茂木植物化石層と松浦玄武岩類

概要

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The Mogi plant bed is mainly consisted of tuff, brecciated tuff and silt, and is disconformably overlain by the plant bearing Kitaura volcanic breccias which are early lake deposits of the Nagasaki volcano. The fossil plants obtained from these plant bearing rocks indicate the upper Pliocene age. On the other hand, the Mogi olivine basalts unconformably overlain by the basal conglomerates of the Mogi plant bed bear a thin conglomerate layer with the pebbles of cristalline schists and quarts at the basal part, resting unconformably upon the granitic rocks of the Cretaceous age. The Kitaura volcanic breccias rest unconformably upon the cristalline schist and the Kitaura bed at Akasakino-hana, and bear a close relation to the Mogi plant bed. These two belong to the early volcanic sedimentz of the Nagasaki volcano, while the Mogi olivine basalts are correlated with the upper Pliocene Matsuura basalts which are widely distributed in both the Karatsu coal field and Nishisonogi peninsula. These basalts exist beyond the limits of the Nagasaki volcanic activity. Although the Mogi plant bed and the Matsuura basalts to which the Mogi basalts belong are of the upper Pliocene age, the Plio-Pleistocene boundary line should be drawn between the Mogi plant bed and the basalts in the Mogi district from the volanic activity.
〔長崎大学教養部〕の論文