly Estonian and Latvian sections (Kiipli & Kallaste 2006; Kiipli et al. 2010a, 2011, 2012a). Some Silurian bentonites of Lithuania have been studied by Kiipli et al. (2008c) using the same methods. The occurrence of bentonites in the Silurian of Lithuania is also described in Lapinskas (1965, 2000) and Motuza et al. (2002). The areal distribution schemes of ca 20 bentonites from Estonia, Latvia and Scandinavia indicate volcanic sources from the Iapetus Palaeo-Ocean in the Telychian and Lower Sheinwoodian (Kiipli et al. 2008b, 2008d, 2010b, 2012a, 2013a). Several other researchers discuss a possible Central European source for ash beds (Batchelor & Jeppsson 1999; Bohnke & Katzung 2001; Hetherington et al. 2011). Thick bentonites and massive volcanic rocks of Silurian age are known from Belgium (Andre et al. 1986) and Poland (Timmerman 2008). So, according to the geological data, two source regions, the Central European and Norwegian Caledonides, were possible and Lithuania is in a key position for discriminating between these sources. The distribution of graptolites in Lithuanian sections has been studied by Paskevicius (1982, 1997), Radzevicius (2006), Radzevicius & Paskevicius (2000, 2005) and Radzevicius et al. (2008). The correlation of graptolite biozones applied in different regions of the world is given in Loydell (2012). We studied in detail two Lithuanian drill core sections. Our aim was to extend bentonite correlations to the south and better recognize volcanic sources from the margins of the Iapetus and Rheic Palaeo-Oceans.

MATERIAL AND METHODS

Forty-six bentonite samples were collected from the Siupyliai-69 and Kurtuvenai-166 drill cores (Fig. 1). Twenty-three bentonites from other Lithuanian cores, seven of which have been published in Kiipli et al. (2008c), are also included in the present report (Table 1). Bentonites in predominantly grey Silurian shales were recognized by their yellowish or bluish colour. They are very thin, mostly only a few millimetres and rarely up to a few centimetres thick.

Biostratigraphy is based on over 200 rock samples taken from the Llandovery-Ludlow interval of the Vidukle-61 (Kiipli et al. 2008c), Siupyliai-69 and Kurtuvenai-161 (Radzevicius & Paskevicius 2000, 2005; Motuza et al. 2002; Kaminskas et al. 2006) drill cores for the study of graptolites. Sampling density increased near the ash layers. Rhabdosomes were extracted from samples using HCl or HF acids. Graptolites were examined under a light microscope in Vilnius University.

To identify major minerals in the sampled interbeds of supposed volcanic origin, bulk samples were analysed by X-ray diffractometry (XRD). An association of illitesmectite and kaolinite as major minerals has been considered to indicate the volcanic origin of the interbeds (Kiipli & Kallaste 2002; Hints et al. 2008). Authigenic K-feldspar forms a significant portion of some bentonites. Host shales are composed of a different association of terrigenous minerals, including illite, quartz, chlorite and minor K-feldspar.

Magmatic sanidine phenocrysts (K,Na,Ca)Al[Si.sub.3][O.sub.8] were analysed in coarse fractions (0.04-0.1 mm) separated from 2 g of bentonite using the method described in detail in Kiipli et al. (2011). Various examples of sanidine XRD spectra are published in Kiipli & Kallaste (2006) and Kiipli et al. (2006, 2010a). All measured XRD spectra of sanidine in Lithuanian bentonites are available in the collections database of the Institute of Geology at Tallinn University of Technology at http://sarv.gi.ee/reference.php?id=2544.

RESULTS

Bulk bentonite mineralogy

Kaolinite is a common major component besides illitesmectite, whereas K-feldspar is relatively rare and occurs in lower concentrations. Pyroclastic quartz is present in almost all bentonites in ca 1% concentration. Reflections of anatase appear on XRD patterns starting from Ti[O.sub.2] concentrations of ca 1%. Authigenic pyrite and its weathering products gypsum and jarosite are frequent in bentonites. Complete weathering of pyrite in bentonites and exceptional abundance of gypsum and jarosite is remarkable in the Siupyliai-69 section. This feature facilitates separation of the pyroclastic material, as the grain fraction does not require treatment with nitric acid for removal of pyrite.

Sanidine composition

Silurian bentonites of Lithuanian cores are mostly characterized by wide and very wide XRD 201 reflections of the main sanidine component (Table 1, Fig. 2). Only 14 of the 59 samples studied contain sanidine with sharp reflection having the best correlation value. Besides the sanidine main component, also other less abundant components are present in samples. These are mostly more potassic than the main component, but sometimes also more sodic like in the Y-bentonite known from Gotland (Kiipli et al. 2008a). The combination of the main and less frequent components often forms a unique shape of the 201 reflection, which can be used for identification of the eruption layers.

