Tectonic and climatic controls on the Late Jurassic-Early Cretaceous stratigraphic architecture of the Xuanhua basin, North China

Abstract

<p>Decoding tectonic and climatic signatures from continental successions has become important in basin analysis. However, tectonic and climatic signatures can still be difficult to discriminate from each other. The late Mesozoic Xuanhua basin in the western Yanshan fold‑and‑thrust belt represents a representative intramontane basin and allows detailed stratigraphic, sedimentological, and provenance analyses. The work entailed an analysis of alluvial fan, fluvial, lake‑delta, and lacustrine systems in the Tuchengzi Fm. Lateral correlation of sedimentary columns reveals two large‑scale upward‑coarsening cyclothems each 80-240m 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 cyclothems were controlled by tectonic uplift and accommodation change related to the Likouquan and the Mapu thrusting. In the lower upward‑coarsening cyclothem, stacking of small‑scale (3-16 m thick) upward‑fining cyclothems was revealed and argued to have been generated by alternating wet‑dry cycles. The wet half‑cycle started with discharge and deposition 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 with increased evidence of subaerial exposure indicated by rooting, paleosols and mudcracks resulting from falling of the lake level under dry conditions.</p>