Discovery of mangrove (<i>Kandelia</i> sp.) pollen from the Miocene Kadonosawa Formation, Ninohe district, Iwate Prefecture, Northeast Japan

Abstract

Molluscan and plant fossils from ancient mangrove swamps are known from upper Lower to lower Middle Miocene sediments in Southwest Japan. Given that the mangrove-swamp-dwelling bivalve Geloina was recently found in the Tate Sandstone Member of the Kadonosawa Formation in the Ninohe district, northeastern Japan, it was expected that mangrove pollen would also be found at this site. To investigate this possibility, samples were collected from the Tate Sandstone Member at two sites Tate and Kitadate . The pollen composition at both sites is characteristic of the NP-zone of Neogene pollen zones Yamanoi a . Mangrove pollen Kandelia sp. fossils were first found in the uppermost part of the Tate Sandstone Member at the Kitadate site, representing the northernmost record of Miocene fossil mangrove in Japan. Based on presentday mangrove assemblages and distribution, the average wintertime temperature in the Ninohe area at the time represented by the pollen fossils is estimated to have been about higher than that of today.CThe Geological Society of Japan 2010 114

Oligocene–Neogene fossil history of Asian endemic conifer genera in Japan and Korea

“…Consequently, those from the late Burdigalian–early Langhian are more dominated by various evergreen species and some conifers typical of warmer climate conditions: e.g., Keteleeria , Pseudolarix , Cunninghamia , and Calocedrus . Pollen grains of mangrove plants have been recorded from several localities dated around the Burdigalian–Langhian boundary throughout the Japanese Islands (Yamanoi et al, ; Saito et al, ; Yamanoi et al, , , ). A number of tropical and subtropical faunal elements also have been recorded at this time (Ogasawara, ).…”

“…The latter is called the "Mid Neogene Climatic Optimum" (Tsuchi, 1986) or the "mid-Miocene Climatic Optimum" (Zachos et al, 2001) and is characterized by northward expansion of NBEF until the northern end of Honshu. Mangrove vegetation appears to have developed several places in central and northern Honshu during this time period (Yamanoi et al, 1980;Saito et al, 1995;Yamanoi et al, 2008aYamanoi et al, , 2008bYamanoi et al, , 2010. Most parts of northern Japan subsequently were drowned due to rapid transgression during the Langhian.…”