Many places on Mars show rocks arranged in layers.
Rock can form layers in a variety of ways.
Volcanoes, wind, or water can produce layers.


A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars.
Layers can be hardened by the action of groundwater.
Martian ground water probably moved hundreds of kilometers, and in the process it dissolved many minerals from the rock it passed through.
When ground water surfaces in low areas containing sediments, water evaporates in the thin atmosphere and leaves behind minerals as deposits and/or cementing agents.
Consequently, layers of dust could not later easily erode away since they were cemented together.

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Many places on Mars show rocks arranged in layers. Rock can form layers in a variety of ways. Volcanoes, wind, or water can produce layers.

A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars. Layers can be hardened by the action of groundwater. Martian ground water probably moved hundreds of kilometers, and in the process it dissolved many minerals from the rock it passed through. When ground water surfaces in low areas containing sediments, water evaporates in the thin atmosphere and leaves behind minerals as deposits and/or cementing agents. Consequently, layers of dust could not later easily erode away since they were cemented together. 
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Iapygia quadrangle