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PROFESSOR T. J. JEHU AND DR ROBERT CAMPBELL ON 
Faults . — In the preceding pages mention has been made of the most important 
fault lines : — the Leny Fault, the Fault which forms the northern boundary of the 
belt of metamorphic rocks, the Jasper Fault, the Gualann Fault, and the Highland 
Fault, all of which trend north-east and south-west. 
The Highland Fault and the Jasper Fault, which may be regarded as a branch 
of the former, are upthrusts from the north-west. The Jasper Fault can be traced 
eastwards from Gualann to a point in the Boninty Burn just south of Clashbeg 
Wood, where it is cut by a dip fault which shifts the main Highland Fault (see 
fig. 7). Beyond this point the Jasper Fault joins the main Fault. The Highland 
Fault, or rather complex of faults, is continuous along the southern margin of the 
Highland Border Rocks. It is of pre-Upper Old Red Sandstone age. 
The Gualann Fault and the northern boundary Fault of the metamorphic belt 
are normal faults with downthrow to the north-west. From local evidence the 
former is seen to be of post-Upper Old Red Sandstone age ; the later is subsequent 
to the folding of the Margie beds. 
The Leny Fault may belong to the period of the post-Margie movements, which 
resulted in the folding, faulting, and crushing of the Highland Border Rocks, or it 
may be a normal fault of somewhat later origin. 
In addition to the above strike faults, the rocks of the area are traversed by 
numerous dip faults which trend north-west and south-east. The courses of some 
of the more important of these are shown in the accompanying map (Plate YI). 
XIII. Summary of Results. 
1. The Highland Border Rocks in the district can be arranged in two divisions : — 
(а) The Lower Series, consisting of cherts, cherty shales, and black shales 
overlying and in less measure interleaved with spilitic lavas, and 
associated with igneous intrusions and with a group of highly meta- 
morphosed rocks of both igneous and sedimentary origin. 
(б) The Upper or Margie Series, made up of grits, shales, and limestone, along 
with a remarkable basal breccia. 
2. The sediments of the Lower Series point to deposition in clear water near 
the verge of sedimentation, from which coarse terrigenous material was excluded 
and in which Radiolaria thrived ; the lavas indicate submarine volcanic eruptions. 
The beds of the Upper Series are unconformable to the Lower Series, and their 
constituent materials are in part the result of the denudation of the Lower Series. 
The Margie grits and shales are due to the accumulation of comparatively coarse 
terrigenous material laid down on a slowly subsiding land area. The basement 
breccia affords evidence of a recrudescence of volcanic activity at the beginning of 
Margie times. 
3. The Lower Series is either of Upper Cambrian age or belongs to the Passage 
Beds between the Cambrian and the Ordovician. 
