ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

MARGOT BOSE
Glacial landforms in Taiwan
Institut fur Geographische Wissenschaften, Physische Geographie,
Freie Universitat Berlin, Grunewaldstrasse 35, 12165 Berlin, Germany
Situated at the edge of the western Pacific, between the
Philippine plate and Eurasia, the island of Taiwan is about
377 km long and 142 km broad at its widest point. A
young, tilted fault-block range occupies the central part of
Taiwan. The mountains are very steep and exhibit signs of
strong neotectonic activity. About 20 massifs have higher
elevations than 3,000 m, the highest mountain being Yu
Shan (3,952 m), located on the tropic of Cancer.
In 1935 Panzer reported evidence of Pleistocene glaciation,
glacially modified valley heads and a possible lateral
moraine, from the two massifs of Yu Shan (Niitakama)
and Hsueh Shan (Tsugitakayama). He attributed this moraine
to the penultimate glacial stage because its shape
did not resemble alpine moraines of the last glacial: a debatable
conclusion, since weathering and erosion processes
in monsoonal Taiwan differ from those in the Alps.
Annual precipitation in the Yu Shan area ranges between
-2,500 and .....4,500 mm. Further observations on possible
glacial landforms in Nanhu Ta Shan (Nankotaizan) are
found in Tanaka & Kano (1934) and are also discussed by
Panzer.
Owing to the island's steep relief, the resulting short valleys
draining to sea level, and to neotectonic activity, intense
fluvial erosion and many earthflows are the dominant
processes in the Taiwanese mountains. Hence, relict
glacial landforms may be expected only in protected positions
in the midst of the mountains, unaffected by strong
headward erosion. Current palaeoclimatic studies by
Taiwanese researchers mainly concentrate on vegetation
changes at lower and medium elevations and have revealed
pronounced temperature and precipitation changes
during the last glacial. To supplement this work, research
on the elevation zone above 2,600 m and on glacial deposits
in selected valleys is necessary. Suitable study areas
were selected from maps constructed from air photographs
of Hsueh Shan, Yu Shan, and Nanhu Ta Shan.
Areas of weak recent denudation, possible deposition
areas at high altitudes, putative glacial landforms, and the
long profiles of valleys were mapped. These results and
preliminary field observations have clearly shown the former
presence of short valley glaciers in the highest mountain
regions of Taiwan. .
Measurements at Yu Shan (3,858 m), the only climate station
in the high mountains of Taiwan, record frequent frost
changes during winter seasons. Frost weathering is causing
the formation of talus ramparts and initial nivation
forms, especially above the tree line (.....3,500-3,200 m).
My research visit to Taiwan was funded by the National
Science Council of Taiwan and by the Deutsche Forschungsgemeinschaft.
TAIEB BOUMEAZA ', ANDRE PISSART 2 & F. VITA 3
Evolution du cours inferieur de la Moulouya au cours du
Quaternaire (Maroc nord-oriental): propositions nouvelles
1 Departernent de Geographie, Universite Hassan II,
Mohammedia bp. 546 Mohammedia, Maroc
2 Departemenr de Geographie Physique, Universite de Liege B. 11,2,
Allee du 6 Aout, Sart Tilman Liege, Belgique
3 Department of Geomorphology, College of London, U.K.
La vallee de la Moulouya constitue la principale artere et le
plus important bassin versant du Maroc mediterraneen,
Sur son cours inlerieur mediterraneen, il n' existe que des
formations fluviales d'age holocene. L'emboitement des
formations dilferenciees est tres rare ainexistant. Pourtant,
durant Ie quaternaire, des vestiges de depots fluviaux ont
marque la totalite de ses affluents .
Les formations fluviales qui batissent les terrasses sont limoneuses
a limono-argileuses stratifiecs sans charge grossiere,
Leur evolution s'est produite en forme de depots de
crues et liee a l'eustatisme marin au cours de la derniere
transgression. L' eustatisme, s'est fait sentir a l'interieur sur
un parcour de 25 km, neamoins, la neotectonique recente
a joue un role dans la position actuelle de ces niveaux alluviaux.
Des datations ont ete pratiquees apartir des coquilles
d'Helix et ont donne un age relatif de 10.950 ± 450 ans
BP pour les niveaux inferieurs et 3.150 ± 200 ans BP.,
pour les niveaux superieurs, Toutefois, ce niveau superieur
paraissait raviner une topographie de creusement anterieure
a sa mise en place, ce qui peut tre interprete comme
une petite phase de regression qui s'est deroulee il y'a plus
de 4.000 ans BP (datation a l'appuit) permettant ala Moulouya
de pratiquer un creusement dans les depots anterieurs,
avant que Ie niveau marin ne revienne et favorise
l' accumulation des niveaux situes au sommet et qui sont
dates de 3150 ± 200 BP. Le cailloutis d'oued est fossilise
depuis Ie littoral jusqu'a 28 km vers I'interieur par des
depots fins limoneux. A partir de la il apparait plus eleve
que Ie lit mineur de presque 3 a 8 m. Cette denivelletion
est liee surtout a un decalage d'ordre tectonique puisqu'il
est identique partout OU il apparait .
Hormis ces depots holocenes, les formations anciennes
sont absentes, et non jamais pu resister au ravinnement et a
l'erosion de la Moulouya. Toutefois, les formations holocenes
fossilisent des colluvions limono-argileux roses, qu'on
rapporte au Soltanien (Wiirm). Celle-ci sont fossilisees par
Ie cailloutis d' oued.
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