Open AccessHigh‐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
Author(s) -
Spahn Z. P.,
Kodama K. P.,
Preto N.
Publication year - 2013
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1002/ggge.20094
Subject(s) - magnetostratigraphy , sedimentary depositional environment , geology , cyclostratigraphy , paleontology , milankovitch cycles , paleomagnetism , sedimentary rock , glacial period , structural basin
A new magnetostratigraphy and magnetic susceptibility cyclostratigraphy from Middle Triassic basinal sediments at Rio Sacuz, northern Italy, suggests a depositional duration of ~1 myr for most of the 670 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 strike remagnetizations. Our Rio Sacuz study was unaffected by lightning. Using thermal demagnetization, we show a Normal‐Reversed‐Normal‐Reversed 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‐age remanence. Measurement of magnetic susceptibility at 1 m 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 scale of 1–2 kyr for the Latemar platform's meter‐scale rhythmic bedding and provides strong evidence for nonorbitally driven climate change in the Middle Triassic.