The geology and the paleontology of the Cretaceous Misakubo Formation have been investigated. The Misakubo Formation is narrowly distributed along the eastern side of the Sambagawa Belt and the Miocene Tokizawa Formation in the northern part of Misakubo, Hamamatsu, Shizuoka Prefecture. This formation consists mainly of black mudstone, fossils yielding bivalves, ammonoids, gastropods and crinoids. Late Albian mid-Cretaceous ammonoids such as Mortoniceras rostratum, Desmoceras latidorsatum, Desmoceras sp., Mariella sp., and Lechites sp. are found in the upper part of the formation. Shallow marine bivalve assemblage yielded in the formation is predominated by Pterotrigonia pustulosa. The fossil bivalve assemblage is compositionally similar to the inner shelf assemblages of the Enokuchi Formation of the Goshoura Group; the Miyanohara Formation, the Fukkoshi Formation and the Nagase Formation of the Sotoizumi Group and the Mikasa Formation of the Yezo Group. The range of these trigoniids might be incorrect, because Pterotrigonia mifunensis and Pterotrigonia monobeana yielded with M. rostratum.