Graptolites

Graptolite studies started in Lithuania in the middle of the 20th century (Paskevicius & Radzevicius 2006). Earlier overall results of graptolite biozonation are available in Paskevicius (1982, 1997). Later research has focused on certain intervals, e.g. the Wenlock-Ludlow boundary (Radzevicius 2006; Radzevicius et al. 2008). New data allowed revision of the Silurian graptolite biostratigraphy of Lithuania (see Fig. 3). However, the graptolite stratigraphic scale presented in Fig. 3 is not accurate. It has some shortcomings that will be discussed below.

Graptolites near the Aeronian-Telychian boundary need revision. The appearance of Rastrites linnaei (Barrande) is marked by the lower boundary of the Telychian in Lithuania. According to Loydell (2012), the base of the linnaei Biozone does not conform to the base of the Telychian, since R. linnaei appears in the upper part of the Aeronian. So, he recommended that the Stimulograptus halli Biozone should be included in the upper part of the Aeronian, the Spirograptus guerichi Biozone in the lower part of the Telychian and the linnaei Biozone rejected.

Another problematic interval, which should further be investigated in Lithuania, is the upper part of the lapworthi Biozone in the upper Llandovery. According to Loydell (2012), the Cyrtograptus insectus Biozone occurs between the lapworthi and centrifugus biozones. The insectus Biozone has not been defined in Lithuania, because no findings of Cyrtograptus insectus Boucek are known in that region and therefore this biozone is tentatively included into the lapworthi Biozone. The insectus Biozone is distinguished in the Kaliningrad district (Suyarkova 2012).

The third problematic interval is near the Gorstian-Ludfordian boundary. The interval from the upper boundary of the scanicus Biozone to the lower boundary of the balticus Biozone has been called the Pseudomonoclimacis tauragensis Biozone (Paskevicius 1997). The base of the tauragensis Biozone is marked by the appearance of P. tauragensis (Paskevicius). The identification of this biozone is not very reliable, because (1) Pseudomonoclimacis tauragensis has long biostratigraphical range, (2) P. tauragensis is hardly distinguishable from P. haupti (Kuhne), (3) it is impossible to trace the Gorstian and Ludfordian boundary using P. tauragensis, (4) there exist better biozonal index species such as Saetograptus leintwardinensis, S. linearis, Bohemograptus bohemicus tenuis and others with short biostratigraphical ranges. So, this interval as well needs detailed study in future.

Stratigraphical distribution and correlation of bentonites

Only one bentonite has been found in the Rhuddanian of Lithuania and another is known from the Ohesaare core in Estonia (Kiipli & Kallaste 1996). The Aeronian, however, shows signs of remarkable volcanic activity. Five bentonites were established in the Aeronian part of the Dobele Formation in Lithuania. Most of these bentonites are characterized by a wide or weak sanidine reflection (Figs 2, 4, Table 1), while in some bentonites sanidine is absent at all. This type of sanidine does not allow well-proved correlations by the XRD method. The ca 1 cm thick Geniai Tuff, characterized by an unusually high content of REE elements up to 3%, occurs near the Aeronian-Telychian boundary in the Geniai-1 core (Kiipli et al. 2012b).

Seventeen bentonites are found in the Telychian in Lithuanian sections. This number is significantly less than in Latvia and Estonia where bentonites from ca 50 eruptions have been described and correlated (Kiipli et al. 2010b). Two bentonites from the Kurtuvenai-166 core (depths 971.2 and 971.7 m) may also belong to the upper Telychian. However, as graptolite finds from this level are not sufficiently complete and geochemical data allow correlations with lower Sheinwoodian bentonites, we attributed these layers provisionally to the Sheinwoodian. On the basis of the characteristic XRD reflections of the sanidine and graptolite zonation, three Lithuanian bentonites can be correlated with Estonian and Lithuanian ones (Figs 2, 4, Table 1). These include the ash bed at a depth of 1466.7 m in the Kurtuvenai-166 core correlating with the Osmundsberg Bentonite. The bentonite at 992.5 m in the Kurtuvenai-161 core interestingly reveals two sharp sanidine reflections, hinting at the mixture of two eruptions. These eruptions can be correlated with 842.0 and 842.1 m bentonites in the Ventspils-D3 core. Sanidine in other bentonites is characterized by wide or weak XRD reflections or shows no reflection at all.

