GEOLOGIC MAP OF TERRA CIMMERIA, MARS: POTENTIAL IMPLICATIONS FOR REGIONAL PALEOMAGNETISM, PLANETWIDE PRIMORDIAL TECTONIC GEOMORPHOLOGY, AND THE STRUCTURAL HISTORY OF THE THARSIS RISE

A 1:1M preliminary geologic map is prepared for the Terra Cimmeria region of Mars (5 to 40^oS, 130 to 170^oE). Mapping in this region identified numerous parallel linearized basin contacts which extend for hundreds of km. These structurally-controlled lineaments also dextrally influence the rectilinear geometry of Al-Qahira Vallis. Furthermore, the geomorphic lineaments appear to coincide with transitions between extensive gravity anomaly lineations that form an intersecting lattice pattern. This lattice appears to extend uninterrupted beneath the crustal dichotomy, Tharsis, and the Hellas and Argyre impact basins, spanning the entirety of the areoid.

We theorize that these features comprise a global fracture network – the earliest fracture fleets appearing to have predated and survived the emplacement of the dichotomy – which is represented on the MRO110B2 anomaly dataset. We invoke planetary reorientation as a possible explanation for the emplacement of these hypothetical global basement features. Furthermore, we believe that the invocation of this fracture network enables a novel and detailed explanation for the incipience and structural history of the Tharsis Rise. We offer a preliminary form of this hypothesis in this presentation.

The initial purpose of our geologic mapping efforts in Terra Cimmeria was to clarify possible far-reaching tectonic effects of the Tharsis Rise in the eastern hemisphere of Mars. While obvious surficial evidences of these tectonic effects were not found, subsurface effects are considered. We argue that the incipience of the Tharsis Rise (at the Claritas tectonic center) induced the compression of Tharsis aquifers, triggering the filling of the Eridania paleosea and widespread subsurface metasomatism prior to the shutdown of the core dynamo. We infer that the strong magnetic lineations in terrae Cimmeria and Sirenum could be attributed to this process instead of plate tectonics.