High-resolution stratigraphy and zircon U–Pb geochronology of the Middle Triassic Buchenstein Formation (Dolomites, northern Italy): precession-forcing of hemipelagic carbonate sedimentation and calibration of the Anisian–Ladinian boundary interval

Published on 2017-08-30T22:43:40Z (GMT) by
Orbitally forced cyclic variations in sedimentary sequences provide evidence for short-term fluctuations of Earth climate and a tool for high-resolution timescale calibration. We here present stratigraphic and geochronological evidence for precession-forcing in Middle Triassic hemipelagic limestones of the Buchenstein Formation (Dolomites, northern Italy). Highresolution stratigraphy of several correlative sections of the Buchenstein Formation documents a coherent cycle pattern. Isotope dilution thermal ionization mass spectrometry zircon U–Pb geochronology of tuffs bracketing the cyclic interval reveals an average cycle duration of 18.5 ± 2.1 kyr, consistent with a shorter climatic precession cycle in the Middle Triassic compared with today. This suggests a predominantly precession-controlled climate in this low-latitude setting of the western Tethys and allows high-precision calibration of the Anisian–Ladinian boundary interval. From integrating cyclostratigraphic and U–Pb geochronological constraints, our best estimate for the age of the Anisian–Ladinian boundary is 241.464 ± 0.064/0.097/0.28 Ma. We also provide precise estimates for lithostratigraphic boundaries, biostratigraphic markers and magnetic reversals within the boundary interval. Stratigraphic intervals with elevated sedimentation rate record a sub-Milankovitch signal that may be equivalent to patterns in adjacent carbonate platforms such as the Latemar platform. The origin of this sub-Milankovitch signal remains unknown but highlights the potential to investigate shorter-term climatic variations in Mesozoic sedimentary sequences.

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Wotzlaw, Jörn-Frederik; Brack, Peter; Storck, Julian-Christopher (2017): High-resolution stratigraphy and zircon U–Pb geochronology of the Middle Triassic Buchenstein Formation (Dolomites, northern Italy): precession-forcing of hemipelagic carbonate sedimentation and calibration of the Anisian–Ladinian boundary interval. figshare.

https://doi.org/10.6084/m9.figshare.c.3861817.v2

Retrieved: 10:28, Sep 24, 2017 (GMT)