Twenty-six bentonites, representing 22 eruption layers, were found in the Sheinwoodian part of the section in Lithuania. Six of these bentonites were already described in Kiipli et al. (2008c), but are included also in Table 1. The volcanic record starts with three bentonites (Virbalis-5, 1122.4 m; Kurtuvenai-166, 971.7 m; Kurtuvenai-166, 971.2 m), which can be provisionally correlated with the Lusklint, Storbrut and Ireviken bentonites in Gotland, Latvia and Estonia. Finds of graptolites are not conclusive at this level, therefore these correlations are not finally proved.

The riccartonensis to belophorus graptolite biozones include mostly bentonites with wide and very wide sanidine reflections and correlations are therefore often provisional (Fig. 5). Still, very wide reflections can be differentiated from wide reflections with certainty and used for correlations. Some of Lithuanian bentonites contain a specific type of sanidine giving a wide reflection with the modal value of the Na + Ca component between 26 and 30 mol%. Some bentonites in Lithuania (e.g. at 944.5 and 946.7 m in the Kurtuvenai-166 core) revealed a sharp sanidine reflection and can be correlated with bentonites in Latvia and Estonia (Fig. 5). The Siupyliai-69 1107.0 m bentonite in the antennularius Biozone showed a sharp reflection with 28 mol% of the Na + Ca component and can be correlated with the Vattenfallet Bentonite from the exposure in the town of Visby on Gotland (Kiipli et al. 2008a).

Only four bentonites were found in the upper part of the Sheinwoodian in Lithuania. Among these the Siupyliai-69 1076.0 m bentonite can be correlated with Latvian sections according to the sharp sanidine reflection and Na + Ca component of 30.4 mol%. The Ventspils-D3 and Vidale-263 sections of Latvia contain a large number of bentonites at this level (Kiipli et al. 2010a), while in Estonian sections bentonites are again relatively rare in this interval. Y-bentonite from the Slite Formation of Gotland (Batchelor & Jeppsson 1999) can be correlated by sanidine of specific shape (Kiipli et al. 2008a, 2013a) with bentonites in Estonian (Ohesaare, 275.3 m) and Latvian (Ventspils-D3, 736.4 m) sections (Fig. 5).

A 0.1 cm thick bentonite with a very strong and sharp sanidine reflection and the Na + Ca component 23.4 mol% was found in the lower part of the lundgreni Biozone at the beginning of the Homerian Stage at a depth of 1052.0 m in the Siupyliai-69 section. This very distinctive sanidine composition was analysed also in the Kurtuvenai-166 924.8 m (0.5 cm thick), Ohesaare 215.7 m (6.0 cm) and Ruhnu 337.5 m (0.2 cm) bentonites, indicating correlation close to the lower boundary of the lundgreni Biozone. In total, nine eruption layers were discovered in the lundgreni Biozone in Lithuania (Fig. 5). Nine bentonites have also been recognized in Latvia, partly correlating with the Lithuanian ash beds, and six bentonites are known from the Ohesaare core in Estonia. Considering correlations, up to 18 eruption layers can be counted in the lundgreni graptolite Biozone. Sanidines in these bentonites form two clusters according to the XRD reflections: (1) with sharp reflections and the Na + Ca component between 31 and 36 mol% and (2) with wide reflections with the Na + Ca component 43-56 mol%. Several well-proved correlations occur between Lithuanian and Latvian sections (Fig. 5).

Higher in the Homerian, in the interval from parvus to ludensis graptolite biozones, volcanic ashes were not found in the Kurtuvenai-166 and Siupyliai-69 sections.

The Ludlow part has not been studied in detail in Lithuanian sections. We collected five bentonite samples, one of which, from 707.7 m in the Pilviskiai-142 section, belongs to the upper scanicus Biozone, possibly correlating with the Ventspils-D3 603.0 m bentonite.

DISCUSSION

The number of Aeronian bentonites increases to the southwest from the East Baltic area. For example, Bergstrom et al. (1999) recorded ten bentonites in the Rostanga core, southern Sweden, and Bjerreskov (1975) found eight bentonites in Bornholm. This refers to volcanic sources in the Central European Caledonides from the collision zone of the Avalonia and Baltica plates (Kiipli et al. 2013a, 2013b). A large number of Rhuddanian and Aeronian bentonites are known from the Southern Uplands of Scotland (Batchelor & Weir 1988). This area was in the Laurentian side of the Iapetus Ocean, indicating subduction of the ocean floor and volcanism near the Laurentian margin. Wide sanidine reflections in Telychian bentonites probably indicate other volcanic sources than for ash beds of that age in Estonia and Latvia, many of which are characterized by sharp sanidine XRD reflections. Central European sources from the collision zone of Avalonia and Baltica can be supposed. This result confirms that Telychian volcanic ashes, forming a number of the Estonian-Latvian bentonites which are not found in Lithuania, reached the East Baltic area from the northwestern direction (present-day orientation)--from the margins of the Iapetus Ocean (Kiipli et al. 2008b, 2008c, 2010b, 2012a, 2013a). Scarcity of bentonites in the upper Homerian and Lower Ludlow of Lithuania and their frequent occurrence in Latvian and Estonian sections indicate a source from the northwest in terms of present-day orientation.

