Nanxiong Basin
Nanxiong Basin is a NE-SW elongated intermontane
basin located in norhtern Guangdong and southern Jiangxi provinces.
The strata exposed at the basin are divided into three groups:
(1) The Upper Cretaceous Nanxiong Group consists
of the Yuanpu Formation (fan-glomerate, fluviolacustrine, and
lacustrine facies) and Pingling Formation (fluvial deposits).
(2) The early Tertiary Loufuzhai Group is darker
colored and foner grained than the Nanxiong Group, and is made
up of the Shanghu, Nonshan, and Gucheng formations.
(3) The overlying Danxia Group is a suite of coarse,
sandy conglomerate.
Dinosaur eggs and fossil mammals were first found
at the basin in 1961. Over 1,000 more or less complete eggs and
more than 40,000 eggshell fragments have been collected. Fossil
eggs are restricted to the middle ad uppermost parts of Yuanpu
Formation, and throughout the Pingling Formation. The egg fauna
consists of the following taxa (Zhao Z. K., 1993):
Elongatoolithidae Zhao, 1975
Macroolithus yaotunensis Zhao, 1975
Macroolithus rugustus Young, 1965
Macroolithus sp. nov.
Elongatoolithus andrewsi Zhao, 1975
Elongatoolithus elongatus Young, 1954
Elongatoolithus sp. nov.
Nanshiungoolithus chuetienensis Zhao, 1975
Spheroolithidae Zhao, 1975
Ovaloolithus cf. O. chinkangkouensis Zhao and Jiang,
1974
Ovaloolithus cf. O. laminadermus, Zhao and Jiang,
1974
Ovaloolithus sp. nov.
Shixingoolithus erbeni Zhao et al., 1991
Fam. indet.
Stromatoolithus pinglingensis Zhao et al., 1991
The Nanxiong Group contains four dinosaurian bones:
Tarvosaurus sp., Nanshiungosaurus brevispinus, Nemegtosaurus
sp., and Microhadrosaurus nanshiungensis, as well as a large
turtle -- Nanshiungchelys Wuchingensis.
K/T boundary: Different characteristics below and
above the boundary --
Above the boundary Petrology dark red siltstone with
large calcareous concretions and fossil record of mammal fauna
. Below the boundary is purplish red siltstone with small calcareous
concretions and fossil record of dinosaur eggs and bones.
Zhao and others' study of eggshell structures, trace
elements and O, C isotopes suggests that environmental change
and more arid climage is the main reason why dinosaurs became
extinct.
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