File:The Quarterly journal of the Geological Society of London (13365430884).jpg

1849.. SHARPE ON THE SECONDARY ROCKS OF PORTUGAL. 157
hills about ninety miles long and rarely more than one or two miles
broad, which extends from Monte Junto northwards nearly to the
Mondego, a few miles below Coimbra. This chain does not cross the
Mondego, but as I only followed it northwarrl as far as the spot where
it is crossed by the Lisbon road on the level of Condeixa, I cannot
state its exact termination, which I presume to be on the southern
bank of the Mondego.
The limestone at Monte Junto is about two miles wide and rises to
the height of about 2000 feet* ; the beds are thrown up irregularly
at high angles and dip away from the centre of the hill on three sides,
towards the east, south and west, at angles varying from 40^ to 80° ;
while on the north they are broken oif from the rest of the chain by
a narrow ravine called the Ferradouro, which admits of the passage
of a tolerable road through the chain. No intrusive rock is here
visible, but the force which elevated this long chain appears to have
acted with great intensity at this spot, while it was diminished farther
south, where the Jurassic beds are not raised to sight and the subcre-
taceous rocks are less disturbed. The section No. 6 (fig. 7) shows the
position of the beds at Monte Junto : the effect produced at Alhandra,
which is the most southern point to which this elevation can be traced,
may be seen in section No. 4 (fig. 5) at p. 152.
Fig. 7.
Section No. 6. Across Monte Junto. (15 miles.)
N.W. Monte Junto, Otta, S.E.
Sandstone. Jurassic limestone. Sandstone alternating with limestone. Marsh.
The rock at Monte Junto is a hard, white or greyish argillaceous
limestone with somewhat of a conchoidal fracture, and, in some of its
beds, contains numerous A?nmonites and fragments of Enc?'inites which
are not easily to be extracted : among the specimens brought away I
have identified the following species, from which we may infer that
this limestone belongs to the upper part of the oolitic system : —
Ammonites Boucaultiamis .', D'Oriigny. Ammonites polyplocus, Reinecke.
colubrinus, Reinecke. tortisuleatus, B Orhigny.
From Monte Junto the limestone chain runs for about thirty-five
miles N.N.E. to Carvalhos : the road usually followed from Lisbon to
Coimbra (called the Estrada nova) runs on the east flank of the chain
from Alcoentre to Rio Maior ; after leaving the latter place the road
inclines to the N.W. and crosses the chain at Alto da Serra, where
the limestone is only about a mile broad and of inconsiderable eleva-
tion. The limestone beds here dip at angles of 60° to 70° to the
eastward and are broken through by a mass of trap, as is shown in
section No. 7 (fig. 8), and the Jurassic limestone is overlaid uncon-
formably on both sides by sands of the subcretaceous formation, which
are elevated where they rest on the limestone to angles varying from
20° to 30°.

• There is an establishment at the top for collecting ice for the supply of Lisbon.