Quantitative discrimination of normal fault segment growth and its geological significance: example from the Tanan Depression, Tamtsag Basin, Mongolia

ABSTRACT

This work focuses on quantitative discrimination of fault segment growth and its effect on sedimentation and stratigraphic evolution in the Tanan Depression, the Tamtsag Basin, Mongolia. Integrated seismic data sets and stratigraphic data suggest that normal faults evolve as fault segments grow, link and amalgamate to form a larger fault. Three main stages in the evolution of fault zone are recorded in the syn-rift stratigraphy. This paper applies a method to effectively discriminate the locus of fault segments by ‘three diagrams’ and quantitatively reconstruct process of fault growth by the maximum throw subtraction method. Backstripped to T₂₃ SB event, the F1 fault comprises four hard-linked segments, and the F2 fault is divided into four soft-linked segments (F2-4 and F2-5 segments are shown by hard linkage) at the T₂₃ structural level. The F1 and F2 fault comprise hard-linked segments at the T_23-1 structural level when the F1 and the F2 are backstripped to the T₂₂ (133.9 Ma) SB event. The F1 fault is divided into three soft-linked segments (F1-2 and F1-3 segments are shown by hard linkage), and the F2 fault is divided into four isolated fault segments at the T_23-1 structural level when the F1 and the F2 is backstripped to the T₂₃ SB event. Incorporation of paleo-fault geometry, isochron thickness map and sedimentary facies suggest that the transfer zone provided accommodation space for sediment discharge and deposition, and the depocentres were formed at the locus of maximum throw along a fault segment during its overall deposition.

KEYWORDS:

• Tamtsag Basin
• Tanan Depression
• fault segment growth
• throw backstripping
• transfer zone
• sedimentary stratigraphy

Acknowledgements

The authors gratefully acknowledge the Science and Technology Innovation Team in Heilongjiang Province ‘fault deformation, sealing and fluid migration.’ We highly appreciate the insightful comments and suggestions from Dr Yangwen Pei and another reviewer.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Ministry of Science and Technology of the People's Republic of China The authors gratefully acknowledge financial support from the National Natural Science Foundation of China [grant number 41602129], [grant number U1562214]; the National Science and Technology Major Project of the Ministry of Science and Technology of China [grant number 2016ZX05054-009], [grant number 2016ZX05006-005], the Major Science and Technology Project of PetroChina Company Limited [grant number 2016D-0702] and Northeast Petroleum University Excellent Research Talent Cultivation Fund-Province Innovation Reserve Talents [grant number 2017-KYYWF-0063].