Palaeoweathering and palaeoclimate of the Lower Cretaceous upper Xiguayuan Formation in the Luanping Basin, North China: Implications for early Aptian global cooling

The Early Cretaceous greenhouse climate was interrupted by multiple intermittent cold snaps such as the Valanginian cold snap and late Aptian climate cooling events, but there is currently a lack of terrestrial palaeoweathering and palaeoclimate records for the early Aptian climate cooling event. The relationship between the regional climate of terrestrial lake basins and the global climate during the early Aptian is still unclear. The Luanping Basin, which is located in the northeastern North China Craton (NCC) and contains Lower Cretaceous sediments with a maximum thickness of ∼3,200 m, is an ideal place for analysing the terrestrial weathering and climate. Sixteen mudstone samples were collected from the Lower Cretaceous upper Xiguayuan Formation in the Luanping Basin. The mineral compositions and major, trace and rare earth element contents of the mudstone samples were quantitatively determined via X-ray diffraction (XRD), X-ray fluorescence (XRF), and inductively coupled plasma‒mass spectrometry (ICP‒MS), respectively. Elemental geochemical analyses were carried out to determine palaeoweathering intensity, palaeoclimatic conditions, and their relationships with the global climate. The variation trends in multiple chemical weathering indices are reconstructed after the interference of nonweathering factors is eliminated, reflecting that the source area has experienced mainly weak to moderate weathering. After evaluating the influences of carbonate-sourced elements, we infer that the regional palaeoclimate is arid and cold on the basis of the Sr/Cu ratio, Rb/Sr ratio, C-value, land surface temperature (LST), and mean annual temperature (MAT). All chemical weathering indices and palaeoclimate proxies exhibit similar trends. Moreover, the cooling of palaeotemperatures could have been a response to the early Aptian global cold snap. The regional climate of the Luanping Basin is controlled mainly by global climate change, which provides terrestrial weathering and climate records for the early Aptian global cooling event. • Palaeoweathering indices are reconstructed based on elemental geochemistry, reflecting that the source area experienced weak to moderate weathering. • Quantitative palaeoclimate indicates an environment of arid and cold. • The potential interferences of diagenesis and provenance were excluded by using the corresponding chemical proxies. • The interferences of carbonate-sourced elements on palaeoclimate proxies were evaluated. • The regional climate is controlled by global climate change, which confirms the existence of the early Aptian global cooling.