Sub-Milankovitch and Milankovitch forcing on a model Mesozoic carbonate platform -: the Latemar (Middle Triassic, Italy)

Basic shallowing-upward cycles (shu-cycles) and five-bundled megacycles in the Latemar platform have been widely regarded as a model example for precessional and eccentricity forcing in the Mesozoic. Based on bio-/chronostratigraphic data, recent studies questioned this particular type of Milankovitch forcing on the Latemar cyclic series. We present an integrated model that incorporates (i) new cyclostratigraphic data, (ii) new and existing bio-/chronostratigraphic data and (iii) new spectral analyses. The basic shu-cycles in the Latemar reflect sub-Milankovitch control. Cycle bundles of 1 : 4-5 (megacycles : shu-cycles) indicate precessional forcing. They do not reflect eccentricity superimposed on precessional forcing. Spectral analyses reveal highly significant ratios in the large-scale cycle bundlings. Stacking patterns of 1 : 9.9 and 1 : 24.0 shu-cycles represent obliquity and short eccentricity forcing. Both sub-Milankovitch and Milankovitch forcing potentially controlled shallow subtidal carbonate deposition in Mesozoic greenhouse times. Cyclostratigraphic models require an integrated approach including bio- and chronostratigraphic data.