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Quaternary International xxx (2016) 1e25

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Quaternary International

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Tephra layers of in the quaternary deposits of the Sea of Okhotsk:Distribution, composition, age and volcanic sources

Alexander N. Derkachev a, *, Nataliya A. Nikolaeva a, Sergey A. Gorbarenko a,Maxim V. Portnyagin b, c, Vera V. Ponomareva d, Dirk Nürnberg b, Tatsuhiko Sakamoto e,Koiji Iijima e, Yanguang Liu f, Xuefa Shi f, Huahua Lv f, Kunshan Wang f

a V.I. Il'ichev Pacific Oceanological Institute, FEB RAS, Baltiyskaya st., 43, Vladivostok, 690041, Russiab GEOMAR Helmholtz Centre for Ocean Research, Wischhofstrasse, 3, Kiel, Germanyc V.I. Vernadsky Institute of Geochemistry and Analytical Chemistry, RAS, Moscow, Russiad Institute of Volcanology and Seismology, FEB RAS, Piip Boulevard, 9, Petropavlovsk-Kamchatsky, 683006, Russiae Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061, Japanf First Institute of Oceanography, SOA, Xian-Xia-Ling Road, 6, Qingdao, 266061, China

a r t i c l e i n f o

Article history:Available online xxx

Keywords:TephraTephrostratigraphyQuaternary depositsSea of OkhotskGeochemistry of volcanic glasses

* Corresponding author.E-mail addresses: [email protected] (A.N.

geomar.de (M.V. Portnyagin), vera.ponomareva1@[email protected] (T. Sakamoto), [email protected]

http://dx.doi.org/10.1016/j.quaint.2016.07.0041040-6182/© 2016 Elsevier Ltd and INQUA. All rights

Please cite this article in press as: Derkachcomposition, age and volcanic sources, Qua

a b s t r a c t

The fullest summary on composition, age and distribution of 23 tephra layers detected and investigatedin the Okhotsk Sea Pleistocene-Holocene deposits is presented. Seven tephra layers are surely identifiedwith powerful explosive eruptions of volcanoes of Kamchatka, Kurile and Japanese Islands. For them, theareas of ash falls including which weren't revealed earlier on the land are specified and established. It isestimated that explosive eruptions of volcanoes of the Kamchatka Sredinny Range were the sources forthree tephra layers. Complex investigations of morphological, mineralogical and chemical composition oftephras including composition of rare and earth-rare elements (electron microprobe analysis and laserablation method - LA ICP MS) have been made for all studied layers. They were a basis for tephros-tratigraphic correlation of the regional deposits promoting to specification of stages of volcanic explosiveactivity in this region.

© 2016 Elsevier Ltd and INQUA. All rights reserved.

1. Introduction

The interlayers of the volcanic ashes (tephra) in the continentaland marine deposits contain the critical information of history andcharacter of volcanic eruptions. In the events of the violent volcaniceruptions, an ash falls at spots being at distances of thousands ki-lometers from the eruption centre while the substance related tothe eruptive cloud can have effect on the natural environmentincluding one on the global scale (Ambrose, 1998; Ehrmann et al.,2007; Hamann et al., 2008). Finally, the catastrophic character ofthe volcanic explosions and their destructive effect on the envi-ronmental situation and human life and activities exact to predictthe future behavior of particular volcanoes and to gain theknowledge of possible spatial distribution of the harmful products

Derkachev), [email protected] (V.V. Ponomareva),(X. Shi).

reserved.

ev, A.N., et al., Tephra layersternary International (2016),

of their activities that cannot be reliably ascertained withoutinvestigating the properties of separate interlayers of tephra. Inaddition, the tephra interlayers are very efficient markers forstratigraphic study of the sedimentary sequences and dating of pastevents (Addison et al., 2010; Jensen et al., 2011; Hamann et al.,2008; Hasegawa et al., 2011a, 2011b; Lowe et al., 2008; Lowe,2011; Nakagawa et al., 2002, 2008; Nakamura, 2016; Nakamuraet al., 2009; Preece et al., 2011; Ponomareva et al., 2015a; Smithet al., 2002, and others).

In recent decades, in the entire world, the work on documentingand age dating of the greatest explosive eruptions is carried out(Crosweller et al., 2012; Newton et al., 2007; Siebert and Simkin,2002, and others). However, it should be noted that the globalcatalog of such eruptions even over the past thousands years isnowhere near full: up to now, many greatest eruptions were notrevealed. In addition, even for the established explosive eruptions,the tephra distribution area is often unknown and, as a conse-quence, it is impossible to evaluate a volume of products thrown outby an eruption and to determine the extent of eruptions. This makes

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A.N. Derkachev et al. / Quaternary International xxx (2016) 1e252

it difficult to study the productivity and dynamics of the volcanicactivity as well as the impact of volcanism on the environment andclimate. So, the present differences in evaluating a role of volcanismas a factor of influence on the environment result from theincompleteness of the explosive eruptions record. Only an identi-fication of tephra in the distant sections using data of its age andmaterial composition offers an opportunity to determine the dis-tribution area and volume of tephra as well as magnitudes oferuptions which is crucial for understanding of the volcanism dy-namics and evolution (Addison et al., 2010; Derkachev andPortnyagin, 2013; Hasegawa and Nakagawa, 2016; Hasegawa et al.,2011a, 2011b; Ponomareva et al., 2013a, 2013b, 2015b, and others).

The interlayers of tephra were found out in many marine andcontinental deposits of the Pleistocene-Holocene age within thenorth-west sector of the transition zone from the Asian continentto the Pacific Ocean. They were studied in sufficient detail on landclose to the Japanese Islands, Kamchatka and, to a lesser extent,Kurile Islands (Arai et al., 1986; Aoki and Machida, 2006; Braitsevaet al., 1993, 1997, 1998; Endo et al., 1989; Hasegawa et al., 2008,2009, 2011a, 2011b; Hasegawa and Nakagawa, 2016; Kimuraet al., 2015; Machida and Arai, 2003; Melekestsev et al., 1997;Nakagawa et al., 2008; Nakagawa and Ohba, 2003; Pevzner, 2015;Ponomareva et al., 2004, 2007; Razzhigaeva et al., 2011, 2016;Satoguchi and Nagahashi, 2012; Suto et al., 2007; Zaretskayaet al., 2001, 2007; Yamamoto et al., 2010, and others). However,despite the certain progress in the study of the region tephros-tratigraphy, the North-West Pacific Ocean including the Sea ofOkhotsk remains to be poorly understood.

Over the past fifteen years, during complex expeditions with theparticipation of the Russian, German, Japanese and Chinese re-searchers in the Sea of Okhotsk, 23 tephra layers of in thePleistocene-Holocene deposits were found out in more than 85sediment cores (Fig. 1, Supplement 1). Data on them were pre-sented with different level of detail in a number of publications(Derkachev et al., 2004; Derkachev and Portnyagin, 2013;Gorbarenko et al., 2002; Derkachev et al., 2011, 2012; Sakamotoet al., 2005, 2006; Aoki, 2008 and others). In this paper, we pre-sent the fullest summary on composition, age and distribution of 23layers of tephra detected and investigated by us in the Sea ofOkhotsk deposits.

2. Materials and methods

The basis of this work was formed by the study of sedimentcores taken in the Sea of Okhotsk with respect mainly to theRussian-Germany project КОМЕХ (1998e2003) on board ofresearch vessels “Akademik M.A. Lavrentyev”, “Marshal Gelovani”,“Sonne” and the Russian-Japanese project on board of researchvessels “Miray” and “Yokosuka” (2006e2007). In addition, the datafor two sediment cores taken with respect to the Russian-Chineseproject (2011) as well as materials of the earlier researches car-ried out in the Pacific Oceanological Institute, FEB RAS (Fig. 1,Supplement 1) were used. The composition of tephra from thesediment core MD01-2415 (age is about 1.1 million years) takenduring voyage of the French research vessel “Marion Dufresne”(2004) with respect to the program IMAGES was also investigated(Nürnberg and Tiedemann, 2004; Levitan et al., 2007).

Only material of clean and well visually diagnosable interlayersof tephra was used for investigations. Initially, the sample wasdivided using a standard screen set under a water stream. Thefurther studies were carried out with the use of grain-size fractionsof more than 0.05e0.1 and 0.1e0.25 mm. The morphology of ashparticles was examined under the binocular microscope by re-flected light and scanning electronic microscope (FIO, Qingdao,China). The morphological types of the volcanic glasses are

Please cite this article in press as: Derkachev, A.N., et al., Tephra layerscomposition, age and volcanic sources, Quaternary International (2016),

presented according to a classification (Katoh et al., 2000). A min-eral component of heavy (more than 2.85 g/cm3) fraction of asheswith grain size of 0.05e0.1 mmwas determined by the immersionmethod under the polarization microscope with count of not lessthan 300 mineral grains. The refraction index of volcanic glasseswas determined by K. Iijima in JAMSTEC (Japan) using theimmersion-thermal method on the RIMS-86 (RI measurementsystem, Kyoto Fission) (Supplement 2), partially under the micro-scope in the immersion liquids (Derkachev et al., 2012).

All the layers of tephra from the deposits of the Sea of Okhotskbeing at our disposal were examined by the unified procedure inthe electron microprobe JEOL JXA 8200 in the Leibniz Institute forOcean Research, now GEOMAR (Helmholtz Centre for OceanResearch, Kiel, Germany) (Supplement 3). Investigations, carriedout with the use of this method, allowed also to specify chemicalcomposition of tephra. Volcanic glasses of this tephra wereanalyzed earlier on electronic microscope Quanta-2000 with theenergy-dispersive spectroscopy (EDAX) in FIO (Qingdao, China) andmicroprobe Cameca SX5 (GEOMAR, Kiel, Germany) (Gorbarenkoet al., 2002; Derkachev et al., 2012; Kaiser, 2001); data obtainedwere used as additional source for correlation of sediment cores.

Using the microprobe JEOL JXA 8200, an analysis of volcanicglasses was performed by the defocused up to 5 mm electron beamat accelerating voltage of 15 kV and current of 6 nA. For the devicecalibration and monitoring of analyses quality, the natural certifiedsamples of volcanic glasses (basalt glass USNM 113498/1 VG-A99,rhyolite glasses USNM 72854 VG568 and KN-18) and minerals(scapolite USNM R6600-1) were used (Jarosewich et al., 1980;Mosbah et al., 1991). The results of analysis were corrected inaccordance with the CITZAF program. Every analytic sessionincluding 15e40 h of operation of the instrument in autonomousmode in the previously planned coordinates of measurementpoints was accompanied by analyses of the basic standards (rhyo-lite, basalt and scapolite) at the beginning, every 50e60 analysesand at the end of session. Based on these measurements, thecorrection factors considering a possibility of a slight calibrationshift in a time of analysis were calculated for each analytical ses-sion. In most cases, the values of factors did not exceed those ofstandard error of measurements of standards. After introduction ofcorrections into the measured data, all analyses of glasses wereresulted in the sum of element oxides of 100% and used for con-structing the diagrams presented in this paper and carrying out ofthe geochemical analysis. Method of microprobe analysis is given inour publications in detail (Ponomareva et al., 2013a, 2015a).

When performing the tephrostratigaphical studies, the high-quality chemical analyses carried out with quality control inaccordance with international standards are needed (Froggatt,1992; Hunt et al., 1998; Kuehn et al., 2011). As the results of theinternational interlaboratory comparison of the accuracy of analyticinvestigations of the volcanic glass made upon an initiative of theINTAV group tephrochronologists have shown, a procedure of theglass analysis accepted in GEOMAR is in accord with all the criteriaof high quality of analyses both in accuracy and reproducibility ofresults (Kuehn et al., 2011).

When considering the chemical composition of the major pet-rogenic elements in the volcanic glasses, the representative sampleof 885 new microprobe analyses carried out in recent times inGEOMAR was used (Table 1, Supplement 3).

Determination of rare and rare-earth elements in the volcanicglasses was made by M. Portnyagin with the use of the laser abla-tion method - LA ICP MS (245 analyses) (University of Kiel, Kiel,Germany). For comparison, the data of 45 analyses made by ICP MSmethod in A.P. Vinogradov Institute of Geochemistry, SiberianBranch of RAS, Irkutsk (Sakhno et al., 2010) and in FIO, Qingdao,China (analyst Chen Jihua) were also used.


Fig. 1. The scheme of study of tephra layers from the Holocene-Pleistocene deposits of the Sea of Okhotsk. 1 -2-sediment columns with tephra layers discovered by: 1-authors, 2-Japanese geologists (Sakamoto et al., 2005, 2006); 3-sediment columns without tephra layers. K. tr - Kashevarov Trough, L.R. eLebed Rise, Ac.S.R. - Academy of Sciences Rise.

