GEOLOGICAL AND GEOPHYSICAL INTERPRETATIONS FOR THE FORELAND OF THE LONGMENSHAN, WESTERN SICHUAN

On the basis of the data derived from surface geologic observation and geophysics, the author considers that the Longmenshan Area and its foreland are characterized by the alignment of east-west zones and south-north blocks. Consequently, five fault models are established respectively for listric faults,terrace-faults, undulate faults, dome-faults and strike-slip faults,as well as two folding structural models related to faultings and fault assemblages. Thereafter, it is proposed that the area underwent piggyback shiftings from east to west during the time of the Indosinian-Xishanian and four detachments have been brought about along the four tectonic levels at the bottom of the Upper Sinian, Silurian, Lower and Upper Triassic systems respectively. It is believed that the excellent structural traps closely related to thrusts would develop in the Palaeozoic and Mesozoic systems, at the deeper depth of the Longmenshan Foreland.