Oblique rifting at Tempe Fossae, Mars

Abstract

[1] This work shows the results of a structural study of the faults observed at the Tempe Rift (northeastern Tharsis region), Mars. A new, detailed map of faults and fault systems was used to geometrically characterize the fracture architecture of the Tempe Rift and to measure fault length, displacement, and spacing data, to analyze the spatial distribution of fault centroids, and to investigate the fractal nature of fault trace maps. A comparison with analog models and the use of conventional techniques of fault population analysis show that the Tempe Rift was most probably generated under sinistral oblique-rifting processes, which highlights the importance of the presence of inherited fractures in the tectonic evolution of the Noachian crust. The angle between the extension direction and the rift axis varies along the Tempe Rift, ranging from 50°-60°at its central southern part to 66°-88°to the southwest. Fault scaling relationships are similar to those found at midocean ridges on Earth with exponential fault length-frequency distributions. Localized, inhomogeneous deformation generated weakly interacting faults, spanning the entire thickness of the mechanical layer. This thickness decreased from southwest to northeast along the rift, along with distance from the central part of the Tharsis dome.

Structural Architecture and Deformation History of Tempe Terra, Mars

“…Our work is consistent with their hypothesis, although we suggest that evidence of some obliquity continues further to the southwest than the extent of their study, along the full extent of the TMAT exposed at Tempe Terra. Through comparison with previously estimated oblique extension directions along the rift (Fernández & Anguita, 2007; their Figure 14), we find that set H6 is largely orthogonal to the extension direction, while set H5 is typically more oblique to the extension direction but closer to the orientation of the overall rift axis and the alignment of the TMAT (see Figure S2 in Supporting Information S1). We therefore emphasize that the extension directions shown in Figure 9 are a first approximation only and meant as a visual aid for the variation in fault orientations through time.…”

“…The scale and pronounced curvature of the en echelon structures that form the central part of the Tempe Rift, which is markedly different to structural features across the rest of Tempe Terra, suggest a formation mechanism more complex than just simple fault growth through linkage. Fernández and Anguita (2007) proposed sinistral oblique rifting as this mechanism. Oblique rifting consists of both orthogonal pure shear and rift‐parallel simple shear (Fernández & Ramírez‐Caballero, 2019; Withjack & Jamison, 1986), and is considered the rule rather than the exception for Earth (Brune et al., 2018).…”

“…Oblique extension in Tempe Terra is likely controlled by the interplay of several factors, with local-scale (confined to Tempe Terra) heterogeneities interacting with regional-scale (extending over Tharsis) far-field stresses. Structural inheritance and local changes in extension direction around crustal-scale fractures are explanations favored by Fernández and Anguita (2007), and we would add to this the influence of local magmatism. The rift as a whole appears to be controlled by the location of the TMAT, but the areas of highest obliquity likely have the greatest influence of other local factors.…”

Structural architecture and deformation history of Tempe Terra, Mars

“…Tempe Fossae is a more spatially extensive set of complex faults and graben trending NNE to NE (Figure 2), with some locally curvilinear fault trends and a series of deeper and broader graben (Hauber & Kronberg, 2001;Moore, 2001). Within the Tempe Fossae system is the Tempe Rift (Figure 2), which is a unique feature of the region interpreted as a rift by Hauber and Kronberg (2001) and has been the focus of previous structural studies of Tempe Terra (Fernández & Anguita, 2007;Hauber et al, 2010). The Tempe Rift is 1,400 km long and widens to the southwest along the rift axis (oriented N45-50°E) from a single deep graben to more distributed faulting with a complex set of several shallower, sinuous graben and half-graben (Fernández & Anguita, 2007;Hauber & Kronberg, 2001).…”

“…Within the Tempe Fossae system is the Tempe Rift (Figure 2), which is a unique feature of the region interpreted as a rift by Hauber and Kronberg (2001) and has been the focus of previous structural studies of Tempe Terra (Fernández & Anguita, 2007;Hauber et al, 2010). The Tempe Rift is 1,400 km long and widens to the southwest along the rift axis (oriented N45-50°E) from a single deep graben to more distributed faulting with a complex set of several shallower, sinuous graben and half-graben (Fernández & Anguita, 2007;Hauber & Kronberg, 2001). The Labeatis Mons volcano and a second, older, unnamed volcanic center (which we label as "UV2" in Figure 2) are located within the rift structure and are considered to have been active syn-to post-rift, and pre-to syn-rift, respectively (Hauber & Kronberg, 2001).…”