Marchand-Thébault was involved after 1958 in arranging and describing the archival records related to Madagascar. She managed the archives section of the Office of the High Commissioner of France in Madagascar, while the archives section of the Upper Territory of Madagascar was headed by Jean Valette. She was involved in arranging and describing records series relating to the Malagasy Uprising of 1947 in Madagascar. She renamed a records series relating to the Insurrection of 1947 which also includes the pre-rebellion period. Originally established by the High Commission under "E" it was renamed "R" by Marchand-Thébault. She also added files that she gathered as part of her tour of local districts.