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