File:The Quarterly journal of the Geological Society of London (13889764988).jpg

BASALTIC FORMATIOX IN ICELAND. 95
where great masses of relatively receat lava debouching from moun-
tain valleys on to plains had produced a very sejisible subsidence,
leading to the formation of extensive lakes. In the case of Thing-
valla the plain has sunk at least iOJ feet, leaving perpendicular
cliffs of lava on the slopes at its northern eud, from which the
central mass has been torn. These may possibly throw some light
on the formation of Lough Neagh.J
HusAViK Marine and Freshwater Beds.
By far the most important of the sedimentary deposits connected
with the basalts occurs on the coast 7 miles N.E. of Husavik, in
N. lat. (jQ"^ 10'. They rest upon basalt or a basaltic breccia. In
approaching them ffom Husavik, the first exposure occurs in a
grassy cirque, named Hringvershujlft, or the " little round valley."
The escarpment is about 260 feet high, but slopes at an angle of 45°,
and its base is somewhere about 100 feet above the sea-level. The
fossiliferous beds rest upoa a mass of greenish grey clayey material,
succeeded by 20 feet of pale, more or less laminated sandstone with
plant-remains. These proved unfortunately to be all of a rush-like
nature, much macerated and utterly valueless. Three feet of lignite
followed, and then 10 feet more sandstone with similar plants,
and then four beds of lignite in succession, each 1 foot thick and
Pig. 1. — Cliff-section on coast 9 miles N.E, of HusaviTc^
a. Glacial deposits. h. Greenish-grey tuff.
c. Sandy clay with broken shells. d. Sandy clay, unfossiliferous.
e. Sandy clay with fossils.
/. Sandy clay without fossils, with a band of laminated sandstone with
green grains.
g. Four bands with Cyprina, the bottom layer with Actceon Noce, and
Cardium echinatum.
h. Bands of broken shells, with Cypri/ia, Actceon, and Cardium.
i. Continuous band of comminuted shells of variable thickness, average
2 feet. ^