A.N. Derkachev et al. / Quaternary International xxx (2016) 1e25 3

To estimate the age of tephra layers we used published databased on complex of stratigraphic methods: determination ofphysical parameters of deposits (humidity, density, magneticsusceptibility, paleomagnetic properties), study of diatoms andforaminifera, isotopic-oxygenic analysis of foraminifera, data of


the radiocarbon dating of organic residues. The resultingradiocarbon ages were converted into calendar age by usingthe calibration tool Calib Rev 6.0 (Stuiver and Reimer, 1993)with the Intcal 09 and Marine 09 data sets (Reimer et al.,2009).


Table 1Mean chemical composition of volcanic glasses from tephra layers of the Okhotsk Sea deposits (%).

Index tephra n SiO2 TiO2 Al2O3 FeOt MnO MgO CaO Na2O K2O P2O5 F SO3 Cl Sum

KO 38 76.92(0.46)**

0.23(0.02)

12.83(0.21)

1.44(0.14)

0.05(0.03)

0.23(0.04)

1.49(0.12)

4.53(0.14)

2.06(0.11)

0.02(0.02)

0.02(0.03)

0.01(0.01)

0.16(0.01)

97.03(1.28)

N 15 66.71(1.82)

0.62(0.09)

14.56(0.57)

6.50(0.77)

0.16(0.03)

1.16(0.37)

4.80(0.65)

4.38(0.23)

0.79(0.09)

0.12(0.03)

0.03(0.03)

0.02(0.02)

0.16(0.02)

98.47(0.88)

TR(Zv) 15 72.95(0.48)

0.48(0.02)

13.37(0.24)

3.82(0.15)

0.15(0.04)

0.57(0.03)

2.90(0.14)

4.52(0.03)

0.93(0.02)

0.09(0.02)

0.02(0.01)

0.01(0.01)

0.18(0.01)

97.79(0.99)

K2 92 75.38(0.36)

0.32(0.03)

12.81(0.16)

2.29(0.23)

0.08(0.03)

0.26(0.04)

1.61(0.15)

4.43(0.12)

2.50(0.23)

0.03(0.02)

0.03(0.03)

0.01(0.01)

0.25(0.02)

97.33(1.35)

K3 131 75.44(0.36)

0.32(0.02)

12.84(0.21)

2.26(0.14)

0.08(0.04)

0.26(0.03)

1.62(0.10)

4.36(0.13)

2.47(0.06)

0.03(0.02)

0.04(0.04)

0.01(0.01)

0.26(0.02)

96.98(1.61)

T 65 74.42(1.05)

0.46(0.05)

12.76(0.54)

3.13(0.34)

0.09(0.04)

0.67(0.13)

3.51(0.42)

3.60(0.28)

1.05(0.27)

0.09(0.03)

0.03(0.03)

0.02(0.02)

0.15(0.03)

98.30(1.65)

K4 26 72.07(0.50)

0.58(0.03)

14.18(0.41)

2.87(0.24)

0.12(0.04)

0.74(0.08)

3.15(0.20)

4.65(0.16)

1.27(0.05)

0.09(0.03)

0.04(0.04)

0.03(0.02)

0.20(0.02)

97.68(1.78)

MR1 15 70.21(0.46)

0.54(0.02)

13.84(0.13)

4.50(0.28)

0.10(0.04)

1.03(0.05)

4.26(0.16)

3.90(0.09)

1.28(0.03)

0.15(0.02)

0.04(0.04)

0.03(0.02)

0.12(0.02)

98.38(1.23)

Kc2-3 45 77.21(0.70)

0.34(0.04)

12.32(0.33)

1.58(0.18)

0.09(0.05)

0.30(0.04)

1.57(0.18)

4.30(0.20)

2.04(0.20)

0.03(0.02)

0.03(0.04)

0.02(0.01)

0.17(0.02)

96.91(1.59)

Aso4* 13 73.06(0.27)

0.41(0.02)

15.27(0.1)

1.45(0.05)

0.10(0.03)

0.42(0.03)

0.92(0.05)

3.78(0.20)

4.58(0.17)

n.d n.d n.d n.d

K5 19 77.51(0.19)

0.36(0.02)

12.18(0.08)

1.58(0.12)

0.11(0.04)

0.30(0.02)

1.47(0.04)

4.46(0.11)

1.79(0.07)

0.03(0.02)

0.03(0.03)

0.03(0.02)

0.17(0.01)

95.69(1.51)

AL7.2a (MR2) 34 75.73(0.26)

0.40(0.02)

13.10(0.11)

1.88(0.12)

0.08(0.04)

0.40(0.03)

1.99(0.08)

4.36(0.14)

1.79(0.04)

0.04(0.02)

0.05(0.04)

0.02(0.01)

0.15(0.01)

94.85(1.19)

AL7.2b 51 77.56(0.52)

0.13(0.07)

12.79(0.14)

0.71(0.27)

0.06(0.03)

0.10(0.08)

0.76(0.31)

3.95(0.17)

3.79(0.55)

0.01(0.02)

0.02(0.03)

0.01(0.01)

0.10(0.02)

94.41(1.01)

AL7.4 39 76.36(0.16)

0.13(0.01)

13.33(0.10)

0.73(0.07)

0.07(0.03)

0.06(0.02)

0.50(0.02)

4.18(0.11)

4.51(0.14)

0.01(0.01)

0.03(0.03)

0.02(0.01)

0.09(0.03)

93.70(1.23)

nMR 58 78.17(0.28)

0.19(0.04)

12.25(0.25)

1.18(0.13)

0.06(0.04)

0.20(0.03)

1.40(0.14)

3.84(0.23)

2.50(0.25)

0.02(0.02)

0.02(0.03)

0.01(0.01)

0.15(0.01)

94.10(0.71)

K6 22 69.15(1.83)

0.67(0.10)

14.89(1.25)

3.98(0.70)

0.13(0.05)

0.96(0.14)

4.05(0.82)

4.33(0.25)

1.51(0.16)

0.13(0.05)

0.05(0.05)

0.02(0.01)

0.12(0.02)

97.32(1.73)

MR3 (AL9.22) 74 75.90(0.19)

0.28(0.02)

13.24(0.16)

1.37(0.12)

0.06(0.04)

0.30(0.03)

1.61(0.03)

3.89(0.14)

3.09(0.08)

0.03(0.02)

0.03(0.03)

0.02(0.01)

0.19(0.01)

94.30(1.38)

AL9.22b 17 61.11(0.67)

1.01(0.04)

15.51(0.25)

8.04(0.39)

0.22(0.04)

2.52(0.17)

6.20(0.23)

4.13(0.14)

0.87(0.06)

0.20(0.04)

0.04(0.03)

0.02(0.01)

0.14(0.01)

98.36(0.90)

MR4 (AL9.24) 60 64.03(1.51)

1.09(0.09)

16.13(0.33)

4.82(0.69)

0.18(0.05)

1.59(0.29)

3.98(0.55)

5.30(0.20)

2.27(0.18)

0.35(0.09)

0.07(0.05)

0.06(0.03)

0.09(0.02)

97.64(1.70)

AL10 22 62.56(3.07)

1.22(0.23)

16.06(0.36)

5.31(1.22)

0.17(0.05)

1.98(0.61)

4.46(1.12)

5.08(0.23)

2.40(0.42)

0.50(0.19)

0.08(0.04)

0.09(0.04)

0.10(0.02)

97.74(1.50)

Md1 20 74.04(0.31)

0.46(0.02)

14.06(0.11)

2.50(0.14)

0.13(0.04)

0.40(0.03)

1.67(0.04)

4.55(0.28)

2.01(0.05)

0.06(0.02)

0.00(0.00)

0.02(0.01)

0.11(0.01)

93.88(0.88)

Md2 22 78.18(0.20)

0.11(0.01)

12.63(0.13)

0.65(0.08)

0.06(0.04)

0.10(0.03)

0.76(0.03)

3.76(0.13)

3.62(0.12)

0.01(0.02)

0.00(0.00)

0.01(0.01)

0.11(0.01)

94.68(0.81)

Md3 20 74.45(0.18)

0.40(0.02)

13.48(0.09)

2.36(0.11)

0.09(0.04)

0.33(0.02)

1.60(0.04)

4.40(0.16)

2.64(0.06)

0.05(0.02)

0.00(0.00)

0.02(0.01)

0.18(0.01)

95.44(0.64)

Notes. n.d. - the component wasn't defined; n - quantity of analyses; ** in brackets - standard deviation; * according to Kaiser, 2001. All data normalized to 100%. All analysesare executed with the use of the electron microprobe JEOL JXA 8200 in the Leibniz Institute for Ocean Research, now GEOMAR (Helmholtz Centre for Ocean Research, Kiel,Germany). Analysts is A.N. Derkachev and M.V. Portnyagin.Tephra samples for which chemical analyses of volcanic glasses were carried out: KO - Lv29-110 (345e350), Lv55-9 (545); N - GC12-6a (278e279); TR(Zv) - 9301 (453e456);K2 - So178-11-5 (1390e1391), So178-12-3 (1167e1168), M961 (148e151), Lv28-37-1 (342e344), MD01-2415 (410); K3 - 9313 (126e127), K-68 (90e98), Lv27-15-1(363e367), Ge99-10 (249e250), Lv55-38 (127); T - Lv28-2-4- (470e475), Lv29-72-2 (569e570), Ge99-10 (273e274), So178-3-4 (153e154); K4 - Lv27-15-1 (527e528);MR1 - GC-1A (148e153); Kc2-3 - So178-1-4 (460e470); Aso4* - Lv28-64-5 (1108e1110); K5 - Ge99-38 (273e274);MR2 (AL7.2a) - Lv28-42-4 (656e657); AL7.2b - Lv28-42-4(660e661), Lv28-40-5 (790?); AL7.4 - Lv28-42-4 (736e737); nMR - MD01-2415 (1681), MR0604-PC5R (1111.5e1113.5); K6 - 9305 (450e455), Ge99-38 (404e405); MR3(AL9.22) - Lv28-42-4 (926e927), MR0604-PC7R (1517.6e1520.1); AL9.22b - Lv28-42-4 (926e927); MR4 (AL9.24) - Lv28-42-4 (936e937), MR0604-PC6R (1720.6e1725.6);AL10 - Lv28-42-4 (987e988); Md1 - MD01-2415 (2290e2292); Md2 - MD01-2415 (2806e2809); Md3 - MD01-2415 (3863e3866).


3. Results

3.1. Characteristics of tephra layers

The special features of tephra interlayers are listed in thesequence consistent with their age and stratigraphical position:from young to older ones.

KO tephra is presented by the light-gray (to whitish-gray) siltwith admixedfine sandyparticles. The layer occurs in thedeposits ofthe central andeasternSeaofOkhotsk atmanystations (Supplement1, Fig. 2). The tephra is visually observed in the form of white lensesand laminas of small thickness (0.5e1.0 cm) bioturbated essentiallyby the bottom burrowing organisms (Gorbarenko et al., 2002;


Derkachev et al., 2012). The maximal thickness of tephra (16 cm) isobserved at the station LV29-112 located in the lower part of thecontinental slope nearby Paramushir Island (Fig.1). In the ash layersof increased thickness, the discernible signs of differentiation ofparticles in density and sizes as a consequence of processes of theirtransport and settling to the bottom are noted. As a result, the signsof graded bedding are observed. The transparent fluidal-bubbly andlaminatedglasses (typesB andEaccording toKatohet al., 2000)withthe refraction index N ¼ 1.501e1.507 (mean of 1.503) predominate.In the coarse fractions, the light-gray and white pumiceous glass(typeB)prevails. Aside fromglass, tephra contains also anadmixture(maximum 25%) of crystalloclastics (plagioclases, rock fragments,pyroxenes, dark ore minerals).


Fig. 2. Areals of ash falls established in deposits from the Sea of Okhotsk. 1 -sediment columns with studied tephra layers; 2-sediment columns without tephra layers; 3- sedimentcolumns with tephra layer Aso4; 4-5-sediment columns with tephra layers according to (Okazaki et al., 2005; Sakamoto et al., 2005); 6-location of volcanoes supplied tephra for thefollowing layers: КО (Kurile Lake, Kamchatka), К2, К3 (Nemo III), Zv (TR) (Zavaritsky, Simushir Island), Т (Mashu, Hokkaido Island); 7-12-estimated areals of tephra distribution: 7-КО; 8-К2; 9-К3; 10-Zv (TR); 11-Т; 12-Aso4. Spfa1, Kc-Hb, Kc-Sr - areals of ash falls according to (Machida and Arai, 2003).


Among heavy minerals, the clinopyroxenes and orthopyroxenesprevail (mean of 35.5% and 38.8% in terms of the transparentminerals, respectively). The ratio of clinopyroxene to orthopyrox-ene (Cpx/Opx) is different and varies from 0.57 to 1.4 with a mean


of 0.9. A distinctive feature of the KO tephra is an increased con-centration of hornblende (up to 10e23% with a mean of 16.0%)including brown and basaltic hornblende (mean of 1.0%) enclosedoften in an “envelope” of volcanic glass. The apatite and mica are



also present (amounted to an average of 1.5 and 1.3% respectively).More detailed information on the mineral composition of tephraand peculiarities of the chemical composition of minerals is givenin the paper (Derkachev et al., 2016).

