== liên kết ngoài ==*geowhen database  valanginian*midcretaceous timescale and ühttp//stratigraphysciencepurdueedu/charts/timeslices/5_jurcretpdf jurassiccretaceous timescale] at the website of the subcommission for stratigraphic information of the ics*stratigraphic chart of the lower cretaceous at the website of norges network of offshore records of geology and stratigraphy