ABSTRACTS / RESUMES - Comitato Glaciologico Italiano

Thus burial-related heating cannot easily explain the AF­
TA data, and the lack of correlation of the VR values with
depth also argues against this process. Alternative explanations
are required for the palaeotemperatures recorded.
The heating mechanism may have involved high temperature
groundwaters within the sediments; extensive Late
Cretaceous hydrothermal activity affected the Bowen Basin
to the south (Golding & alii, 1996).
No matter what the process, in the Laura Basin the Vr and
Afta data cannot be used as accurate guides to the amount
of burial and denudation that has occurred.
HERBERT WEINGARTNER 1 & EWALD HEJL 2
New fission-track data from northern Greece
and their consequences for Neogene
surface development interpretation
1Department of Geography, University of Salzburg,
Hellbrunnerstralie 34, 5020 Salzburg, Austria
2 Department of Geology, University of Salzburg,
Hellbrunnerstrabe 34, 5020 Salzburg, Austria
Geomorphological investigations in the Aegean and surroundig
areas have revealed uncountable evidence of paleo
surface- and weathering-elements. The legacy of paleo relief
development is represented by specific geomorphologic
relief features like inselbergs, karst cones, cupola-karst,
karstic and non karstic planation surfaces etc. as well as
paleosoils together with deep chemical weathering horizons
and significant remnants of paleo weathering indicators
like clay (kaolinite, montmorillonite) and heavy minerals
like haematite.
In many cases the distribution of the paleo surfaces is
marked by a distinct steplike arrangement. According to
this steplike relief formation the question arises whether a
piedmont-model of surface development may be applied
or tectonic vertical movements - due to the tectonically highly
active Aegean area - are responsible for the present
planation surface arrangement.
Fission-track dating, which was used to contribute substantially
to the explanation of relief development history
within and at the borders of the northern Aegean, shows
the following preliminary results:
- The fission-track data generally show a high amplitude
of ages.
- From the Pelagonic to the Rhodopoe zone the ages tend
to become younger.
- In the Pelion and Ossa Mountains similar ages in different
altitudes hint post Middle Miocene vertical movements.
- Comparable data in the Symvolon Mountains and on
the island of Thasos prove an isolated island development
of Thasos younger than 8 Ma.
- Growing ages from the borders of the Rila Rhodope
402
Massif towards the center indicate an earlier uplift of the
central Rhodope Massif.
- Higly contrasting ages of samples in Skiathos (20,38 resp.
7,14 Ma) reveal a close neighbourhood between solid
older and younger tectonic active parts of the Aegean microplate.
These new data demand a new estimation of paleo relief
development in the northern Aegaen, which has been too
strongly polarized between the imaginations of tectonic or
subaerial processes.
STEPHEN G. WELLS ', KIRK C. ANDERSON '.
DIANA E. ANDERSON 1, T. WILLIAMSON 2 & Y. ENZEL 3
Geomorphic and sedimentologic responses to Late
Quaternary hydrologic events: implications for
paleo-precipitation regimes across the hyperarid Mojave
River drainage basin of Southern California, USA
1Quaternary Sciences Center, Desert Research Institute,
p.o. box 60220, Reno, NV 89506, USA
2 Department of Soils and Environmental Sciences,
University of California, Riverside, CA, USA
3 Institute of Earth Sciences, Hebrew University, Jerusalem 91904, Israel
A Late Quaternary history of hydrologic events (i.e., increased
fluvial discharge and pluvial lake stands) and their
associated precipitation regimes [herein referred to HyprJ
is reconstructed from geomorphic, sedimentologic, stratigraphic
and 14C analyses of alluvial, lacustrine, and shoreline
deposits within the largest arid fluvial system of the
Mojave Desert. This system, the Mojave River, currently
terminates in the Silver Lake, Soda Lake, Cronese Lake
(Sse) playas, but episodically flowed beyond it present terminus
into the Silurian and Dumont Valley (Sdv) and ultimately
into Death Valley (Dv) playas. The Sdv and Dv were
hydrologically connected to the Mojave River during at
least two times between 18 to 11 ka, as water overflowed
during the major high stand of Lake Mojave. Increased
precipitation within the near-coast San Bernardino Mts,
(Sbm), 200 km away from pluvial Lake Mojave, resulted in
large-scale flooding and concomitant high lacustrine sedimentation
rates (0.8 to 1.4 m/ka), A relatively complete record
of pluvial events is recorded in the Cronese basin,
with the major pluvial periods from 71.5 to 79 ka and 9.9
to 21.5 ka and important but shorter duration lakes circa
5.8 ka, 1.8 ka, 0.7 ka, 0.55 ka, 0.38 ka, and 0.2 ka. Recent
coring and stratigraphic analyses within the Sdv indicates
that perennial lakes with interbedded fan-delta complexes
derived from locally derived fluvial systems existed
between 30 ka and 18 ka. The runoff that formed pluvial
lakes within the hyperarid Sdv area could only have resulted
from significantly increased discharge in the local desert
mountain ranges exceeding approximately 2000 m in
elevation and not from increased discharge and overflow
the ancestral Mojave River system. Reconstructions of Late