Soil Sediment In A Semiarid Quaternary Basin In Southeast Morocco As Source Of Aeolian Dust

We chose the Tafilalt depression area along Ziz River, in Southeast Morocco in an attempt to test in natural settings a package of atmospheric sensing instruments simulating the ESA DREAMS ExoMars payload, programmed to land... [ view full abstract ]

We chose the Tafilalt depression area along Ziz River, in Southeast Morocco in an attempt to test in natural settings a package of atmospheric sensing instruments simulating the ESA DREAMS ExoMars payload, programmed to land on Mars in late 2016. The site met the requirements for a dust source area, with a complex mineralogy derived from sediment accumulation from multiple geologic sources. The combined processes that produced the sediments in the area simulate to a certain degree the expected conditions the ExoMars Schiaparelli payload will encounter in the area of the currently selected landing site in Terra Meridiani.
This study focuses on the detailed analysis of the sediments from the compositional point of view, in order to serve as a basis for the input for interpretation of the simulated payloads measurements (e.g. electric charge, dust opacity) at the site. Furthermore, we characterized the mineral and geochemical signatures related to the identification of sources of sediments for dust provenance type of studies.
We addressed the topics above by means of multiple instrumental laboratory techniques (XRD, SEM-EDS, and FTIR-VIS-NIR-TIR) and target the characterization of detrital dust derived from the exposed Paleozoic-Mezozoic, rocks and their subsequent comminution and weathering in alternating atmospheric/lacustrine environment. The basis for the mineral dust signatures characterization is related to the level of metamorphism in the sediments of the exposed strata, and translate into the quantification of illite (via Kubler index and various derived flavors1,2) and chlorite (via Árkai index3,4) crystallinity in XRD patterns. To strengthen the local characteristic signatures we also addressed the determination of each of the above mineral classes’ polytypes. These parameters indirectly reflect the outcropped material from which the dust is derived, providing a good mineral discriminating fingerprint for the dust derived from this area that sets it apart from other dust sources in NW Africa.

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