Discovery of Ancient Volcanoes in the Okhotsk Sea (Russia): New Constraints on the Opening History of the Kurile Back Arc Basin

Here we present the first radiometric age and geochemical (major and trace element and isotope) data for samples from the Hydrographer Ridge, a back arc volcano of the Kurile Island Arc, and a newly discovered chain of volcanoes (“Sonne Volcanoes”) on the northwestern continental slope of the Kurile Basin on the opposite side of the arc. The 40Ar/39Ar age and geochemical data show that Hydrographer Ridge (3.2–3.3 Ma) and the “Sonne Volcanoes” (25.3–25.9 Ma) have very similar trace element and isotope characteristics to those of the Kurile Island Arc, indicating derivation from a common magma source. We conclude that the age of the “Sonne Volcanoes” marks the time of opening of the Kurile Basin, implying slow back arc spreading rates of 1.3–1.8 cm/y. Combined with published data from the Kurile fore arc, our data suggest that the processes of subduction, Kurile Basin opening and frontal arc extension occurred synchronously and that extension in the rear part and in the frontal part of the Kurile Island Arc must have been triggered by the same mechanism.

A new species of Micardia Butler, 1878 (Lepidoptera, Noctuidae, Eustrotiinae) from China

The genus Micardia Butler, 1878 was described based on M. argentata (the type species; Fig. 1) and M. pulchra, both from Japan; in the same paper, Buter transferred a species described from India, Leucania pulcherrima Moore, 1867 to Micardia. Hampson (1990) considered Micardia a synonym of Eustrotia. However, its generic status was revised by Warren (1913) and retained by subsequent authors (Ueda 1984). There are at present 13 species recognized within Micardia (Table 1), of which, M. quadrilinea Scriba 1921 was described from Japan on the basis of female specimens and without high-quality illustrations, and subsequently treated as of uncertain status by Chen & Xue (2012). The remaining species are as follows: M. simplicissima Berio 1973 was described from Myanmar based on 2 females. M. munda Leech, 1900, was described from Western China (Sichuan, according to Chen & Xue 2012). Chen (1999) extended the range of M. pulcherrima to include China, and Chen & Xue (2012) subsequently reviewed Micardia from China, describing three new species, M. pallens, M. distincta and M. minuta. Four species have been described from Madagascar, M. argentoidea and M. terracottoides by Berio (1954), and M. ikoly and M. itremo by Viette (1982). Because they are geographically separated so widely from their congeners in Asia, Chen & Xue (2012) considered their generic placement in need of confirmation. Moreover, the distribution of M. pulchra Butler was extended to Russia (Kurile Island) by synonymizing it with M. pulchrargentea Bryk, 1942 (Kononenko 2005). In this paper we report a new species, Micardia yixingensis, sp. nov. from Jiangsu, China. The contribution brings the total number of the species in the genus to 14.