Milankovitch Cycles From South China And The Environmental Responds At The End Of The Late Paleozoic Ice Age

At the end of the Late Paleozoic Ice Age(LPIA), Earth’s climate system drifted from extremes of cold with massive continental ice-sheets to mild climate with sparse and sporadic alpine-style glaciations constrained in the eastern Australia. During this climatic transition, the ’megamonsoon’ wasprevalent around the low-middle latitude region and significantly impacted equatorial climate. According to the conodont biostratigraphy records, the Maokou Formation at the Shangsi section and Dukou section coeval to theend of the LPIAranges from late Kungurian to early Capitanian stage and Wordian to middle Capitanian stage, respectively. In this paper, high-resolution magnetic susceptibility(MS), anhystereticremanent magnetization(ARM) as well as XRF analysis were carried out to conduct cyclostratigraphic analysis for extracting the Milankovitch signal and its environmentalresponds documented at the end of the LPIA.Spectral analyses of the covariant MS and ARM datasets reveal presence of complete suite of Milankovitchfrequencies(eccentricity, obliquity and precession).A strong obliquity signal suggests that waning and waxing of the ice sheet in the eastern Australia exerted a significant influence on globalclimate. A ‘floating’ 405 kyr eccentricity cycle-tuned astronomical time scale isdeveloped as a geochronometer for estimating the durations of the conodont zones from these two sections.The 2.1 and 1.8 Myr cycles in the Maokou Formation correspondingto g4-g3 are a little shorter than it predicted for and detected in the Cenozoic Era indicating the instability of the g4-g3 due to chaotic motion of the planets. The1.05 and 0.9 Myr cycles corresponding to s4-s3 are likewise slightly shorter than the1.2 Myr predicted for and detected in the Cenozoic Era. The 2:1 secular resonance ofg4-g3 and s4-s3 is observed throughout the section suggesting that the orbits of Earthand Mars maintained the resonance(s4-s3)-2(g4-g3)=0 at the end of the LPIA.The imprint of obliquity signal in the Maokou Formation indicates awarm-cool-warm climate evolution during the P3 glaciation at the end of Late Paleozoic deglaciation. The cooling stage with accentuated obliquity signal was time-equivalent to the "Kamura event", which suggests that was induced by an abrupt glaciation event with low seasonality at obliquity nodes.The terrigenous detrital influx(Fe/Ti), redox condition(S/Ti,V/Ti and Zn/Ti) and nutrition level(Ba/Ti) and carbonate production(Ca) non-linearly response to Milankovitchforcing.The terrigenous detrital influx(Fe/Ti) reflecting chemical weathering inputs indicates the summer monsoon system was controlled by Milankovitchforcing. At the precession band, the terrigenous inputs cycle nearly opposed to the carbonate production cyclesuggesting that land-derived flux into the oceans prevent carbonateproduction. The maximum of monsoon climate driven the chemical weathering input was ~8kyr before the upwelling intensity, which indicates the marinesystem respond to orbital forced climate change lag behind the land realm. In thispaper, we conclude that marine realm is less immediate respond than the land due tothe buffering mechanism that stabilizes the climate variations.