(a) Magnetic susceptibility curve (SI) with interpreted transgressive-regressive trends in the Upper Cretaceous/Paleogene succession at Erguita. The red line corresponds to the mean MS values, while the black line is the mean MS values with one standard deviation. Legend of the lithostratigraphic column is on Figure 1. The stratigraphy is based on El Bamiki et al. (2020). (b) Scatter plot between the chemical index of alteration and magnetic susceptibility. P-rich sediments are not shown because their formation falsifies the CIA values.