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Bahe Formation

Coordinates: 33°30′N 109°30′E / 33.5°N 109.5°E / 33.5; 109.5
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Bahe Formation
Stratigraphic range: Tortonian
TypeGeological formation
UnderliesLantian Formation
OverliesKoujiacun Formation
Thicknessgenerally >300 m (980 ft)
Lithology
PrimaryConglomerate, sandstone
OtherMudstone, marl
Location
Coordinates33°30′N 109°30′E / 33.5°N 109.5°E / 33.5; 109.5
RegionShaanxi
Country China
Bahe Formation is located in China
Bahe Formation
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."[1] The main fossil locality is in the Jiulaopo region on the left bank of the Bahe River in Lantian.

Geology and environment

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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.[2]

Fossil content

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Mammals

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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 [3]

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[4]

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 [5]

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

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Genus Species Abundance Notes

Testudo

T. sphaerica

Indeterminate emydid remains

References

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  1. ^ Paleobiology Database. "Miomachairodus details".
  2. ^ Kaakinen, Anu (2003). "Sedimentation of the Late Miocene Bahe Formation and its implications for stable environments adjacent to Qinling mountains in Shaanxi, China". Journal of Asian Earth Sciences. 22 (1): 67–78. Bibcode:2003JAESc..22...67K. doi:10.1016/S1367-9120(03)00044-0.
  3. ^ Chow, Minchen. "Tertiary Mammal Faunas of the Lantian Region, Shaanxi Province". Archived from the original on 2011-08-18.
  4. ^ Lucas, Spencer. Chinese fossil vertebrates. Columbia University Press.
  5. ^ Zhamg, Zhao-Qun. "Late Miocene Cricetids from the Bahe Formation, Lantian, Shaanxu Province" (PDF).