in Jurassic and Cretaceous Stratigraphy

Earth Science Frontiers, Vol. 17, Special Issue, Aug. 2010 ISSN 1005-2321
Mesozoic Structural Deformation and Tectonic Evolution in Central
and Eastern Sichuan Basin
350
Bihong Fu 1 , Yongdong Wang 2 , Xiaoping Xie 3 , Ning Tian 2
1. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
2. Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China
3. School of Geography and Tourism, Qufu Normal University, Qufu 273165, China
The Sichuan Basin in southwestern China under-
went significant Mesozoic shortening due to the
collision between the North China Block (NCB) and
South China block (SCB). It is an important tectonic
element of the SCB during Mesozoic age. The basin is
bounded on all edges by fold and thrust belts (FTB),
including the Longmen Shan FTB on the northwest,
Micang Shan and Daba Shan FTB on the northeast,
and east Sichuan FTB on the east, and southwest
Sichuan FTB on the south (Fig.1). Large-scale Meso-
zoic contractional deformation and shortening were
quite strong in front of these FTBs. Thick sedimentary
sequences of Triassic through Cretaceous ages record
a relatively complete history of their tectonic evolution.
Previous studies discussed Mesozoic structural de-
formation and tectonic evolution of Sichuan Basin in a
quite general way, and some detailed work was mainly
concentrated on Mesozoic and Cenozoic tectonics of
the Longmen Shan FTB, western Sichuan Basin,
Micang Shan and Daba Shan. Few studies dealt with
structural deformation and tectonic evolution of the
central and eastern Sichuan Basin. Based on the
analyses of satellite remote sensing images and
seismic reflection profiles combined with the field
investigations, we document the Mesozoic structural
deformation pattern in the central and eastern Sichuan
Basin.
Mesozoic structural deformations are quite
complicated in central and eastern Sichuan Basin and
the two belts are separated by the Huaying Shan fault.
The surface structural pattern in central Sichuan is
characterized by the low-relief and gentle folds with a
few of surface faults. In contrast, the surface geological
structures in eastern Sichuan are characterized by the
Jura-type (ejective) folding structures in which they
appear tight anticlines, open synclines and asymmetry
of limbs. The structural pattern in the study area can be
explained by multi-detachment faulting along various
weak sedimentary layers. Seismic profiles reveal that
detachment faults are certainly to be in existence
beneath these folds. Evaporite, shale and argillite
layers within Lower to Middle Cambrian, Silurian and
Lower Triassic sequences provided weak plastic layers
for detachment folding. Mesozoic deformations in
central and eastern Sichuan basin had undergone at
least two-stage development which was the earlier
thrusting caused by collision from southeast to
northwest between the South and North China blocks
since the late Middle Triassic and ended with
detachment folding due to progressively basinward
intracontinental convergence from the Middle Jurassic
to Late Cretaceous times.
Key words: Jura-type fold; Detachment folding;
Tectonic evolution; Mesozoic; Sichuan Basin