ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

lief formed by glaciers was transformed by numerous geomorphological
processes: fluvioglacial, limnoglacial, solifluctional,
erosion, eolian, thermokarst, littoral, limnic, fluvial,
suffusion, karst, organogenic and anthropogenic. The
action of these processes in different age formations of
Lithuanian glacial relief varied. The duration and intensity
of processes predetermined the degree of transformations.
Most intensive postgenetic changes took place in the
Lithuanian uplands. The largest area of postgenetic change
is taken by erosion, thermokarst, organogenic, fluvioglacial
and fluvial formations. The link was determined between
the age of relief and postgenetic complexes and their intensity
in the morainic massifs and moraine chains.
Age
Postgenetic changes of glacial relief of Lithuania (area, 0/0)
Processes
fluvioglacial fluvial thermokarst erosion organogenic
Morainic massifs
Saale glacier 5,1 0,9 4,11 9,7 6,7
Vistula glacier
Brandenburg stage 2,2 21,4 1,3
Frankfurt stage 1,9 1,2 10,4 11,0 9,8
Pomeranian stage
East Lithuania phase 3,3 12,3 10,0 8,3
South Lithuania phase 0,3 12,6 11,5 6,8
Middle Lithuaniaphase 0,5 7,4 15,4 4,7
Morainic chains
Saale glacier 5,0 1,0 1,4 24,2 0,4
Vistula glacier
Brandenburg stage 4,0 0,5 8,2 13,1 14,8
Frankfurt stage 1,5 12,7 12,4 12,5
Pomeranian stage
East Lithuanian phase 1,1 3,9 11,3 10,4 11,3
South Lithuanian phase 14,6 9,8 10,3
Middle Lithuanian phase 2,2 19,6 9,8 11,0
D. CHANDRASEKHARAM & H.C. SHETH
Significance of flow stratigraphy in deciphering erosional
history of flood basalt provinces
Department of Earth Sciences, Indian Institute of Technology,
Bombay 76, India
In huge continental flood basalt provinces such as the Deccan,
India, multiple eruptive vents are generally the rule,
each having its own sphere of influence. Often it is difficult
to estimate the rate and volume of erosion from topographic
expression only. It must be decided before estimating
erosion rates that the lavas did once extend over the
presently observed valleys. For example the gap between
areas A and B (fig. 1) could have been due to erosion, but
it could as well have existed originally, with A and B being
separate areas of eruption. Thus an independent check for
original continuity becomes necessary. This can be achieved
if flow stratigraphy is superimposed on the topo-
110
graphy. Deccan flood basalts, due to their time of eruption
(Cretaceous - Tertiary) have achieved international importance
and several groups are currently establishing flow by
flow stratigraphy of the Deccan volcanics. (e.g, Subbarao &
Chandrasekharam, 1995). Flow stratigraphy can be established
based on field relationships, petrography, geochemical
and paleomagnetic signatures. One such flow stratigraphic
sequence from the Deccan province (Devey &
Lightfoot, 1986) extending over 300 km is shown in figure
1. Such a flow stratigraphic sequence enables us to decipher
the thickness and attitude of the flows on regional
scale. Thus, as shown in figure 1, if the flow stratigraphic
sequences for areas A, Band C match,original continuity
of the Formations 1 to 4 is confirmed and this can be of
much help in estimating the volume of rock eroded in a
unit area. Such a flow stratigraphy superimposed on topography
would be a useful tool in assessing the erosion caused
geomorphic evolution of flood basalt terrains. In certain
cases, as seen in figure 1, flow stratigraphy would help
in deciphering even the basement topography.
t!ffio
1000
500
o
FIG. 1
JUI-CHIN CHANG
Geomorphological changes on the Tsengwen
coastal plain in Southwestern Taiwan
Department of Geography, National Taiwan Normal University,
162 Sec. 1, East Ho-ping Rd.,Taipei, Taiwan
Tsengwen River, one of the main streams in southwestern
Taiwan, is marked for its meandering channel and high sediment
yield. The coast of this area is significant for the
offshore bars and lagoons. According to the historical archives
available in the last three hundred years and the
comparision of detailed topographical maps in this century,
the «paleo Taichiang Inland Sea», a lagoon with an
area of 350 km', had been filled up and reclaimed as salt
pans and fish ponds since 19 th
century. The coastline had
migrated to the west about 5 km due to rapid sedimentation
during 1904-1990. In addition, the Tsengwen River
had four avulsion events in the typhoon seasons. The interval
of river change was about 50 years in average without
human interference since 19th century. On the other hand,
the sand dune on the offshore bars with a height of 10m,
has decreased its magnitude due to the expansion of built