The Siupyliai-69 1052.0 m bentonite with very distinctive sanidine composition can be used as a marker horizon for tracing the lower boundary of the lundgreni Biozone. In the Ohesaare section this bentonite belongs to the upper part of the Jamaja Formation and in the Ruhnu section to the lower part of the Sorve Formation (Kiipli & Kallaste 2006) in the middle of the Conochitina subcyatha chitinozoan Biozone (Kiipli et al. 2010a). This result confirms the correlation by Nestor (1994) where the lower boundary of the testis graptolite Biozone (roughly corresponding to the lundgreni graptolite Biozone) was correlated with the middle of the C. subcyatha chitinozoan Biozone. We propose the stratigraphic name 'the Siupyliai Bentonite' for this marker horizon. This bentonite has not been found in the Ventspils-D3 and Vidale-263 cores, possibly because the sea current (Kiipli et al. 2012a, 2013a) has washed small ash falls away.

The Grotlingbo Bentonite occurs within the Mulde Event in the Homerian Stage (Calner et al. 2006; Dahlquist et al. 2012). Previously we studied a 7 cm thick bentonite in the parvus Biozone from the Vidukle-61 drill core (depth 1308 m) and correlated it with the Grotlingbo Bentonite (Kiipli et al. 2008c; Dahlquist et al. 2012). Now doubts have risen about that correlation. This bentonite occurs closely above the lithologically easily recognizable Ancia Member (finely laminated limestone), e.g. in the parvus graptolite Zone and within the lower carbon isotope positive excursion. The only unexplained fact is that the bentonite at 1308.0 m in the Vidukle-61 core did not contain biotite, which is typically abundant in the Grotlingbo Bentonite in other locations (Dahlquist et al. 2012). This correlation was followed by Cramer et al. (2012). Later Kiipli et al. (2010c) assigned the 10 cm thick bentonite, occurring 10 m above the Ancia Beds in the Priekule core, within the second carbon isotope positive excursion in the nassa graptolite Zone, to the Grotlingbo Bentonite. The reasons were significant thickness of the ash bed and abundance of biotite mentioned in core description. Kiipli et al. (2011) provisionally correlated the Grotlingbo Bentonite with the biotite-rich bentonite in the Ventspils-D3 core, 8 m higher than the Ancia Beds in the nassa Biozone. Thus, there are two ways of correlating the Grotlingbo Bentonite with graptolite zonation.

SUMMARY AND CONCLUSIONS

Study of Silurian bentonites in Lithuanian sections enabled us to extend correlations to the south. A wider study area allows better discrimination of volcanic sources from the Laurentia-Baltica and Avalonia-Baltica collision zones. Volcanic sources from the Avalonia-Baltica collision were significant in the Aeronian. In the Telychian this zone yielded ashes with a wide sanidine reflection to Lithuania, but the northern and central Baltic area was reached by a number of ashes from the Laurentia-Baltica collision area. Both sources were active also in the Sheinwoodian, but in the early Homerian the main source direction shifted to the west or northwest (in present-day orientation). Only a northwestern source can be recognized in the late Homerian and Early Ludlow. Volcanic activity almost ended in the Late Ludlow. Only a few ash beds are known in the latest Silurian of Lithuania, indicating again a possible southern volcanic source.

Correlation of the 1107.0 m bentonite of the Siupyliai-69 core in the antennularius Biozone with the Vattenfallet Bentonite on Gotland shows correlation of the Hogklint Formation on Gotland with the antennularius Zone. At the lower boundary of the Homerian Stage (lower lundgreni Zone) a new marker layer, the Siupyliai Bentonite, indicates correlation with the Jamaja (Ohesaare core) and Sorve (Ruhnu core) formations in Estonia. This integrated bio- and chemostratigraphical study can serve as reference in future correlation works in the region.

doi: 10.3176/earth.2014.02

Acknowledgements. This study was financed by the Estonian Science Foundation (grant 8963) and targeted financing project SF0140016s09. Sigitas Radzevicius was supported by the Science Council of Lithuania (project No. MIP-034/2012). The authors thank R. A. Batchelor and an anonymous reviewer for useful comments and suggestions. This research is a contribution to IGCP project 591.

