376 SECTIONAL TRANSACTIONS.—C. 
which are attributable to earthquakes and accompanying submarine landslips and 
tsunamis (sea-waves). The phenomena reproduce many features of the Early 
Palzozoic succession of the Province of Quebec, but have escaped complication by 
subsequent mountain-making movement. 
The fault mentioned above has been traced from near Golspie, north-east by 
Brora and Helmsdale, a distance of 20 miles. Everywhere in this part of its course 
it separates pre-Mesozoic rocks (schists, granite and unconformable Middle Old Red 
Sandstone) on the north-west, from Mesozoic rocks (Trias and Jurassic) on the south- 
east. The downthrow is estimated as over 2,000 feet, for this measure is probably 
exceeded by the combined thickness of the Mesozoic rocks still preserved. 
The pre-Kimmeridgian portion of the Mesozoic succession is quite normal for 
Scotland. It starts with continental Trias, succeeded by marine Jurassic, with, as 
elsewhere, an estuarine development of the Bathonian. The Kimmeridgian, the only 
important development of the group known in Scotland, is of extraordinary character. 
It consists of black shales and boulder beds, continually interbedded. The black 
shales are full of remains of land plants and often contain ammonites. They have 
evidently accumulated in a tranquil sea not far from the shore. The boulder beds 
are composed of angular and subangular fragments, boulders and masses of Middle 
Old Red Sandstone, generally set in a matrix of shelly sand, crowded with broken 
oyster, reef coral, Rhynchonella, etc. 
Two main hypotheses have been advanced in regard to these boulder beds: the 
material has either been carried by ice or has been dropped from a cliff. The ice- 
transport hypothesis is universally abandoned at the present time, because: (1) the 
boulders are unstriated and the boulder beds are certainly not boulder clays ; (2) float- 
ing ice would drop boulders rather than boulder beds; (3) the associated plants and 
animals provide unquestionable indices of a warm climate. 
Thus, all observers now agree that the material has been dropped from a cliff. 
Some regard the cliff as a product of marine erosion, others as a product of faulting. 
The former view seems to us incredible because : (1) the Jurassic succession at Golspie 
is seen to rest on the Trias, the usual position in Britain outside of East Anglia ; (2) the 
cliff ran straight for over eight and a half miles, and everywhere coincided, at any rate 
approximately, with a subsequent fault; (3) the deposit of recurrent shales and 
boulder beds is, in our opinion, of great thickness, at least 1,000 feet. 
The marine erosion and fault hypotheses can be usefully contrasted in regard 
to one of the largest boulders that has been identified, the so-called ‘fallen stack’ 
of Portgower. This mass of Old Red Sandstone measures 100 by 90 by 30 feet. Its 
unusually great dimensions have led certain authors to assume that transport was 
out of the question. It has therefore been taken as certain that this boulder is a 
stack that has fallen over on its side. 
The difficulties of this interpretation are: (1) the great boulder is only one item 
contained in an extensive 50-foot boulder bed, which latter remains unexplained on 
the ‘fallen stack’ hypothesis; (2) exposures show shales and interbedded boulder 
beds emerging from under this particular boulder bed. Similar relations hold every- 
where for 84 miles. The Kimmeridgian everywhere proclaims the proximity of a 
cliff, but in spite of constant changes of dip, its base is never exposed. Thus we are 
driven to admit that the Portgower boulder has slipped for a third of a mile along the 
sea bottom from the neighbouring fault-scarp. 
Of prime importance also is evidence of ephemeral currents that accompanied 
almost every landslip. Such evidence is afforded by: (1) the distribution of the 
material as boulder beds; (2) the smoothing of the tops of individual boulder beds 
with unrounded rubble and shell debris; (3) many striking erosional phenomena. 
As the boulder beds, with their shelly debris, continue right up to the fault, it 
is clear that the fault-scarp was wholly submarine and that it separated a shelly, 
sandy, submarine platform from a muddy, tranquil deep. 
Mr. D. L. Linton. 
By means of isopachyte data plotted on a series of four maps it has been possible 
to demonstrate that throughout Upper Cretaceous times contemporary warping 
occurred in South-east England. 
The tectonic features produced appear to be of two clearly defined but contrasted 
types. In the first type broad areas of subsidence are associated with heavy loading 
and are margined by areas of peripheral uplift. Such isostatic movement was an 
