THE GEOLOGY OF SOUTH-EASTERN KINCARDINESHIRE. 951 
volcanoes. ‘The lavas from the Crawton centre have undergone a considerable amount 
of contemporaneous erosion, but the boulders thus derived form quite an insignificant 
proportion in the composition of the imterbedded ‘‘ Highland” conglomerates—they 
never give rise to volcanic conglomerates such as have been produced from the 
prolonged denudation of the acid lavas of the Highland group. 
(c) The Montrose Centre.*—From this centre came the thick accumulation of 
hypersthene andesites, hypersthene basalts and olivine basalts which constitute the 
lava contents of the Arbuthnott and Garvock groups. Tuffs again are absent. The 
reddened character of the upper surfaces of the flows suggested that considerable 
intervals of time may have elapsed between the outpouring of successive lavas. There 
is not, however, so much evidence of contemporaneous erosion as in the rocks 
belonging to the other two centres. ‘‘Sandstone-veining” is everywhere a conspicuous 
feature, and finely bedded shales and mudstones are sometimes intercalated in the lava 
series of the Arbuthnott group. From such shales in the trap rocks of this series at 
Ferryden the Rev. Hueu MitcHe.t made a collection of impressions which recall the 
“Upland Fauna of the Old Red Sandstone Formation of Carrick” described by JoHn 
Smita. The specimens, now in the Montrose Museum, show trails and footprints of 
several kinds, burrows, and rain prints. The hypersthene-bearing lavas are remarkable 
for their fine development of agates ; the vesicles of the basalts of the Garvock group 
contain good specimens of calcite, desmine, and analcite. 
The lavas belonging to this centre are present in great force where they appear in 
the southern limb of the Montrose anticline, but they gradually thin out, and the inter- 
calations of sandstone and conglomerate become thicker as they are traced to the south- 
west. They thin out in similar fashion in Kincardineshire as they are followed to the 
north-east ; and since no signs of volcanic vents are found in the inland sections, one can 
only conjecture that the centre or centres of eruption must be concealed to the eastward 
on the floor of the North Sea. 
XI. HypasyssaLt Inrrusions or Lower Oup Rep Sanpstone AGE. 
The hypabyssal intrusions include dykes of quartz porphyry and biotite porphyry, 
and thin sills and dykes of lamprophyre and dolerite. Quartz porphyry dykes are 
found at Cowie, at Clochnahill, at Allardice Castle, and on the shore near Hallgreen 
Castle ; the peculiar Lintrathen type occurs in the North Esk and Clattering Bridge 
sections. A group of dykes, appearing at intervals along a line extending from the 
Carron. Water near Mill of Forest by the Hill of Seabeg and Fawside, Kinneff, to the 
coast at the Pintill Stone, may be classed as biotite porphyries. An intrusion of olivine 
dolerite, which behaves sometimes as a sill, sometimes as a dyke, has been traced from 
Cadden Castle to Shieldhill, and, shifted by the Whistleberry fault, again appears in the 
neighbourhood of Crowhillock. It has produced marked contact alteration in the tuffs 
* See also Ancient Volcanoes of Great Britain, vol. i. p. 299. 
