Vol. 34 (2015): The ammonites of the Middle Jurassic Cranocephalites beds of East Greenland

John H. Callomon, Peter Alsen & Finn Surlyk

The Mesozoic sedimentary succession of eastern Greenland is renowned for its Boreal Jurassic ammonite record. The marine Middle Jurassic deposits of the Jameson Land Basin in central East Greenland are particularly rich in ammonites and have been the subject of much detailed taxonomic and stratigraphic study since the first collections at the beginning of the 20th century. Over the last fifty years, much of the work on the Middle Jurassic ammonite faunas has been undertaken by John H. Callomon, working initially under Lauge Koch’s last expeditions and subsequently with the University of Copenhagen and the Geological Survey of Greenland (GGU, now GEUS).

This bulletin presents the culmination of these endeavours, published after John H. Callomon’s death. It focusses on the so-called Cranocephalites beds of the Ugleelv area of Jameson Land where a detailed ammonite stratigraphy comprising thirty-four faunal horizons is established for the Borealis, Indistinctus and Pompeckji Standard Zones. The Pompeckji Zone is subdivided into four new subzones and four new species are described. This detailed taxonomic and stratigraphic analysis confirms the status of the Jameson Land succession as the key Boreal reference section for this time interval, and furthermore allows a high-resolution study of the evolution of the ammonites which on this time-scale appears to be continuous.