Arguments for recognizing autogenic vs. allogenic signals in the stratigraphic record are still far from settled, as is the decoding of unsteady allogenic responses to climate vs. tectonic forcing. We offer the case of late Mesozoic Xuanhua basin in the western Yanshan fold-and-thrust belt of North China to make these points. The study area is an intramontane basin that has allowed detailed structural, sedimentological, and provenance analyses in a kilometre-thick succession (the Tuchengzi Formation) of alluvial fan, fluvial, lake-delta and lacustrine deposits. Extensive geological mapping provided confidence of near-basinwide later correlation of strata, revealing two large-scale upward-coarsening (CU) successions each 80–240 m thick, with prominent vertical changes from lacustrine through deltaic and fluvial to alluvial fan deposits. Two intervals of thrust-related growth strata identified in the Tuchengzi Fm suggest that the CU successions were the signals of tectonic uplift and accommodation change related to Likouquan and the Mapu thrusting. In the lower CU succession, there is a stacking (30+) of small-scale (3–16 m thick) upward-fining cyclothems that are argued to have been generated by alternating wet-dry climate cycles. The wet half-cycle is argued to have initiated with high sediment and water discharge of flood-generated mass flows into the lake and ended with accumulation of lacustrine mudstones as lake level rose. The lake deposits include the maximum flooding during the wet half-cycle. The dry half-cycle was characterized by continued lacustrine deposits, but increased evidence of subaerial exposure (rooting, paleosols, and mudcracks) argued to result from falling of the lake level under dry conditions.

Article link: https://doi.org/10.1111/bre.12616