Miocene to present kinematics of fault-bend folding across the Huerguosi anticline, northern Tianshan (China), derived from structural, seismic, and magnetostratigraphic data

Abstract

We combine surface structural measurements, subsurface seismic imaging, and magnetostratigraphic dating to retrieve, through geometric modeling, the detailed history of fold growth and sedimentation across the Huerguosi anticline, on the northern Tianshan piedmont, taking advantage of a beautifully exposed section of growth strata. The model assumes a fault-bend folding mechanism, consistent with subsurface fold geometry. The shortening history is obtained by least-squares fi tting of the measured dip angles of the growth strata. The shortening rate across the anticline is shown to have been remarkably constant: it increased only slightly from 0.84 ± 0.04 mm/yr between 10 and 4 Ma to 1.14 ± 0.02 mm/yr over the past 4 m.y. This approach also allows correcting syntectonic sedimentation rates for the effect of the fold growth and shows that the sedimentation rates in the piggyback basin increased abruptly from ~0.4 to ~0.7 mm/yr ca. 4 Ma.