N tephra was found out in the sediment core GC12-6А from theKashevarov trough in the central Sea of Okhotsk among the Holo-cene terrigenous-diatomic deposits. The silt-size tephra layer islight-grey in color; the layer thickness is about 1 cm; its edges areindistinct, with lenticular-spotted structure. The pumiceous fine-porous volcanic glass (type A) being light-grey with a greenishtone predominates. Among the heavy minerals, the clinopyroxenesand dark ore minerals dominate, in the subordinate quantity, theorthopyroxene occurs.

TR(Zv) tephra was found out in five sediment cores to the southof the Academy of Sciences Rise, on the north-eastern slope ofKurile basin (Figs. 1 and 2, Supplement 1). The grey-colored tephralayer 1e2 cm thick is predominantly presented by the fine-sandyparticles. In the tephra composition, the colorless, with greyishtint volcanic glasses having a pumiceous-cellular and elongated-cellular forms (types A and B) predominate; the coarse-cellular-plate grains (types C and E) with refraction index of 1.505e1.507occur more rarely (Supplement 2). The olive-brown fragmentaryglass with the higher refraction index occurs as an admixture.There, the grains with numerous inclusions of microlites of py-roxenes and plagioclases are also present. The distinctive feature oftephra is an occurrence of a large crystal clastic admixtures (up to15e20%) represented by fragments of plagioclases and pyroxenesas well as glassy shards of the greenish-brown rocks with in-clusions of minerals’ microlites. In the mineral assemblage, a pre-dominance of orthopyroxene over clinopyroxene is observed (Cpx/Opx ¼ 0.55e0.96).

K2 tephra is distributed in the sediments of the central Sea ofOkhotsk and was found out in many sediment cores (Derkachevet al., 2004; Cruise Report …, 1999, 2000, 2003; Derkachev et al.,2011, 2012; Derkachev and Portnyagin, 2013; Gorbarenko et al.,2002; Sakamoto et al., 2006) (Fig. 2, Supplement 1). In the exam-ined sediment cores, it occurs as layers with varying thicknesses of1e22 cm (Fig. 2) and small lenses 0.3e0.6 cm in diameter. Themaximum thickness of tephra (up to 22 cm, station M969) wasobserved in the sediment cores located in the lows of the bottomrelief between the Institute of Oceanology and Academy of SciencesRises (Derkachev and Portnyagin, 2013). In most cases, the tephraconsists of the silt-fine sand sized particles. With increase of dis-tance from the explosive source, the size of ash particles lowers tothat of silt. In the thickest interlayers, the signs of the gravitysorting of particles as a result of their settling from the ash cloud arewell noted; the lower levels of the tephra layers are enriched inbigger particles. The bottom interface of ash layers is, as a rule,sharp and even or, less frequently, twisting while the top one isirregular and oftenwithmarks of deformations and flow structures.One of the most important diagnostic properties of this tephra is itscolor (grey, with a visible brownish tone).

In the tephra composition, the colorless volcanic glass of thefragmentary-vesicular and fluidal-cellular form (type E) pre-dominates. In the coarser fraction, the pumiceous particles (type C,rarely, type B) dominate. The refraction index of glasses N is1.504e1.510 (mean of 1.507) (Supplement 2). In the tephracomposition, the phenocrystals of plagioclases, pyroxenes, dark oreminerals, rarely, hornblende (crystalloclastics) enclosed often in an“envelope” of volcanic glass occur as admixtures (first percents). Anadmixture of resurgent material e fragments of rocks and particlesof andesite-basalt glass e is also noted.

In the heavy fraction, a not large predominance of orthopyrox-enes over clinopyroxenes is observed (Cpx/Opx ¼ 1.02 on average)at average contents of 44.8 and 48.1%, respectively. The


concentrations of amphiboles is low (less than 9.0%; mean of 2.8%),apatite is present in a small quantity (less than 4.0%; mean of 1.6%)(Derkachev and Portnyagin, 2013; Derkachev et al., 2016).

K3 tephra occurs in the sediments of the Academy of SciencesRise and adjacent areas extending in the sublatitudinal direction asa broad zone at a distance of up to 600 km west of Kurile Islands(Fig. 2). This tephra layer is visible as the strongly expressed againstthe background of enclosing sediments grey horizon with thepredominantly coarse-grain composition represented by sandsfrom fine- and medium-grained to medium- and coarse-grained,with a large amount of pumice particles up to 2e7 mm in size. Inthe layers of great thickness (up to 16 cm, station Ge99-38), anincrease in sizes of particles is observed toward the bottom of ho-rizon. In the bottom of the interlayer, a decrease in grade of thevolcaniclastic material to fine-grained sand with a considerableadmixture of silt is noted. The characteristic feature of the layer,apart from its coarseness and grey color, is a presence of a largequantity of the pumice and crystalloclastics fragments (large phe-nocrystals of plagioclases, pyroxenes and dark ore minerals as wellas their clots in the “envelope” of the volcanic glass). In this case,the crystalloclastics is present in both fine and coarse fractionsreaching 40e50% of total quantity of fractions (Gorbarenko et al.,2002). The specified features of K3 tephra distinguish it slightlyfrom the K2 tephra stratigraphically close to it (see above).

On the other hand, the signs of the similarity of the tephra understudy to K2 tephra are found out. In the first place, the signs of thesimilarity are manifested in the morphology of volcanic glasses andindex of their refraction (N¼ 1.502e1.512; mean of 1.507) as well asin closeness of mineral associations and chemical composition ofvolcanic glasses and minerals (Derkachev and Portnyagin, 2013;Derkachev et al., 2016). In the mineral assemblage, the associa-tion of the clino- and orthopyroxenes predominates (on average,46.4 and 43.5%, respectively). The content of hornblende is low (lessthan 7.5%), individual grains of brown hornblende occur. The rela-tive enrichment with hornblendes registered in a number of sam-ples is, probably, a consequence of pollution of these samples withan admixture of the terrigenous material. As a rule, an increase inthe quantity of epidote and other terrigenous fragments is regis-tered in the same samples. As a small admixture, the grayish-brownglass with numerous inclusions of microlites of pyroxenes and,rarely, dark-grey glass occur.

Т tephra was found out in 6 sediment cores taken in the south-western Sea of Okhotsk, on the slope of the Kurile basin west of theAcademy of Sciences Rise (Figs. 1 and 2, Supplement 1). It is visiblein cores as small lenses 0.2e0.6 cm in diameter filled in with theyellowish-grey silt. In the composition of tephra, the colorlessvolcanic glass of pumiceous-fine-cellular form (type A) pre-dominates, the glasses of pumiceous-fluidal form (types B and C)are less common and an admixture of crystalloclastics is alsoobserved. As admixtures, the glasses of more basic composition arenoted in this tephra. The refraction index of glasses N is1.501e1.502. In the mineral assemblage, the orthopyroxene andclinopyroxene (Cpx/Opx ¼ 0.22e0.38) dominate (Derkachev andNikolaeva, 2010; Derkachev et al., 2016). We assume that pres-ence of a small amount of hornblende (up to 5e10%) in T tephra iscaused by outside impurity because of error during sampling. It isknown, that hornblende is absent in products of explosive erup-tions of Masyu volcano (Hasegawa et al., 2012).

K4 tephra was found out in the one sediment core Lv27-15 onthe slope of Kurile basin in its north-east closing in the latitude ofthe Shiashkotan Island (Kurile Islands) (Fig. 1, Supplement 1). Thetephra in the core is visible as the isolated grey lenses with thick-ness of about 1 cm filled with the silt-sand particles with rare in-clusions of the pumice piece of the gravel size. In its composition,the colorless, predominantly pumiceous volcanic glass with



numerous irregularly located small cavities (type A) dominateswhile the pumiceous-fluidal glass (type B) is less common. Themore basic glass whose color varies from greenish-gray togreenish-brown is present as an admixture. The distinctive featureof the mineral assemblage is a predominance of clinopyroxene overorthopyroxene (Cpx/Opx ¼ 1.79) and presence of hornblendes (upto 12%) including a brown hornblende.

MR1 tephra in the form of beige-colored lenses with thicknessesof up to 3e4 mm was found at stations MR0604-PC-7R andMR0604-PC6R in the central Sea of Okhotsk. Among the ash par-ticles, the colorless glass of the coarse-cellular form predominateswhile, in the fine fraction, a fine-porous pumiceous one (types A, Fand, more rarely, type B) was predominantly found out. Therefraction index of glasses N is 1.511e1.514 (mean of 1.513). Amongthe heavy minerals, the clinopyroxenes (49.8%) and orthopyrox-enes (22.4%) prevail while the content of hornblendes is up to 11%.As an admixture, the increased content of terrigenous particles(epidote, mica, actinolite etc.) is observed (Derkachev et al., 2012,2016).

Kc2-3 tephra was recovered in the sediment core So178-1-4from the south-western part of Kurile basin. In this core, thenumerous layers of turbidites are registered. Tephra is traced in theform of badly defined lenses enriched in particles of sand-and-gravel size and represented mainly by pumice. The dispersed vol-caniclastics occurs in a large amount also among the material ofturbidites at the depths of 460e470 cm. The white fine-porousparticles of the pumiceous shape (types A and B; colorless in thinpieces) dominate. As the admixtures, the colorless glasses of frag-mentary type (fragments of great bubbles of C and E types) and,more rarely, the brownish glasses of the same morphological typeare observed. The occurrence of the considered volcaniclastics inthe turbidite sediments suggests its redeposited character. Thewell-defined interlayer of this tephra was found in the sedimentcore MD01-2412 taken southward, on the slope of the HokkaidoIsland (Sakamoto et al., 2006).

Аso4 tephra was recovered in the lower part of three sedimentcores taken on the north-west slope of Kurile basin (Figs. 1 and 2,Supplement 1). It is traced as the readily visible light-grey layerswith thickness of 0.7e3 cm represented by particles of silt size. Thistephra was also found in the southern Sea of Okhotsk off theHokkaido Island coast (Sakamoto et al., 2006, Aoki, 2008). Thetephra is characterized by the homogeneous composition andformed by the colorless, predominantly thin-walled volcanic glassof fragmentary form (fragments of great bubbles) (types D, E and,more rarely, C). The refraction index of glasses N is 1.507e1.510(Supplement 2). Among the mineral inclusions, the two-pyroxeneassociation (Cpx/Opx ¼ 1.03) dominates at relatively high contentof amphiboles (up to 29%). The distinctive feature of tephra is apresence of hornblendes with decreased magnesiality(Mg# ¼ 62.7) which distinguishes them from amphiboles fromother tephra layers of the Sea of Okhotsk (Derkachev et al., 2016).

K5 tephra was detected in three sediment cores taken in theAcademy of Sciences Rise (Fig. 1, Supplement 1) as the light-greylayers with thicknesses of 1e6 cm. Tephra consists of the silt-sand particles represented by predominantly colorless volcanicglass of the fluidal-cellular form (type B and, more rarely, E). In themineral assemblage, the pyroxenes dominate at similar contents ofclino- and orthopyroxenes (Cpx/Opx ¼ 0.91) and relativelyincreased content of amphiboles (up to 10%) (Derkachev et al.,2016). An admixture of terrigenous particles is present.

MR2 (AL7.2a) tephra was found in sediment cores (Lv28-42-4and MR0604-PC7R) in the central Sea of Okhotsk as a visible layer1e4 cm thick, represented by particles of the silt-fine sand size. Dueto bioturbation, some lenses of this tephra penetrate 3e5 cm belowthe main level. The possible analog of this tephra is thin layers and


lenses (up to 1e2 mm in thickness) observed in the sediment coresMR0604-PC6R, andMR0604-PC5R (Derkachev et al., 2012). The ashparticles are mainly presented by the colorless glass of thefragmentary-vesicular and, more rarely, fluidal-pumiceous form(types E, C and, more rarely, B) with refraction indexN ¼ 1.505e1.510 (mean of 1.508). In the composition of heavyfraction, the clinopyroxene (mean of 41.6%) dominates overorthopyroxene (mean of 26.7%) and the increased content of am-phiboles (mean of 9.9% on average) is noted. The distinctive featureis a presence of brown mica (biotite) (up to 3.0e10.0%), brown andbasaltic hornblende (oxyhornblende) (up to 2.2%). On the upperhorizons of tephra layer, a notable admixture of terrigenous parti-cles is recorded (Derkachev et al., 2012, 2016).

AL7.2b tephra is observed in the sediment core Lv28-42-4several centimeters below the layer MR2 (AL7.2a) as a thin,strongly bioturbated white layer with thickness of about 1 cm(Cruise Report…, 1999). In the composition of tephra, the colorlessglass (types C, B and, more rarely, E) predominates. The refractionindex of glass N is ~1.497e1.498. The distinctive feature of thistephra is a high content of biotite (up to 45.5e67.4%) and horn-blendes (up to 12.5e19.6%) with subordinate role of pyroxenes(Derkachev et al., 2016).

