Helsingin seudun taajamakartoitus - Arkisto.gsf.fi - Geologian ...

GEOLOGICAL SURVEY OF FINLAND
DOCUMENTATION PAGE
Date / Rec. no.
Authors
Marit Wennerström, Meri-Liisa Airo, Tuija Elminen,
Sari Grönholm, Matti Pajunen, Markus Vaarma, Pekka
Wasenius
Type of report
Archival document, Final report
Commessioned by
Geological Survey of Finland
Title of report
Helsingin seudun taajamageologia (Urban geological mapping in the Helsinki Region)
Abstract
In the project rock types and tectonic and structural properties were mapped in the areas of Sipoo, Kerava, Järvenpää,
Tuusula, Nurmijärvi, Hyvinkää and Kirkkonummi. Knowledge in the evolution of the Svecofennian bedrock
is very important for the activities utilizing the bedrock. Tectonic, magmatic and metamorphic evolution has determined
the recent distribution of the rock types, its structural anisotropy and the factors determining the distribution
and characters of the brittle structures. These are important for all kind of bedrock applications. The principal
characters of the evolution of the Svecofennian bedrock are presented for the analysis of applications.
The regional geophysical data were used for defining geophysically different sub-areas and in the interpretation of
the structures of bedrock.
The faults that pierce the bedrock in the area were classified according to their origin. Groups with different properties
that also contribute the recent quality of the rock were distinguished. The fault structures were also divided
into three different classes of zones of weakness, which give estimate on the rock quality for engineering purposes.
Based on jointing properties bedrock has been fractured around zones of weakness, borders between major tectonic
units and in the hinge areas of the reoriented gneisses. Generally bedrock is relatively unbroken all over the
mapping area except along the zones of weakness.
Volcanic rocks and quartzites in Hyvinkää are sources of high quality aggregates. Bedrock areas in the other
places of the study area contain mainly raw materials for poor quality aggregate (quality classes II – III, TVH
1988). Gabbros and quartzites from Hyvinkää and the Obbnäs rapakivi granite from Kirkkonummi have been used
as natural stones. In this report 9 aggregate quarrys and 3 already closed natural stone quarrys are described.
Different themes: lithology, tectonic structures, faults, zones of weakness and fracturing of sub-areas are presented
at maps in the scale 1:250 000. Information on aggregates and natural stones are presented with relation to the
Counties.
Keywords
bedrock, deformation, structural analysis, faults, shear zones, joints, rock aggregates, dimensional stones, geophysical
methods, urban geology
Geographical area
Finland, Southern Finland Province, Uusimaa, Hyvinkää, Järvenpää, Kerava, Kirkkonummi, Nurmijärvi, Tuusula,
Sipoo
Map sheet
2031, 2032, 2034, 2041, 2042, 2043, 2044
Report serial
Urban geology
Total pages
94
Language
Finnish
Unit and section
Southern Finland Unit, Bedrock & Mineral Resources
Signature/name
Archive code
K 21.42/2006/6
Price
Project code
2704000
Signature/name
Confidentiality
Public