Geoscience Reference
In-Depth Information
8.3.4 Reconstruction of Palaeocoastlines
The reconstruction of palaeocoastlines and bathymetry were based on GIS analysis,
from which interpolated surfaces of water levels were subtracted from the modern
20 m was generated using
the linear solution of the Natural Neighbour interpolation using different sources of
elevation data. Elevation data for the mainland were derived from the Estonian Basic
map on a scale of 1:10,000 (western part), the Soviet military topographic map on
a scale of 1:25,000 (eastern part) and the Baltic seabed from the bathymetric maps
maps were transformed into L-EST national reference system. The vertical datum
for the elevation data and DTM modelling was national height system BK77 based
on Kronstadt zero level.
DTM-based palaeoreconstructions have some limitations due to the impact of
deposition subsequent to the time being modelled. Therefore the thicknesses of
the DTM before the palaeocoastline reconstruction.
×
Fig. 8.6
General cross-sections showing the principles of palaeoreconstructions. Topography
related to the isostatically deformed (uplifted) sea/lake water-level surface today (
a
) and during
sea/lake formation (
b
)
8.4 Modelling Results
The distribution of the Baltic Ice Lake water-level surface isobases and shorelines in
the Pärnu area is presented in Fig.
8.7a-i
for nine time slices since the deglaciation
of the area. The created spatial and temporal model made it possible to reconstruct
the palaeo-water levels and coastlines for the times for which coastal landforms
data are lacking, for instance the lowstands of the Ancylus Lake and Littorina Sea
The main characteristics of interpolated water-level surfaces are summarized in