AL7.4 tephra was identified in sediment core Lv28-42-4 (Kaiser,2001; Gorbarenko et al., 2002; Nürnberg and Tiedemann, 2004). Itis visible in the form of white layer about 1 cm thick. Later it wasfound in sediment core MD01-2415 as a thin lens by thickness ofabout 2 mm (Bubenshchikova et al., 2015). The tephra was formedby predominantly colorless volcanic glass (types C and E predom-inate while types B and A are less common) of the silt-fine sandsize). The refraction index of glasses N is 1.490e1.498. The mineralassemblage is presented by pyroxenes (Cpx/Opx ¼ 1.5) with sig-nificant quantities of hornblendes and biotite (up to 38.4 and 7.3%;34.6 and 5.9% on average respectively). A considerable admixture ofterrigenous minerals (mainly, epidote) is present (Derkachev et al.,2016).

nMR tephra was recorded in two sediment cores taken on thesouth slope of the Lebed Rise (central Sea of Okhotsk) (Fig. 1,Supplement 1, Table 3). The light-grey (almost white) layer has athickness of about 2 cm. In its composition, the colorless glass(types A and B; more rarely, type E) dominates; the refraction indexof glasses N is 1.499e1.503 (mean of 1.501). The mineral assem-blage contains, nearly in equal quantities (Cpx/Opx ¼ 0.9e1.2), theclinopyroxenes and orthopyroxenes. For the layer, the high contentof hornblende (up to 20e25%) is characteristic.

K6 tephra was found out in two sediment cores from the southslope of the Academy of Sciences Rise (Fig. 1, Supplement 1). Thegrey layer formed by glass of sand-silt size is about 5 cm thick. Theglass is mainly presented by the colorless particles of fine-porous-pumiceous and fluidal form (types A and B). A considerableadmixture of the light-grey and grayish-light-brown glasses isobservedwhile the dark-brown glass of plate shape is less common.In the mineral assemblage, the pyroxenes (up to 74e92% in total)dominate.

MR3 (AL9.22) tephra is identified as a visible yellowish-grey layerwith thickness of 1 cm (station Lv28-42-4) to 6 cm (stationMR0604-PC7R) which is represented by the silt-fine-sand particles. Over andunder the interlayer, to thedepthof3e5cm, the signsof bioturbation(small lenses of oval shape filled in with the same ash material) areobserved. The volcanic glass is represented by the colorless grains(types E and B and,more rarely, type A). The refraction index of glassN is 1.504e1.508 (mean of 1.505). In the mineral assemblage, py-roxenes prevail and clinopyroxene dominates slightly over ortho-pyroxene (mean of 34.9 and 33.5%, respectively). The distinctivefeature of MR3 tephra is an increased content of hornblendes (up to29.2; 26.0% on average) and apatite (up to 3.2%).



On the horizon of 928e930 cm in sediment core Lv28-42-4under MR3 (AL9.22) tephra, the thin lenses of dark-gray volcanicashes differing markedly from the overlying ashes in their prop-erties were identified (Cruise Report …, 1999). In view of thestratigraphical closeness with MR3 (AL9.22) tephra, we assignthese lenses to the independent layer under the name of AL9.22b. Inthe composition of this tephra, the greenish-gray volcanic glassesof pumiceous shape (type A, rarely type B) predominate, the moredark-colored varieties (to dark-brown and black) and, rarely,colorless glasses of the similar shape occur as the admixtures. Manyparticles of glasses contain numerous microlites of plagioclases andpyroxenes.

MR4 (AL9.24) tephrawas found out in two sediment cores as thelayers with thicknesses of 1 cm (station Lv28-42-4) to 5 cm (stationMR0604-PC6R) and presented by greenish-gray with yellowish-brown tint silt and fine sand. In the composition of tephra, thedark-gray with greenish-light-brown tint volcanic glass of pumi-ceous shape (type A, rarely type B) predominates. There is aconsiderable admixture of dark-brown (to black) volcanic glasseswith numerous inclusions of microlites of minerals. The refractionindex of glasses is high (N > 1.530). In some grains, more acidicglass is also present in the form of colorless pumiceous particles. Inthe composition of tephra, there is in quantities an admixture ofcrystalloclastics in the envelope of volcanic glass. In the mineralassemblage, the pyroxenes predominate drastically (up to89e96.5%) with slight variations in content of clinopyroxenes andorthopyroxenes (Cpx/Opx¼ 0.7e1.2; 0.9 on average). The relativelyincreased content of apatite (up to 3e6.8%) is noted (Derkachevet al., 2016).

AL10 tephrawas identified only in one sediment core Lv28-42-4as a dark-gray layer with thickness of about 1 cm (Gorbarenko et al.,2002; Kaiser, 2001; Nürnberg and Tiedemann, 2004). Among thevolcanic glasses, the variety both in morphology and color of grainsis observed. The glasses of types A and C dominate while grains of Band E types occurmore rarely. The light-gray (to colorless) and lightbrown glasses occur practically in equal quantities. The deep-colored (dark brown and black) glasses containing large quanti-ties of inclusions of microlites of minerals occur more rarely. Therefraction index of volcanic glasses varies from 1.520 to 1.548. Forthe tephra considered, a predominance of orthopyroxenes overclinopyroxenes (Cpx/Opx ¼ 0.73) and low content of the horn-blendes are characteristic.

Md1, Md2 and Md3 tephras were identified by us in the lower,most ancient (Early-Middle Pleistocene) part of sediment coreMD01-2415 on the horizons of 2290e2292, 2806e2809 and3863e3866 cm respectively. In the composition of tephrasMd1 andMd2, the thin-walled, colorless, fragmentary and fluidal-cellularglasses of E and C types and, more rarely, B type dominate. InMd3 tephra, the colorless pumiceous glass (type A and, rarely, typeB) and fragmentary-cellular (type E) glass predominate. Thedistinct feature of tephra Md2 is a presence of biotite admixture.

Characteristics of glass chemistry which is the most useful foridentification and correlation, will be shown next chapter.

3.2. Chemical composition of volcanic glasses

One of the most important diagnostic properties of tephra is thechemical composition of volcanic glasses (Table 1, Supplement 3).

3.2.1. Distribution of major elementsThe typification of volcanic glasses is given in accordance with

recommendations in paper (Le Bas et al., 1986) (Fig. 3) and addi-tions on (Klassifikatsiya …, 1997). According to the classificationdiagram AFM (Irvine and Baragar, 1971), the majority of chemicalcompositions of glasses from the tephra studied resemble calc-


alkaline rock series. The glasses of tephras N and AL9.22b and in-dividual grains of tephras MR4 (AL9.24) and AL10 conform to thederivates of tholeitic magmas.

As to the chemical composition, the volcanic glasses of thetephra layers examined are mainly homogenous and belong torhyolites (more rarely, rhyodacites) with normal (standard) alka-linity of calc-alkaline rock series (Fig. 3, Table 1). Of the majority ofthem, a predominance of Na2O over K2O 1.3e2.7 times is charac-teristic. The low-alkaline and medium-alkaline tephras are lesswidespread. In the low-alkaline glasses of tephras T, TR (Zv) and,partially, K4, this proportion increases to 3.2e5.5. According to theAl* ¼ Al2O3/(FeO*þMgO) ratio, the tephras considered belong torather high-aluminous varieties with values Al* ¼ 4.8e7.2 and,more rarely, 7.3e10.7 (KO and nMR tephras) due to their lowermagnesiality and ferruginosity (Figs. 4 and 5). The glasses of Md2tephra (Al* ¼ 16.9e19.6) fall into category of the extremely high-aluminous varieties. The volcanic glasses of the low-potassiumrhyolites-rhyodacites of tephras T and TR (Zv) are characterized bythe decreased alumina (Al* ¼ 2.1e4.3) (Fig. 4c). Distinctive sign forthem is higher ferruginosity of glasses from tephra TR (Zv) (Fig. 4c).

Glasses of three tephra layers (AL7.4, AL7.2b, Aso4) belong to themedium-alkaline trachyrhyolites of the calc-alkaline rock series atrelatively increased content of K2O (up to 3.5e4.7%wt of K2O). Aratio Na2O/K2O for them varies from 0.7 to 0.9 for tephra Aso4 to0.9e1.2 for tephras AL7.4 and AL7.2b. The volcanic glasses of theselayers belong to rather high-aluminous and extremely high-aluminous varieties with values of Al* equal to 5.9e8.2 and13.6e17.7 for tephras Aso4 and AL7.4, AL7.2b, respectively (Table 3).

Glasses of the tephras belonging to andesites (AL9.22b), dacitesand rhyodacites (K6, N, MR1 and, partially, T) (Fig. 3) are lesswidespread in the Sea of Okhotsk deposits. Based on relation SiO2-Na2Oþ K2O, SiO2-K2O, they belong to low-potassium and medium-potassium rocks of normal and low alkalinity (Figs. 3e5, Table 1).According to value of Na2O/K2O, they are characterized by thepotassium-sodium (K6, MR1) and sodium (N, AL9.22b) specializa-tionwith the average values of 2.6e3.1 and 4.8e5.7, respectively. Tothe petrochemical features of glasses from these tephras, theincreased content of FeO (up to 4.6e8.1%wt on average), MgO (up to1.0e2.5%wt on average) and CaO (up to 4.6e8.1%wt on average)should be assigned. According to value of Al*, they belong to thehigh-aluminous (N, AL9.22b) and rather high-aluminous (K6, MR1)rock varieties.

Glasses of two tephra layers (MR4 (AL9.24) and AL10) belong tomedium-potassium (partly, high-potassium) trachyandesite-tra-chydacites of medium-alkaline rock series (Figs. 3 and 5, Table 1)which are related to the rather high-aluminous varieties(Al* ¼ 2.0e2.3). Despite the relative proximity of the compositionof volcanic glasses of the considered tephra layers, a number ofdifferences is observed. So, of the tephra AL10, the more hetero-geneous chemical composition and relatively increased content ofFeO*, MgO, CaO, K2O (Table 1) are characteristic. In a number of theHarker diagrams, the distinctive features of the chemical compo-sition of these tephras are clearly visible (Fig. 5).

The discriminant analysis is very effective method estimatingdegree of distinction of material composition of rocks including achemical composition of volcanic glasses (Pearce and Cann, 1973;Bourne et al., 2010). We divided preliminarily the initial data onchemical composition of glasses from the tephra layers into twoarrays grouped in accordance with ages of tephra layers. The firstgroup included data for tephra layers of the Late Pleistocene-Holocene age (less than 120 thousand years). The second groupcontained data for tephra layers of the Middle-Pleistocene age. Tothese data arrays, a procedure of discriminant analysis was appliedwith calculation of equations of discriminant functions and esti-mating their significance and efficiency of the division of initial data


Fig. 3. SiO2-NaO þ K2O variation diagram (Le Bas et al., 1986) of glass shards of tephra layers from the Sea of Okhotsk. Notes and indexes of tephra layers see in the text.


into groups. During calculation, the programs of the discriminantanalysis from the application package of computer programsSTATGRAPHICSwere used. The results obtainedwere plotted on thediagrams taking into account the values of the first and second,most significant discriminant functions (Fig. 6). As it follows fromthis Figure, a division of the tephra layers according to chemical


composition of volcanic glasses was fairly efficient. The compactareas of the scattering of imaging points of the composition forseparate tephra layers are well-defined. The exception is providedby a tephra of the heterogeneous composition or tephra with asimilar composition of glasses (for example, K2 and K3, MR4(AL9.24) and AL10 tephras).


Fig. 4. Bi-component Harker's diagrams of a chemical composition of volcanic glasses from tephra layers in the Late Pleistocene-Holocene deposits of the Sea of Okhotsk (age lessthan 220 kyr). Notes and indexes of tephra layers see in the text.


As the indicated diagrams were developed with due consider-ation of all the spectrum of content of major elements of the vol-canic glasses and with the following calculation of the values ofdiscriminant functions, their use accelerates and facilitatesconsiderably the procedure of carrying out of the comparativeanalysis of new data on tephra composition, its identification and,therefore, correlation of the deposits under study.

3.2.2. Distribution of microelementsOne of the correct methods of correlation and identification of the

tephra layers is an analysis based on microelements and rare-earthelements (Aksu et al., 2008; Pearce et al., 2004; Sakhno et al., 2006,2010; Tomlinson et al., 2012 and others). In accordance with resultsof cluster analysis on the distribution of rare-earth elements, 6 rela-tively independent groups of tephra layers are identified. Into the firstgroup, the tephras N, Zv (TR), K4 and AL9.22b (low-potassiumrhyodacites-rhyolites, dacites and andesites) are included. They arecharacterized by unfractionated spectra of distribution of the rare-


earth elements normalized to chondrite (Fig. 7a). The values of La/Yband La/Sm are 0.92e1.24 and 0.88e1.05, respectively. The europiumanomaly is slightlymanifestedorabsent at all (Eu/Eu*¼0.76e0.97).OfK4 tephra, a slightly enhanced background of contents of the lightlanthanides (LREE) in relation to heavy (HREE) and medium (MREE)ones (La/Yb ¼ 1.29, La/Sm ¼ 1.19) is characteristic (Table 2).

