Middle to Upper Triassic marine carbonates and siliciclastic sedimentary rocks derived from the South Qinling orogenic belt and resting depositionally on rocks of the northern Yangtze passive continental margin provide an estimate of the initial contact between the continental parts of the South China Block (SCB) and North China Block (NCB). Our results of high-resolution sequence stratigraphy analysis of the Middle Triassic Leikoupo Formation of the Sichuan Basin in the northern Yangtze Block indicate that these successions were deposited in restricted-evaporative marine platform environments and experienced obliquely tectonic compressional deformation and uplift. Detrital zircon geochronology indicates a proportion of the detritus was from the South Qinling orogenic belt during deposition of the Leikoupo Formation. We, therefore, propose that the northern Yangtze Block had transformed from a passive continental margin into a peripheral foreland basin in response to the initial collision between the SCB and NCB by the Anisian age, ~20 Myr earlier than previous estimates. The shallow marine carbonates of the Leikoupo Formation and the contemporary Luzhou-Kaijiang paleouplifts are considered to be distal foredeep deposits and products of forebulge flexure of the peripheral foreland basin, respectively. The westward retreat of seawater in response to the synchronous westward growth of the paleouplifts further supports the oblique suturing between the two blocks and intense north-south contraction of the Songpan-Garze Terrane, which resulted in new transpressional flexural subsidence in front of the thrust belts, leading to deposition of the terrestrial in the Late Triassic.