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Loydell, D. K., Mannik, P. & Nestor, V. 2003. Integrated bio stratigraphy of the lower Silurian of the Aizpute-41 core, Latvia. Geological Magazine, 140, 205-229.

Motuza, V., Radzevicius, S. & Paskevicius, J. 2002. Influence of Caledonic volcanic activity for marine paleoenvironment: evidence from the Llandoverian graptolites of Baltic Sedimentary Basin. In The Fifth Baltic Stratigraphical Conference "Basin Stratigraphy--Modern Methods and Problems" (Satkunas, J. & Lazauskiene, J., eds), pp. 132-124. Vilnius.

Nestor, V. 1994. Early Silurian chitinozoans in Estonia and North Latvia. Academia, 4, 1-163.

Paskevicius, J. 1982. Some questions on the distribution, development conditions and correlation of the Silurian fauna in Lithuania and the neighbouring countries. Geologija (Vilnius), 3, 17-51 [in Russian].

Paskevicius, J. 1997. The Geology of the Baltic Republics. Geological Survey of Lithuania, Vilnius, 387 pp.

Paskevicius, J. & Radzevicius, S. 2006. Rytiniu baltijos krastu siluro graptolitu tyrimu istorija ir ju zonine skale [The history of investigation of the Silurian graptolites and their zonal scale in the Eastern Baltic countries]. In Science in the Nature Science Faculty: Fourth Scientific Conference on 23-24 November 2006, the Presentations (Ruksenas, O., ed.), pp. 194-209. Vilniaus universiteto leidykla, Vilnius [in Lithuanian, with English summary].

Radzevicius, S. 2006. Late Wenlock biostratigraphy and the Pristiograptus virbalensis group (Graptolithina) in Lithuania and the Holy Cross Mountains. Geological Quarterly, 50, 333-344.

Radzevicius, S. & Paskevicius, J. 2000. Pristiograptids (Graptolites) and their adaptive types of the Wenlock (Silurian) in Lithuania. Geologija (Vilnius), 32, 88-109.

Radzevicius, S. & Paskevicius, J. 2005. Pristiograptus (Graptoloidea) from the Upper Wenlock of the Baltic Countries. Stratigraphy and Geological Correlation, 13, 159-169.

Radzevicius, S., Paskevicius, J. & Meidla, T. 2008. Kai kurii siluro graptoliti evoliucija ir filogenija [Evolution and phylogenesis of some Silurian graptolites]. Geologijos akiraciai, 2, 35-12 [in Lithuanian, with English summary].

Ray, D. C., Collings, A. V. J., Worton, G. J. & Jones, G. 2011. Upper Wenlock bentonites from Wren's Nest Hill, Dudley; comparisons with prominent bentonites along Wenlock Edge, Shropshire, England. Geological Magazine, 148, 670-681.

Suyarkova, A. 2012. Biostratigrafiya pogranichnykh otlozhenij llandoveri-venloka Kaliningradskoj oblasti po graptolitam [Biostratigraphy of the Llandovery-Wenlock boundary deposits of Kaliningrad District based on graptolites]. Regional naya Geologiya i Metallogeniya, 52, 15-20 [in Russian].

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Tarmo Kiipli (a), Sigitas Radzevicius (b) and Toivo Kallaste (a)

(a) Institute of Geology at Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia; tarmo.kiipli@ttu.ee, toivo.kallaste@ttu.ee

(b) Department of Geology and Mineralogy, Vilnius University, M. K. Ciurlionio 21/27, LT03101, Vilnius, Lithuania; sigitas.radzevicius@gf.vu.lt

Received 10 October 2012, accepted 22 October 2013

Table 1. Bentonites in Lithuanian sections: biostratigraphy,
sanidine properties and correlations

