A sedimentological mineralogical investigation of the Tertiary sediments from the borehole M-2X in Central Trough, North Sea

Grain size and mineralogical analyses have been carried out on samples (cuttings) of Paleocene to Upper Miocene age from the M-2X borehole in the Central Trough of the North Sea.

The Paleocene sequence and the Lower Eocene ash series are dominated by smectite , while kaolinite has not been detected. However kaolinite occurs in large amounts in the younger Eocene sediments. At the transition from the Paleogene to the Neogene the grain size increases abruptly , the amount of smectite decreases and that of kaolinite and illite increases. Kaolinite indicates a subsequent supply of terrigenous weathering products presumably from the Baltic area and / or from the land areas of Scotland. The large amounts of smectite in the Paleocene and Lower Eocene is thought to be a result of a halmyrolytic transformation of the volcanic material. The distinct change in the type of sediment s in the Upper Oligocene is thus believed to have been a response to the uplift of the surrounding landmasses and / or a lowering of the sea level.