A considerable hiatus at the Frasnian/Famennian boundary in the Rhenish shelf region of northwest Germany

The Frasnian/Famennian (F/F) boundary interval on the Rhenish shelf carbonate platform of northwestern Germany is characterized by a remarkable stratigraphic gap in two reference sections, which was caused by a rapid regression phase leading to the omission of the whole triangularis Zone. This eustatic fall in sea level is connected with the occurrence of phosphatic ooids and phosphatized hardgrounds. The overall duration of the regression is from Early triangularis to Early crepida Zone, about 1.5 million yr, followed by a transgression phase within the Middle crepida Zone, as indicated also by conodont biofacies shifts. At least the phosphatized discontinuity surfaces over cm or dm intervals represent time spans of longer starvation and non-deposition. Thus, several prominent features of the global Upper Kellwasser Event in the F/F transition, typically recorded in the Variscan basinal facies, are recognizable also in the extremely shallow water Rhenish shelf settings.