Stratigraphy    Graptolite zone        Core               Depth, m

Ludfordian      balticusl              Geniai-1           1493.1
Gorstian        scanicus               Pilviskiai-142      707.7
Gorstian        scanicus-progenitor    Vidukle-61         1232.8
Gorstian        progenitor             Baubliai-2         1638.5
Gorstian        nilssoni               Vidukle-61         1269.1
Homerian        parvus                 Vidukle-61         1308.0
Homerian        lundgreni              Kurtuvenai-166      892.1
Homerian        lundgreni              Kurtuvenai-166      898.0
Homerian        lundgreni              Kurtuvenai-166      901.8
Homerian        lundgreni              Siupyliai-69       1017.0
Homerian        lundgreni              Kurtuvenai-166      906.2
Homerian        lundgreni              Kurtuvenai-166      906.3
Homerian        lundgreni              Siupyliai-69       1032.3
Homerian        lundgreni              Siupyliai-69       1035.0
Homerian        lundgreni              Kurtuvenai-166      906.8
Homerian        lundgreni              Kurtuvenai-166      909.0
Homerian        lundgreni              Siupyliai-69       1047.6
Homerian        lundgreni              Kurtuvenai-166      924.8
Homerian        lundgreni              Siupyliai-69       1052.0
Sheinwoodian    perneri-radians        Siupyliai-69       1076.0
Sheinwoodian    perneri-radians        Kurtuvenai-166      933.8
Sheinwoodian    perneri-radians        Siupyliai-69       1081.5
Sheinwoodian    perneri-radians        Kurtuvenai-166      937.4
Sheinwoodian    belophorus             Siupyliai-69       1096.5
Sheinwoodian    belophorus             Kurtuvenai-166      944.0
Sheinwoodian    belophorus             Kunkojai-12        1289.7
Sheinwoodian    belophorus             Kurtuvenai-166      944.5
Sheinwoodian    belophorus             Kurtuvenai-166      946.7
Sheinwoodian    belophorus             Kunkojai-12        1296.0
Sheinwoodian    belophorus             Kurtuvenai-166      950.5
Sheinwoodian    belophorus             Lygumai-47         1343.0
Sheinwoodian    belophorus             Lygumai-47         1343.4
Sheinwoodian    belophorus             Vidukle-61         1385.6
Sheinwoodian    antennularius          Kurtuvenai-166      953.0
Sheinwoodian    antennularius          Kurtuvenai-166      955.0
Sheinwoodian    antennularius          Siupyliai-69       1107.0
Sheinwoodian    antennularius          Siupyliai-69       1109.0
Sheinwoodian    riccartonensis         Kurtuvenai-166      958.8
Sheinwoodian    riccartonensis         Siupyliai-69       1111.0
Sheinwoodian    riccartonensis         Kurtuvenai-166      959.8
Sheinwoodian    riccartonensis         Kurtuvenai-166      960.5
Sheinwoodian    riccartonensis         Kurtuvenai-166      960.7
Sheinwoodian    murchisoni             Kurtuvenai-166      971.2
Sheinwoodian    murchisoni             Kurtuvenai-166      971.7
Sheinwoodian    murchisoni             Virbalis-5         1122.4
Telychian       lapworthi              Siupyliai-69       1125.0
Telychian       lapworthi              Siupyliai-69       1127.8
Telychian       spiralis-lapworthi     Siupyliai-69       1128.5
Telychian       spiralis-lapworthi     Siupyliai-69       1130.0
Telychian       spiralis               Vidukle-61         1418.8
Telychian       spiralis               Lygumai-47         1383.7
Telychian       crenulata              Kurtuvenai-166      985.2
Telychian       crenulata              Kurtuvenai-166      987.4
Telychian       griestoniensis         Kurtuvenai-166      991.0
Telychian       crispus                Kurtuvenai-166      992.5
Telychian       crispus                Kurtuvenai-166      992.5
Telychian       crispus                Ramuciai-2         1993.8
Telychian       crispus                Rukai-2            1876.2
Telychian       turriculatus           Kurtuvenai-161     1466.7
Telychian       linnaei-turriculatus   Geniai-1           1751.0
Telychian       linnaei-turriculatus   Kurtuvenai-166     1002.2
Telychian       linnaei-turriculatus   Kurtuvenai-166     1002.2
Telychian       linnaei-turriculatus   Geniai-1           1752.1
Aeronian        sedgwickii             Maldtinai-1        1692.2
Aeronian        sedgwickii             Maldunai-1         1692.3
Aeronian        sedgwickii             Paroveja-9          714.2
Aeronian        sedgwickii             Kurtuvenai-166     1003.2
Aeronian        sedgwickii             Kurtuvenai-166     1004.5
Rhuddanian      cyphus                 Aukstupiai-1       1788.0

                                            Na + Ca
                             Width of       component
                             the sanidine   in modal
                Thickness,   reflection,    sanidine,
Stratigraphy    cm           deg            mol%         Biotite

