Sedanka lava field is located immediately west of the Sredinny Range axis and is formed by dominantly mafic lavas from small strato- and shield-like volcanoes and >100 cinder and lava cones of the late Pleistocene-Holocene age (Figs. 1 and 2). The lava field has an area of ~1500 km². Holocene activity includes Titila (GVP #1000-56, Fig. 3) and Gorny Institute (GVP #1000-55, Fig. 4) volcanoes as well as a number of cinder cones including Terpuk (GVP # 1000-512, Fig. 5) and Sedankinsky (Fig. 6).

Sedanka lava field is located north of the edge of the subducting Pacific Plate, that is beyond an active subduction zone e.g. Gorbatov et al., 1997, Levin et al., 2002, Park et al., 2002), so the origin of magmatism in this area is unclear (Dirksen et al., 2004; Volynets, 2006; Volynets et al., 2005, 2006). The investigation of melt inclusions in Ol phenocrysts revealed the existence of two types of parent melts in some samples: low-K tholeite and medium-K high-Ti basalts. The presence of these melts suggests the mixing of different parent melts during magma generation (Pletchov et al., 2003).

Detailed geological and tephrochronological studies have permitted identification of three main periods of volcanic activity within the Sedanka lava field: late Pleistocene, when most of the stratovolcanoes were formed; then 10-8 ka BP, and finally 3-2.5 ka BP (¹⁴C), when a number of large cinder cones were formed and the last eruption from Titila volcano occurred.

Holocene soil-pyroclastic cover in the area (Fig. 7) includes more than ten marker tephra layers. Most of these tephras originated from Shiveluch volcano, located ~100 km to the southeast. In addition, there are regional marker tephras including KHG from Khangar volcano (6850 ¹⁴C yr BP) and KS₁ from Ksudach (1800 ¹⁴C yr BP). These tephras have permitted reconstruction of local eruptive activity.

Titila (57°24' N, 160° 07' E; Fig. 3) is a small shield-like volcano. It started to form in the late Pleistocene time. The volcano was active 10-8 and 3-2.5 ka BP (14C) (Dirksen et al., 2003, 2004). Titila eruptives are transitional from medium to high-K basalt.

Gorny Institute volcano (57°20' N, 160°11' E; Fig. 4) is believed to have repeatedly erupted during the Holocene (Pevzner, 2006). Sedankinsky lava flow (Fig. 6) at the southern slope of the volcano was erupted ~6.2 ka BP (Pevzner, 2006).

Literature

Dirksen O. V., Bazanova L. I., and M. V. Portnyagin (2003) Chronology of the Holocene volcanic activity in the northern part of the Sredinny Range, Kamchatka (Sedanka Dol lava field). Volcanism and Geodynamics. Abstracts of the II All-Russia Symposium on Volcanology and Paleovolcanology (Ekaterinburg, 2003), pp. 871–874 [in Russian].

Dirksen O.V., Bazanova L.I., Pletchov P.Yu., Portnyagin M.V., Bychkov K.A. (2004) Volcanic activity at Sedankinsky Dol lava field, Sredinny Ridge, during the Holocene (Kamchatka, Russia). Linkages among tectonics, seismicity, magma genesis, and eruption in volcanic arcs. IV International Biennial Workshop on Subduction Processes emphasizing the Japan-Kurile-Kamchatka- Aleutian Arcs. Petropavlovsk-Kamchatsky. August 21-27, 2004, p. 55. http://www.kscnet.ru/ivs/conferences/kasp/tez/contents.htm

Ogorodov N. V., Kozhemyaka N. N., Vazheevskaya A. A., and A. Ogorodova (1972) Volcanoes and Quaternary Volcanism in the Sredinnyi Ridge of Kamchatka. Nauka, Moscow [in Russian]

Pevzner M.M. (2006) Holocene volcanism of Northern Kamchatka: The spatiotemporal aspect. Doklady of the Russian Academy of Sciences, Earth Sciences, Vol. 409A, No. 6, pp. 884–887. Original Russian text published in Doklady Akademii Nauk, 2006, Vol. 409, No. 5, pp. 648–651.

Pletchov P.Yu., Bychkov K.A., Dirksen O.V., Ariskin A.A. (2003) Study of melt inclusions in the olivines from basalts in the Terpuk volcano region, Sredinny Range, Kamchatka. Abstracts, Moscow State University. Siebert L, and Simkin T (2002-). Volcanoes of the World: an Illustrated Catalog of Holocene Volcanoes and their Eruptions. Smithsonian Institution, Global Volcanism Program, Digital Information Series, GVP-3, (http://www.volcano.si.edu/world/).

Volynets, A. O. (2006), Pleistocene-Holocene volcanism of Sredinny Range, Kamchatka: rock composition and geodynamic interpretation, Ph. D. thesis, Moscow State University, 195 pp.(In Russian).

Volynets A.O., T.G. Churikova, and G. Wörner (2005), Geochemistry of the volcanic rocks of Sredinny Range, Kamchatka, Vestnik KRAUNC, Earth science series, 2(6), 21-33 http://www.kscnet.ru/kraesc/2005/2005_6/2005_6.html (In Russian).

Volynets A., Woerner G., Churikova T., and P. Layer (2006), The source of Pleistocene-Holocene volcanism in the Sredinny Range back arc, Kamchatka: constraints from trace elements and isotopic compositions, Abstracts of the 5th Biennial Workshop on Subduction Processes emphasizing the Japan-Kurile-Kamchatka-Aleutian Arcs. Sapporo, Japan, 40-42.