Third-order depositional sequences reflecting Milankovitch cyclicity

The origin of third-order depositional sequences remains debatable, and in many cases it is not clear whether they were controlled by tectonic activit y and/or by eustatic sea-level changes. in Oxfordian and Berriasian-Valangi nian carbonate-dominated sections of Switzerland, France, Germany and Spain , high-resolution sequence-stratigraphic and cyclostratigraphic analyses sh ow that the sedimentary record reflects Milankovitch cyclicity. Orbitally i nduced insolation changes translated into sea-level fluctuations, which in turn controlled accommodation changes. Beds and bedsets formed in rhythm wi th the precession and 100-kyr eccentricity cycles, whereas the 400-kyr ecce ntricity cycle contributed to the creation of major depositional sequences. Biostratigraphical data allow the correlation of many of the 400-kyr seque nce boundaries with third-order sequence boundaries recognized in European basins. This implies that climatically controlled sea-level changes contrib uted to the formation of third-order sequences. Furthermore, this cyclostra tigraphical approach improves the relative dating of stratigraphic interval s.