Аннотация
This thesis was conducted in the framework of the German Research
Foundation's priority program "Mars and the Terrestrial Planets".
The aim was to improve and/or verify the existing chronostratigraphic
system of Mars and to understand globally the geologic evolutionary
history of Mars focusing on the volcanic, fluvial, and possible glacial
processes. This implies the photogeologic analysis of all available
types of Martian imagery in order to cover the diversity of Martian
landforms in time and space. Therefore, crater frequencies are determined
for appropriate geologically mapped units and absolute ages derived.
The lunar crater production function and the chronology model was
confirmed for the Martian case, e.g. the theoretical crater production
function was proven over the entire (50 meters to 500 kilometers).
Any deviation from the confirmed Martian standard crater production
function indicate resurfacing events. In such cases the method of
age determination has been improved. The influence of secondary cratering
on a measurement is at most 10 percent. Type areas of the Martian
epochs (Noachian, Hesperian and Amazonian) such as Noachis Terra,
Hesperia Planum, northern lowland regions, Amazonis and Elysium Planitia,
have been examined, to understanding the role of water during the
Martian geologic evolution. The younger fluvial erosion is closely
related to volcanic activity and occurred in episodes over the last
2 billion years. Extensive measurements in volcanic units allowed
for the interpretation of the evolutionary history of Martian volcanic
activity. An interplay of volcanic processes with ancient and more
recent fluvial and glacial activity is confirmed. Globally, the volcanic
activity started very early in the Martian evolution. Most of the
volcanoes achieved their present dimensions at least until 3.5 Ga
ago. Later volcanic resurfacing indicates a weakening of the volcanic
activity after the construct-forming period. Another major finding
is that the volcanic activity on Mars continued until very recently
(e.g. 2 Ma at the flanks of Olympus Mons), and is more wide--spread
than believed earlier. The crystallization ages of basaltic Martian
meteorites (about 180 Ma, 450 Ma and 1.3 Ga) confirm this finding.
The enigmatic Medusae Fossae formation could be dated for the first
time indicating that explosive volcanic eruption occurred even as
recently as 1.6 Ga ago. By understanding the evolutionary history
of Martian volcanic constructs, the formation time of large impact
basins, as well as the evolution of the northern lowlands and the
dichotomy boundary, essential time--markers have been gathered in
this work, and a coherent view on the global geological evolution
of Mars is derived from these ages. Providing that the time--frame
outlined in this study is correct, the timing for the thermodynamical
evolution of Mars can be assessed. This study revealed that the youngest
epoch, the Amazonian, is reflected in a variety of landforms, and
includes an absolute time span of three-quarters of the geological
record of Mars. This implies that the Amazonian--Hesperian time--stratigraphic
boundaries have to be revisited. urn:nbn:de:kobv:188-2006000335
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