The Songliao Basin is one of the largest non-marine petroliferous basins in the globally and contains nearly complete Cretaceous terrestrial sedimentary records [1,2].The Shahezi Formation,named after Shahezi Village, Changtu County, Liaoning Province,is a thick terrestrial clastic sedimentary succession deposited during the rift period of the Songliao Basin [1].Accordingly, it is significant for research on initial basin history restoration and global continental-marine stratigraphic correlation, to certificate the deposition time of the Shahezi Formation [2-4].This formation is always met when wells are drilled in fault basins of the Songliao Basin [1], and its outcrops are discontinuously distributed along the southeastern margin of the basin (Fig.1a).Limited by the discontinuous cores and outcrops, previous studies on the deposition time of the Shahezi Formation were based only on volcanic rock ages from the overlying Yingcheng Formation [5] and underlying Huoshiling Formation [6], and suggested that the Shahezi Formation was deposited from the late Berriasian to middle Aptian (140-121 Ma).Recently, Yu et al.[7] obtained a secondary ion mass spectrometry (SIMS) U-Pb age of 113.9 ± 0.9 Ma from a tuff layer in the upper part of the Shahezi Formation in the International Continental Scientific Drilling Program (ICDP) borehole SK2, and An [8] obtained a clastic zircon laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb age of 111.13 ± 0.84 Ma from sandstones near the top of the Shahezi Formation in the same borehole.These ages provide key anchor points for the end of the deposition of the Shahezi Formation.The present study is based on a centimeter-scale description of the continuous and nearly complete cores from SK2.One rhyolite crystal tuff layer and one sedimentary tuff layer were found at the bottom of the Shahezi Formation, and U-Pb isotopic dating of zircons in the samples was conducted.