茨城県那珂湊市附近の第三系 : 茨城県の地質・その四

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Since the discovery of ammonites from the coast of Nakaminato in the central part of Ibaraki Prefecture, the existence of Cretaceous deposits has been established. However, owing to that very little is known of the Tertiary rocks, I have made an investigation of them with the following. 1) The Tertiary rocks in the Nakaminato and Oarai areas can be classified into the following lithological units, in ascending order, namely ; Tonoyama muddy sandstone, Isozaki tuffaceous mudstone, and Azigaura pumiceous tuff. 2) The stratigraphic relation between the Tertiary formations and the basement of Cretaceous rocks is one of clino-unconformity, the former overlapping the latter. Although a para-unconformity is expected to exist between the Tonoyama and Isozaki formation judged from their relation to the surrounding regions, it has not been observed in the field. A clino-unconformity of gentle inclination separates the Isozaki from the Azigaura formation. 3) The geologcial structure of the
茨城大学文理学部の論文