According to the nature of REE distribution, the majority ofexplored tephra layers are close against each other and they werecombined into the second (tephras K2, K3, K5, MR2 (AL7.2a), Kc2-3,Md1, Md3) and third (tephras KO, T, MR1, K6) groups (Fig. 7 b, c, d).Most of them belong to the medium-potassium rhyolites anddacites-rhyodacites (more rarely). The spectra of REE distributionare characterized by low and medium degrees of fractionating ofthe light lanthanides relative to the heavy and medium ones (La/Yb ¼ 1.67e2.23, La/Sm ¼ 1.46e1.95). In most cases, they have thewell-defined, negative europium anomaly (Eu/Eu* is 0.52e0.74 onaverage) that is more strongly manifested in K2, K3, K5 tephras(Fig. 7b and c). Of the glasses from tephras falling under the third


Fig. 5. Bi-component Harker's diagrams of a chemical composition of volcanic glasses from tephra layers in the Middle Pleistocene deposits of the Sea of Okhotsk (age more than220 kyr).


group, the slightly decreased concentrations of REE (lower than75 ppm) as compared with tephras of the second group are char-acteristic (Table 2). As it follows from Table 2 and Fig. 7c and d, the Tand K6 tephras contain an admixture of glasses having differentcomposition which is also confirmed by data of content of majorelements in these glasses (Figs. 3e5).

The fourth group includes the layers of MR4 (AL9.24) and AL10tephras which belong to trachyandesites-trachydacites. Of them, incontrast to previous groups, the spectra of REE distribution with


more pronounced degree of fractionating (La/Yb ¼ 2.74e3.61, La/Sm ¼ 1.7e2.13) are characteristic. The spectra of normalized REEconcentrations have a gentle slope in the light part with gradualflattening in the area of heavy lanthanides (Gd/Yb ¼ 1.21e1.6). Theeuropium anomaly is unexpressed (Eu/Eu* ¼ 0.84e0.96) (Fig. 7e).

The fifth group contains the glasses from tephra layers of AL7.2b,MR3 (AL9.22), nMR and Md2 which are represented by themedium-potassium rhyolites. Despite the general similarity of theREE distribution curves to ones for previous layers of tephras (fourth


Fig. 6. The discriminant diagram of a chemical composition of volcanic glasses of tephra layers from the Sea of Okhotsk. df1, df2 - values of 1st and 2nd discriminant functions: (A) -for the Late Pleistocene-Holocene tephra layers: df1 ¼ �0.5866 SiO2-1.128 TiO2-0.757 Al2O3-2.792 FeOþ0.011 MnOþ2.615 MgO-1.963 CaO-0.647 Na2Oþ5.249 K2Oþ55.73;df2 ¼ �1.287 SiO2þ1.94 TiO2þ0.514 Al2O3þ2.706 FeO-2.196 MnO-3.898 MgO-0.973 CaO-0.865 Na2Oþ4.059 K2Oþ81.46. Oval figures designate areas characterizing the compositionof volcanic glasses found on the land (Aso4, Zavaritsky, Mashu, Kutcharo, Kurile Lake volcanoes); (B) - for the Middle Pleistocene tephra layers: df1 ¼ 1.89 SiO2-6.061 TiO2-1.166Al2O3-0.355 FeO-2.535 MnO þ 4.264 MgOþ2.821 CaO-0.455 Na2O þ 1.598 K2O-130.69; df2 ¼ �0.691 SiO2-7.72 TiO2 þ 1.157 Al2O3 þ 0.84 FeO þ 3.511 MnO þ 1.68 MgO-1.907 CaO-1.215 Na2O þ 4.347 K2Oþ32.19. Indexes of tephra layers see in the text.


Please cite this article in press as: Derkachev, A.N., et al., Tephra layers of in the quaternary deposits of the Sea of Okhotsk: Distribution,composition, age and volcanic sources, Quaternary International (2016), http://dx.doi.org/10.1016/j.quaint.2016.07.004

Fig. 7. Distribution of REE normalized to chondrite (Sun and McDonough, 1989), in tephra layers from the Okhotsk Sea sediments. Note. Initial data are listed in Table 2. Methods: alldata -LA ICP MS, Christian-Albrechts University, Kiel, Germany (M. Portnyagin is analyst); Aso4 - ICP MS A.P. Vinogradov Institute of Geochemistry, Siberian Branch of RAS, Irkutsk(Sakhno et al., 2010) and in FIO, Qingdao, China (analyst is Chen Jihua), Aso4 (1) e (Kimura et al., 2015).



Table 2Mean composition LA ICP MS analyses of trace and rare earth elements on glass shards in tephra layers of Pleistocene-Holocene deposits from the Sea of Okhotsk.

Sample name Lv29-110 GC12-6a 9301 Lv28-37 Lv55-38 Lv29-72-2 GC-12-1A Lv27-15-1 So178-1-4

Tephra index KO N TR (Zv) K2 К3 T MR1 K4 Kc2-3

n 9 5 13 13 14 9 4 11 7 13 2La 11.6 5.7 6.9 14.0 13.8 8.2 13.8 9.2 9.1 14.0 13.5Ce 28.2 14.5 18.6 33.0 34.5 18.8 31.2 21.1 22.2 32.9 29.9Pr 3.5 2.3 2.8 4.4 4.5 2.5 4.3 2.9 3.2 4.3 3.7Nd 15.6 12.6 14.6 20.5 20.4 12.2 20.6 14.0 16.8 20.2 15.8Sm 4.0 4.2 4.8 5.6 5.5 3.6 5.2 3.8 4.9 5.5 4.0Eu 0.9 1.4 1.4 1.1 1.0 0.9 1.0 1.1 1.7 1.4 0.8Gd 4.3 5.5 6.7 7.2 6.3 5.2 6.7 5.3 6.5 6.4 4.1Tb 0.7 0.9 1.1 1.1 1.0 0.8 1.1 0.9 1.1 1.1 0.7Dy 5.0 6.2 7.5 7.5 7.0 5.3 7.4 5.8 7.1 7.2 4.6Ho 1.1 1.4 1.7 1.7 1.5 1.2 1.6 1.3 1.6 1.6 1.0Er 3.5 4.1 5.2 5.3 4.8 3.5 5.1 3.8 5.0 4.9 3.2Tm 0.5 0.6 0.8 0.8 0.7 0.5 0.7 0.6 0.8 0.7 0.5Yb 3.8 4.2 5.4 5.5 5.2 3.6 5.6 3.9 5.1 5.2 3.8Lu 0.6 0.7 0.8 0.9 0.8 0.6 0.9 0.6 0.8 0.8 0.6Sum REE 83.3 58.6 78.3 108.6 107.0 66.9 105.2 74.3 85.9 106.2 86.2Cs 2.6 1.4 1.8 3.2 3.2 4.5 3.0 3.8 2.6 2.7 2.8Rb 41.4 11 13.6 45.6 46.4 29.9 44.1 30.7 24.7 42.3 47Ba 514 176 218 447 454 432 433 415 347 546 613Th 2.9 0.8 0.9 4.3 4.1 2.4 4.1 2.8 1.9 4.7 5.7U 1.3 0.3 0.4 1.6 1.6 1.1 1.5 1.0 0.7 1.4 1.7Nb 3.1 1.2 1.8 4.3 4.4 3.1 4.1 3.3 1.7 2.7 2.3Ta 0.2 0.1 0.2 0.3 0.3 0.3 0.3 0.2 0.1 0.2 0.2Pb 12.6 9.2 10.7 15.7 16.0 44.6 14.7 20.4 16.9 19 15.4Sr 111 212 166 111 110 194 116 216 242 135 120Zr 182 98 127 226 207 83 228 115 128 156 167Hf 5.2 2.6 3.7 6.3 5.7 2.4 6.2 3.4 4.0 4.5 4.6Y 31.7 38.4 46.3 48.5 43.9 34.6 50.0 37.3 43.7 44.2 30.9

Sample name Ge99-38 Lv28-42-4 Lv28-42-4 MR0604-PC7R Lv28-42-4 MD01-2415 Ge99-38 Lv28-42-4

Tephra index K5 MR2 (AL7.2a) AL7.2b MR3 (AL9.22) AL7.4 nMR K6 MR4

n 13 14 5 22 6 11 7 3 3 5La 14.3 14.6 20.6 15.5 28.0 10.4 14.0 9.6 14.2 22.3Ce 33.8 34.4 39.2 32.0 55.4 21.6 31.5 22.2 30.9 50.9Pr 4.4 4.5 4.0 3.7 6.0 2.5 4.4 2.9 4.3 7.2Nd 20.9 20.7 14.3 14.6 21.6 9.7 20.5 13.5 20.7 33.4Sm 5.6 5.6 2.2 3.0 3.9 2.0 6.7 2.8 4.9 8.5Eu 1.5 1.4 0.4 0.7 0.5 0.5 1.7 1.1 1.6 2.4Gd 6.8 6.5 2.0 2.8 3.4 1.9 6.9 4.1 6.3 8.5Tb 1.1 1.1 0.3 0.5 0.5 0.4 1.2 0.7 1.0 1.4Dy 7.59 7.1 2.2 3.0 3.2 2.3 7.6 4.2 7.3 8.7Ho 1.7 1.5 0.4 0.6 0.7 0.5 1.6 0.9 1.8 2.0Er 5.2 4.8 1.5 2.0 2.1 1.7 4.6 3.1 5.5 5.6Tm 0.8 0.7 0.2 0.3 0.3 0.3 0.7 0.5 0.8 0.8Yb 5.6 5.2 1.7 2.4 2.4 2.1 5.1 3.4 4.6 5.9Lu 0.9 0.8 0.3 0.4 0.4 0.3 0.8 0.5 0.8 0.9Sum REE 110.2 108.9 89.3 81.5 128.4 56.2 107.3 69.5 104.7 158.5Cs 2.5 2.7 2.4 2.7 2.3 2.6 2.7 1.8 3.0 1.9Rb 39.7 41.2 86.5 63.9 91.5 42.3 34.8 27.6 40.1 42.2Ba 55.3 582 679 789 159 568 509 346 507 669Th 4.8 4.8 6.9 4.7 7.2 3.1 3.9 2.4 4.2 2.8U 1.6 1.6 3.2 1.9 3.5 1.3 1.2 0.8 1.5 1.2Nb 2.8 2.8 16.0 4.2 21.2 2.6 2.5 2.0 2.8 8.0Ta 0.2 0.2 1.5 0.4 1.5 0.2 0.2 0.2 0.2 0.5Pb 16.1 17.1 12.8 14.8 16.7 11.1 13.6 7.6 16.9 12.2Sr 126 163 71 156 18 113 232 192 255 332Zr 167 168 76 193 112 125 150 115 153 263Hf 5.0 4.9 2.9 4.9 3.5 3.4 4.1 2.6 4.7 6.5Y 48.0 44.9 13.3 19.7 20.6 16.3 45.6 28.7 47.4 50.3

Sample name Lv28-42-4 Lv28-42-4 MD01-2415 MD01-2415 MD01-2415

Tephra index AL9.22b AL10 Md1 Md2 Md3

n 12 9 2 12 13 13La 6.6 21.6 27.8 12.5 13.7 16.3Ce 17.0 50.0 62.8 30.7 26.5 37.8Pr 2.6 7.0 8.0 4.4 2.8 5.2Nd 13.7 33.7 35.7 20.4 9.6 24.1Sm 4.1 8.1 8.4 5.6 1.7 6.1Eu 1.5 2.6 1.9 1.4 0.3 1.3Gd 5.1 8.3 7.8 6.1 1.5 6.6Tb 0.9 1.3 1.3 1.0 0.3 1.1



Table 2 (continued )

Sample name Lv28-42-4 Lv28-42-4 MD01-2415 MD01-2415 MD01-2415

Tephra index AL9.22b AL10 Md1 Md2 Md3

Dy 5.7 7.1 8.1 6.8 1.6 7.2Ho 1.2 1.6 1.8 1.5 0.3 1.6Er 3.7 4.6 5.0 4.5 1.1 4.8Tm 0.6 0.7 0.8 0.7 0.2 0.7Yb 3.8 4.3 5.7 5.0 1.5 5.1Lu 0.6 0.7 0.9 0.8 0.2 0.8Sum REE 67.1 151.6 176.0 101.4 61.3 118.7Cs 1.1 1.6 3.0 2.1 3.7 3.2Rb 12.2 39.6 77.0 40.0 82.7 60.1Ba 177 634 891 542 915 746Th 1.1 3.0 5.2 2.2 4.5 3.8U 0.5 1.2 2.1 1.3 2.7 1.6Nb 1.9 7.6 11.7 5.6 3.8 5.4Ta 0.1 0.5 0.7 0.4 0.4 0.4Pb 9.1 12.1 14.0 9.9 9.2 10.7Sr 298 455 177 119 67 106Zr 85 237 388 196 65 249Hf 2.5 6.0 9.5 5.2 2.2 6.6Y 33.5 45.0 47.7 41.9 10.6 44.8

Note. Methods and institutes: LA ICP MS, Christian-Albrechts University, Kiel, Germany (M. Portnyagin is analyst).


group), they differ from them in the lower content of both light andheavy lanthanides (Fig. 7f) at slightly larger values of La/Yb (up to8.82) and La/Sm (up to 6.12). A tendency to increase in heavy lan-thanides from Ho to Lu is clearly evident. The negative europiumanomaly (Eu/Eu* ¼ 0.57e0.77) (Table 2) was also revealed.

