Dividing and classifying the Carboniferous succession

Rock successions can be divided and categorised in a number of different ways, including subdivision according to the characteristics of the rocks themselves, zonation by the nature of fossils contained in the rocks, or correlation utilising a combination of both methods. Lateral variation in the nature of the Carboniferous rocks across Northumberland has long presented geologists with problems in attempting to correlate them across the county. In 1863, on the basis of the sequence in north Northumberland, particularly in the River Tweed, George Tate of Alnwick, proposed a simple fourfold division of the Carboniferous of northernmost England. Numerous subsequent surveys and publications have added to the complexity of the nomenclature and have, to an extent, tended to confuse matters rather than clarify them. Such a situation is not confined to Northumberland and, in order to clarify regional understanding, a lithostratigraphical scheme encompassing the Carboniferous rocks of the entire onshore of Great Britain has recently been adopted. Although not yet used widely on BGS maps these regional group names will be implemented in future publications. Accordingly, the description of Carboniferous rocks in the district follows these new divisions, listed below with the youngest at the top:

• Pennine Coal Measures Group
• Yoredale Group
• Border Group
• Inverclyde Group

The rocks of these groups are described in the pages below, starting with the oldest.