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Brief Notes on the Geology of Oorbridge, Northumberland. 

 By G. A. Leboue, M.A., F.G.S., Professor of Geology in 

 the University of Durham College of Physical Science, 

 Newcastle-on-Tyne. 



The Tyne, where Oorbridge stands on its left bank, runs in a 

 broad valley bounded on the north by the Blyth-Pont and Tyne 

 watershed and on the south by that between Tyne and Derwent. 

 The geology of this valley about the Oorbridge meridian though 

 not specially complicated yet offers several points of interest to 

 the student of Glacial deposits and of the Oarbonif erous series. 



The formations occurring in the immediate neighbourhood will 

 now be noticed seriatim, beginning with the newest and highest. 



Alltjvial Deposits: Under this head may be classed the 

 material forming the low flat haughs by the river — loam, sand 

 and gravel residting from the regular and occasional overflows 

 of the Tyne. Between Oorbridge and Hexham these flood 

 accumulations are extensively developed on the south or right 

 bank, and form the ground chosen for the many market and 

 nursery gardens established hereabouts. The terraces, though 

 much lower and fewer in number than the remarkably fine ones 

 higher up the valley about Hay don Bridge and Bardon Mill, are 

 clearly traceable running east and west parallel to the line of 

 railway — each serving as a measure of the thalweg of the Tyne 

 in ancient times. At this particular spot these old alluvial ter- 

 races do not reach very much above the level of still possible 

 floods, and may therefore be grouped without impropriety with 

 the true recent deposits of the lowest flats. Nevertheless it must 

 be noted that whilst the material of the latter is really the alluv- 

 ium — or matter brought and deposited by the river itself — the 

 higher, more denuded, and consequently less distinct terraces are 

 carved, to a great extent, out of the thick sands and gravel to be 

 next noticed. 



Sands and Gbavels of the Driet : These are beautifully ex- 

 hibited along the railway. Oapping the Boulder Olay and rising 

 to a considerable height up the southern flank of the Tyne 

 valley, they frequently merge, as has already been observed, into 

 the true river alluvium below. But whereas the latter consists 

 for the most part of such detritus as is derivable from the rocks 

 of the district — grits, sandstones, limestones, and basalt — the 

 former contain a very large percentage of rounded fragments' 



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