Ohyamashimo Formation

{{short description|Geologic formation in Japan}}

{{Infobox rockunit

| name = Ohyamashimo Formation

| image =

| caption =

| type = Geological formation

| age = Albian
~{{fossil range|112.1|106.4}}

| period = Albian

| prilithology = Conglomerate, Sandstone, Mudstone

| otherlithology = Tuff

| namedfor = Ohyamashimo, Tamba-Sasayama

| namedby = Hayashi et al., 2017{{Cite journal |last1=Hayashi |first1=Keiichi |last2=Fujita |first2=Saki |last3=Koarai |first3=Kazuto |last4=Matsukawa |first4=Masaki |date=2017-09-15 |title=Stratigraphy and paleoenvironment of the Cretaceous Sasayama Group in the Sasayama area, Hyogo Prefecture, western Japan |journal=The Journal of the Geological Society of Japan |language=en |volume=123 |issue=9 |pages=747–764 |doi=10.5575/geosoc.2017.0016 |issn=0016-7630|doi-access=free }}

| region = Hyōgo Prefecture

| country = Japan

| coordinates = {{coord|35.1|N|135.1|E|display=inline,title}}

| paleocoordinates = {{coord|47.9|N|132.8|E|display=inline}}

| unitof = Sasayama Group

| subunits =

| underlies = Sawada Formation

| overlies = Basement (Unconformity)

| thickness =1300 metres

| extent =

| area =

| map = {{Location map+ | Japan

| relief = 1

| width = 250

| float = center

| places =

{{Location map~ | Japan

| lat_deg = 35.1

| lon_deg = 135.1

| mark = Green pog.svg

| marksize = 12

}}

}}

| map_caption =

}}

The Ohyamashimo Formation(大山下層) is an Early Cretaceous (Albian) geologic formation in Japan. It has been dated to the early-mid Albian, between 112.1 ± 0.4 Ma and 106.4 ± 0.4 Ma. Dinosaur remains have been discovered from this formation, including the sauropod Tambatitanis, the theropod Hypnovenator and the ceratopsian Sasayamagnomus. Other representative fossils from the formation include the monstersaurian lizard Morohasaurus and eutherian mammal Sasayamamylos. The depositional environment represents a fluvial system with a subhumid to semi-arid climate. The Ohyamashimo Formation was called the 'Lower Formation' of the Sasayama Group before it was named in 2017.