Ludfordian      nd           No                          +
Gorstian        nd           0.211          27.4         +
Gorstian        nd           No                          ++
Gorstian        nd           No                          -
Gorstian        nd           Wide                        +
Homerian        7.0          No                          +
Homerian        0.1          No                          +++
Homerian        3.0          0.206          48.1         +
Homerian        1.0          0.213          48.7         +
Homerian        0.4          0.081          34.4         -
Homerian        0.1+         0.098          35.9         +
Homerian        0.1          0.157          44.2         ++
Homerian        0.1?         0.246          40.8         -
Homerian        2.0          0.388          36.4         -
Homerian        1.0          0.145          49.2         ++
Homerian        2.0          0.274          50.0         +
Homerian        0.1          0.269          42.9         +
Homerian        0.5          0.086          22.9         +++
Homerian        0.1          0.066          23.4         ++
Sheinwoodian    0.1?         0.262          30.4         +
Sheinwoodian    0.2          0.399          34.6         ++
Sheinwoodian    1.0          0.269          26.6         +
Sheinwoodian    0.1          0.333          35.4         ++
Sheinwoodian    0.3          0.317          21.2         -
Sheinwoodian    0.1          0.358          17.9         +
Sheinwoodian    6.0          0.06           30.5         ++
Sheinwoodian    2.0          0.185          30.9         +
Sheinwoodian    0.5          0.143          32.9         +
Sheinwoodian    5.0          0.22           35.0         +
Sheinwoodian    0.5          0.105          39.9         +
Sheinwoodian    nd           Very weak                   -
Sheinwoodian    nd           0.32           26.7         -
Sheinwoodian    1.0          0.3            26.5         -
Sheinwoodian    4.0          0.371          30.4         +
Sheinwoodian    0.1          0.258          30.5         +
Sheinwoodian    0.5          0.062          28.1         ++
Sheinwoodian    0.1          0.095          23.8         +++
Sheinwoodian    1.0          0.3            27.8         +
Sheinwoodian    1.0          0.316          26.2         -
Sheinwoodian    0.2          No                          +++
Sheinwoodian    1.5          ca 0.3         ca 28        -
Sheinwoodian    1.5          ca 0.3         ca 31        -
Sheinwoodian    1.0          0.214          30.3         +++
Sheinwoodian    3.0          0.207          30.0         +
Sheinwoodian    0.2          0.24           35.0         +
Telychian       1.0          Weak                        +
Telychian       3.0          0.306          27.9         +
Telychian       0.5          0.311          25.3         ++
Telychian       0.5          Weak                        ++
Telychian       nd           0.3            29.4         +
Telychian       nd           0.395          26.5         +
Telychian       1.0          0.25           27.4         ++
Telychian       0.1          0.355          22.1         +
Telychian       0.3          0.316          27.1         ++
Telychian       0.2          0.117          24.7         ++
Telychian       0.2          0.156          44.2         ++
Telychian       nd           No                          -
Telychian       nd           0.425          24.8         +++
Telychian       1.0          0.075          21.2         +
Telychian       1.0          0.441          23.1         -
Telychian       0.2          0.229          44.0         ++
Telychian       0.5          0.242          41.9         +
Telychian       1.0          No                          nd
Aeronian        nd           0.406          26.1         -
Aeronian        nd           0.452          20.0         -
Aeronian        nd           Wide                        -
Aeronian        1.2          ca 0.45        ca 35        -
Aeronian        0.8          ca 0.35        ca 41        +
Rhuddanian      nd           Weak                        +

