Third-order depositional sequences reflecting Milankovitch cyclicity |
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| Authors: | André Strasser Heiko Hillgärtner Wolfgang Hug & Bernard Pittet |
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| Institution: | Institut de Géologie, Universitéde Fribourg, Pérolles, CH-1700 Fribourg, Switzerland;Centre Sciences de la Terre, Universitéde Lyon I, 27–43 bd. du 11 novembre 1918, F-69622 Villeurbanne cedex, France |
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| Abstract: | The origin of third-order depositional sequences remains debatable, and in many cases it is not clear whether they were controlled by tectonic activity and/or by eustatic sea-level changes. In Oxfordian and Berriasian–Valanginian carbonate-dominated sections of Switzerland, France, Germany and Spain, high-resolution sequence-stratigraphic and cyclostratigraphic analyses show that the sedimentary record reflects Milankovitch cyclicity. Orbitally induced insolation changes translated into sea-level fluctuations, which in turn controlled accommodation changes. Beds and bedsets formed in rhythm with the precession and 100-kyr eccentricity cycles, whereas the 400-kyr eccentricity cycle contributed to the creation of major depositional sequences. Biostratigraphical data allow the correlation of many of the 400-kyr sequence boundaries with third-order sequence boundaries recognized in European basins. This implies that climatically controlled sea-level changes contributed to the formation of third-order sequences. Furthermore, this cyclostratigraphical approach improves the relative dating of stratigraphic intervals. |
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