We have developed a refined geologic map and stratigraphy for lower Mount Sharp using coordinated analyses of new spectral, thermophysical, and morphologic orbital data products. The Mount Sharp group consists of seven relatively planar units delineated by differences in texture, mineralogy, and thermophysical properties. These units are (1–3) three spatially adjacent units in the Murray formation which contain a variety of secondary phases and are distinguishable by thermal inertia and albedo differences, (4) a phyllosilicate‐bearing unit, (5) a hematite‐capped ridge unit, (6) a unit associated with material having a strongly sloped spectral signature at visible near‐infrared wavelengths, and (7) a layered sulfate unit. The Siccar Point group consists of the Stimson formation and two additional units that unconformably overlie the Mount Sharp group. All Siccar Point group units are distinguished by higher thermal inertia values and record a period of substantial deposition and exhumation that followed the deposition and exhumation of the Mount Sharp group. Several spatially extensive silica deposits associated with veins and fractures show that late‐stage silica enrichment within lower Mount Sharp was pervasive. At least two laterally extensive hematitic deposits are present at different stratigraphic intervals, and both are geometrically conformable with lower Mount Sharp strata. The occurrence of hematite at multiple stratigraphic horizons suggests redox interfaces were widespread in space and/or in time, and future measurements by the Mars Science Laboratory Curiosity rover will provide further insights into the depositional settings of these and other mineral phases.

Ground-based bedding orientation measurements are critical to determine the geologic history and processes of sedimentation in Gale crater, Mars. We constrain the dip of lacustrine strata of the Blunts Point, Pettegrove Point, and Jura members of the Murray formation using a combination of regional stratigraphic correlations and bed attitude measurements from stereo Mastcam images taken by the Mars Science Laboratory Curiosity rover. In situ bed attitude measurements using a principal component analysis-based regression method reveal a wide range of dips and dip azimuths owing to a combination of high stereo errors, postdepositional deformation of strata (e.g., fracturing, rotation, and impact cratering), and different primary depositional dips. These constrain regional dips to be within several degrees of horizontal on average. Stratigraphic correlations between targets observed in the Glen Torridon trough and at the Pettegrove Point-Jura member contact of Vera Rubin ridge (VRR) constrain dips to be between 3°SE and 2°NW, consistent with nearly flat strata deposited horizontally on an equipotential surface. The Jura member is determined to be stratigraphically equivalent to the northern portion of the Glen Torridon trough. Rover-based dip magnitudes are generally significantly shallower than the orientation of VRR member contacts measured from High Resolution Imaging Science Experiment-based traces, suggesting the sedimentary strata and VRR member contacts may be discordant.Plain Language Summary The orientation of sedimentary strata is one of the most fundamental measurements of structural geology because it records information about the processes of deposition and subsequent deformation of those strata. For the last 7 years, the Curiosity rover has traversed predominantly fluviolacustrine (river-and lake-deposited) strata. Recently, the rover traversed the Vera Rubin ridge (VRR), a topographic rise within a larger collection of strata with rock exposures whose orientation can be measured using overlapping (stereo) images taken by cameras aboard the rover. By measuring the orientation of beds in stereo rover images and comparing the elevation of similar rock lithologies found along the traverse, we constrain the strata that comprise the VRR to be horizontal or only shallowly dipping. This result is consistent with the sediment that formed the VRR being deposited on a nearly horizontal surface, suggesting that at least the strata that make up the lower portion of Mount Sharp, the large sedimentary mound in Gale crater that dips more steeply outward, may not have directly contributed to its primary formation. The near-flat orientation also indicates that some portion of the VRR occurs at the same elevation as the region south of the ridge called Glen Torridon.

