Martian Strain History : Alba and Syria :

Introduction and Objectives: The centers work of Anderson et al. (2001) [1] identified two prominent centers in the Tharsis region, Syria Planum and Alba Patera (Stage 2 and Stage 4 respectively). Because of their perceived influence on the geologic and possible paleoclimatic histories of Mars, Mars Orbiter Laser Altimetry (MOLA) along with published stratigraphic and paleotectonic information (including the centers information) were analyzed using Geographic Information Systems (GIS) to perform a comparative investigation of their strain histories through time. This investigation highlights their similarities and distinctions, including their topographic and morphologic signatures, deformational extent, and intensities and durations of activity. Syria P lanum: Syria Planum is the site of long-lived (Noachian to Late Hesperian) magmatic-driven activity, displaying distinct episodes of intensive early magmatic/tectonic activity. Located within the southern part of the Tharsis Magmatic Complex (TMC), its dominant characteristics include: (1) local and regional centers of uplifts, (2) extensional and contractional tectonism, (3) magmatism including the formation of shield fields and the emplacement of dikes [2] and voluminous sheet lavas [3,4], and (4) a central summit region that exhibits a topographic low to the west and shield fields to the east surrounded by an annulus of extensional faults [3]. Alba Patera: Oneof the largest shield volcanoes found on the martian surface [3], the Alba Patera r egional center of magmatic-driven tectonism, is located in the northern region of the Tharsis magmatic complex. Alba Patera displays many of the characteristics of Syria Planum, including concentric and radial fault systems of varying relative ages, pit crater chains, and lava flow fields. Distinctions include: (1) a prominent shield volcano marked by summit calderas central to the concentric and radial fault systems (perhaps marking a central vent), (2) a scarcity of shield fields, and (3) wrinkle ridges that transect the summit [3]. Methodology and results: In order to determine the durations and intensities of tectonic activity for each center, the deformational extent of each center was first calculated. This was completed by analyzing MOLA-based cross-sections for each center in order to determine their topographic extent. Since the size of the magma bodies are at best poorly understood at depth, the topography, in our opinion, best constrains the source for the observed radial strain. Next, the Vector Analysis approach [1] was applied to a subset of the western equatorial paleotectonic dataset using only the simple grabens. Simple grabens were used because they represent the dominant structural …