Stratigraphy    Correlations                Source

Ludfordian                                  Present study
Gorstian        Ventspils-D3 603.0          Present study
Gorstian                                    Present study
Gorstian                                    Present study
Gorstian                                    Present study
Homerian                                    Kiipli et al. 2008c
Homerian                                    Present study
Homerian                                    Present study
Homerian        Vidale-263 634.1?           Present study
Homerian        Ventspils-D3 709.5          Present study
Homerian        Ventspils-D3 709.5          Present study
Homerian        Siupyliai-69 1032.3?        Present study
Homerian        Kurtuvenai-166 906.3?       Kiipli et al. 2008c
Homerian        Siupyliai-69 1032.3         Present study
Homerian        Ventspils-D3 714.1          Present study
Homerian        Vidale-263 646.8            Present study
Homerian        Ventspils-D3 718.7?         Present study
Homerian        Ruhnu 337.5                 Present study
Homerian        Ohesaare 215.7              Present study
Sheinwoodian    Ventspils-D3 738.6          Present study
Sheinwoodian    Siupyliai-69 1076.0         Present study
Sheinwoodian    Ventspils-D3 745.4          Present study
Sheinwoodian                                Present study
Sheinwoodian    Kurtuvenai-166 944.0        Present study
Sheinwoodian    Ohesaare 287.8              Present study
Sheinwoodian    Ohesaare 288.4              Kiipli et al. 2008c
Sheinwoodian    Ohesaare 288.4              Present study
Sheinwoodian                                Present study
Sheinwoodian                                Kiipli et al. 2008c
Sheinwoodian                                Present study
Sheinwoodian                                Kiipli et al. 2008c
Sheinwoodian    Vidukle-61 1385.6           Kiipli et al. 2008c
Sheinwoodian    Lygumai-47 1343.4           Kiipli et al. 2008c
Sheinwoodian                                Present study
Sheinwoodian                                Present study
Sheinwoodian    Vattenfallet Bentonite      Present study
Sheinwoodian                                Present study
Sheinwoodian    Siupyliai-69 1111.0         Present study
Sheinwoodian    Kurtuvenai-166 958.8        Present study
Sheinwoodian                                Present study
Sheinwoodian                                Present study
Sheinwoodian                                Present study
Sheinwoodian    Ireviken Bentonite?         Present study
Sheinwoodian    Storbrut Bentonite?         Present study
Sheinwoodian    Lusklint Bentonite ID 150   Present study
Telychian                                   Present study
Telychian                                   Present study
Telychian                                   Present study
Telychian                                   Present study
Telychian                                   Present study
Telychian                                   Present study
Telychian                                   Present study
Telychian                                   Present study
Telychian       Paatsalu Bentonite 1D755    Present study
Telychian       Mustjala Bentonite ID795    Present study
Telychian       Ventspils-D3 842.1          Present study
Telychian                                   Present study
Telychian                                   Present study
Telychian       Osmundsberg B. ID851        Present study
Telychian                                   Present study
Telychian       Aizpute-41 966.4 ID880      Present study
Telychian                                   Present study
Telychian       Geniai TuffID890            Present study
Aeronian                                    Present study
Aeronian                                    Present study
Aeronian                                    Present study
Aeronian        Aizpute-41 969.4 ID920      Present study
Aeronian                                    Present study
Rhuddanian                                  Present study

Biotite abundance: -no biotite, + 1-10 flakes, ++ 10-100 flakes,
+++ more flakes in the fraction of >0.04 mm separated from 2 g
of bentonite; nd, not determined. Thickness of some beds not
determined (nd). ID numbers of bentonites according to Kallaste
& Kiipli (2006).

Fig. 3. List of Lithuanian graptolite biozones mentioned in
text and in figures.

 System      Series        Stage        Reg.          Lithuanian
                                        stage     graptolite biozones
                                                  (Paskevicius 1997;
                                                   Radzevicius 2006)

SILURIAN     Ludlow     Ludfordian    Pagegiai      Formosograptus
                                                       formosus

                                                      Monograptus
                                                       balticus

                                                  Pseudomonoclimacis
                                                      tauragensis

                         Gorstian      Dubysa         Lobograptus
                                                       scanicus

                                                      Lobograptus
                                                      progenitor

                                                   Neodiversograptus
                                                       nilssoni

            Wenlock      Homerian      Geluva        Colonograptus
                                                       ludensis

                                                     Colonograptus
                                                        deubeli

                                                     Colonograptus
                                                      praedeubeli

                                                  Gothograptus nassa

                                                    Pristiograptus
                                                        parvus

                        Sheiwoodian   Jaagarahu      Cyrtograptus
                                                       lundgreni

                                                     Cyrtograptus
                                                        perneri

                                                      Monograptus
                                                      belophorus

                                                    Streptograptus
                                                     antennularius

                                        Jaani         Monograptus
                                                    riccartonensis

                                                     Cyrtograptus
                                                      murchisoni

                         Telychian     Adavere       Cyrtograptus
                                                      centrifugus

                                                     Cyrtograptus
                                                       lapworthi

                                                  Oktavites spiralis

                                                     Monoclimacis
                                                       crenulata

                                                     Monoclimacis
                                                     griestonensis

                                                    Streptograptus
                                                        crispus

                                                     Spirograptus
                                                     turriculatus

                                                   Rastrites linnaei

           Llandovery    Aeronian     Raikkula      Stimulograptus
                                                      sedgwickii

                                                     Lituigraptus
                                                      convolutus

                                                     Campograptus
                                                       millepeda
                                                     Demirastrites
                                                      pectinatus

                        Rhuddanian                   Demirastrites
                                                     triangulatus

                                                     Coronograptus
                                                        cyphus

                                        Juuru              ?

                                                           ?
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Author:Kiipli, Tarmo; Radzevicius, Sigitas; Kallaste, Toivo
Publication:Estonian Journal of Earth Sciences
Article Type:Report
Geographic Code:4EXLT
Date:Mar 1, 2014
Words:6071
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