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Middle Triassic orbital signature recorded in the shallow-marine Latemar carbonate buildup (Dolomites, Italy)

¹ Department of Geology, Paleontology and Geophysics, University of Padova, Via Giotto, 1, 35137 Padova, Italy
² Morton K. Blaustein Department of Earth and Planetary Sciences, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA
³ Department of Geology, Paleontology and Geophysics, University of Padova, Via Giotto, 1, 35137 Padova, Italy

A new time-frequency analysis of sea-level–controlled carbonate-platform cycles in the Middle Triassic Latemar massif (Dolomites, Italy) reveals a strong depositional signature with characteristics of dominant forcing by climatic precession. Modes corresponding to long and short precession components at 1/(21.7 k.y.) and 1/(17.6 k.y.) underwent amplitude modulations matching Earth's orbital eccentricity with major frequency components at 1/(400 k.y.), 1/(125 k.y.), and 1/(98 k.y.). Obliquity appears as a minor component at 1/(35.4 k.y.). The Latemar signature thus constitutes the oldest pristine Milankovitch signature yet observed in the geologic record. Its fidelity rivals that of the Pliocene-Pleistocene record originally used to confirm the theory of orbitally forced climates. This evidence deepens a widely noted disagreement between radiometric and cyclostratigraphic time scales for the Latemar buildup. The Latemar cycles indicate that orbitally forced sea-level oscillations were operative in the ice-free Middle Triassic hothouse world.

Key Words: Milankovitch theory • precession index • carbonate-platform cycles • Middle Triassic • Latemar massif

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