TECTONIC
ACTIVITRY PHASES IN CENOZOIC PERIOD ALONG THE CAO BẰNG - TIÊN YÊN FAULT
ZONE, TIÊN YÊN - LẠNG SƠN SECTION
Truong Thanh Phi
Hanoi
Univesity of Natural Resourses and Envinronment
Corresponding author: thanhgislab@gmail.com
Abstract: The Cao Bang - Tien Yen
(CB-TY) fault zone, Tien Yen - Lang Son (TY-LS) section is about 100 km long,
running in the NW-SE direction, the northeastern part of the Red River fault
zone. The field survey is conducted at 21 locations, including the description
of lithological characteristics, fracture orientation measurement,
stratigraphic displacement, and the evidence of striation motion on the fault
surface… The analytical results of 59 striations on the fault surface along the
CB-TY fault zone, TY-LS section identified that the lateral strike-slip stress
states with the four compression phases E-W, NE-SW, NW-SE and N-S. From evidences
obtained in the field, together with the comparison of previous studies, the
main tectonic phases are arranged in the order of directions: 1) NW-SE; 2) E-W;
3) NE-SW and 4) N-S. In particular, the first compression phase of the NW-SE direction severely
destroyed the old rocks of the Jurassic age and earlier, encountered at many
survey locations along the CB-TY fault zone, TY-LS section; the second
compression phase of the E-W direction occurred during the Cenozoic period,
caused the left displacement of the Red River fault zone in the
Oligocene-Miocene period and the left motion along the CB-TY fault zone formed
the Neogen sedimentary basins: Cao Bang, That Khe, Lang Son, Na Duong; the
third compression phase of NE-SW direction occurred during the Mid-late
Miocene, caused a tectonic inversion of the NW-SE faults in the northern part
of the Red River basin, which are located in the southeast area of the CB-TY
fault zone; the final compression phase of the N-S direction, occurred during
the Pliocene-Quaternary period, caused the right motion along the CB-TY fault
zone and the Red River fault zone.
Keywords: CB-TY fault zone, Red River fault zone, Cao Bang basin,
Neogene Na Duong basin, TY-LS section.
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