SEPTEMBER 7, 1899 | 
WaALURE 
445 
thrust of the folds towards the south, the northwardly-convex 
curves by overthrust of the folds towards the north. This law 
agrees with the movements which Prof. Suess has described 
along the curved lines of Alpine upheaval, and finds further 
confirmation in the curious effects of reversal of thrust-move- 
ments which are so highly characteristic of all the great 
transverse Alpine arches. To cite one example, compare the 
great overthrusts round the south curves of the western Alps with 
the northwardly-directed overthrusts in the Bernese Oberland. 
The drawing (Fig. 3) shows that the eastern and western fold- 
ares associated with any transverse direction of faulting provide 
the same fundamental conditions of peripheral overthrusts with 
reference to definite centres which I demonstrated in Enneberg. 
And as the centres are comprised in the very highest transverse 
Alpine arches which were determined during the later epoch of | 
Alpine upheaval, it is here that, according to torsional laws, the | 
highest individual massives should be present. 
The essential structure is the same, whether it be exempli- | 
fied in the variously-shaped dolomite massives or in the 
variously-shaped central massives—elliptical, lenticular, or 
elongated, clearly or less clearly defined from one another— 
all may be regarded as an inevitable result of crust-torsion. 
Even when considerable subsequent faulting and lateral 
displacement might seem to have obliterated the original relation- 
ship of opposite torsion-curves, there are long streaks or inter- 
rupted appearances of igneous injections along the main fault- 
line, which afford evidence of a probable 
original connection between eastern and 
western fold-arcs now fairly remote from 
one another. 
The more or less sickle-shaped form of 
some Alpine curves represents a north 
and south fold-are on the same side of a 
transverse direction of shearing. The 
Enneberg curve (Langs-da-Fiir, Campo- 
lungo, Cherz Hill) is an example on a 
small scale, the Banat curve round the 
Roumanian Plain isan example on a grand 
Scale. 
The chief line of fault there is the 
«* Banat” line, which in its tectonic rela- 
tions bears a strong resemblance to the 
Judicarian line. It runs north and south 
and separates a western area of mica schists 
from an eastern depressed area of Jurassic 
and Cretaceous strata, eruptive rocks 
occurring at intervals along the fault. In 
describing the Banat fault, Prof. Suess never 
doubts the Tertiary age of the folds and of 
the eruptive rocks associated both with the 
folds and with the fault. Ie notes the 
twisting character of the strike, and ex- 
pressly states that the eruptive rocks 
““must have been Tertiary notwith- 
standing the resemblance almost amounting to identity which 
they present with those of the Judicarian and Predazz0 
areas (‘‘Antlitz,” i. p. 623 and pp. 210-213; the italics 
are mine). Further, he quotes Dr. Posepny’s opinion “ that 
these eruptive masses are not masses exerting pressure, but 
themselves pressed. The subsidence of a neighbouring dis- 
trict induces such eruptions, but the eruptive masses themselves 
are pressed into the dykes by the pressure of the sinking masses” 
(2. ¢. p. 210). Similar reasoning was followed by Dr. Salomon 
in his paper on the Peri-Adriatic eruptive masses, wherein he 
advocated the theory that the Peri-Adriatic masses originated in 
consequence of the Peri-Adriatic subsidence, and were of the age 
of the subsidence. 
I would be inclined to class both the Judicirian and Banat faults 
as phenomena of torsional eruptivity which may, upon the 
evidence of the sedimentary strata involved in the folds, be 
referred to the Mid-Tertiary epoch of Alpine upheaval. 
Two great internal torsion-basins within the Alpine systems 
of southern Europe are the Hungarian and the west Mediter- 
ranean. The arrangement of the Carpathian mountains round 
the Hungarian basin presents all the characteristic features of 
torsion. Mountain fold-arcs have formed peripherally, and 
broken arches have been thrust outwards and upwards from 
the basin, while fold-slices produced by normal faulting have 
had an involute movement inward and downward. Eruptivity 
has been particularly active in the main septal zone between 
NO. 1558, VOL. 60] 
the oppositely moving portions of the fold-arcs. The Dalmatian 
mountains represent a series of peripheral folds whose arches 
have moved towards the south-west, while the eastern Alps 
betray the influence of this movement of folding, and also a co- 
ordinated movement to north-west. 
The centrifugal movements round the periphery of the 
western part of the Mediterranean basin have caused the up- 
| folding of the Apennines towards the north-east, and again an 
igneous zone runs irregularly between the area of peripheral 
out-thrust and inward down-throw. _ It is still further within the 
igneous zone that we must look for the buckling-up of new 
rock-folds, but the new folds can never be absolutely parallel 
with the predecessors, sévce crwst-torsion zs going on all the time. 
Hence the virgation of successively formed ranges in great 
mountain systems would appear to rest upon much the same 
principle as the virgation of fold-arcs illustrated at Groden Pass 
in Enneberg (Q.7.G.S., August 1899, /.c., Plate I.). 
While torsion-basins tend by reason of repeated buckling to 
narrow within themselves, the tendency of the regions outside 
the outermost peripheral fold-arcs is to subside towards the 
torsional sag. To such return involute movements we may 
probably attribute the present subsidence going on in the 
Adriatic areas, as also the tendency for lakes and plains to form 
on the outer skirts of torsional mountain-systems. 
The Caucasus mountains afford an example of the occurrence 
of an internal area of down-throw in various parts of which 
Fic. 3.—The leading oblique arches and troughs of the Tertiary upheaval of the Alps. (The trouzhs 
are shaded, the arches are between the troughs, and the chief fold-arcs of the mountain masses 
are indicated within the arches by shading and broken lines.) 
vulcanicity has been active, and of outer areas along which 
overcast folds of immense size have been gradually involuted. 
The Alps show at the present day an advanced phase in their 
torsional history. Earlier outer folds have been broken down 
owing to dynamic as well as aérial causes of denudation, and 
have disappeared along interrupted outer shear-zones which I 
would identify as those occupied by ‘‘ Flysch” rocks of what- 
ever age. These rocks represent the necessary deformation of 
older and less twisted folds by the process of involution during 
the gradual evolution of later and more twisted folds. 
Such an explanation of the relation of the Flysch to the present 
Alps would agree with the observed fact that fragments of gran- 
itoid and metamorphic rocks contained in the Flysch show less 
metamorphic change than those in the central massives of the 
Alps, since it would relate the Flysch to lost earlier folds which 
had undergone a smaller degree of torsion than the succeeding 
folds. 
The widely-extended subsidence during Jurassic and the greater 
part of Cretaceous time in Europe seems to have been the turning- 
point in the history of Alpine upheaval, since previously, in Alpine 
regions, the resultant forces had acted more strongly from north 
and south than from east and west, and afterwards the move- 
ments came almost transversely. Hence the long continuation 
of the great Mesozoic epoch of deposition and subsidence, in 
inducing the strong action of east and west crust-strains over a 
region where previously the action of north and south crust- 
