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Table of Contents


Vol. 9 - 2010

Vol. 8 - 2009

Vol. 7 - 2008
SP 1 - 2008

Vol. 6 - 2007
Vol. 5 - 2006
Vol. 4 - 2005
Vol. 3 - 2004
Vol. 2 - 2003
Vol. 1 - 2001-2002

Notes for Authors
(PDF - 80 kb)



GeoActa Special Publication 1 2008


Acquisto online

GeoActa
an international Journal of Earth Sciences


Monica Pondrelli1, Angelo Pio Rossi2, Lucia Marinangeli1, Ernst Hauber3, Antonio Baliva1
1International Research School of Planetary Sciences, Università d'Annunzio, Viale Pindaro 42, 65127 Pescara, Italy. E-mail: monica@irsps.unich.it, luciam@irsps.unich.it, baliva@irsps.unich.it
2
International Space Science Institute (ISSI), Hallerstrasse 6, 3012 Bern, Switzerland. E-mail: arossi@issibern.ch
3DLR - Institute fur Planeterforschung, Tutherfordstrasse 2, 12489 Berlin-Adlershof, Germany. E-mail: Ernst.Hauber@dlr.de

An application of sequence stratigraphy to Mars: the Eberswalde fan delta



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Abstract

We present a review of our work on an intriguing feature on Mars, the Eberswalde delta-like feature, based on detailed geological analyses aimed to recognize and map the depositional environments and to infer their evolution through time. The topset-foreset-bottomset geometry, typical of delta progradation, has been observed in the Eberswalde outcrops allowing to interpret this feature as a fan delta. We distinguished delta plain, delta front and prodelta depositional sub-environments in the exposed stratigraphic succession. The delta plain is made of distributary channels and interdistributary areas, in which crevasse splays delivered coarser sediments from the channels. Polygonal shrinkage cracks formed probably after exposure in the interdistributary areas. At places the polygons have been reworked by more recent distributary channels causing the formation of intrabasinal breccia. In the delta front inertia and friction-related processes appear to be dominant in different phases of the fan delta evolution, suggesting fluctuations of the controls on sedimentation through time.
The dynamics of the recognized depositional environments has been evaluated in terms of sequence stratigraphy, recognizing geometries such as offlap and downlap, erosional truncations and stacking patterns, entering them in a stratigraphic framework. The sedimentary architecture of the fan delta appears to be organized in three cycles, which we tentatively interpreted as depositional sequences. The evolution of these sequences would have been controlled by relative water level fluctuations showing a longer term trend toward decreasing water content inside the basin.
The evolution of the Eberswalde fan delta appears to be controlled by autogenic processes within the single discharge lobes. Allogenic processes, such as tectonic activity and/or climatic forcing, would have instead caused fluctuations of the level of the water table in the lake, consequently driving the switching among the deltaic lobes.

Keywords: Mars surface geology, Fan delta, Sequence stratigraphy.