Boso TTT-Type Triple Junction: Formation of Miocene to Quaternary Accretionary Prisms and Present-Day Gravitational Collapse - Accretionary Prisms and Convergent Margin Tectonics in the Northwest Pacific Basin - page 63

Fig. 6 Topographic sketch ( top ) of the dive area of ROV KAIKO-10K dive 148 from videotape,
and photos of rock samples ( bottom ). Both rock samples are diatomaceous mudstone. Sample
10K#151 R-001 yielded middle Miocene diatoms. Sample 10K#148 R-002 was barren, but the
similar lithologies of the two samples suggest they may correlate
North Pacific diatom zonation (Akiba 1986 ), on the basis of the presence of
Neodenticula seminae without Proboscia curvirostris . This assignment is supported
by the absence of Thalassiosira jouseae , for which the last known occurrence was
at 0.3 or 0.4 Ma. Four of these samples (10K#148 R1-5 (11, 12), 10K#150 C-2, and
10K#151 C-1) contained warm-water marker diatoms, so we also used the low-
latitude diatom biostratigraphy of Barron ( 1985 ) for them. The occurrence of
Fragilaropsis doliolus (= Pseudoeunotia doliolus ) and the lack of Nitzschia reinholdii
allowed the assignment of these samples to the P. doliolus Zone (NTD17, 0-0.6 Ma)
of the low-latitude diatom zonation. These samples contained reworked Miocene
and Pliocene diatoms. The Miocene diatoms included Actinocyclus ingens f. ingens ,