Into the sixth group, the layers of Aso4 and AL7.4 tephras (tra-chyrhyodacites-trachyrhyolites) were included. They differ from allother tephra layers from the Sea of Okhotsk in the highest degree offractionating of REE: La/Yb from 5.09 to 6.89 (Aso4) to 8.48 (AL7.4).The higher values are also characteristic of La/Sm: 2.53e3.32 and4.67 respectively. The specific feature of the tephras underconsideration is a well-defined negative europium anomaly (Eu/Eu* ¼ 0.42e0.63) (Fig. 7g) which suggests a higher degree of frac-tionating for plagioclases in the initial magmas.

The spectra of distribution of rare and rare-earth elementsnormalized to the primitive mantle (Sun and McDonough, 1989)exhibit the typically island-arc signs (Churikova et al., 2001;Portnyagin et al., 2005; Duggen et al., 2007; Martynov et al.,2010; Miyagi et al., 2012, and others). So, based on key geochem-ical indices, the analyzed tephras are products of oversubductionvolcanites of which the high contents of large-ionic lithophils (LILE)(Rb, Ba, U as well as Pb) and low concentrations of high fieldstrength elements (HFSE) (Nb, Ta) (Fig. 8) are characteristic. Of themajority of tephras, a presence of the strongly-expressed negativeTa-Nb anomaly is peculiar. A minimum of Sr the value of whichdecreases (or is entirely absent) in the more basic on silica contenttephras (N, TR (Zv), K4, AL10) is also well traced. By the value of Ta-Nb anomaly, the tephras layers can be sorted (in order ofdescending) in the following sequence: N, TR (Zv), K4, AL9.22b, K6,K2-K3, KO, K5, AL7.2a, K6, Kc2-3, N, nMR, MR1, Md1, Md3, MR3,Md2, AL10, MR4 (Fig. 8). Against this background, the tephras Aso4,AL7.4 and AL7.2b stand out. In their spider-plots, the negative Ta-Nbanomaly smoothes out almost completely but the Ba minimumappears with simultaneous increasing Sr minimum (Fig. 8e). Inmore details, the distinctive signs of tephras related to rare andrare-earth elements are noticeable in the binary diagrams (Fig. 9).

4. Discussion

4.1. Age and identification of tephra layers

In the process of the tephrostratigraphical studies, data on age ofdeposits and results of identification of tephra interlayers with


known occurrences of explosive volcanism on adjacent land are of agreat importance. We used the published materials for a number ofstandard sediment cores from the Sea of Okhotsk for which thecomplex of methods of deposits correlation was involved as a basisof stratigraphic position of the tephra layers under study(Gorbarenko, 1991; Ivanova and Gorbarenko, 2001; Barash et al.,2001, 2006; Derkachev et al., 2004; Levitan et al., 2007;Gorbarenko et al., 1998, 2002, 2004, 2007, 2010, 2012, 2014;Greinert et al., 2002; Kaiser, 2001; Nürnberg and Tiedemann,2004; Okazaki et al., 2005; Sakamoto et al., 2005, 2006). In addi-tion, data of age and chemical composition of known layers oftephra in the Pleistocene-Holocene soil-pyroclastic cover of theadjacent land (Kamchatka, Kurile and Japanese Islands) were used(Bazanova et al., 2005; Melekestsev et al., 1991,1996,1997;Machidaand Arai, 2003; Machida, 1999; Aoki, 2008; Aoki and Arai, 2000;Arai et al., 1986; Braitseva et al., 1993, 1995, 1997; Hasegawaet al., 2008, 2009, 2011, 2012; Hunt and Najman, 2003; Katohet al., 1995; Kyle et al., 2011; Kishimoto et al., 2009; Machida andArai, 2003; Matsumoto, 1996; Nakagawa et al., 2008; Okumura,1991; Pevzner, 2015; Ponomareva et al., 2004, 2007; Zaretskayaet al., 2001, 2007; Yamamoto et al., 2010 and others). The resultsof these comparative complex studies were summarized in thetotal table which characterizes the basic features of the examinedtephra layers of the Sea of Okhotsk and, on the other hand, presentsthe stratigraphic positionwith estimation of their age over a periodof up to 350 thousand years (for station MD01-2415 of RV “MarionDufresne” - up to 900 thousand years) (Table 3). The frequency ofoccurrence of the tephra layers in the Sea of Okhotsk depositsduring different periods of the Pleistocene-Holocene history can betraced in Fig. 10 in which the stratigraphic position of the tephralayers was compared against the known age isotopic-oxygeniccurve (Bassinot et al., 1994).

Of all examined tephra layers in the Sea of Okhotsk deposits, wehave earlier identified the KO, TR (Zv), K2 and K3 tephras(Derkachev and Portnyagin, 2013; Derkachev et al., 2011, 2012;Gorbarenko et al., 2002).

The stratigraphic position of KO tephra from sediment cores ofthe Sea of Okhotsk (Gorbarenko et al., 2002, 2012; Kaiser, 2001) aswell as the chemical composition of the volcanic glasses are com-parable to those of the known KO tephra layer found in the Holo-cene deposits on the adjacent land (Fig. 6, Table 3). This tephracorresponds to the great caldera-forming explosive eruption of theKurile Lake volcano in the south Kamchatka that took place,


Fig. 8. Primitive mantle-normalized (Sun and McDonough, 1989) trace element patterns for glass shards in tephra layers from the Okhotsk Sea sediments. Initial data are listed inTable 2.




according to different sources, 7.43e7.98 thousand years (14C) or8.0e8.4 thousand calibrated years ago (Braitseva et al., 1997;Hasegawa et al., 2011; Ponomareva et al., 2004, 2007; Zaretskayaet al., 2001, 2007). By the volume of erupted pyroclastic material(about 170 km3), this eruption is one of the greatest in the Kam-chatka happened during Holocene. A zone of ash fall has stretchednorth-westward and was traced at a distance of more than onethousand kilometers from the eruption centre (Braitseva et al.,1997; Ponomareva et al., 2004, 2007; Derkachev et al., 2011,2012; Melekestsev et al., 1991) (Fig. 2).

TR (Zv) tephra layer which is tracked in eastern areas of the Seaof Okhotsk adjacent to a middle part of the Kurile Island arch(Fig. 2) is rather confidently identified. Earlier, this tephra layercalled TR was connected with the Holocene eruption of the Tao-Rusyr volcano on the Onekotan Island (Derkachev et al., 2004;Gorbarenko et al., 2002). However, new data on the tephracomposition in the soil-pyroclastic cover of the Kurile Islandsshowed that the tephra under consideration belongs to the markerlayer of Zv-Su tephra (Zavaritsky-Shumshu). The source of thistephra is a violent explosive caldera-forming eruption of theZavaritsky volcano on the Simushir Island (central part of KurileIslands) the age of which is estimated about 8.0 thousand calendaryear (Nakagawa et al., 2008). On a chemical composition of volcanicglasses, TR (Zv) tephra is very close to the GA tephra which wasfound on the Paramushir Island (north part of Kurile Islands) and itsage makes near 8.54 (14C) thousand year (Hasegawa et al., 2011).This is also confirmed by data of sediment cores recovered in theSea of Okhotsk (Gorbarenko et al., 1998, 2002; Kaiser, 2001). Highcoincidence of the chemical compositions of the rhyolite glassesfrom TR (Zv) layer and Zv-Su tephra is clearly visible in Figs. 6, 7aand 9.

The areas of the ash falls for K2 and K3 tephras on land wereunknown but, at sea, they were clearly traced in the north-west (K2tephra) and sublatitudinal (K3 tephra) directions from the eruptioncenters which were located on the Onekotan Island (northern partof the Kurile Island arc) (Gorbarenko et al., 2002; Derkachev et al.,2011, 2012; Derkachev and Portnyagin, 2013) (Fig. 2). Based oncomplex studies, it was found that the most probable source ofpyroclastics was the great caldera-forming explosive eruptions ofthe Nemo volcano in the north part of the Onekotan Island(Melekestsev et al., 1997; Derkachev and Portnyagin, 2013). Ac-cording to the data of radiocarbon analysis, the age of layers with K2tephra is estimated at 25.71e26.6 thousand years (14C)(Gorbarenko et al., 2002, 2007, 2010; Greinert et al., 2002) or30.46e31.2 thousand calendar years respectively (Table 3). Thecaldera-forming eruption of the Nemo-III volcano being 24.5thousand years ago (14C) is most similar in time (age) one amongthe known in this region great explosive eruptions (Melekestsevet al., 1997). According to our calculations, the volume of pyro-clastics of this explosive eruption is about 9 km3 (Derkachev andPortnyagin, 2013) which is consistent with data of paper(Melekestsev et al., 1997).

It was suggested (Derkachev and Portnyagin, 2013) that thecaldera-forming eruption of the Nemo-II volcano relatively close intime to the following strong eruption of Nemo-III could be thesource of explosive material when forming the K3 tephra(Melekestsev et al., 1997). According to researches of these authors,the directed explosion took place north-westward, toward the Seaof Okhotsk. The material traces of this strong eruption were notkept on land due to the denudation processes. It was stated that K3tephra in sediment core Ge99-10 is younger than the T tephra layer(Artemova et al., pers. com.) and the age of the latter is about 35e38thousand years (see below).

The T tephra, represented by the low-potassium rhyolites-rhyodacites, was recorded in several sediment cores recovered on


the slope of the Kurile basin (western Sea of Okhotsk). According tothe results of litho- and biostratigraphic correlation of sedimentcores from the Sea of Okhotsk and data on oxygen isotopy offoraminifera in them, the stratigraphic position of T tephra falls onthe end of isotopic stage 3 (MIS 3) and is very close to position of K3tephra (Ivanova and Gorbarenko, 2001; Derkachev et al., 2004;Artemova et al., in press).

A comparison of the composition of volcanic glasses of T tephrawith the chemical composition of the tephra found in the LatePleistocene deposits on the Hokkaido Island points at their essen-tial similarity to the products of explosive eruptions of the Mashuvolcano (Fig. 6a). Here, it is pertinent to note that the low-potassium volcanic glasses are characteristic of both Holocenerocks and rocks of the older eruptions of this volcano (Kishimotoet al., 2009; Okumura, 1991; Hasegawa et al., 2009, 2012). TheLate Pleistocene episodes of the strong explosive eruptions of theMashu volcano (with volume of up to 10 km3) were fixed in thesoil-pyroclastic cover to the east and north of this volcano. Thethick pumice layers of the Nakashumbetsu (Upper Nakashumbetsu)series (Nu-r, Nu-p, Nu-n) and, north of the volcano, the pumicelayers YmP and HkP (Yambetsu and Higashikayano pumice) areconfined to the time period to which the T tephra layer is related(Hasegawa et al., 2012; Yamamoto et al., 2010). A formation of thesepumice deposits has taken place in the time interval of 35e38thousand calendar years (30.32e34.69 thousand years according to14C) (Yamamoto et al., 2010). The layers of tephra Ds-Oh and Kc-Sr(KpI) which age is estimated at 32.6 thousand years (14C) are alsoadditional marking (refining) age reference points (Okumura, 1991;Hasegawa et al., 2012; Yamamoto et al., 2010). Therefore, this dataof age are in good agreement with the established by us strati-graphic position of T tephra found in sediment cores of the Sea ofOkhotsk (Table 3).

The Kc1 (Kc-Sr), Spfa-1 and Kc4 (Kc-Hb) tephras which areconnected with the explosive activity of Kutcharo and Shikotsuvolcanoes on Hokkaido Island can be placed into the category ofidentified tephra layers of the Sea of Okhotsk. Their age is estimatedat 34.69e34.9, 39.43e40.12 (14С) and 115e120 thousand yearsrespectively (Table 3) (Yamamoto et al., 2010; Katoh et al., 1995;Aoki and Arai, 2000; Hunt and Najman, 2003). These tephralayers were not discovered in sediment cores studied by us. Butthey were found in sediment core MD01-2412 recovered on theslope of Hokkaido Island: Kc1(Kc-Sr) and Spfa-1 with ages of ~32.5and 42e43 thousand calendar years respectively (Okazaki et al.,2005; Sakamoto et al., 2006).

