Abstract
Diatom biostratigraphy was re-examined for the Miocene marine sequence distributed along the Arakawa River in the northern part of the Hiki Hills area, central Japan. Thirteen out of 24 collected samples yielded age diagnostic diatom fossils, which are restricted between diatom biohorizons D41 (15.7Ma) and D41.5 (15.6Ma) in the lower Denticulopsis lauta Zone (NPD 4A). A thin conglomerate layer, which is previously presumed as an unconformably overlying basal conglomerate, is sandwiched between the last occurrence (LO) biohorizon of D. praelauta (D41:15.7Ma) and first occurrence (FO) of D. ichikawae. As the maximal duration between these two biohorizons is estimated as about 20, 000 yr., it is concluded that there is no unconformity along the studied section. Temporal change in the diatom assemblage suggests a transgression in the examined interval.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
