DOI Page / Citation link:
https://doi.org/10.11588/diglit.748#0248
INVESTIGATIONS AT ASSOS, 1881. 205
it is very probable that rocks which are here included under the
trachytes when they are better known will be classed among other
groups.
The trachyte which in The Geology of Assos has been called the
first trachyte, occupies a large portion of the area between Behram
and the great plateau further westward, as well as a considerable
district about the base of Coslou-dagh towards the east. Its color
is usually dark-purplish, but varies greatly. The compact uniform
groundmass contains varying quantities of small porphyritic crystals
of feldspar, a few of which have the characteristic striae of plagio-
clase, but orthoclase is by far the most abundant. The ground-
mass usually contains a small quantity of minute scales of mica and
other dark-colored crystals, some of which are probably hornblende.
The upper portion of the trachyte is frequently cellular and scoria-
ceous, like the surface of a modern lava-flow, and can often be
recognized among the pebbles ol the tertiary conglomerate of the
western and southern coasts, — a fact which clearly indicates that
it is one of the oldest trachytes, and yet it occasionally occurs also
in the position of the most recent rocks of its kind. About four
and a half kilometres northwest of Behram the trachyte distinctly
overlies the ashy beds at the top of the tertiary series, and must be
younger than the beds upon which it reposes.
In the vicinity of Balabahny, upon the plateau directly north of
the site of Polymedion, a trachyte occurs containing numerous
small but distinct crystals of mica and many thin tabular, glassy
crystals of orthoclase, some of which attain a length of eigh<" milli-
metres. The crevices of this rock are often coated with beautifully
colored chalcedony. It is much lighter colored than the first tra-
chyte at Behram, and does not appear to have an extensive distribu-
tion. The same trachyte occurs near Baba-calessi, where the crystals
are so small that if plagioclase is present it cannot be recognized
with a hand-lens. A fresh fracture shows only a small, quantity of
the accessory minerals, but upon a weathered surface they are more
distinctly seen; the small black crystals of mica and greenish horn-
blende occasionally give to the rock a peppered appearance
Upon the north side of the Touzla, similar rocks appear near
Gulfal, about ten kilometres northwest of Behram, and extend east-
ward, occupying most of the area immediately north of the river as
it is very probable that rocks which are here included under the
trachytes when they are better known will be classed among other
groups.
The trachyte which in The Geology of Assos has been called the
first trachyte, occupies a large portion of the area between Behram
and the great plateau further westward, as well as a considerable
district about the base of Coslou-dagh towards the east. Its color
is usually dark-purplish, but varies greatly. The compact uniform
groundmass contains varying quantities of small porphyritic crystals
of feldspar, a few of which have the characteristic striae of plagio-
clase, but orthoclase is by far the most abundant. The ground-
mass usually contains a small quantity of minute scales of mica and
other dark-colored crystals, some of which are probably hornblende.
The upper portion of the trachyte is frequently cellular and scoria-
ceous, like the surface of a modern lava-flow, and can often be
recognized among the pebbles ol the tertiary conglomerate of the
western and southern coasts, — a fact which clearly indicates that
it is one of the oldest trachytes, and yet it occasionally occurs also
in the position of the most recent rocks of its kind. About four
and a half kilometres northwest of Behram the trachyte distinctly
overlies the ashy beds at the top of the tertiary series, and must be
younger than the beds upon which it reposes.
In the vicinity of Balabahny, upon the plateau directly north of
the site of Polymedion, a trachyte occurs containing numerous
small but distinct crystals of mica and many thin tabular, glassy
crystals of orthoclase, some of which attain a length of eigh<" milli-
metres. The crevices of this rock are often coated with beautifully
colored chalcedony. It is much lighter colored than the first tra-
chyte at Behram, and does not appear to have an extensive distribu-
tion. The same trachyte occurs near Baba-calessi, where the crystals
are so small that if plagioclase is present it cannot be recognized
with a hand-lens. A fresh fracture shows only a small, quantity of
the accessory minerals, but upon a weathered surface they are more
distinctly seen; the small black crystals of mica and greenish horn-
blende occasionally give to the rock a peppered appearance
Upon the north side of the Touzla, similar rocks appear near
Gulfal, about ten kilometres northwest of Behram, and extend east-
ward, occupying most of the area immediately north of the river as