Stability of the 405-kiloyear Jupiter–Venus cycle

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RayTomes
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Stability of the 405-kiloyear Jupiter–Venus cycle

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The fourth Milankovitch cycle is 405,000 years in the eccentricity of the Earth's orbit. This cycle is present throughout the ages in geological deosits also.
The Newark–Hartford astrochronostratigraphic polarity timescale (APTS) was developed using a theoretically constant 405-kiloyear eccentricity cycle linked to gravitational interactions with Jupiter–Venus as a tuning target and provides a major timing calibration for about 30 million years of Late Triassic and earliest Jurassic time. While the 405-ky cycle is both unimodal and the most metronomic of the major orbital cycles thought to pace Earth’s climate in numerical solutions, there has been little empirical confirmation of that behavior, especially back before the limits of orbital solutions at about 50 million years before present. Moreover, the APTS is anchored only at its younger end by U–Pb zircon dates at 201.6 million years before present and could even be missing a number of 405-ky cycles. To test the validity of the dangling APTS and orbital periodicities, we recovered a diagnostic magnetic polarity sequence in the volcaniclastic-bearing Chinle Formation in a scientific drill core from Petrified Forest National Park (Arizona) that provides an unambiguous correlation to the APTS. New high precision U–Pb detrital zircon dates from the core are indistinguishable from ages predicted by the APTS back to 215 million years before present. The agreement shows that the APTS is continuous and supports a stable 405-kiloyear cycle well beyond theoretical solutions. The validated Newark–Hartford APTS can be used as a robust framework to help differentiate provinciality from global temporal patterns in the ecological rise of early dinosaurs in the Late Triassic, amongst other problems.
From https://www.pnas.org/content/115/24/6153
Ray Tomes
ray@cycles.org
Science Director of Foundation for the Study of Cycles
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