in Jurassic and Cretaceous Stratigraphy

Earth Science Frontiers, Vol. 17, Special Issue, Aug. 2010 ISSN 1005-2321
Non-marine Jurassic Ostracod Assemblages from Northern China
Y.Q. Wang 1 , M.Z. Cao 2
1. State Key Laboratory of Palaeobiology and Stratigraphy (LPS), Nanjing Institute of Geology and Palaeontology,
Chinese Academy of Sciences, Nanjing 210008, China (E-mail: yqw0620@hotmail.com)
2. Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
Many non-marine ostracod fossils play an
important role in stratigraphical subdivision and
correlation of Jurassic rocks in the northern China. The
Early and early Middle Jurassic ostracod is simple, but
the ostracod diversity has tended to increase since the
late Middle Jurassic. According to the previous
ostracod researches, we established five ostracod
assemblages in the northern China as following.
1. Darwinula sarytirmenensis–D. Magna–Timi-
riasevia Assemblage
This ostracod assemblage has a very wide dis-
tribution in northern China. It has been recorded from
the Toutunhe and Qiketai formations of northern
Xinjiang and Qiakemake Formation of the Tarim Basin.
It is also found from the Maao Formation of Henan
province, Jiulongshan Formation of Hebei province,
Wangjiashan Formation of Gansu province, Caishiling
Formation of Qinghai province, Zhiluo and Anding
formations of Shanxi province, and Xiahuayuan
Formation of Inner Mongolia. In southern China, it also
presents in coeval horizons, such as Shanglufeng,
Yaojie, and Hepingxiang formations in Yunnan
province, Tongshan Formation in Zhejiang province,
and Shaximiao Formation in Sichuan province.
The representative forms of this ostracod assem-
blage are: Darwinula sarytirmenensis, D. impudica, D.
magna, Timiriasevia epidermiformis, T. bella, T.
catenularia, T. mackerrowi, etc.
Of them, D. sarytirmenensis, D. impudica, T.
epidermiformis, and T. catenularia were first dis-
covered from the Jurassic coal-bearing strata of
Saleitimian section which is located in the northern
slope of the Karatan Mountain (Каратау) of eastern
coast of Caspian Sea (Маngyshlak). According to
Mandelstam (1947), this section was subdivided into 30
beds, the top 30th bed contains Callovian ammonite and
bivalve fossils, and the 26 th -16 th beds contain ostracods
as above. According to the age of overlying strata and
comparison with adjacent areas, these ostracods are
considered to be the Middle Jurassic in age (Ye et al.,
1977). Neustrueva (1974) also found identical
ostracods in the middle and upper part of Jurassic
coal-bearing strata in the Fergana Valley. Darwinula
magna was first established by Jiang Xianting in 1963
(but published in 1977), thereafter it was widely found
in the Middle Jurassic continental strata of China, it
usually coexists with the first two Darwinula species, D.
sarytirmenensis and D. impudica mentioned above, and
also was found in the Middle Jurassic strata of Fergana.
Furthermore, it should be noted that Timiriasevia
epidermiformis has distinct features, particularly there
is a lateral ridge near the ventral edge of both valves. In
Kazakhstan, the assemblage is seen in continental strata
below marine Bathonian of Middle Jurassic; in
northwestern Sardinia, in Italy, it comes from Bajocian
continental deposits with marine intercalation (Malz et
al., 1985); in southern Tunisia, early Bajocian–early
Bathonian (Mette, 1995), Oxfordshire in the UK, the
Bathonian of the marine Sandwich is relatively stable
(Bate, 1965). These ostracod fossils are generally from
the continent intercalations of marine Bajocian-
Bathonian deposit. This assemblage widely produced
Shanxi-Gansu-Ningxia region Zhiluo Formation, Maao
Formation in Henan province, Tarim Basin Qiakemake
Formation, Turpan-Hami basin Qiketai Formation, and
Lower Xiaximiao Formation Sichuan province.
Therefore, the age of this assemblage should be
Bajocian–Bathonian, below Callovian.
2. Darwinula–Djungarica–Timiriasevia Assem-
blage
The assemblage is distributed in Qigu Formation
of northern Xinjiang, Taerga Formation of the Tarim
Basin and Kushuixia Formation of Gansu province.
The main members of the assemblage include: Djun-
garica yunnanensis, Dj. tracta, Dj. postiacuminata,
Darwinula sarytirmenensis, D. paracontracta, Timi-
riasevia mackerrowi, Clinocypris spp., Limnocythere
wangjiashanensis ect.
The composition of this assemblage is similar to
that of Bazhulu Formation in Yunnan province (for-
merly upper part of this Hepingxiang Formation).
Besides Darwinula and Timiriasevia which occurred in
the first assemblage above, there are a lot of Djungarica
fossils. The morphology and size of those Djungarica
are similar to so-called Callovian marine Bythocypris?
or Clinocypris and Paracypris? From a continental
intercalation of marine Callovian beds (Mette, 1995) in
southern Tunisia. Therefore this assemblage may be
Callovian age.
3. Cetacella–Djungarica–Damonella Assem-
blage
This assemblage has been recorded from the
Hongshuigou Formation of Tsaidam Basin, Kuzigong-
su Formation of Tarim Basin and Suining Formation of
Sichuan province. Besides in China, Cetacella is the
leading forms of the Kimmeridgian (Late Jurassic)
ostracods in Germany, Spain, Portugal ect. A few
species of Cetacella can be found from early Oxfordian
53