An Anisian peripheral foreland basin in the northern Yangtze Block, implications for the collision between the South and North China Blocks

<p>LA-ICP-MS zircon U-Pb isotopic data for the sandstone samples from the Middle to Upper Triassic successions in the northern Sichuan Basin and Zigui Basin.</p> <p>Four sandstone samples were collected from the lowermost Upper Triassic strata that unconformably overlie the Leikoupo Formation for detrital zircon analysis. The Upper Triassic Xujiahe Formation is generally considered to mark the transition from a marine platform to a terrestrial basin on the upper Yangtze Block (Meng et al., 2005). In the Guangyuan and Wangcang areas, we collected three sandstone samples from the lower portion of the Xujiahe Formation. At the Ma&rsquo;antang train station, we collected one sandstone sample from the Ma&rsquo;antang Formation, which is a transitional deposit from marine to terrestrial environments in front of Longmen Shan.</p> <p>The analysis was conducted with laser ablation inductively coupled plasma mass spectrometer (LA-ICPMS) at the Key Laboratory of Continental Collision and Plateau Uplift, Chinese Academy of Sciences (CAS). Analytical methods were described in detail by Cai et al. (2012) and are briefly described here. A total of 362 zircon grains from 4 samples produced data of sufficient precision for geochronological interpretation.</p>