High Resolution Estimate for the Depositional Duration of the Triassic Latemar Platform: A New Magnetostratigraphy and Magnetic Susceptibility Cyclostratigraphy from Basinal Sediments at Rio Sacuz, Italy

[1] A new magnetostratigraphyand magnetic susceptibility cyclostratigraphyfrom Middle Triassic basinal sediments at Rio Sacuz, northern Italy, suggests a depositional duration of ~1myr formost of the670 m carbonate Latemar Platform, giving a high resolution estimate for the duration for the Latemar's deposition. The new magnetostratigraphy from Rio Sacuz clarifies the ambiguities in a previous magnetostratigraphic study of the Latemar caused by lightning strikeremagnetizations.Our Rio Sacuzstudy was unaffected by lightning. Using thermal demagnetization, we show a N-R-N-R sequence at the Latemar-correlated locality of Rio Sacuz. With a polarity interval duration of ~0.25-0.5 myr for the Middle Triassic, this gives a depositional duration of ~1-2 myr. Rock magnetic experiments show that the magnetic carrier is magnetite, suggesting a primary, depositional-ageremanence .Measurement of magnetic susceptibility at one meter intervals from Rio Sacuz reveals eight short eccentricity cycles (~95-125 kyr) bundled into slightly more than two 405 kyr long eccentricity cycles indicating a more precise duration for the Rio Sacuz section of 0.8 to 1 myr. The shorter depositional duration required by this study forces a sub-Milankovitch time scaleof 1-2 kyrfor the Latemar platform's meter-scalerhythmic bedding and provides strong evidence for non-orbitally driven climate change in the Middle Triassic.