Mathematics – Logic
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufm.p23d0092p&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #P23D-0092
Mathematics
Logic
5419 Hydrology And Fluvial Processes
Scientific paper
The Eberswalde crater represents a spectacularly exposed example of water-related activity on Mars past geological history [1,2,3,4,5,6,7]. Eberswalde Crater at about 24.9° S., 33.7° W., lies just NE of Holden Crater and Uzboi Valles in Margaritifer Terra, Mars. We investigated the geology of this crater using MOC NA and HRSC imagery in combination with MOLA and HRSC derived DTM in order to recognize water-related processes and to infer depositional environments and depositional architecture. The fan delta located in the easternmost part of the crater presents well developed morphologies [1,2,3,4,5,6,7]. It consists of five lobes, suggesting prevalence of input related processes [4], even if wave- related processes seem to have been present as well [7]. Some of these lobes are coeval with the emplacement of synsedimentary tectonics and their morphology appears at least partly structural-controlled. The delta is made of bright and dark interlayered deposits. Some of the bright layers consist of very poorly sorted material, with boulders up to 10 meters of diameter floating in a finer matrix suggesting an emplacement as mass flows. Other layers consist of finer and better-sorted material. Most of the lobes display a low-dipping proximal area (1°-2°), a distal high-dipping area (6°-10°) and a more distal low-dipping area (1°-2°). We interpret the low dipping proximal part as delta plain consisting of distributary areas, mostly built by coalescing point bars [4,5], and interdistributary areas, in which crevasse splays flooded into the plain [7]. At places the topset-foreset-bottomset architecture typical of fan delta is present. In other cases, friction-related processes appear to be dominant. We interpret the high-dipping part of the fan delta as delta front deposits [7]. The oldest lobe display a transgressive-regressive cycle with a retrogradational stacking pattern at the base on top of which progradation develops. We interpret the retrogradational stacking pattern as formed during a Transgressive System Tract and the progradational stacking pattern related to a HighStand System Tract. The transition among these systems is marked by a Maximum Flooding Surface. A change in the morphology of the distributary channels from meandering to braided associated with a distal shift of the system appear to be related to a drop of the water level depicting a forced regression scenario. We interpret this lobe as formed during a Falling Stage System Tract. Friction-related processes appear to be dominant in this shallow-water type fan delta. The following lobe was deposited during another phase of rising water table which displays an overall aggradational stacking pattern [6,7] suggesting a certain equilibrium between sedimentary input, tectonic subsidence and level of the water table. The youngest two lobes do not display such a well developed depositional architecture, suggesting more episodic sedimentary activity. References 1. Malin, and Edgett, Science, 302, 1931-1934, 2003.2. Moore et al., Geophys. Res. Lett., 30, 24, 2292, doi: 10.1029/2003GL019002, 2003.3. Jerolmack et al., Geophys. Res. Lett., 31, L21701, doi: 10.1029/2004GL021326, 2004.4. Bhattacharya et al., Geophys. Res. Lett., 32, L10201, doi: 10.1029/2005GL022747, 2005.5. Wood, GSA Bulletin, 118, 5-6, 557-566; doi: 10.1130/B25822.1, 2006.6. Lewis and Aharanson, J. Geophys. Res., 111, E06001, doi: 10.1029/2005JE002558, 2006.7. Pondrelli et al., LPSC XXXVII, abstract 1555, 2006.
Baliva Antonio
Gwinner Klaus
Hauber Ernst
Marinangeli Lucia
Pio Rossi Angelo
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