| Abstrakt: |
The lithosphere of Mars accommodates horizontal shortening through folding and faulting, producing landforms described as wrinkle ridges or lobate scarps. Despite this nomenclature, we lack a deep understanding of the drivers of morphological differences observed between landform types. This study aims to develop a quantitative model for shortening landform classification based on surface morphology, subsurface architecture, and strain accommodation, facilitating interpretations of where and how lithospheric stresses are recorded. We developed this model by mapping 100 shortening landforms in a Geographic Information System, recording 12 unique geomorphic parameters such as length and asymmetry, and estimating the strain of each landform. We conducted a Discriminant Function Analysis (DFA) using surface morphometrics. This DFA produced a predictive linear function for categorizing wrinkle ridges and lobate scarps and for quantifying which landforms were exemplars within those categories. The three most influential variables on the surface morphometry DFA were the maximum width, forelimb slope, and back limb length. We then modeled the subsurface structural geology of 50 landforms using MOVE Structural Geology Modeling Software and conducted a second DFA based on subsurface metrics. DFA was most influenced by the dip and depth of the lower ramp base. When both surface morphology and subsurface geometry are input into single DFA, wrinkle ridges and lobate scarps can be distinguished quantitatively 96% of the time. Our results also show that lobate scarps accommodate more strain and imply that studies should consider landform type when interpreting local, regional, and global geological stress histories. Plain Language Summary: The tectonic structures of a planet record its geologic history. Some of these structures, such as those classified as lobate scarps and wrinkle ridges, account for the horizontal shortening of the planet's surface. These two groups of shortening structures are observed on the surface of almost every rocky planet. Planetary geologists have historically assumed that wrinkle ridges and lobate scarps represent different types or amounts of shortening based on differences in their visual morphologies. In this work, we mapped 100 of these landforms on Mars and quantified their surface characteristics. We then further analyzed 50 landforms using a structural geology modeling software to assess their subsurface fault and fold geometries. Using the parameters we measured, we applied a statistical analysis called a Discriminant Function Analysis to quantify and learn about the differences between these landform types. We find that lobate scarps are rooted by faults that extend deeper into the subsurface than faults that underly wrinkle ridges, and that because of the greater variability in landform characteristics, lobate scarps may represent a range of stages in the formation of these landforms while wrinkle ridges developed entirely during one phase of the geologic history of Mars. Key Points: Shortening landforms on Mars were analyzed at the surface and subsurface to quantify their morphometrics and structural geometriesTraditional definitions of lobate scarps and wrinkle ridges are end member descriptions of landforms that exist across a morphological spectrumLobate scarps are fault‐dominated structures while wrinkle ridges are fold‐dominated structures [ABSTRACT FROM AUTHOR] |
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