Cycle Research Of Early Cretaceous Climate Change: Constraint From CaCO₃, Color And Magnetic Susceptibility Of Sediments From Liupanshan Group

Cyclical factors that affect global changes, such as solar activity and changes in Earth’s orbital parameters has the characteristics of continuity, can be recorded at different formation of different time period, this provides the possibility to recognize the orbital parameters driving mechanism of climate change. As the most recent "greenhouse" period, the Cretaceous with extensive developed cycles of sedimentary strata, is an ideal material for the research on orbital parameters driving mechanism of past climate change. Based on the astronomical climate theory and spectral analysis technique, this paper chooses Huoshizhai section of Lower Cretaceous from Liupanshan Group, which has been already strictly constrained by high-density magnetostratigraphy, as the reseach section, through high-resolution sampling and anylysis of CaCO3 content, color, susceptibility, discussed the continetal climate period evolution from 125 to 110Ma of early Cretaceous, comparing with the contemporary marine stratigraphy research and achieved the following results:1) rock rhythm duration roughly have the length as astronomical orbital period, the average rhythmic duration of Liwaxia formation is 38.7ka, corresponding to the astronomical orbital tilt; the average rhythmic duration is 22.9ka, corresponding to 20ka precession cycle.2) The power spectrum analysis shows that, the CaCO3 content changes with 20ka precession cycle; the luminance parameter (L*) changes with the cycles of eccentricity (425,146 kyr tilt cycle) and title (41.9kyr), redness (a*) value changes with the cycles of eccentricity (425,146 and 134kyr), yellowness (b*) values vary with cycles of eccentricity (425,146 and 134kyr) and tilt (47 and 41kyr); frequency magnetic susceptibilitychanges with cycles of eccentricity(417,131 and 94kyr) and precession (27,26and25 kyr).3) the climate change of Liupanshan region during the Cretaceous period is clearly driven by astronomical parameter, and is controlled by eccentricity (400ka and 100ka), obliquity (40ka) and the precession (23ka) control; eccentricity cycle are stable in the whole profiles, dominate the climate fluctuations stage. Spectral analysis results are similar with contemporary low latitude marine strata record, and illustrate that in the low latitude Cretaceous climate driven mainly by two eccentricity and precession.