Landscape Evolution of Kasei Valles

Kasei Valles is the second largest valley on Mars. This study focuses on landforms created by surface processes in the central part of the southern branch of Kasei Valles. We mapped the landforms and built a morphostratigraphical chronology using numerical crater dating and cross-cutting relationships of the landforms. We interpret that surface processes formed various landforms in the study area, including plateau surfaces, deeply incised canyons, colluvial fans, landslide, topographic barriers, trim lines, terraces and platy-textured valley floor fill. These features aligned within the deeply incised valley of the valles indicating incision of the plateau surface. The most common landforms are colluvial fans. Two colluvial fans and a landslide temporarily blocked the valles, forming topographical barriers to impound fluids (e.g lava, mudflow, water). The trim lines in area may indicate the presence of water like liquid in the valley, even for a short time. Terrace surfaces are very evident between these trim lines. The surface texture of the terrace surfaces implies that they were probably formed by a water-like fluid that stagnated and regressed for a period and fluctuated to carve terrace staircases. Crater statistics reveal two different temporal clusters of colluvial fan formation. The age of the older colluvial fans cluster in the Early Amazonian period (around 1.74 - 1.14 Ga), and the age of the younger colluvial fans cluster in the Late-Middle Amazonian period (around 307 Ma). The landslide is much younger, and it is estimated to have formed 122 Ma before present. The youngest studied geomorphic features are the platy-textured deposits emplaced either as lavas or mudflows, aged 90 Ma, covering the floor of the valles. Our data suggest that the presence of well-developed terraces between trim lines require the presence of a Newtonian fluid (e.g. water) that ponded into the study area and the climatic conditions for this fluid to remain stable over short timescales enough to form terraces.