200 MISS a. L. ELLES AND MISS I. L. STATER ON THE [May I906, 



III. Tectonics. 



The main structural features of the district appear to be due to 

 the superposition of two sets of earth-movements — rocks upon which 

 a Caledonian trend had been impressed, being affected at a later 

 time by pressure from the south, the previously-folded beds being 

 held by some rigid mass on the north, presumably that of the 

 Longmynd massif. Hence, the main folds of the neighbourhood of 

 Ludlow, while chiefly due to this (Armorican) movement from the 

 south, run east-north-east and west-south-west, the dips on their 

 northern limbs being everywhere steeper than those on their 

 southern sides. 



Along Wenlock Edge the rocks retain their Caledonian trend, 

 and consequently the beds between "Wenlock Edge and Ludlow 

 have been dragged round to accommodate themselves as best they 

 may to the later influence. 



The faulting is intimately connected with the folding ; the main 

 dislocations are of the nature of septal faults, associated with the 

 folds the axes of which run in an east-north-easterly direction. 

 With these are connected a system of relief-faults running in a 

 direction at right-angles to them. 



The unyielding nature of the Aymestry Limestone in the west 

 has given rise to a series of dip-faults of accommodation ; while in 

 a few places, as for example at Onibury, stresses seem to have 

 found relief along older Caledonian lines. 



The main anticline, with an axis running east-north-east and west- 

 south-west through Ludlow town, pitches away to east-north-east : 

 it is cut by an oblique fault all along its northern side, throwing 

 down the beds to the north ; with the result that all the different 

 beds of the highest Silurian rocks are brought in turn against the 

 Old Red Sandstone, though the abutting of the Mocktree Shales 

 and Lower WhitclifFe Elags, north-east of Whitcliffe Cottages, is 

 largely helped by the steepness of the ground relatively to the dip at 

 that point. 



Eor the greater part of its course the fault has a dow T nthrow to 

 the north; but, near Downton Castle, where the beds begin to sweep 

 round, the t hrow gradually changes over to the south side, and appears 

 to die out altogether a little farther west. A well-marked relief- 

 fault, nearly half a mile in length, crosses the river at Downton- 

 Castle Bridve, running a little west of north; while another sub- 

 sidiary relief-fault, running north 30° east, occurs close to Downton- 

 on-the-Eock. A subsidiary earth-wave finds expression in the 

 Downton-Castle inlier, the intervening trough being occupied by 

 the Old Red Sandstone ; while, a little farther north again, a third 

 wave is faintly indicated by the east- north-easterly extension of the 

 main north-to-south line of outcrop. 



Lightbody thought that the gorge of the Teme at Ludlow was 

 due to faulting, since the lowest beds seen in the western cliff are not 

 visible in the eastern. He also considered that the structure of the 

 western cliff demanded the existence of two faults. The lower beds 



