Supplementary data for Lacustrine Varves from the Early Cretaceous Dakangpu Bed of Yixian Formation, NE China: Insights for sub-decadal paleoclimatic evolution

Understanding climate variability and stability under warming climate in the past is essential for future climate predictions. However, the scarcity of high-resolution, deep-time archives has limited our knowledge of interannual and sub-decadal climate variability in the pre-Quaternary/deeptime. This study investigated the annual laminations/varves from the Early Cretaceous Yixian Formation in Western Liaoning, NE China. Four different types of laminar microfacies (LMf) have been identified in the Dakangpu Bed of the Yixian Formation, including the LMf 1 (calcareous clay-rich couplet), LMf 2 (siliciclastic clay-rich couplet, LMf 3 (calcareous siliciclastic couplet) and LMf 4 (Organic calcareous couplet). All LMfs exhibit clear light-and-dark laminar couplets. However, evidences suggest LMfs 1-3 are varve couplets, whereas LMf 4 is likely due to rhythmic flooding couplets. A warming and drying paleoclimate, indicated by integrated geochemical, mineralogical, geophysical, and palynological proxies of the Dakangpu Bed, was crucial factors controlling the formation of these LMfs. The spectral analysis of varve couplet thickness and Ca/Ti ratios from representative varves in the middle and upper sections of the Dakangpu Bed reveals that the main signals are identified within the ranges of the Schwabe sunspot cycle and the El Niño-Southern Oscillation (ENSO) cycles. These results confirm the persistent solar cycles in earth’s history and the presence of robust ENSO-like signals in a warming climate.