Migration of a volcanic front inferred from K-Ar ages of late Miocene to Pliocene volcanic rocks in central Japan

A new species of the termite genus Gyatermes Engel & Gross (Archotermopsidae) is described and figured from a beautifully preserved forewing in late Neogene sediments of Nagano Prefecture, central Japan. The approximately 27-mm long forewing of Gyatermes naganoensis Engel & Tanaka, new species, is preserved in Late Miocene (late Messinian) mudstone of the Ogawa Formation (ca. 6 Ma), and is distinguished from its slightly older and larger congener G. styriensis Engel & Gross, from the early Tortonian of Styria, Austria. Comments are provided regarding the paleoclimatic implications of a giant termite in the Miocene fauna of Nagano.

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Petrology of Myogazawa and Kazamiyamada volcanic rocks distributed in northern Utsunomiya, central Japan

Japanese Magazine of Mineralogical and Petrological Sciences ◽

10.2465/gkk.160229 ◽

2016 ◽

Vol 45 (5) ◽

pp. 138-152

Author(s):

Ryuichi SHIMIZU

Keyword(s):

Volcanic Rocks ◽

Central Japan

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Melt equilibration depths as sensors of lithospheric thickness during Eurasia-Arabia collision and the uplift of the Anatolian Plateau

Geology ◽

10.1130/g46420.1 ◽

2019 ◽

Vol 47 (10) ◽

pp. 943-947 ◽

Cited By ~ 3

Author(s):

M.R. Reid ◽

J.R. Delph ◽

M.A. Cosca ◽

W.K. Schleiffarth ◽

G. Gençalioğlu Kuşcu

Keyword(s):

Late Miocene ◽

Large Scale ◽

Middle Miocene ◽

Volcanic Rocks ◽

Suture Zone ◽

Arabian Plate ◽

Seismic Structure ◽

Eurasian Plate ◽

Lithospheric Thickness ◽

Anatolian Plateau

Abstract A co-investigation of mantle melting conditions and seismic structure revealed an evolutionary record of mantle dynamics accompanying the transition from subduction to collision along the Africa-Eurasia margin and the >1 km uplift of the Anatolian Plateau. New 40Ar/39Ar dates of volcanic rocks from the Eastern Taurides (southeast Turkey) considerably expand the known spatial extent of Miocene-aged mafic volcanism following a magmatic lull over much of Anatolia that ended at ca. 20 Ma. Mantle equilibration depths for these chemically diverse basalts are interpreted to indicate that early to middle Miocene lithospheric thickness in the region varied from ∼50 km or less near the Bitlis suture zone to ∼80 km near the Inner Tauride suture zone. This southward-tapering lithospheric base could be a vestige of the former interface between the subducted (and now detached) portion of the Arabian plate and the overriding Eurasian plate, and/or a reflection of mantle weakening associated with greater mantle hydration trenchward prior to collision. Asthenospheric upwelling driven by slab tearing and foundering along this former interface, possibly accompanied by convective removal of the lithosphere, could have led to renewed volcanic activity after 20 Ma. Melt equilibration depths for late Miocene and Pliocene basalts together with seismic imaging of the present lithosphere indicate that relatively invariant lithospheric thicknesses of 60–70 km have persisted since the middle Miocene. Thus, no evidence is found for large-scale (tens of kilometers) Miocene delamination of the lower lithosphere from the overriding plate, which has been proposed elsewhere to account for late Miocene and younger uplift of Anatolia.

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