Bahe Formation

Bahe Formation
Stratigraphic range: Tortonian
Type	Geological formation
Underlies	Lantian Formation
Overlies	Koujiacun Formation
Thickness	generally >300 m (980 ft)
Lithology
Primary	Conglomerate, sandstone
Other	Mudstone, marl
Location
Coordinates	33.5°N 109.5°E / 33.5; 109.5
Region	Shaanxi
Country	China
Bahe Formation (China)

The Bahe Formation is a Late Miocene (Tortonian/Vallesian/Bahean, about 11.6 to 9.0 mya) geological formation in Shaanxi, China. It has "a complex lithology of predominantly orange-yellow conglomerates, sandstones, tan-yellow sandy mudstones, and tan-red mudstones." The main fossil locality is in the Jiulaopo region on the left bank of the Bahe River in Lantian.

Geology and environment

Six general facies have been identified in the region: (1) massive or crudely bedded conglomerates, (2) cross-stratified conglomerate and sandstone deposits, (3) minor sandstone deposits, (4) fine-grained deposits, (5) gritty mudstone and sandstone deposits and (6) marl deposits.

The presence of these types of facies suggest active channels, crevasse splays, sheet floods, and floodplains with paleosols and lakes. Thick and laterally pervasive units of fine-grained sediments, formed as suspension fall-out on the floodplain, indicating low-energy conditions and a relatively gentle surface gradient in the area, are by far the most common sedimentary component. Channel-related sandstones and conglomerates indicate that the rivers had a low-sinuosity and were braided, to anastomosing types.

Fossil content

Mammals

Genus	Species	Abundance	Notes
Acerorhinus	A. sp.		A rhinocerid
Chleuastochoerus	C. stehlini		A suid
Dicerorhinus	D. ringstromi		A rhinocerid. One member of this genus is still alive today: Dicerorhinus sumatrensis, the Asiatic One-Horned Rhinoceros
Erinaceus	E. sp.		Of order Erinaceomorpha, the hedgehogs, four species from this genus are alive today.
Hipparion	H. (Hippotherium) weihoense	Relatively common in this region	An early equid. Appeared very horse-like, roughly the size of a pony, but still had three toes: one large, central toe that carried most of its weight, and two vestigial toes, one on each side. The skull bears a diastema.
	H. chiai	Relatively common in this region
Miomachairodus	M. pseudaeluroides	rare	an early machairodont, member of tribe Machairodontini, related to Hemimachairodus and Machairodus.
Palaeotragus	P. decepiens		An early giraffid
	P. microdon		An early giraffid
Samotherium	S. decipiens		An early giraffid
Tetralophodon	T. exoletus		A ten-foot tall proboscid who is known generally from fossilized teeth, known for its four ridges.
Dinocrocuta	D. gigantea		A large carnivore within the family Percrocutidae, closely related to family Hyaenidae, containing today's hyenas. They appeared slope-backed and had powerful jaws.
Gazella	G. gaudryi		Still a common genus in Africa, central and southeast Asia. Usually light and swift, adapted to open areas and sprints. Six species are still alive today, including Gazella thomsoni, the Thomson's gazelle, and Gazella dorcas, Dorca's gazelle.
Shaanxispira
Nannocricetus	N. primituvus	well documented, but not wildly abundant in any formation, unlike closely related species Sinocrietus	Holotype for Nannocricetus primituvus discovered in the Bahe Formation

Turtles

Genus	Species	Abundance	Notes
Testudo	T. sphaerica
Indeterminate emydid remains