Planet movement as geologic chronometer

 

Refining the Early Devonian time scale using Milankovitch cyclicity in Lochkovian–Pragian sediments (Prague Synform, Czech Republic).

2016

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Da Silva, A.C., Hladil, J.; Chadimová, L.; Slavík, L.; Hilgen, F.J.; Bábek, O.; Dekkers, M.J.

Earth and Planetary Science Letters, 455, 125-139

 

Understanding the past and geological events requires a clear view of time (see "Time Matters"). When an event occurs and how long it lasts are essential questions (see: "Planet movement influenced past events"). In this article we are working on the Lower Devonian, which began about 420 million years ago. The uncertainties about the durations and limits of the geological stages at this time are of the order of 3 million years. The Pragian stage, for example, lasted only 3.2 million years and the uncertainties on its base and top are of 3.5 and 4.2 million years, which is longer than its total duration. This makes the work of geologists extremely complicated.
 

In this work, we use magnetic susceptibility measurements taken on samples collected in geological outcrops in the Czech Republic. We first test whether these magnetic measurements contain a climate signal (see Looking for the lost climate). Then we identify the Milankovitch climatic cycles (via mathematical signal analysis techniques) that have a definite duration (see: Milankovitch cycles). We count these cycles, which allows to clearly improve the geological time scale at this time. We estimate the uncertainty on our calculations and propose new durations for the geological stages that would be up to 6 times more accurate than the old scales.
 

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