A tephra discovered in sediment core So-178-1-4 recovered inthe Kurile basin coincides fully with tephra Kc2-3 in sediment coreMD01-2412 taken on the slope of Hokkaido Island in the chemicalcomposition of volcanic glasses (Okazaki et al., 2005; Sakamotoet al., 2006). This tephra is similar in composition of both majorand rare and rare-earth elements to the pumice deposits KpII/III onHokkaido Island identified near the Kutcharo volcano (Hasegawaet al., 2011; Hoang et al., 2011). According to different sources,the age of these pumice deposits is estimated at the interval of84e90 thousand years (Machida and Arai, 2003; Machida, 1999;Yamamoto et al., 2010). In this case, the series of pumice KpII/IIIis stratigraphically situated above the marker layer of Aso4 tephra(about 88 thousand years) well represented on the Japanese Islandsand adjacent seas (Aoki, 2008; Oba et al., 2006; Hasegawa et al.,2012; Okumura, 1991; Machida and Arai, 2003). In sediment coreMD01-2412, Kc2-3 tephra comparable with KpII/III is also strati-graphically higher (i.e. younger) than the Aso4 tephra in the de-posits of isotopic stage 5.2 (Sakamoto et al., 2006). According to theage scale for this core, the age of Kc2-3 tephra is about 79e80thousand years (Okazaki et al., 2005; Sakamoto et al., 2006). Thus,the performed comparison of the composition of volcanic glasses of


Fig. 9. Indicative variations of ratios among rare and rare earth elements characterizing a contribution of different sources into the processes of magma genesis. Arrows show thetrends of intensified influence of elements supply in fluid phase and due to melting of subducting sediments (Duggen et al., 2007).


tephra from sediment core So-178-1-4 affords ground to identifythis tephra with the caldera-forming eruption of Kutcharo volcanoon Hokkaido Island.

A layer of Aso4 tephra belonging to the greatest Late-Pleistoceneexplosive eruption of the Aso volcano on Kyushu Island is wellidentified (Machida and Arai, 2003). This tephra layer was revealedin the deposits of the southern Sea of Okhotsk (Fig. 2). As wasshown above, (Figs. 3, 5e9), it differs markedly in geochemicalcharacteristics from composition of tephras, the sources for whichwere the explosive eruptions of volcanoes of the Sea of Okhotskframing. The results of our investigations of this tephra are in goodagreement with data on composition of Aso4 tephra widespreadboth in deposits of land (Japanese Islands, southern Kurile Islands)and in the adjacent areas of the Sea of Japan and north-westernPacific Ocean (Fig. 6) (Aoki, 2008; Machida and Arai, 2003; Aoki


and Arai, 2000; Hunt and Najman, 2003; Sakamoto et al., 2006).According to the latest data, the age of Aso4 tephra falls on theisotopic stage MIS 5.2 and is estimated at 86.6e87.3 thousand years(Aoki, 2008; Oba et al., 2006) while the age of tephra from sedimentcore MD01-2412 is about 88 thousand years (Okazaki et al., 2005;Sakamoto et al., 2006).

For the majority of other tephra layers (16 of 23 studied by us),the sources of volcanic explosions remain unknown due to ourincomplete knowledge about the volcanic activity of the adjacentland. Even with availability of the highly representative databasewhich are available at our disposal (about 20 thousand microprobechemical analyses) of the chemical composition of tephras (pre-dominantly Holocene volcanic eruptions in Kamchatka and, morerarely, on Kurile Islands), we failed to find the close analog in thedeposits of land and, consequently, the source of explosive


Table 3Characteristic features of tephra layers from the Okhotsk Sea Quaternary deposits.

Index oftephralayer

Thickness oftephra layer,cm

Color oftephralayer

Mineralcomplex

Geochemicalseries

Chemicalcompositionof volcanic glass

Color ofvolcanicglass.

Age, kyr Supposedsource

Marine Terrestrial

KO 0.5e16 white Opx � Cpx:Hb

Med-Krhyolite

SiO2 - 75.8e8.4(76.9%)**K2O - 1.96e2.6(2.1%)TiO2 - 0.17e0.28(0.23%)

colorless 7.8 (14C) - 8.6(cal. kyr)(Gorbarenkoet al., 2002)7.4 (14C) - 8.4(cal. kyr) (Sakamotoet al., 2005)8.0e8.1 (cal. kyr)(Kaiser, 2001)8.2e8.6 (cal. kyr)(Barash et al., 2005)

7.5-7.98 (14C)kyr- 8.0-8.4(cal. kyr) (Braitsevaet al., 1995, 1997;Melekestsevet al., 1991;Ponomarevaet al., 2004, 2007;Zaretskayaet al., 2001)7.43 (14C)(Hasegawaet al., 2011)

Kurile Lakecaldera(SouthKamchatka)

N ~1 (lenses) light grey Cpx > Opx Low-Kdacite

SiO2 - 64.5e69.9(66.7%)K2O - 0.6e0.9(0.8%)TiO2 - 0.46e0.72(0.62%)

grey ~8.5 kyr n.d Gamchen(?), Kamchatka

TR (Zv) 1e2 grey Opx > Cpx Low-Krhyolite

SiO2 - 71.7e73.7(73.0%)K2O - 0.9e1.0(0.9%)TiO2 - 0.45e0.51(0.48%)

colorless,light grey

8.0 (14С) (Gorbarenkoet al., 1998, 2002)8.0e8.05 (14C)(Kaiser, 2001)

8.0 cal kyr(Nakagawaet al., 2008)~8.54 (14C)kyr- (Hasegawaet al., 2011)

Zavaritskycaldera(Simushyr,MiddleKurile Island)

K2 1e22 grey withreddishshade

Cpx � Opx:(Hb)

Med-Krhyolite

SiO2 - 73.4e76.3(75.4%)K2O - 2.3e2.7(2.5%)TiO2 - 0.14e0.44(0.32%)

colorless 25.71 (14C) kyr(Greinert et al., 2002)26.6 (14C) - 31.2(cal. kyr) (Gorbarenkoet al., 2004)30.46e30.49(cal. kyr) (Gorbarenkoet al., 2007, 2010)

24.5 (14C) kyr(Melekestsevet al., 1997)

Nemo-III(Onekotan,North Kurile)

K3 grey Cpx � Opx:(Hb)

Med-Krhyolite

SiO2 - 73.5e77.2(75.4%)K2O - 2.3e2.7(2.5%)TiO2 - 0.25e0.41(0.32%)

colorless;crystallo-clastics

Late Pleistocene,the end of MIS 3 -(Kaiser, 2001;Derkachev et al., 2004;Derkachev andPortnyagin, 2013)

LatePleistocene -(Melekestsevet al., 1997)

Nemo-II?(Onekotan,North Kurile)

T 0.2e0.6(lenses)

yellowish-grey

Opx > Cpx Low-Krhyolite

SiO2 - 65.7e77.1(74.4%)K2O - 0.5e1.1(1.0%)TiO2 - 0.29e0.78(0.46%)

colorless,lightbrown (rare);crystallo-clastics

Late Pleistocene,the end of MIS 3 -(Kaiser, 2001;Ivanova andGorbarenko, 2001;Derkachev et al., 2004)

30.32e34.69(14C) - 35e38(cal. kyr) -(Hasegawaet al., 2009, 2012;Yamamotoet al., 2010)

Mashuvolcano,HokkaidoIs., Japan

Kc1 (Kc-Sr)* 17 dark grey(top),light grey(base)

Opx > Cpx Med-Krhyolite

SiO2 - 78.2%*K2O - 2.5%TiO2 - 0.26%

32.5 (cal. kyr)(Okazaki et al., 2005;Sakamoto et al., 2006)

30-32(cal. kyr)(Okumura, 1991;Arai et al., 1986;Machidaand Arai, 2003)34.69e34.9(14C) - 40.03e40.23(cal. kyr) -(Yamamotoet al., 2010)

Kutcharocaldera,HokkaidoIs., Japan

Spfa1* 5 light grey Opx: Hb Med-Krhyolite

SiO2 - 77.9%*K2O - 2.7%TiO2 - 0.14%

~42e43(cal. kyr) - MIS 3.13(Sakamoto et al., 2006)

39.43e40.12(14C) kyr (Katohet al., 1995)39.5e40.1(cal. kyr) (Aokiand Arai, 2000;Hunt andNajman, 2003)

Shikotsucaldera,HokkaidoIs., Japan

K4 ~1 (lenses) grey Cpx > Opx:Hb

Low-Krhyolite

SiO2 - 70.6e73.1(72.1%)K2O - 1.1e1.3(1.3%)TiO2 - 0.46e0.72(0.58%)

Colorless;green-grey(rare), lightbrown (rare)

~50 kyr - MIS 3.3(Kaiser, 2001)

unknown unknown

(continued on next page)




Index oftephralayer


Color oftephralayer

Mineralcomplex

Geochemicalseries




Marine Terrestrial

MR1 0.3e0.5(lenses)

beige Cpx > Opx: Hb Med-Kdacite

SiO2 - 69.4e71.0(70.2%)K2O - 1.2e1.4(1.3%)TiO2 - 0.52e0.57(0.54%)

colorless ~65e67kyr - MIS 4(Gorbarenkoet al., 2010, 2012, 2014)

unknown unknown

Kc2-3 turbidite light grey Opx > Cpx Med-Krhyolite

SiO2 - 73.9e78.1(77.2%)K2O - 1.7e2.4(2.0%)TiO2 - 0.26e0.56(0.34%)

colorless;a lot of pumice

~79e80 kyr - MIS 5.2(Sakamoto et al., 2006)

~84e90 kyr -(Machida,1999;Machida andArai, 2003)~85e86 kyr -(Yamamotoet al., 2010)

Kutcharocaldera,HokkaidoIs., Japan

Aso4 0.7e3 light grey Hb > Cpx �Opx

High-Ktrachy-rhyolite

SiO2 - 72.7e73.6(73.1%)K2O - 4.3e4.9(4.6%)TiO2 - 0.38e0.43(0.41%)

colorless 88 kyr - MIS 5.2(Okazaki et al., 2005;Sakamoto et al., 2006)MIS 5.2 -(Ivanova andGorbarenko, 2001;Cruise Report, 2003)

86-90 kyr -(Machida andArai, 2003)86.8e87.3 kyr -(Oba et al., 2006;Aoki, 2008)~89 kyr -(Matsumoto, 1996)

Aso caldera,KyushuIs., Japan

Kc4 (Kc-Hb)* 13.5 yellowish-grey(top), darkgrey (base)

Opx > Cpx:(Hb)

Med-Krhyolite

SiO2 - 78.0%*K2O - 2.1%TiO2 - 0.31%

~115 kyr (Okazakiet al., 2005; Sakamotoet al., 2006)

100-130 kyr(Machidaand Arai, 2003)115-120 kyr e(Hasegawaet al., 2008; 2011;Yamamotoet al., 2010)

Kucharocaldera,HokkaidoIs., Japan

K5 1e6 light grey Opx > Cpx Med-Krhyolite

SiO2 - 77.2e77.8(77.5%)K2O - 1.7e2.0(1.8%)TiO2 - 0.32e0.4(0.36%)

colorless ~115e120 kyr -MIS 5.4(Gorbarenko, 1991;Gorbarenkoet al., 2002; Barashet al., 2001)

unknown unknown

MR2(AL7.2a)

1e4 light grey Cpx > Opx:Hb

Med-Krhyolite

SiO2 - 74.9e76.3(75.7%)K2O - 1.7e1.9(1.8%)TiO2 - 0.36e0.46(0.4%)

colorless ~206 kyr - MIS 7.2(Kaiser, 2001;Nürnberg andTiedemann, 2004)~200e210 kyr -MIS 7.2 (Barashet al., 2006)~199.7 kyr - MIS7.1 (Gorbarenkoet al., 2010, 2014)

unknown unknown

AL7.2b 1 white Bi > Hb >Cpx > Opx

Med-High-Ktrachy-rhyolite

SiO2 - 76.7e76.6(77.6%)K2O - 3.6e4.2(3.8%)TiO2 - 0.08e0.15(0.13%)

colorless ~206e210 kyr -MIS 7.2 (Kaiser, 2001;Nürnberg andTiedemann, 2004)

unknown Volcanoesof KamchatkaSredinnyRange

AL7.4 1 white Hb > Cpx >Opx

High-Ktrachy-rhyolite

SiO2 - 76.0e76.6(76.4%)K2O - 4.3e5.0(4.5%)TiO2 - 0.09e0.15(0.13%)

colorless ~229 kyr - MIS 7.4(Nürnberg andTiedemann, 2004)~230e235kyr - MIS 7.4(Barash et al., 2006;Levitan et al., 2007)

Magadan city(Uptar mine) -(Melekestsevet al., 1991)

Volcanoesof KamchatkaSredinnyRange

nMR 2 very lightgrey(almostwhite)

