A TECHNOLOGY OF PALEOPRECIPITATION RESTORATION BASED ON CHANGES OF INLAND LAKE LEVEL——WITH REFERENCE TO THE DAIHAI LAKE IN INNER MONGOLIA

The Daihai Lake,situated in the south of the Inner Mongolia Plateau, is a rift inland lake with a drainage area of 2621.6 km^2 and an annual average precipitation (AAP) of 436.8mm. Remarkable changes of the Daihai Lake have taken place since the Holocene.

Quantitative estimation of global mean precipitation throughout the Phanerozoic era

Quantitatively estimating the global mean precipitation(GMP)throughout Earth's history is crucial for enhancing our understanding of long-term climate evolution and the hydrological cycle.However,currently there is no established methodology for estimating global mean paleoprecipitation.Here,we present the first study that estimates GMP in the Phanerozoic era.The relationship between GMP and global mean surface temperature(GMST)is investigated by analyzing data from 23 models in the Coupled Model Intercomparison Project phase 6(CMIP6).The result reveals consistent and significant impact of temperature on precipitation,with a sensitivity range of 2–3%K^(-1).Additionally,we propose a method for accessing latitudinal variations in precipitation caused by land area distributions and paleo-Koppen climatic belts.These climatic belts are determined based on geological indicators such as coals,evaporites,and glacial deposits.The GMP is thus quantitatively estimated by combining variations in GMST,land area distributions,and paleo-koppen climatic belts,spanning from 540 Ma to the present day.The quantitative GMP curve demonstrates fluctuations in GMP about 500 mm yr^(-1),with values ranging from 948 to1442 mm yr-1over the Phanerozoic era.This curve aligns closely with findings derived from numerical simulations.The presented paleoprecipitation variations facilitate a more comprehensive understanding of the interconnected geological and paleoclimatic developments.

Middle Jurassic climate oscillations from paleosol records of the Sichuan Basin,SW China

The Middle Jurassic is characterized by major plate tectonic changes,variable atmospheric CO_(2)concentrations(pCO_(2)),and climate oscillations in both marine and terrestrial realms.However,the limited evidence from the terrestrial sedimentary records hampers a comprehensive understanding of global climate state in this period.Well-exposed strata of the Shaximiao Formation in the Sichuan Basin,Southwest China,preserve successions of paleosols that offer the possibility of evaluating the terrestrial paleoclimatic changes during the Middle Jurassic(Bajocian to Callovian).A total of 151 paleosol profiles belonging to four paleosol types(Entisol-like,Inceptisol-like,Aridisol-like and argillic Inceptisol-like paleosols)were identified and characterized.The quantitative paleoclimate reconstructions based on the bulk geochemistry of paleosol horizons and depths of carbonate nodules indicate a generally semiarid-subhumid climate alternating with arid-humid and cool/warm-temperate climates during this time interval.This dynamic climate terminated in a dry,subhumid,humid/perhumid and superhumid moisture regime characterized by steppe/wet or rain forest floral provinces.We suggest that these climatic fluctuations may have been related to global geodynamic(e.g.,the fragmentation of Pangea,“megamonsoonal”circulation,and bolide impacts)and regional tectonic uplift(e.g.,the uplift of the Longmenshan Mountains in the South China Block)during the Middle Jurassic.The pCO_(2)estimates suggest relatively low pCO_(2)levels within the range of~100 ppm-~890 ppm during the Bajocian to Callovian.Our results coincide with the threshold for the initiation of glaciation and may help to explain the occurrence of cool intervals in the generally warm Jurassic.These pCO_(2)fluctuations,which coincide with paleotemperature variations in the low paleolatitudes of the Northern Hemisphere,are possibly attributable to global geological events(e.g.,wildfire events,eustatic sea-level oscillations,and the transient development of glaciations)in the Middle Jurassic.