Paleoclimate reconstruction constrained by black-white-red climatic cycles and new insights into history of Earth's surface temperature

Accurate paleoclimate reconstruction is crucial for understanding the long-term evolution patterns of Earth's climate system and for reasonably predicting future climate trends. Current mainstream reconstruction models overly rely on geochemical proxy indicators and fail to sufficiently integrate lithologic markers, such as coal and red beds, that directly reflect climate zones. This limitation may lead to systematic biases in temperature estimates for geological periods. Based on the analogical principle of "using the present to interpret the past", this study conducted in-depth research on paleoclimatic changes by systematically analyzing the latitudinal zoning patterns of climate-sensitive lithologies in modern and Meso-Cenozoic sedimentary records, combined with experimental data and utilizing climate-sensitive lithologies. The results demonstrated that coal seams and black shales, traditionally considered to form in high-productive, warm or anoxic environments, actually mainly developed in cold-humid climates of the cool-temperate zone with relatively low primary productivity, and could serve as reliable cold indicators ("black"). Evaporites indicated mid-latitude arid zones ("white"), while red beds represented low-latitude tropical rainforest climates ("red"). These three lithologies exhibited latitudinal zoning in space, and their temporal succession sequences directly recorded climatic cycles. On this basis, a "black-white-red climatic cycle" theory was proposed, providing effective constraints on paleotemperature reconstruction. The study concludes that the modern climate lies within a medium temperature range of geological history, and that existing paleotemperature reconstruction models tend to underestimate the temperature fluctuation amplitudes and overestimate minimum temperatures for different geological periods. This research not only challenges traditional perspectives on coal-forming environments and the genesis of black shales, but also provides a new theoretical foundation for revising current mainstream climate models based on geochemical indicators. Moreover, it offers crucial constraints for more accurately revealing the evolutionary patterns of Earth's temperature.