Ancient stratigraphy on Isidis Basin's western margin records the history of water on early Mars. Noachian units are overlain by layered, basaltic composition sedimentary rocks that are enriched in polyhydrated sulfates and capped by more resistant units. The layered sulfates—uniquely exposed at northeast Syrtis Major—comprise a sedimentary sequence up to 600 m thick that has undergone a multistage history of deposition, alteration, and erosion. Siliciclastic sediments enriched in polyhydrated sulfates are bedded at meter scale and were deposited on slopes up to 10°, embaying and thinning against preexisting Noachian highlands around the Isidis Basin rim. The layered sulfates were modified by volume loss fracturing during diagenesis. Resultant fractures hosted channelized flow and jarosite mineral precipitation to form resistant ridges upon erosion. The structural form of the layered sulfates is consistent with packages of sediment fallen from either atmospheric or aqueous suspension; coupling with substantial diagenetic volume loss may favor deepwater basin sedimentation. After formation, the layered sulfates were capped by a “smooth capping unit” and then eroded to form paleovalleys. Hesperian Syrtis Major lavas were channelized by this paleotopography, capping it in some places and filling it in others. Later fluvial features and phyllosilicate‐bearing lacustrine deposits, sharing a regional base level of ∼−2,300 m, were superimposed on the sulfate‐lava stratigraphy. The layered sulfates suggest surface bodies of water and active groundwater upwelling during the Noachian‐Hesperian transition. The northeast Syrtis Major stratigraphy records at least four distinct phases of surface and subsurface aqueous activity spanning from late Noachian to early Amazonian time.

The orientations of planar rock layers are fundamental to our understanding of structural geology and stratigraphy. Remote sensing platforms including satellites, unmanned aerial vehicles, and Light Detection and Ranging scanners are increasingly used to build three‐dimensional models of structural features on Earth and other planets. Remotely gathered orientation measurements are straightforward to calculate but subject to uncertainty inherited from input data, differences in viewing geometry, and the plane‐fitting process, complicating geological interpretation. Here, we improve upon the present state of the art by developing a generalized means for computing and reporting errors in strike‐dip measurements from remotely sensed data. We outline a general framework for representing the error space of uncertain orientations in Cartesian and spherical coordinates and develop a principal component analysis (PCA) regression method, which captures statistical errors independent of viewing geometry and input data structure. We also introduce graphical techniques to visualize the uniqueness and quality of orientation measurements and a process to increase statistical power by jointly fitting bedding planes under the assumption of parallel stratigraphy. These new techniques are validated by comparison of field‐gathered orientation measurements with those derived from minimally processed satellite imagery of the San Rafael Swell, Utah, and unmanned aerial vehicle imagery from the Naukluft Mountains, Namibia. We provide software packages supporting planar fitting and visualization of error distributions. This method increases the precision and comparability of structural measurements gathered using a new generation of remote sensing techniques.

The orientations of planar rock layers are fundamental to our understanding of structural geology and stratigraphy. Remote sensing platforms including satellites, unmanned aerial vehicles, and Light Detection and Ranging scanners are increasingly used to build three-dimensional models of structural features on Earth and other planets. Remotely gathered orientation measurements are straightforward to calculate but subject to uncertainty inherited from input data, differences in viewing geometry, and the plane-fitting process, complicating geological interpretation. Here, we improve upon the present state of the art by developing a generalized means for computing and reporting errors in strike-dip measurements from remotely sensed data. We outline a general framework for representing the error space of uncertain orientations in Cartesian and spherical coordinates and develop a principal component analysis (PCA) regression method, which captures statistical errors independent of viewing geometry and input data structure. We also introduce graphical techniques to visualize the uniqueness and quality of orientation measurements and a process to increase statistical power by jointly fitting bedding planes under the assumption of parallel stratigraphy. These new techniques are validated by comparison of field-gathered orientation measurements with those derived from minimally processed satellite imagery of the San Rafael Swell, Utah, and unmanned aerial vehicle imagery from the Naukluft Mountains, Namibia. We provide software packages supporting planar fitting and visualization of error distributions. This method increases the precision and comparability of structural measurements gathered using a new generation of remote sensing techniques.