Greinar (Vísindafélag Íslendinga) - 01.01.1976, Side 105

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framing the Westem Neovolcanic Zone, is traced to the north up
to the Húnaflói Bay and divides the field of the Miocene plateau-
basalts into two areas: the North-Westem Peninsula and the Central-
Northem Iceland.
The general dip of rocks, younger than the Miocene plateau-
basalts, towards the Neovolcanic Zones is extremely gentle (Fig.
2B and D). The near horizontal deposition combined with compara-
tively small thickness of formations lying above the plateau-basalts,
makes the superposition of the Pliocene basalts over the Miocene
ones form very wide bands, as observed in the exposures on the
flanks of the syncline.
The secondary zone of the Pliocene and Quatemary effusions oc-
cupies the Snaefellsnes Peninsula in the west of Iceland. This zone
has a latitudinal strike.
Recent tectonic structure of Iceland
The main tectonic features in the stmcture of Iceland are two
marginal quiet zones and an inner zone much more complicated.
The former cover the flanks of a large syncline, the latter is its
inner part (Fig. 1 and 2-B).
The marginal quiet zones are the surface regions of the plateau-
basalts: the north-westem peninsula and the eastem margin of the
island. In the first region the plateau-basalts are generally tilted to
the south-east at angles of 3—5°; in some places they lie horizontally.
In the second region the basalts are tilted to the west-north-west
at similar angles. In both places this gentle inclination of rocks is
disturbed by bands of steeper dips (20-30°), i.e. flexures of very
local importance. In the eastem region steeper dips are observed
in the lower part of the formation (up to 8°) and a more gentle dip
characterizes its upper part (Fig. 2D). Consequently a supposition
arises that the plateau-basalts of the eastem region become thicker
towards north-west, i.e. in the direction of the Neovolcanic Zone
(6, 19, 20).
The plateau-basalts are pierced by basalt and dolerite dikes, as
a rule perpendicular to the enclosing layers and, therefore, very
steeply dipping to the east and east-south-east on the eastem peri-