Cpx � Opx:Hb

Med-Krhyolite

SiO2 - 77.4e78.6(78.2%)K2O - 2.3e2.7(2.5%)TiO2 - 0.15e0.22(0.19%)

colorless ~290e300 kyr -MIS 8.6 (Nürnbergand Tiedemann, 2004;Levitan et al., 2007)

unknown unknown

K6 5 grey Opx � Cpx Med-Kdacite

SiO2 - 65.1e72.1(69.2%)K2O - 1.1e1.7(1.5%)TiO2 - 0.4e0.81(0.67%)

colorless,light grey,dark brown(rare)

~310e320 kyr -MIS 9.1e9.2(Derkachev et al., 2004)

unknown unknown

MR3(AL9.22)

1e6 yellow-grey Cpx � Opx:Hb

Med-Krhyolite

SiO2 - 75.3e76.2(75.9%)K2O - 2.9e3.3

colorless ~311 kyr - MIS 9.22(Nürnberg andTiedemann, 2004)

unknown unknown




Index oftephralayer


Color oftephralayer

Mineralcomplex

Geochemicalseries




Marine Terrestrial

(3.1%)TiO2 - 0.24e0.37(0.28%)

~290e310 kyr - MIS9.1e9.2 (Barashet al., 2006)~307 kyr - MIS 9.1e9.2(Gorbarenkoet al., 2010, 2012, 2014)

AL9.22b 0.5e0.9(lenses)

dark grey n.d. Low-Kandesite

SiO2 - 60.2e62.4(61.1%)K2O - 0.8e1.0(0.9%)TiO2 - 0.94e1.08(1.01%)

green-grey,light-brownand darkbrown(rare) - bothwithmicrolitesof minerals

~310e315? kyr -MIS 9.1e9.2 - (CruiseReports, 1999)

unknown unknown

MR4(AL9.24)

1e5 grey withyellowish-brownshade

Opx � Cpx Med-Ktrachy-andesite-trachyda-cite

SiO2 - 60.6e68.3(64.02%)K2O - 1.8e2.7(2.3%)TiO2 - 0.77e1.32(1.09%)

dark grey,greenish-lightbrown, darkbrown(rare) withmicrolitesof minerals

~319e320 kyr -MIS 9.24 (Nürnbergand Tiedemann, 2004)~320 kyr - MIS 9.2(Barash et al., 2006)MIS 9.2 (CruiseReport, 2003)

unknown unknown

AL10 0.5e0.9 dark grey Opx > Cpx Med-K trachy-andesite-trachyda-cite

SiO2 - 58.7e69.2(62.6%)K2O - 1.9e3.5(2.4%)TiO2 - 0.7e1.5(1.22%)

light anddark grey,dark brown(rare) withmicrolitesof minerals

~330 kyr - MIS 10(Nürnberg andTiedemann, 2004)

unknown unknown

Md1 2 yellow-grey

Cpx � Opx:Hb

Med-Krhyolite

SiO2 - 73.6e74.8(74.0%)K2O - 1.9e2.1(2.0%)TiO2 - 0.42e0.5(0.46%)

colorlesswith yellowishshade

~400e410 kyr -(Nürnberg andTiedemann, 2004);MIS 11 (Levitanet al., 2007)

unknown unknown

Md2 3 beige Cpx � Opx:Bi, Hb

Med-Krhyolite

SiO2 - 77.8e78.4(78.2%)K2O - 3.4e3.9(3.6%)TiO2 - 0.08e0.13(0.11%)

colorless ~530e540 kyr -(Nürnberg andTiedemann, 2004);MIS 14 (Levitanet al., 2007)

unknown Volcanoesof KamchatkaSredinnyRange

Md3 3 beige Opx > Cpx:Ap

Med-Krhyolite

SiO2 - 74.0e74.9(74.5%)K2O - 2.5e2.7(2.6%)TiO2 - 0.36e0.44(0.4%)

colorlesswith lightgrey shade

~890e900 kyr -(Nürnberg andTiedemann, 2004);MIS 23? (Levitanet al., 2007)

unknown unknown

Stations where tephra layers were found: KO: M946, Lv27-8-4, Lv28-42-5, Lv28-43-5, Lv28-44-3, Lv29-106-2, Lv29-108-4, Lv29-110-2, Lv29-112-2, Lv55-9, MD01-2415,MR0604-PC6R, V34-98, XP98-PC1. N: GC12-6A. TR(Zv): 9301, 9304, Lv27-10-5, Lv27-15-1, V34-90. K2: 9306, 9307, M918, M924, M927, M934, M945, M961, M968, M969,Ge99-32, Ge99-36, K-68, K-72, K-74, K-78, K-105, Lv27-5-5, Lv27-6-2, Lv27-7-3, Lv27-8-3, Lv27-8-4, Lv28-37-1, Lv28-40-4, Lv28-40-5, Lv28-41-4, Lv28-41-5, Lv28-42-4,Lv28-42-5, Lv28-43-5, Lv29-53-1, Lv29-56-1, Lv29-63-1, Lv29-100-1, Lv29-114-2, Lv32-21, Lv32-25, Lv40-03, Lv40-04, Lv40-09, Lv40-15, Lv40-16, Lv40-17, Lv40-18-2,Lv40-19, Lv40-20, MD01-2415, MR0604-PC6R, MR0604-PC7R, So178-11-5, So178-12-3, So178-62-1, GC-12-1B, GC-12-5A, GC-12-6A, XP98-PC1, XP98-PC2. K3: 9313,Ge99-10, Ge99-38-5, K-68, Lv27-9-4, Lv27-10-5, Lv27-12-3, Lv27-12-4, Lv27-15-1, Lv55-38. T: Ge99-10, Lv28-2-4, Lv28-64-5, Lv29-70-2, Lv29-72-2, So178-3-4. Kc1 (Kc-Sr):MD01-2412*. Spfa1: MD01-2412*. K4: Lv27-15-1, XP98-PC1. MR1: MR0604-PC6R, GC-12-1A. Kc2-3: MD01-2412*, So178-1-4. Aso4: Ge99-10, Lv28-64-5, Lv29-70-2, MD01-2412. Kc4 (Kc-Hb): MD01-2412*. K5: 9305, Ge99-38-5, K-68, Lv29-114-2 (?). MR2 (AL7.2a): Lv28-42-4, MR0604-PC7R. AL7.2b: Lv28-42-4. AL7.4: Lv28-42-4, MD01-2415.nMR:MD01-2415, MR0604-PC5R. K6: 9305, Ge99-38-5.MR3 (AL9.22): Lv28-42-4, MR0604-PC7R. AL9.22b: Lv28-42-4.MR4 (AL9.24): Lv28-42-4, MR0604-PC6R. AL10: Lv28-42-4. Md1: MD01-2415. Md2: MD01-2415. Md3: MD01-2415.*- data of Sakamoto et al., 2006.**- minimum-maximum values, in brackets - mean values. Minerals: Cpx - clinopyroxene, Opx - ortopyroxene, Hb - hornblende, Bi-biotite, Ap-apatite.


volcanism. This applies especially to identifying the tephra layers ofthe Pleistocene age as their traces on the adjacent land were notpreserved due to denudation processes during Pleistocene-Holocene periods.

A certain assistance in the questions of the further identificationcan be rendered by an analysis of the mineral and chemical com-positions of tephra if the known tendencies in the crossmineralogical-geochemical zonality of the volcanism products ofthe island-arc systems are taken into account (Kuno, 1959; Geptnerand Ponomareva, 1979; Volynets et al., 1990; Volynets, 1994;Avdeyko et al., 1991; Podvodny Vulkanizm …, 1992; Braitseva


et al., 1997; Churikova et al., 2001; Smith et al., 2002; Portnyaginet al., 2005 ; Duggen et al., 2007; Jensen et al., 2008, 2011;Addison et al., 2010; Martynov et al., 2010; Preece et al., 2011, andothers). In the volcanites of the frontal zone of the island arcs, apredominance in the composition of phenocrysts of clinopyroxeneand olivine is marked; at the same time, the subordinate role oforthopyroxene which quantity increases gradually as the volcanicfront moves away from the trench axis with the appearance of theorthopyroxene-clinopyroxene mineral parageneses is noted. As arule, the hornblende is absent here or is rare. In the rocks (espe-cially, with increased silica content) of the backarc of island arcs,


Fig. 10. Tephrostratigraphic scheme of the Pleistocene-Holocene deposits from the Sea of Okhotsk.


the quantity of hydrous silicates (amphiboles) in phenocrysts and,in a number of cases, biotite with subordinate role of pyroxenesincreases (Podvodny Vulkanizm …, 1992; Volynets et al., 1990,Braitseva et al., 1995, 1997; Smith et al., 2002, and others).

The signs of geochemical zonality cross strike of arc based on themicroelement composition are visible for the volcanic rocks ofKamchatka in the direction from the East volcanic front (EVF)through (across) the Central-Kamchatka Depression (CKD) to thebackarc of the Kamchatka Sredinny Range (SK) (Churikova et al.,2001; Portnyagin et al., 2005).


In this article, we do not present a detailed analysis of the dis-tribution of microelement composition in the studied volcanicashes of the Sea of Okhotsk with estimating their belonging tovolcanites of the frontal or backarc parts of the island arcs. It is asubject-matter of independent publication. Here, the onlyfollowing can be noted. Taking in consideration the above ten-dencies, the tephras AL7.2b, Md2, nMR and AL7.4 in which themineral associations with high content of amphiboles and biotite(especially, for AL7.2b and Md2 tephras) are clearly discovered canbe unambiguously assigned to the backarc volcanites (Derkachev



et al., 2016). The geochemical characteristics of volcanic glasses ofthese tephras differ also from those of other tephras and corre-spond, to a greater extent, to the backarc volcanites (Table 2, Figs. 5,7e9). Themost probable source of the pyroclastic material for thesetephras is the volcanoes of the Kamchatka Sredinny Range(Churikova et al., 2001; Portnyagin et al., 2005). Unfortunately, it isnot possible to perform now the perfect identification of the abovetephras. The most probable sources can be the explosions of theKhangar, Alney-Chashakondzha, Opala, Ichinsky volcanoes. Thevolcanic glasses similar in composition to AL7.4 tephra were foundamong the lacustrine deposits near Magadan over a distance ofmore than one thousand kilometers from the supposed source(Melekestsev et al., 1991).

5. Conclusion

The fullest information on distribution, composition and age of 23tephra layers in the Pleistocene-Holocene deposits of the Sea ofOkhotsk is presented. The integrated data including themineralogicaland numerousmicroprobe chemical analyses (among them, analysesof rare and rare-earth elements) is a reliable basis for the tephros-tratigraphical correlation of the regional deposits. The tephras KO, TR(Zv), K2 and K3, T, Kc2-3, Aso4 are identified with the most confi-dence. For them, the sources of pyroclastic material were establishedand they include the volcanoes of the Kurile Lake (Kamchatka),Zavaritsky (Simushir Island, Kurile Islands), Nemo (Onekotan Island,Kurile Islands), Mashu and Kutcharo (Hokkaido Island), Аsо (KyushuIsland). An assumption of the effect of explosions of the KamchatkaSredinnyRange volcanoes on the formation of the tephra layers AL7.4,AL7.2b,Md2wasmade. The areas of ash falls for a number of the greatexplosive eruptions of volcanoes located in Kamchatka and KurileIslands were specified and established.

The obtained results of the complex investigations of tephrasallow us to essentially supplement the data on the great explosiveeruptions of volcanoes in the region and offer an opportunity todevelop the generalized tephrochronological scale of the Quater-nary deposits of this region which is necessary for the strati-graphical correlation of deposits, estimation of environmentalchanges caused by these eruptions, paleooceanological and paleo-geographical reconstructions.

Acknowledgements

This work was conducted within International Russian-German(KOMEX), RussianeJapan (Grant no 06-05-91576 of JP, JSPS) andNational Nature Science Foundation of China (Grant no U1406404,40431002), China National Programme on Global Change and Air-Sea Interaction (GASI-01-02-01-04). Analytical investigationswere financially supported by both the Russian-German ProjectKALMAR and the Russian Foundation for Basic Research (Project no11-05e00506a, 16-55-53048, 16-05-00127). M. Portnyagin and V.Ponomareva acknowledge support from the Russian ScienceFoundation grant #16-17-10035.

The authors thank Dieter Garbe-Sch€onberg (University of Kiel)and Mario Th€oner (GEOMAR) for their help with the microprobeanalyses.

We are grateful to the participants of cruises on the R/V Aka-demik M.A. Lavrentyev, Marshal Gelovani, Sonne, Miray, andYokosuka for their help and for the opportunity to obtain bottomsediments cores.

Appendix A. Supplementary data

Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.quaint.2016.07.004.


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http://dx.doi.org/10.3389/feart.2015.00083

http://dx.doi.org/10.3389/feart.2015.00083

















































http://www.volcano.si.edu/world/

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tephra layers of in the quaternary deposits of the sea of okhotsk ... › ... › lehre_skripte ›...

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