The Carboniferous Stratigraphy of the Roman Wall District in Western Northumberland

Abstract

Summary The stratigraphy of part of the Yoredale Bernician Limestone Group succession of western Northumberland is described. The western extremity of the area concerned lies at the eastern margin of the Brampton district (Trotter and Hollingworth, 1932). During the present re-survey a series of 11 Yoredale Cyclothems, some of them multiple, have been traced 17 miles from the margin of the Brampton district eastwards to the River North Tyne. The succession changes considerably when traced from west to east across this area owing to variations in lithology and the splitting of some of the limestone horizons. The stratigraphical sequence in the eastern part of the area is similar to that in north Northumberland, and the Oxford Limestone, an important marker band in north and central Northumberland, has been recognized in the North Tyne region. The Yoredale Cyclothems of western Northumberland are in detail different from those of other regions. A series of minor rhythms is normally present towards the top of each cyclothem and a pyritic shale phase, sometimes with goniatites, occurs in the marine shales. An unusual reef-limestone facies is present in association with two of the limestones. Faunal bands are of use in lateral correlation of the succession and zonal fossils confirm that the sequence ranges from upper Viséan to lower Namurian. A faunal change occurs below the Viséan-Namurian boundary where there is also a lithological change.

Carboniferous biostratigraphy of the Rookhope Borehole, Co. Durham

“…It is noteworthy that many of the horizons in the borehole that produced fragmentary goniatites have also produced these fossils elsewhere in the northern England. Thus mainly identifiable goniatites have previously been recorded from the Four Fathom, Three Yard, Five Yard, Scar and Smiddy cyclothems (Johnson 1959;Johnson et al 1962;Johnson & Dunham 1963;Rayner 1953;Mitchell 1958). The fragmentary condition of the goniatites from Rookhope is caused by a combination of the shallow-water, high-energy environment in the centre of the Alston Block and the, fragile nature of the thin-shelled goniatite genera recorded.…”

“…In compound cyclothems the primary coarsening upwards sequence from limestone through to the first seatearth and possibly coal horizon is termed the initial cycle in this paper and is often more than 20 m thick. It is followed by smaller coarsening upwards cycles, here called minor cycles, that are normally less than 6 m thick and vary in number; none are present in some cyclothems and in others up to four minor cycles are found (Johnson 1959(Johnson , 1984. Initial and minor cycle distinguishing features are given in Table 1.…”

“…The mean thickness of the Four Fathom Limestone on the Alston Block is 6-7 m which agrees quite well with four fathoms or 7-32 m. The limestone is typically of medium-grey colour, fine-grained in thick beds with bands of chert nodules. It is not rich in macrofossils on the Alston Block, but contains conspicuous coral biostromes both to the North and South of the block (Turner 1956;Johnson 1959). The limestone is overlain by a thick marine mudstone that contains many fossils towards the base.…”