| Summary: | Sedimentological records provide the only accessible archive for unraveling Earth’s orbital variations in the remote geological past. These variations modulate Earth’s cli- mate system and provide essential constraints on gravitational parameters used in solar system modeling. However, geologic documentation of midlatitude response to orbital climate forcing remains poorly resolved compared to that of the low-latitude tropics, especially before 50 Mya, the limit of reliable extrapolation from the present. Here, we compare the climate response to orbital variations in a Late Triassic midlatitude tem- perate setting in Jameson Land, East Greenland (∼43°N paleolatitude) and the tropical low paleolatitude setting of the Newark Basin, with independent time horizons pro- vided by common magnetostratigraphic boundaries whose timing has been corrobo- rated by uranium-lead (U-Pb) zircon dating in correlative strata on the Colorado Plateau. An integrated cyclostratigraphic and magnetostratigraphic age model revealed long-term climate cycles with periods of 850,000 and 1,700,000 y ascribed to the Mars–Earth grand orbital cycles. This indicates a 2:1 resonance between modulation of orbital obliquity and eccentricity variations more than 200 Mya and whose periodicities are inconsistent with astronomical solutions and indicate chaotic diffusion of the solar system. Our findings also demonstrate antiphasing in climate response between low and midlatitudes that has implications for precise global correlation of geological records.
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