Marr Bank Formation

Glacial Prehistory 

Marr Bank Formation

The Marr Bank Formation is described as being deposited in a shallow estuarine environment in "The geology of the central North Sea. United Kingdom offshore regional report by R W Gatliff".

"Sand, fine-grained, poor- to well-sorted, soft to firm, grey to red brown with abundant lithic granules and pebbles. Locally silty."

"The Marr Bank Formation includes "muddy sediments, especially towards the north-west but it is generally formed of sands of varying grain sizes and degrees of sorting (Stoker et al., 1985). Gravelly layers contain a variety of lithic clasts of Scottish provenance, and wood fragments and clay balls occur sporadically. No dinoflagellate cysts have been recovered from the formation."

"A poor ostracod fauna and a moderately abundant population of foraminifera (Thomson, 1978) indicate that the shallow waters in which the formation was deposited were high-boreal to arctic in temperature, and inner shelf to estuarine in character." (Gatliff)

 

The chart above indicates the bathymetry of the North Sea. Generalised contours are marked on the plan. A 40 metre contour is marked around Dogger Bank in the south. Further north the 80 metre contour extends up the middle of the North Sea separating the Marr Bank Formation from the Norwegian Channel and coast. 

The base floor of the Marr Bank Formation is 100 metres below sealevel while the seabed at 80 metres below sea level is made up of outcropping formations of the MIS 6, Coal Pit Formation, and older Formations. 

This would indicate that sediments have been lost here and that Marr Bank lagoon was eroded out, initially in MIS 4 and that there was at least a 20 metre height difference between Marr Bank and the Norwegian Channel. 

North of Marr Bank is the Witch Ground, a very deep area of the northern North Sea which is likely to have been carved out by impact valleys cutting down into the Swatchway Formation, and being filled by the Witch Ground Formation.

  

 The section drawing above describes the relationship between the Wee Bankie and Marr Bank Formations. They merge together,  the Wee Bankie Formation being harder than the Marr Bank Formation. It is likely that the Marr Bank Formation was once as thick as the Wee Bankie Formation,  but, as a soft material, was winnowed away during deglaciation. 

During the Last Glacial Maximum, the Marr Bank was a shallow lagoon of unfrozen water along the British coast. It was separated from the Norwegian channel by a ridge of land that reached from dogger bank to the Atlantic ocean north of Norway

The chart demonstrates how the Marr Bank Formation links through the Wee Bankie Formation to the Bolders Bank Formation. 
 

Jeffery Nicholls 

South Ronaldsay 

Orkney 

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