Relative ages and the geologic evolution of Martian terrain units
Existing Martian relative age chronologies rely entirely or predominantly on Mariner 9 images, extrapolated numbers of craters, and craters < 10 km in diameter. All of these factors produce uncertainties in the resulting cumulative size, frequency distribution curves from which the chronologies are derived. Data used in this study include craters greater than or equal to 8-km diameter mapped from Viking 1:2M photomosaics. Crater size/frequency distribution curves were determined for a variety of Martian terrain units using the relative plotting technique. Approximately 60% of the Martian surface dates from the period of heavy bombardment, including not only the heavily cratered uplands and intercrater plains of the southern highlands but also units commonly assigned to younger periods, such as many of the small volcanic constructs. Size/frequency distributions of ridged plains show unquestionably that these plains date from near the end of heavy bombardment, solving the controversy over the relationship of these units to the period of heavy bombardment. The remaining 40% of the surface has formed since the end of heavy bombardment. The northern plains are divided into a number of regional units and a range of formation ages is found for these localized regions. More regions are studied than in previous chronologic studies, resulting in better definitions of age relationship among units and determination of contemporaneous and non-contemporaneous units.
- Research Organization:
- Arizona Univ., Tucson (USA)
- OSTI ID:
- 7222376
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
Similar Records
Constraints on early events in Martian history as derived from the cratering record
Martian ages