Abstract
Earth’s orbital variations on timescales of 104–105 years, known as Milankovitch cycles, have played a critical role in pacing climate change and ecosystem dynamics, through glacial and/or monsoon dynamics. However, the climatic and biotic consequences of these cycles on much longer (~ 107 years) timescales remain unclear, due to a lack of long proxy records with precise age constraints. Here, we show ~ 10-Myr scale variations in early Mesozoic (250–180 Ma) records of lake-level, desert distribution, biogenic-silica burial flux, atmospheric CO2 levels (pCO2), and sea-surface-temperature (SST). Their phase relationships, coupled with carbon cycle modeling results, suggest that orbitally-paced summer monsoon dynamics modulates changes in terrestrial weatherability by ~ 20%, affecting changes in pCO2 of up to 500–1,000 ppmv and 3–7 °C SST. We also infer that these ~ 10-Myr scale climatic variations could have been causally linked to biotic turnover, size variations in dinosaur footprints, and tetrapod dispersal, potentially through spatio-temporal variations in resource availability and arid-hot climatic barriers at low-middle latitudes.
Highlights
Earth’s orbital variations on timescales of 104–105 years, known as Milankovitch cycles, have played a critical role in pacing climate change and ecosystem dynamics, through glacial and/or monsoon dynamics
Ten-Myr scale variations (~ 7–13 Myr variations) have been found in carbon isotope data of marine carbonates (δ13Ccarb) across at least last 250 Myr, which is interpreted as a result of orbitally-paced monsoon dynamics and related secular changes in climate and carbon t ransfers[5,7,8,9]
To our knowledge, quantitative estimates for ~ 10-Myr scale monsoon dynamics and the impact of this variability on climate related to the carbon cycle have not been explored, primarily because monsoon records longer than several tens of Myr are rare
Summary
Earth’s orbital variations on timescales of 104–105 years, known as Milankovitch cycles, have played a critical role in pacing climate change and ecosystem dynamics, through glacial and/or monsoon dynamics. Our data consist of (1) ~ 30 Myr lake level proxies of the Newark Basin (North America)[11,22,23], (2) ~ 70 Myr terrestrial silicate weathering rate derived from BSi burial flux of pelagic deep-sea bedded chert sequence in the Inuyama area (Japan)[13], (3) spatio-temporal distribution of eolian
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