Searching for long cycles in short sections

Long sedimentary cycles with periods of 400 thousand to two million years are difficult to establish. The main reasons are a lack of stationarity in stratigraphic time series and unknown changes in sedimentation rates. Filtering, trend removal and time scale transformations can help to interpret stratigraphic sequences, but the application of any such method has to be justified by geological arguments. The effects of filtering, scale transformation and trend removal are explored using sets of field data from the Carboniferous (NW Ireland), the Cretaceous (Gubbio, Italy) and Pliocene (Sicily). Their location and stratigraphy are described.