Geoscience Reference
In-Depth Information
Fig. 8.2
Digital terrain model of the study area in SW Estonia and the location of the investigated
geological and archaeological sites. Sites with buried organic matter and dated peat sequences are
marked with
black dots
. The locations of the coastal landforms of the Baltic Ice Lake (
blue dots
),
Ancylus Lake (
light blue dots
) and Littorina Sea (
red dots
) are also shown on the map. Peat bogs
are marked by
brown hatching
and the reference site for the water-level curve at Paikuse by a
triangle
At present the late glacial and Holocene shoreline databases cover more than
1,200 sites in Estonia, although statistical analyses show that roughly half of this
data does not match water-level reconstruction requirements due to inaccurate coor-
dinates, elevations or the erroneous correlation of different shore marks. Therefore
the reliability of shoreline displacement data was verified using different methods.
First, sites with altitudes that did not match neighbouring sites were eliminated.
Second, point kriging interpolation with linear trend was used to create interpolated
surfaces of water level, with a grid size of 5
5 km. Kriging is useful because it
interpolates accurate surfaces from irregularly spaced data and shows the outliers in
the data set. Residuals (the difference between the actual site altitude and the inter-
polated surface) were calculated and used to check data reliability, so that sites with
residuals more than
×
1 m were discarded. Then the final interpolated water-level
surfaces were calculated using for BIL stages A
1
- 52, BI - 111, BIII - 164 sites;
for Ancylus Lake 110 sites; and for Littorina Sea 176 sites. Timing of the surfaces
was derived from the ages of the ice marginal positions and varvochronology for the
±
