DOI Page / Citation link:
https://doi.org/10.11588/diglit.2532#0114
GEOLOGICAL HISTORY OF THE REGION
93
composed of a gray, compact, line-grained limestone. This limestone, which underlies,
and hence is older than, the Lygonrio shales, is referred by Philippson ' rather doubt-
fully to the Jurassic Period, and the Lygourio shales to the Lower Cretaceous. Lepsius'"
thinks that it is Cretaceous. Owing to the paucity of good fossil remains, the question
is difficult to decide definitely, hut I am inclined to agree with Lepsius as to its age,
especially on the ground of its petrographic resemblance to the Cretaceous limestones of
Attica and the similar occurrence of gabbros and serpentine, which are found in several
places breaking up through the limestone.
Geological History of the Region. — During Cretaceous and Eocene times the region
which now forms the Argolic Peninsula was beneath the level of the sea, and the beds
of limestone were heing accumulated largely through the growth of marine organisms on
the shallow and slowly sinking sea-bottom. The accumulation was aided by the depo-
sition of sediment brought from then existing land areas near by, which have in part
disappeared through denudation and subsidence, and in part are left on the mainland of
Greece and in the Cyclades.
In Post-Neogene time there was an elevation of this area, and the immense mass of
rock which had been forming and hardening for ages beneath the sea was raised slowly
many thousand feet into the air. This elevation, though gradual, was the means of still
further consolidating the rock-mass through pressure and partial metamorphism, and
was accompanied by much cracking of the crust.
Indeed, the Aegean Sea and the surrounding countries have been the scene of so much
disturbance that the whole region is, as Cold puts it, crossed by a " network of cracks."
One of the most important of these is that which, beginning at Cos, curves round
through Saiitorini, Melos, and Aegina to the Isthmus of Corinth, and thence along the
Gulf of Corinth. It is on part of this line that the Greek volcanoes have been formed.
In fact, it is to these cracks that the main configuration of these Aegean countries is
due, with their lines of islands and peculiar coastal features.
Only two of these fracture-lines, however, concern us. One is the volcanic line
already mentioned, which cuts off Argolis abruptly on the east, and on which we find
the volcano of Methana, the small eruptive mass of Poros, and the small outflows of
dacite near Kalamaki. The other is that which runs in a southeasterly direction from
about Phlius, through the Argive plain and out into the Gulf of Nauplia. This latter
separated the massif of Argolis from that of Arcadia.
As soon as the Argolic massif had been raised above sea level, it became subject to
the destructive effects of the atmosphere, rain and wind, heat and frost, which agencies
are constantly tending to reduce all elevations of the earth's surface to a so-called base
level, which would be eventually (if other forces did not come into play) that of the sea.
The rain fell on the upraised surface of the old sea-bottom, and dissolved it and washed
it off. The heat of the sun and the frost of Avinter split up the rocks, and vegetation
springing up aided the disintegration. The surface material was washed seaward, the
rainfall gradually forming regular channels for itself, as one can see in miniature on a
sandy road after a heavy rain.
The main lines of drainage would be determined by the two fracture-lines, which
would offer channels for the drainage, and which would be the parts toward which the
surface water would flow. Toward these, then, the small streams made their way, gradu-
ally widening and deepening their own channels and cutting back farther and farther
1 Op. cit. p. 390. a Op. cit. p. 81.
!
93
composed of a gray, compact, line-grained limestone. This limestone, which underlies,
and hence is older than, the Lygonrio shales, is referred by Philippson ' rather doubt-
fully to the Jurassic Period, and the Lygourio shales to the Lower Cretaceous. Lepsius'"
thinks that it is Cretaceous. Owing to the paucity of good fossil remains, the question
is difficult to decide definitely, hut I am inclined to agree with Lepsius as to its age,
especially on the ground of its petrographic resemblance to the Cretaceous limestones of
Attica and the similar occurrence of gabbros and serpentine, which are found in several
places breaking up through the limestone.
Geological History of the Region. — During Cretaceous and Eocene times the region
which now forms the Argolic Peninsula was beneath the level of the sea, and the beds
of limestone were heing accumulated largely through the growth of marine organisms on
the shallow and slowly sinking sea-bottom. The accumulation was aided by the depo-
sition of sediment brought from then existing land areas near by, which have in part
disappeared through denudation and subsidence, and in part are left on the mainland of
Greece and in the Cyclades.
In Post-Neogene time there was an elevation of this area, and the immense mass of
rock which had been forming and hardening for ages beneath the sea was raised slowly
many thousand feet into the air. This elevation, though gradual, was the means of still
further consolidating the rock-mass through pressure and partial metamorphism, and
was accompanied by much cracking of the crust.
Indeed, the Aegean Sea and the surrounding countries have been the scene of so much
disturbance that the whole region is, as Cold puts it, crossed by a " network of cracks."
One of the most important of these is that which, beginning at Cos, curves round
through Saiitorini, Melos, and Aegina to the Isthmus of Corinth, and thence along the
Gulf of Corinth. It is on part of this line that the Greek volcanoes have been formed.
In fact, it is to these cracks that the main configuration of these Aegean countries is
due, with their lines of islands and peculiar coastal features.
Only two of these fracture-lines, however, concern us. One is the volcanic line
already mentioned, which cuts off Argolis abruptly on the east, and on which we find
the volcano of Methana, the small eruptive mass of Poros, and the small outflows of
dacite near Kalamaki. The other is that which runs in a southeasterly direction from
about Phlius, through the Argive plain and out into the Gulf of Nauplia. This latter
separated the massif of Argolis from that of Arcadia.
As soon as the Argolic massif had been raised above sea level, it became subject to
the destructive effects of the atmosphere, rain and wind, heat and frost, which agencies
are constantly tending to reduce all elevations of the earth's surface to a so-called base
level, which would be eventually (if other forces did not come into play) that of the sea.
The rain fell on the upraised surface of the old sea-bottom, and dissolved it and washed
it off. The heat of the sun and the frost of Avinter split up the rocks, and vegetation
springing up aided the disintegration. The surface material was washed seaward, the
rainfall gradually forming regular channels for itself, as one can see in miniature on a
sandy road after a heavy rain.
The main lines of drainage would be determined by the two fracture-lines, which
would offer channels for the drainage, and which would be the parts toward which the
surface water would flow. Toward these, then, the small streams made their way, gradu-
ally widening and deepening their own channels and cutting back farther and farther
1 Op. cit. p. 390. a Op. cit. p. 81.
!