This environmental impact assessment for Kriegers flak ... - Vattenfall

66 PRESENTATION OF THE AREA
11.1.1 General information about Kriegers
Flak
Kriegers Flak is a raised seabed/submarine bank in the
southern Baltic Sea. Water depth within central parts
of the area is 16-17 metres, increasing to 20-25 metres
at the borders. Outside the area the depth increases
sharply to 40 metres or more. The seabed is made up
of sediments from the last ice age on top of sediments
from the cretaceous period.
The border between the top of the sedimentary bedrock
and the quaternary deposits is located within the
actual area at a depth of between 50 and 60 metres.
The upper part of the layer, deposited before the
quaternary period, consists of limestone, comparable
to glacially deformed lime at nearby Møns Klint in
Denmark. The nearest core drilling to great depth is
at Smygehuk between the Danish and the Swedish
economic zones, and marked Smygehuk I (Lat.N55°
18’ 16.22”, Long. E13° 03’ 02.25”).
There, the top 350 metres of the sedimentary
Overview of Kriegers Flak with isochrones showing the water depth. The yellow line indicates the
border between the Swedish and the Danish economic zones (GEUS Report 2004/97).
bedrock consist of white, soft limestone with a rich
occurrence of ß int (up to 30%) in the upper part, but
declining with depth and only sporadically occurring
on greater depths than 150 metres. The changeover
between quaternary sediment and the sedimentary
bedrock was found to be at a depth of 42 metres below
the surface, which indicates that the top level of the
pre-quaternary deposits are likely to show small variations
in depth and therefore assumed to be horizontal
within the present area. Characteristics and quality for
the upper layer of the bedrock is in line with the evaluations
of the drillings Smygehuk I.
The composition and powerfulness of the removed
sediment layers from the last ice age depend partly on
the water depth and partly on local water conditions
(currents, speed of water etc). In shallow waters, i.e.
the central area of Kriegers Flak, quaternary sediments
are found with powerfulness of generally less than
20 meters, while the sediment powerfulness south of
Krieger Flak (Arcona basin) is more than 40 meters.