Geology of the early Eocene Fur Formation, a unique deposit in the North Sea Basin. Excursion guide to geological key localities on Mors and Fur, northern Denmark. Prepared for Wintershall Norge AS

An area in the western part of Limfjorden, northern Jylland, is locally called the „moler‟ area, because it is unified by the occurrence of a spectacular and unique set of geological features exposed in coastal cliffs. „Moler‟ is the local, Danish name for a marine Eocene diatomite, which is interbedded with grey to black layers of volcanic ash. The ash layers record the dramatic volcanic eruptions during the early break–up of the continents bordering the North Atlantic Ocean about 56 million years ago. The Eocene diatomite (the Fur Formation) is overlain by Quaternary sediments.

The diatomite contains exceptionally well-preserved fossils, including birds, turtles, insects, fish and plants. The diatomite formed in a depositional environment, which preserved the fossils very well, hence the term „Fossil Lagerstätte‟. These fossils are significant because they represent faunas and floras documenting the responses to the brief greenhouse event termed the Paleocene–Eocene Thermal Maximum (PETM). The PETM occurred only 10 million years after the mass-extinction at the Cretaceous–Tertiary boundary.

The coastal cliffs expose sections through glaciotectonic complexes characterized by folds and thrusts. These structures are enhanced by the black layers of volcanic ash interbedded in the pale yellow diatomite. The glaciotectonic deformation elevated the Eocene strata to their present position above sea level and created the hilly landscape, which is so characteristic of the moler area.

The aim of this report is to present the geology of the moler area, which include the detailed sedimentology of the early Eocene marine clayey diatomite and its lithostratigraphic setting and the correlation of the Fur Formation to the Palaeocene–early Eocene development in the North Sea region. It is prepared for Winthershall Norge AS on the occasion of the field trip arranged June 11-12, 2013. Thus the description of the locality in the second part of this report follows the planned route for the field trip. Due to the request from Winthershall examples of Quaternary sequence stratigraphy and formation of modern dunes are included as well as demonstration of Danian limestone.